SYSTEMATIC REVIEW published: 07 December 2021 doi: 10.3389/fsurg.2021.792380 Location, Clinical Presentation, Diagnostic Algorithm and Open vs. Arthroscopic Surgery of Knee Synovial Haemangioma: A Report of Four Cases and a Literature Review José A. Hernández-Hermoso 1,2*, José Moranas-Barrero 3 , Ester García-Oltra 1,2 , Fernando Collado-Saenz 1,2 and Sylvia López-Marne 3 1 Department of Orthopedic Surgery and Traumatology, Hospital Universitari Germans Trias i Pujol, Badalona, Spain, 2 Department of Surgery, Faculty of Medicine, Universitat Autònoma de Barcelona, Bellaterra, Spain, 3 Department of Orthopedic Surgery and Traumatology, Hospital Universitari Bellvitge, L’Hospitalet de Llobregat, Spain Objective: The aim was to report 4 patients with intra-articular knee synovial haemangioma (KSH) and to perform a systematic review to describe the patient Edited by: characteristics, patterns of tumor location, clinical presentation, usefulness of imaging Yang Lv, examinations, pros and cons of arthroscopic vs. open resection, and follow-up in Peking University Third Hospital, China the literature. Reviewed by: Yu Mei, Design: From 1996 to 2016, four patients with KSH were retrospectively reviewed. A Peking University Third Hospital, China literature search was conducted in PubMed from 2000/01 to 2020/06 using the search Dong Jiang, Peking University Third Hospital, China terms “synovial haemangioma” and “knee.” Fifty full-text articles that included a total of *Correspondence: 92 patients were included for further discussion. José A. Hernández-Hermoso dr.hernandezhermoso@gmail.com Results: Four adults (20–40 years) were diagnosed with KSH. Three lesions located in orcid.org/0000-0002-9167-3782 the suprapatellar pouch, two eroding the patella and one the supratrochlear bone, and one in the posterior compartment. Persistent anterior knee pain was the main complain. Specialty section: MRI revealed a benign tumor mass in all cases except one. Open excisional biopsy This article was submitted to Orthopedic Surgery, and regional synovectomy were performed in three patients, and by arthroscopy of a section of the journal the posterior compartment in the fourth. Histological type was arteriovenous in three Frontiers in Surgery cases and capillary in one. A pain-free knee without recurrence was achieve in all Received: 10 October 2021 Accepted: 15 November 2021 cases except one, which was successfully reoperated. Average follow-up time was Published: 07 December 2021 3.5 years. A literature review showed that KSH appears most frequently in children Citation: and teenagers (64.6%) and does not differ by gender. The suprapatellar and patella- Hernández-Hermoso JA, femoral joint compartment was the most frequent location (47.9%). The bony tissue of Moranas-Barrero J, García-Oltra E, Collado-Saenz F and López-Marne S the knee was rarely affected (13.5%). Pain, swelling and haemarthrosis were frequently (2021) Location, Clinical Presentation, reported (88.2, 66.7, and 47.1%). MRI was the most commonly used imaging test (98%). Diagnostic Algorithm and Open vs. Arthroscopic Surgery of Knee Synovial Treatment consisted of regional synovectomy by open surgery or arthroscopy in 66.7 and Haemangioma: A Report of Four 15.6% of cases, respectively. Cases and a Literature Review. Front. Surg. 8:792380. Conclusions: KSH should be considered in the differential diagnosis of adult patients doi: 10.3389/fsurg.2021.792380 with chronic low-intensity knee pain. MRI is the most useful exam because it establishes Frontiers in Surgery | www.frontiersin.org 1 December 2021 | Volume 8 | Article 792380 Hernández-Hermoso et al. Knee Synovial Haemangioma Literature Review the location, extent and benign characteristics of the tumor. Definitive diagnosis requires histological examination. We believe excisional biopsy and regional synovectomy by arthroscopy should be the treatments of choice for intra-articular tumors, but we recommend open surgery when the lesion extends to the tendons, muscle or bone. Keywords: synovial, haemangioma, knee, magnetic resonance, arthroscopy INTRODUCTION the real value of imaging examinations and follow-up results after arthroscopic or open surgery, is important for making informed Synovial haemangioma (SH) is a rare benign tumor accounting decisions on the need for invasive imaging examinations and on for 0.07% of all soft tissue tumors and 0.78% of all excised the differential effectiveness of open vs. arthroscopic treatment in haemangiomas (1). While this type of lesion is usually light of the evidence. monoarticular (2), more than one mass can occur in different The aim of the study was to describe four patients with intra- locations within the joint (3). SH has been reported in many articular KSH, two with the previously undescribed phenomenon joints but is most common in the knee (4). of patellar bone erosion and one with an unusual tumor location Knee synovial haemangioma (KSH) can present as diffuse or in the posterior compartment, and to perform a systematic review localized intra-articular, juxta-articular or intermediate (intra- of PubMed publications on KSH from 2000 to 2020 to describe and juxta-articular) synovial tissue masses (2, 5–7). Extra- the characteristics of the patients (age, gender, knee side, previous synovial and intra-synovial locations have been described for trauma), the patterns of tumor location, the non-specific clinical joint tumors (8), with intra-synovial locations being more likely presentation, the usefulness of imaging examinations, the pros to affect cartilage (8). It can be a part of an angiodysplastic lesion and cons of arthroscopic vs. open resection, and the follow-up of the extremities (Klippel-Trénaunay syndrome) with diffuse time and recurrence after treatment. (9, 10) or localized (11) involvement of the joint. Most are located in the anterior compartment of the knee (7, MATERIALS AND METHODS 12). Only eight localized cases have been reported in the posterior compartment [one intermediate (5), three juxta-articular (1, 12) Clinical Cases and four intra-articular (13–17)], one of which was reported Based on hospital records, we identified four patients with twice (14, 15). Most reports are single case studies (1–3, 11, 13– KSH who were seen between 1996 and 2016. Demographic 50), while case series are less common (4–10, 12, 51–57). data, symptoms, imaging tests, treatment and follow-up were The clinical presentation is non-specific, with symptom onset retrospectively reviewed. All patients underwent surgical usually occurring in childhood and young adulthood, although treatment by one surgeon (JHH). Written informed consent was it has been described at later ages, probably due to delayed obtained from the patients in all cases, and the retrospective diagnosis. Various imaging modalities have been used, but all are study was approved by the hospital ethical committee (approval non-specific, and there is no clear diagnostic algorithm (2, 4, 9, number PI-20-196). The procedures followed were in accordance 13, 18, 25, 28–30, 32, 33, 38, 45, 48, 50, 55, 57, 58). with the ethical standards of the responsible committee on Once a benign synovial lesion is suspected, it is unsettled if a human experimentation (institutional and national) and with biopsy is needed or if excisional biopsy and regional synovectomy the Helsinki Declaration of 1975, as revised in 2000. with histological examination can confirm the diagnosis and simultaneously accomplish definitive treatment. Whether open Literature Review (2–5, 8–10, 16, 21, 37, 38, 57) surgery is preferable to arthroscopic A PubMed literature search was performed for full text (6, 38, 39) surgery remains controversial, especially in localized publications between 2000/01 and 2020/06; these dates were intra-articular lesions. There is no clear information on the selected because MRI was widely available in this period. The recurrence rate after surgical treatment. search terms were as follows: (synovial haemangioma) AND Further investigation is warranted, particularly because the (Knee) AND (2000/01:2020/06). Selection was restricted to single existing information is scattered and based mostly on isolated case reports or case series of KSH that described the diagnosis and clinical cases. An understanding of the differences in patient at least four items in our study objectives. Only original reports characteristics and clinical presentation, along with knowledge of or studies written in English, Spanish or French and available in full-text form were included. Abbreviations: KSH, knee synovial haemangioma; SH, synovial haemangioma; Each original manuscript was scrutinized, and search results LPVNS, localized pigmented villonodular synovitis; MR, magnetic resonance; on the number of cases described, the age and gender of the MRI, magnetic resonance imaging; MRGd, magnetic resonance enhanced with patients, the side of the affected knee, the tumor location, the gadolinium; US, ultrasound; ED, echo Doppler; CT, computed tomography; history of previous trauma, the symptoms and signs, the presence Sc, scintigraphy; CTArt, computed tomography arthrography; CTA, computed of cutaneous haemangioma, the delay in diagnosis, the image tomography angiography; MDCTA, multi-detector computed tomography angiography; RBCSc, red blood cell scintigraphy; SPECT, single-positron emission examinations performed, the presence of bone involvement, the computed tomography; TKA, total knee arthroplasty; PCL, posterior cruciate type of treatment, the histological type and the follow-up time ligament. were screened and collected in a database by two reviewers Frontiers in Surgery | www.frontiersin.org 2 December 2021 | Volume 8 | Article 792380 Hernández-Hermoso et al. Knee Synovial Haemangioma Literature Review TABLE 1 | Clinical case demographics, tumor location, clinic, image examinations, treatment, histology, and follow-up. Age Gender Side Location Trau Symptoms/Signs CH DeD Image Examinations BA Treat Histology F-up Rec Case 1 20 M R SP-Q No P-H Nr 5y XR-Sc-MRI Yes OS AV 4y Yes Case 2 22 M R SP-Q No P Nr 6y XR-MRIN-MRI Yes AN-OS AV 5y No Case 3 31 M R SP No P-PA-S-T Nr 8y XR-MRI Yes OS Cp 4y No Case 4 40 M R PC No P-PA Nr 10 y XR-MRI No AS AV 1y No Trau, previous trauma; CH, Cutaneous haemangioma; DeD, Delay in diagnosis; BA, Bone Affected; Treat, Type of treatment; F-up, Follow-up; Rec, Recurrence; y, years; F, Female; M, Male; R, Right; L, Left; SP, Suprapatellar; PC, Posterior compartment; Q, Quadriceps; P, Pain; PA, Pain with Activity, Tenderness H, Hemarthrosis; XR, radiography; Sc, Scintigraphy; MRI, Magnetic resonance image; MRIN, MRI negative; OS, Open surgery; C, Curettage; AN, Arthroscopy Negative; AS, Arthroscopic Surgery; Cp, Capillary; AV, Arteriovenous; Nr, not reported. independently (JHH, JMB) to ensure accuracy and then stored was characterized by hyperintensity on T2-weighted images and on a Microsoft Excel spread sheet. Any discrepancy in the data hypo-/isointensity to muscles on T1 sequences (Figures 1A,B). collected was reviewed by both reviewers until an agreement A non-specific benign synovial knee tumor, either SH was obtained. The review was limited to reporting variables that or localized pigmented villonodular synovitis (LPVNS), was were obtained in each publication; when a variable was omitted, suspected. An open excisional biopsy, partial synovectomy and it was registered as not reported. The results are presented as curettage of bone were performed. Histological examination the number of cases and the percentage with respect to the reported proliferation of arterial and venous vessels in a fibrous total number of cases, except for symptoms and signs and stroma, consistent with the diagnosis of arteriovenous-type SH image examinations, which are presented as the number of (Figure 2). manuscripts where they are reported and the percentage with Recurrence of the tumor was observed on MRI follow-up respect to the total number of manuscripts reviewed. Age, delay 5 years later. MRI revealed diffuse involvement of the sub- in diagnosis and follow-up time are presented as the mean ± quadriceps synovial lining and tendon (Figures 3A,B). An open standard deviation of data available, and the percentage of cases wide regional synovectomy of the sub-quadriceps synovia and not reporting those data was also specified. In order to avoid tendon was performed. Two months postoperatively, the patient multiple reports of the same study, studies with the same authors was engaging normally in activities of daily living, and at 5 were double-checked, and comparisons of case descriptions and months, he resumed his amateur sport routine. Four years after treatments were performed. Neither of the review authors was the second surgery, the patient remained asymptomatic with no blinded to the journal titles or the study authors or institutions. recurrence on follow-up MRI. Case 2 RESULTS A 22-year-old male was referred to our hospital for persistent anterior right knee pain lasting 6 years. He had moderate pain Results tabulated by age, gender, affected knee side, tumor that did not limit activities of daily living but prevented him from location, history of previous trauma, clinical symptoms and practicing sports. He had no history of prior trauma, although signs, presence of cutaneous haemangioma, time in diagnosis he had experienced minor impacts during sports. On physical delay, imaging test used, bone involvement, type of treatment, examination, he had lower limb varus alignment, no muscle histology, follow-up time and recurrence are shown in Table 1 atrophy, no effusion, normal range of motion, a stable knee, and for the clinical cases and Table 2 for the literature review. normal meniscal and neurovascular examinations. Radiographic images were normal. MRI was reportedly Clinical Cases normal. Due to the persistence of symptoms despite analgesics Case 1 and muscle strength exercises, diagnostic arthroscopy was A 20-year-old male suffering from sudden intense pain in the performed. We detected no evidence of joint damage. right knee with swelling presented to the emergency room. He Histological and microbiological tests of the synovial lining had had occasional pain for 5 years, but never at that intensity. from various areas were normal. Palpation of the external aspect of the patella was painful. However, owing to worsening symptoms 2 years later, another There was no patellar instability; meniscal, ligamentous and MRI was performed, revealing a tumor in the synovial lining just neurovascular examinations were normal. over the proximal pole of the patella; the tumor was isointense Plain radiographs were normal. Joint aspiration revealed a on T1 and hyperintense on T2, with intra-osseous invasion of the haemarthrosis. Anterior knee pain syndrome due to patella- upper pole of the patella (Figures 4A,B), suggestive of SH. femoral cartilage damage or synovial derangement was Upon open surgery, the synovial lining above the upper pole suspected. Bone scintigraphy with 99mTc revealed an increase of the patella was swollen and bluish brown, with poorly defined in uptake in the anterior portion of the knee. MR revealed margins, and there was invasion of the quadriceps tendon and the a suprapatellar and supratrochlear synovial tumor extending superior pole of the patella. We resected the tumor and half of the medially and eroding the supratrochlear cortical bone; the tumor quadriceps tendon to healthy margins and curetted the superior Frontiers in Surgery | www.frontiersin.org 3 December 2021 | Volume 8 | Article 792380 TABLE 2 | Knee synovial haemangioma literature review summary 2000–2020. Frontiers in Surgery | www.frontiersin.org Hernández-Hermoso et al. N◦ Age Gender Side Location Trau Symptoms/Signs CH DeD Image BA Treat Histology F-up Examinations Our series 2020 4 20-22- 4M 4R SP (3) Q (1)- No P-PA-S-T-H Nr 7.2 y XR-Sc-MRIN- Yes (3) OS (3)-AS AV (3)-Cp 3.5 y (1 R) 31-40 PC MRI y Muramatsu et al. 10 12.4 y (4 5 F-5 M Nr PFL (3)-PFM yes P-H-LRM No 2.5 y XRP (1)-MRI No AB-OS C (2)-Cp 1y (12) m−17 y) (2)-IP (1)-PC (6)-CCp (2) (2)-D (2) Tohma et al. (3) 1 41 y M R MC Nr P-S- PTM-LRM Nr 30 y XRB-MRI- Yes OS AV 4y MRA Goki-Kemei et al. 1 38 y F R MC No PA-S-T-E-LRM Nr Nr MRI No AB-OS SH 3m (25) Bawa et al. (21) 1 25 y F R PFL No P-S-E-PTMF No 20 y XR- MRI No AS C Nr Beltrame et al. (23) 1 7y F R IP Nr P-S Nr Nr MRGd No Nr Nr Nr Begly et al. (22) 1 39 y M R IN Yes P-L-LRM-T-E-H No 1w XR-MRI No AS SH Nr Wen et al. (46) 1 14 m F R IPL-IN No RW-Lu-PTM-H Nr 3w XRS-US- No OS C Nr MRGd- Derzsi et al. (1) 1 13 y M L PC Yes S-PTM-A-LRM Nr 2y XR-MRI No OS AV 21 m Masquefa et al. 1 37 y F Nr PC Nr Nr Nr Nr MRI No AS SH 22 m (15) Dunet et al. (14) Yes P No 9m Rx-CT-MRGd No C 5y Lopez-Oliva et al. 4 22 y 2 F-2 M Nr IN-MC-SP-IP Nr P-S-A-LRM-H Nr 3y XRP (1)-XRO No OS (3)-Ob Nr (4) 6.8 y 4 (54) (6–43 y) (3)-MRI Arslan et al. (19) 1 23 y M L SP-VMO Nr P-S-T Nr 1.5 y XR-US-CT- No AB-Nr SH Nr MRGd Guler et al. (27) 1 19 y M Nr SP Nr P-S-T Nr Nr XR-MRGd No Nr Nr Nr Andrea Parra et al. 1 2y M R SP-VL Nr P-S-M Nr 18 m XRS-ED-MRI No OS VVM Nr (50) Mrani Alaoui et al. 1 7y M L D Yes P-S-L-LRM-A No 12 m XR-MRGd Yes OS Cp 36 m (R) (34) De Gori et al. (26) 1 67 y M L D Nr P-S-Cl-Cr-T-LRM Nr 15 y XRO-MRI No TKA SH 2y Kim et al. (30) 1 7y M R IP Nr S-H Nr 1y MRI-RBCSc- No OS V Nr Knee Synovial Haemangioma Literature Review SPECT/CT December 2021 | Volume 8 | Article 792380 Maeyama et al. 1 15 y F R MC No PA-S-A-LRM Nr 7y XRBO-Ar-CT- Yes AS SH 5 y (SP) (33) MRI Tahmasebi et al. 1 45 y F R PFM No PA-S-PTM-H Nr Nr XR-MRI No AS C 1y (42) Wong et al. (48) 1 5y M R IPM No P-S Nr 2y MRI No OS SH 32 m Dalmonte et al. (8) 14 5y 8 M-6 F Nr SIE-IIE-II (4 in Nr P-S-LRM-H Yes (7) 26 m XRS (6)-XRP No AB-OS IAVM (14) 46 m (2 R) (3 (2.5–13 two or more) (2)-US-MRI SP) y) Hospach et al. (28) 1 15 y M R SP-Q-B Nr P-S-LRM Nr 6y XR-US-ED- No AN-AS C Nr MRIN-MRGd (Continued) Frontiers in Surgery | www.frontiersin.org Hernández-Hermoso et al. TABLE 2 | Continued N◦ Age Gender Side Location Trau Symptoms/Signs CH DeD Image BA Treat Histology F-up Examinations Lin et al. (32) 1 11 y M L SP-IN No P-S-LRM-H Yes 1y XR-MDCTA No Cor-Bblo Nr 2m Sasho et al. (59) 2 37–60 y F-M R (2) IP-SP Nr P-H Nr 19 y XR-MRGd No AN-AS C (2) 2y Vakil-Adil et al. (44) 1 12 y M L SP-VMO Nr P-S-PTM flexion No 3y XR-MRI No OS C Nr Watanabe et al. 1 3y F L IP No P-S-Li-E No 6m XRB-Sc- Yes AB-Ob C 6 m (R) (SP) (45) MRGd Holzapfel et al. (2) 1 29 y M L MC No PA cross leg No 3m XRB-Sc-CT- Yes OS-C-BG C Nr MRGd Ares-Rodriguez 1 10 m M L IPM Yes P-Ed-Li-H Nr 24 h Ar-MRI No OS AV 4y et al. (18) Rajni et al. (37) 1 10 y F R No D Nr 4y XRS-MRI No AB-OS CCp Nr Tzurbakis et al. 1 34 y M R IN Yes P-S-L-A Nr 5y XR-MRI No AS Cp 4y (43) Barakat et al. (60) 1 24 y F L PFM No P-H Nr 15 y ED-MRI No AN-AS C 12 m Carrol and Higgs 1 10 y M R SP No S-W-LRM-H Nr 8y XRC-US-MRI Nr Nr Nr Nr (24) Sanghi et al. (38) 1 7y F L SP Yes RW-LRM-PTM Nr 3y XR-ED-MRGd No AS C Nr Silva et al. (40) 1 20 y M R SP No P-S Nr 6m XR-MRI No AS SH 2y Yercan et al. (55) 3 11 y-21 3F 2 R-l L SP (3) VMO No P-S-B-T-E-A- Nr 6y XRS-CT-MRI Yes (1) AB-OS-C CCp (1)-Nr (2) 38 m y-22 y (1) PTM-LRM-H 5 Zarza Pérez et al. 1 37 y F R IP Nr P-S-B-A-H SA 5y XR-MRI No AS SH 1y (11) De Filippo et al. 4 19–24 y 3 F-1 M Nr IP (1)-Nr (3) Nr P-S-E Nr 6y XR-MRGd No AB-Nr C (4) Nr (52) Winzenberg et al. 1 34 y F R IN Yes P-Li-GW-L Nr 20 y XR-MRIN No AS Cp 18 m (47) Coulier (13) 1 19 y F Nr PC Yes P Nr 3y XR-CTArt- No Ob Nr Nr CTA-MRI Okahashi et al. 1 24 y F R PFM No P-S-T-A NR 20 y XR-MRI No AB-OS Cp 2y (35) Ramseier et al. 4 9-5-7-10 2 F-2 M 3 L-1 R SPM-SPL- Yes (1) PW-LL-S-PTM KT (2) 3.9 y XRO-XRP No OS SH (3)-C 2.7 y (1 R) (4 Knee Synovial Haemangioma Literature Review (10) y IPM-IP (1)-MRI SP) December 2021 | Volume 8 | Article 792380 Yilmaz et al. (49) 1 25 y M R SP-Q No P-S-E-A Yes 10 y XR-V-MRI No AB-Ob VVM 1y Akgün et al. (6) 4 19-22- 2 F-2 M 4R 2 D-2 SP Yes P-S-B-E-H Yes (2) 4.5 y XRO (1)-MRI Yes (1) AB-Ob (2) SH (3)-C 2.6 y (2 SP) 13-35 OS-AS y Bonaga et al. (9) 4 4-18-20- 1 F-3 M 3 L-1 R D (4) Nr P-SL-LRM-H SA Nr XRO (1)-V-Ar- No AB-OS AV (4) 10 y (1 SP) 49 (2)-KT (2) MRGd y (Continued) Frontiers in Surgery | www.frontiersin.org Hernández-Hermoso et al. TABLE 2 | Continued N◦ Age Gender Side Location Trau Symptoms/Signs CH DeD Image BA Treat Histology F-up Examinations Del Notaro and 1 30 y F L PC Yes PA-Li-E-LRM-H Nr 1y XR-MRI No ASF-OS C Nr Hug (17) Neel et al. (16) 1 10 y M L PC Yes P-L-E No 2m XR-MRGd Yes OS SH Nr Suh et al. (41) 1 59 y M L SPL Nr P-S-PTM-LRM Nr 40 y XR-MRI No AB-OS Cp 6m Abe et al. (5) 3 5-12-16 2 F-1 M 2 R-1 L SPL Nr P-S-A-LRM-H Nr 8.3 y XRP (2)-XRO No AB-OS C (2)-Cp 7y y VL-SP-PF Q (2)-MRI Gn Lassoued et al. 1 25 y M R D No P-H No 20 y XRO-XRB- Yes AN-OS C 4y (31) MRI Silit et al. (39) 1 39 y M R MC Nr P-S-H No 10 m XR-MRGd Yes ASI CCp 1y Aynaci et al. (20) 1 15 y F L IPL No P-T-A Nr 6m XR-MRI No AS VVM 1y Total 96 Cases Cases Cases Cases Cases Manuscript Cases Cases Manuscript Cases Cases Cases Cases X ± SD F 47 R 38 SP-PF 46 Yes 13 P 45 (8.2%) Yes 19 X ± SD XR 47 Yes 13 OS 64 C 27 (28.1%) X±SD 21.7 ± (49%) (39.6%) (47.9%) (13.5%) PA 17 (17.6%) (19.8%) 6.8 ± (86.3%) (13.5%) (66.7%) Cp 2.7+-2.2y 14.7 y M L 23 IP 14 (14.6%) No 38 CL 1 (2%) No 28 8.6 y MRI 50 No 82 AS 15 13 (13.5%) Nr 0–10 y 49 (51%) (24.0%) IN 4 (4.2%) (39.6%) Cr 1 (2%) (29.2%) (98.0%) (85.4%) (15.6%) CCp 5 (5.2%) (36%) 34.4% Nr 35 MC 7 (7.3%) Nr RW 1 (2%) Nr MRGd 15 Nr 1 TKA 1 AV 7 (7.3%) R: 3.1% 11–20 y (36.5%) PC 9 (9.4%) 45 (46.9%) L 3 (5.9%) 49 (51.0%) (29.4%) (1.0%) (1.0%) VVM SP: 11.4% 30.2% D 13 (13.5%) Li 7 (13.7%) Ar 4 (7.8%) Ob 8 17(17.7%) 21–30 y Nr 3 (3.1%) Lu 1 (2%) V 2 (3.9%) (8.3%) SH 6 16.7% LL 1 (2%) US 5 (9.8%) Nr 8 19 (19.8%) 31–40 y SL 1 (2%) ED 4 (7.8%) (8.3%) Nr 8 (8.3%) 11.5% B 3 (5.9%) CT 3 (5.9%) 41–50 y GW 1 (2%) CTArt 1 4.2% A 11 (21.6%) (2.0%) >51 S 34 (66.7%) CTA 1 (2%) y 3.1% T 10 (19.6%) MDCTA 1 W 1 (2%) (2%) E 9 (17.6%) Sc 3 (5.9%) PTM 7 (13.7%) RBCSc 1 LRM 17 (33.3%) (2%) H 24 (47.1%) SPECT/CT Knee Synovial Haemangioma Literature Review 1 (2%) December 2021 | Volume 8 | Article 792380 Trau, previous trauma; CH, Cutaneous haemangioma; DeD, Delay in diagnosis; BA, Bone affected; Treat, Type of treatment; F-up, Follow-up; m, Months; y, Years; w, Weeks; R, Recurrence; SP, Symptoms persisted; F, Female; M, Male; R, Right; L, Left; PFL, Patello-femoral lateral; PFM, Patello-femoral medial; IP, Infrapatellar (Hoffa fat pad); IPL, Infrapatellar Lateral; SP, Suprapatellar; SPL, Suprapatellar Lateral; MC, Medial Compartment; IN, Intercondylar Notch; PC, Posterior compartment; D, Diffuse; VMO, Vastus Medialis Obliquus; VL, Vastus Lateralis; Q, Quadriceps; Gn, Gastrocnemius; P, Pain; PA, Pain with Activity; Cl Claudication; Cr, Crepitus; RW, Patient Refused Weightbearing; L, Locking; Li, Limping; Lu, Lump; LL, Long Leg; SL, Short Leg; B, Buckling; GW, Giving Way; S, Swollen; T, Tenderness; W, Warmth; E, Effusion; A, Atrophy; PTM, Palpable tumor mass; PTMF, Palpable Tumor Mass more pronounced in Flexion; LRM, Limited Range of motion; H, Haemarthrosis; SA, Systemic Angiomatosis; KT, Klippel-Trénaunay; XR, radiography; XRS, XR Soft Tissue Mass; XRO, XR Osteoarthritis; XRB, XR Bone Involvement; XRP, XR Phleboliths; Ar, Arteriography; V, Venography; US, Ultrasound; ED, Echo Doppler; CT, Computed Tomography; CTArt, CT Arthrography; CTA, CT Angiography; MDCTA, Multi Detector Computed Tomography Angiography; Sc, Scintigraphy; RBCSc, Red blood cell scintigraphy; SPECT/CT, single-positron emission computed tomography-computed tomography; MRI, Magnetic resonance image; MRIN; MRI negative; MRA, MRI angiography; MRGd, MRI gadolinium enhancement; OS, Open surgery; C, Curettage; BG, Bone Graft; AN, Arthroscopy Negative; AB, Arthroscopic biopsy; AS, Arthroscopic Surgery; ASF, AS Failed. ASI, AS Incomplete; TKA, Total Knee Arthroplasty; Cor, Corticosteroid; Bblo, Beta blockers; C, Cavernous; Cp, Capillary; AV, Arteriovenous; CCp, Cavernous and capillary; SH, Synovial haemangioma; VVM, Venous Vascular Malformation; IAVN, Intraarticular Vascular Malformation; Nr, not reported; X ± SD: media ± standard deviation. Hernández-Hermoso et al. Knee Synovial Haemangioma Literature Review FIGURE 2 | Case 1: histology. Histological findings showing proliferation of arterial and venous vessels in a fibrous stromal tissue type (haematoxylin and eosin stain, 40×). The histological diagnosis was arteriovenous synovial haemangioma. At the 6-week follow-up, the patient had a stiff knee with a range of motion of 0–30◦ . At 10 weeks, we performed arthroscopic arthrolysis and obtained new biopsy samples. Histological examination showed no evidence of a tumor. At the 5-year follow-up, the patient had a pain-free knee and a normal range of motion. A repeat MRI showed no evidence of recurrence. Case 3 A 31-year-old man presented with an 8-year history of diffuse right knee pain, which persisted at rest and was aggravated with activity. The pain limited his participation in sports but not his activities of daily living. On physical examination, the knee was well-aligned but had mild swelling and tenderness adjacent to the medial patellar facet. There was no muscle atrophy or warmth. The range of motion and stability were normal, as were the meniscal and neurovascular examinations. Plain radiographs were normal. On aspiration, the joint fluid was clear, and the cell count was normal with no microcrystals. We suspected anterior knee pain syndrome due to patella- femoral osteoarthritis. MR revealed an intra-articular synovial mass located superior and medial to the patella that had FIGURE 1 | Case 1: suprapatellar SH MRI. Conventional sagittal T1 (A) and eroded into the superior patellar cortex. Heterogeneous lower T2 (B) MRI showing synovial haemangioma in the suprapatellar and signal intensity on T1-weighted imaging and isointensity on supratrochlear synovial lining extending medially and eroding the T2-weighted imaging suggested LPVNS (Figures 5A,B). supratrochlear cortical bone, with features of hyperintensity on T2-weighted imaging and hypo-/isointensity to muscles on T1. *Location of the Synovial Open excisional biopsy and partial synovectomy were Haemangioma tumor in the knee. performed. Two small intra-osseous cystic lesions in the medial and superior poles of the patella were curetted until healthy trabecular bone was observed. Histological exam showed synovial proliferation with subjacent capillaries, consistent with patellar bone lesions back to normal trabecular bone. Histological capillary-type SH (Figure 6). examination revealed blood vessels with multiple arterial and The patient had an uneventful postoperative recovery, with venous vessels in the stroma, confirming the diagnosis of restoration of full range of motion and good muscle strength. arteriovenous SH. He resumed amateur sports. Four years after surgery, he had Frontiers in Surgery | www.frontiersin.org 7 December 2021 | Volume 8 | Article 792380 Hernández-Hermoso et al. Knee Synovial Haemangioma Literature Review FIGURE 4 | Case 2: suprapatellar SH MRI. Isointense T1 (A) and hyperintense T2 (B) sagittal MR images showing a synovial tumor just over the proximal pole of the patella with intra-osseous invasion of the upper pole of the patella. *Location of the Synovial Haemangioma tumor in the knee. onset. He had no history of trauma. Pain occurred when he performed maximum knee flexion or intense cycling but not during activities of daily life. On clinical examination, both lower limbs were aligned in varus. There was no muscular atrophy, swelling, tenderness or joint effusion. The range of motion of the knee was normal, but the patient reported discomfort at maximum flexion. The knee was stable, and the meniscal and neurovascular examinations FIGURE 3 | Case 1: suprapatellar MRI tumor recurrence. MRI showing were normal. recurrence of the lesion. A heterogeneous hyperintense lesion is observed on Plain radiographs were normal. MRI showed a well-defined sagittal T2-weighted imaging (B); it contains fibrous septa and is intra-articular synovial mass in the posterior compartment of hypo-/isointense to muscles on the T1 sequence (A), with diffuse involvement the knee, behind the PCL. On T1-weighted sequences, the of the sub-quadriceps synovial sac and tendon. *Location of the Synovial mass was isointense to the surrounding muscle signal with Haemangioma tumor in the knee. peripheral heterogeneous areas, and on T2-weighted imaging, it was hyperintense (Figures 7A,B). A benign synovial tumor was a normal pain-free knee, and there was no evidence of tumor suspected, with the possibility of LPVNS or SH. recurrence on MR. The patient opted for observation and regular follow-up. Four years later, his pain had increased and was more frequently Case 4 limiting his activities of daily living. Repeat MRI showed features A 40-year-old male presented with a 10-year history of similar to what had been observed previously, but the patient progressive anterior and posterior right knee pain with insidious elected to proceed with surgery. On arthroscopy, we observed a 1 Frontiers in Surgery | www.frontiersin.org 8 December 2021 | Volume 8 | Article 792380 Hernández-Hermoso et al. Knee Synovial Haemangioma Literature Review FIGURE 6 | Case 3: histology. Histological examination showing synovial proliferation and capillaries below, suggesting a capillary-type synovial haemangioma (haematoxylin and eosin stain, 40×). bipolar radiofrequency probe (Dyonics RF Ablation 90◦ probe, Smith & Nephew, US). Histological exam confirmed arterial and venous proliferation in the synovial stroma, consistent with arteriovenous SH. Three months after surgery, the patient progressively resumed recreational sports. One year after surgery, the patient was asymptomatic, even when cycling. There was no evidence of recurrence on repeat MRI. Literature Review We identified 75 abstracts from articles located through the literature search. Eight articles on KSH case descriptions were not reviewed because six were in other languages (three in Chinese, one in Serbian, one in Portuguese and one in Italian), one full- text article from an Indian journal was not available and one was an open radiology case. Four articles described SH in other joints, and 13 did not focus on KSH clinical cases or case series. Ultimately, we reviewed 50 full texts that focused on case or case series descriptions, including a total of 92 clinical cases. A flow chart of the literature search is shown in Figure 9. The literature review showed that KSH appears more frequently in children and teenagers (64.6% of cases). The average FIGURE 5 | Case 3: suprapatellar SH MRI. MR sagittal images showing an age of presentation was 21.7 ± 14.7 years, and the prevalence intra-articular synovial mass located superior and medial to the patella that was not related to gender (51% males). The right knee was more eroded the superior patellar cortical bone; the mass was heterogeneously frequently affected (39.6%). hypointense on T1-weighted imaging (A) and isointense on T2-weighted The tumor mass could appear anywhere in the joint, but an imaging (B). *Location of the Synovial Haemangioma tumor in the knee. anterior knee location in the suprapatellar and patella-femoral (47.9%) joint space was the most frequent, followed by the infrapatellar (14.6%), posterior (9.4%) and medial compartment × 0.5 × 0.5 cm pale bluish vascular lesion in the synovial lining (7.3%) and the intercondylar notch (4.2%). Usually, there was no of the posterior capsule just behind the PCL (Figures 8A,B). previous trauma (39.6%), or it was not reported (46.9%). An excisional biopsy was performed with a Williams-type Pain, swelling and haemarthrosis were the most frequently discectomy forceps positioned in the posteromedial portal and described clinical presentation form (88.2, 66.7, and 47.1%, the arthroscope in the anterolateral portal. We performed partial respectively), although the symptoms and signs associated with resection of the surrounding normal synovial lining with a KSH were multiple and non-specific (see Table 2). Cutaneous Frontiers in Surgery | www.frontiersin.org 9 December 2021 | Volume 8 | Article 792380 Hernández-Hermoso et al. Knee Synovial Haemangioma Literature Review FIGURE 8 | Case 4 posterior compartment SH arthroscopic view and puncture. (A). Arthroscopic view of the synovial haemangioma via the anterolateral portal, showing a pale bluish vascular lesion in the synovium lining the posterior capsule, just behind the PCL (1 × 0.5 × 0.5 cm). (B) Puncture of the synovial tumor produced acute bleeding that differentiated it from other tumors, such as LPVNS. (MRGd). Ultrasound (US), echo Doppler (ED), arteriography, computed tomography (CT) or scintigraphy (Sc) were used less frequently (9.8–5.9%) In rare cases (3.9–2%), venography, CT FIGURE 7 | Case 4: posterior compartment SH MRI. Sagittal MRI sequences showing a well-defined intra-articular synovial mass in the posterior arthrography (CTArt), CT angiography (CTA), multi-detector compartment of the knee, behind the PCL. On T1-weighted (A) sequences, computed tomography angiography (MDCTA), red blood cell the mass was isointense to the surrounding muscle with peripheral scintigraphy (RBISc) or single-positron emission computed heterogeneous areas; the mass was hyperintense on T2-weighted images (B). tomography (SPECT) were reported. Knee bone erosion was *Location of the Synovial Haemangioma tumor in the knee. occasionally observed (13.5%) on image exams. Synovectomy was the treatment of choice and was more frequently performed by open surgery (66.7%) than by haemangioma was scarce (19.8%) and usually not reported arthroscopy (15.6%). Treatment options such as observation, (51%). The diagnosis was normally made late and the average pharmacological treatment (corticosteroids and beta blockers), delay was 6.8 ± 8.6 years. and TKA were rarely recommended (7.3, 1, and 1%, respectively). The most commonly reported image tests were plain XR Biopsy prior to treatment was infrequent (9.4% of cases). (86.3%) and MRI (98%) alone or enhanced with gadolinium The most frequent histologic type was the cavernous type Frontiers in Surgery | www.frontiersin.org 10 December 2021 | Volume 8 | Article 792380 Hernández-Hermoso et al. Knee Synovial Haemangioma Literature Review FIGURE 9 | Flow chart of information through the different phases of the systematic review. (28.1%), followed by the venous vascular malformation, capillary, muscle involvement. Recurrence after surgery is low (3.1%) but arteriovenous and cavernous-capillary types. persistence of symptoms is more frequent (11.4%), especially in The average follow-up time was 2.7 ± 2.2 years, but the follow- diffuse forms. up time was unreported in 36% of cases. Reported recurrence was In the last 20 years, only nine cases (9.4%), including ours, low (3.1%), as it was the persistence of symptoms (11.4%). had localized lesions in the posterior compartment of the knee. One was an intermediate tumor (5) that extended into the quadriceps and gastrocnemius. Three were juxta-articular, one DISCUSSION with an intramuscular component in the popliteal fossa (1) and two behind the posterior cruciate ligament (PCL) (12). The other Synovial haemangioma have been described in various joints, five were intra-articular, of which three previously reported cases but the knee is the most common (4). Up to 2015, one paper plus our case 4 were behind the PCL (13–16) and one was just reported more than 275 cases of KSH (1). Since then, another 24 cranial to the PCL (17). cases have been reported (PubMed only), with the present four Our other three cases were local sessile intra-articular SH cases bringing the total to 303. There are a number of small case located near the superior pole of the patella, by far the most series (4–10, 12, 51–57, 61), the largest describing 14 cases (8). frequent location in the anterior compartment of the knee (5– Most reports describe single clinical cases (1–3, 11, 13–50), which 8, 19, 21, 24, 27–29, 38, 40, 42, 44, 50, 53–57), followed by highlights the rarity of this type of tumor. the infrapatellar fat pad (11, 18, 23, 30, 45, 59), the posterior This is the first study that performs a detailed revision compartment, the medial compartment (2–4, 25, 35, 39, 42, 54, of a large number of KSH (96 cases) and describes its more 61) and the intercondylar notch (22, 43, 46, 47, 54). The three frequent location and clinical presentation forms. The major reported patients with KSH near the superior pole of the patella finding of this study is that plain radiographs and MRI image had the rare phenomenon of bone erosion, which was localized studies appear to be enough for the differential diagnosis, in the patella in two cases, a previously undescribed location for that will be confirmed after histology exam. Being a tumor KSH bone erosion, and in the supratrochlear cortical bone in mass of benign characteristics on image studies rarely a one case. It is most frequent in tumors located in the medial biopsy is indicated previous to treatment, an excisional biopsy compartment (2, 3, 6, 39) or diffusely distributed (31, 34). and regional synovectomy can be performed for diagnosis KSH usually occurs in children and teenagers (4, 8, 12), and treatment purposes before diagnostic confirmation. although the average age is 21.7 ± 14.7 years. For that reason, Although open surgery has been the treatment of choice, the diagnosis is not typically suspected in middle-aged or older nowadays arthroscopy seems to offer advantages in the adults, as occurred in our patients. The average delay in diagnosis treatment of intraarticular KSH without bone, tendon or was 6.8 ± 8.6 years, larger than the average noted in one report Frontiers in Surgery | www.frontiersin.org 11 December 2021 | Volume 8 | Article 792380 Hernández-Hermoso et al. Knee Synovial Haemangioma Literature Review (6), although two reported patients had a delay in diagnosis of recurrence. Intravenous administration of gadolinium for MRGd more than 40 years (3, 41). produces inhomogeneous enhancement of the synovial tumor All four of our patients were male, but we found no differences image (9, 14, 27, 34, 38, 46, 59) and permits differentiation in sex distribution, and the exclusively male composition of our between cystic synovial hyperplasia (52) and liquid or intra- sample is probably merely a matter of sample size. The right articular haemangioma (2, 7, 38, 57). MRA and MDCTA have knee is more frequently affected than the left knee. Previous replaced arteriography, and while both are invasive and non- trauma appears to be rare and is often not reported. Symptoms specific methods (20, 50), they may be justified for planning and signs associated with SH of the knee are non-specific. Low- surgery in diffuse or extended cases (3, 32, 46) and in cases where intensity and long-duration pain is the most frequent symptom complete excision is not possible and where embolization might (4), but it rarely limits activities of daily living except in phases be considered (7, 57). of exacerbation (5, 12, 59). It is usually aggravated with activity Ultrasound may (19, 23, 24, 46) or may not (8) help and relieved by rest (2, 3, 5, 10, 42, 49). Pain is typically in the distinguish solid vs. liquid masses or those with heterogeneous anterior aspect of the knee but can be posterior (14) or diffuse. content. Echo Doppler may suggest a vascular lesion (23, 38, 46, Swelling, tenderness, effusion (5, 9–11, 17, 21, 23, 26, 30, 33, 34, 50, 60), but not always (28). CT is useful in determining the 44, 49, 50, 55) and haemarthrosis (5, 9, 11, 12, 18, 22, 30, 31, 37, presence and extent of bone involvement (2, 7, 33, 55). Tc99 39, 41, 46, 50, 54, 55, 57, 59) are frequent and can be recurrent. scintigraphy may show increased uptake in cases where bone Occasionally, a palpable soft tissue mass (3, 4, 10, 44, 46, 55, 61) is affected (2, 45), RBCSc reveals increased blood pool activity can be noted. Anterior masses are more evident in complete (30), and SPECT/CT shows a radioactive mass (30); however, the flexion of the knee (3, 21, 44) and can be compressible, refilling information provided is non-specific, so a scan would be justified when pressure is released (21). Limitation of motion (3, 5, 8– only in a patient where other imaging examinations are normal. 10, 12, 17, 25, 28, 33, 37, 38, 46, 61) and mild muscular atrophy Diagnostic arthroscopy may be useful in localizing a synovial (5, 11, 33, 34, 36, 49, 55) can be present. Joint locking is infrequent tumor and ruling out unrelated intra-articular lesions (6, 33, 45, but has been described when synovial haemangioma is located 47). Arthroscopy allows lesion localization; biopsies for frozen in the intercondylar notch (22, 47) or in the suprapatellar pouch section (16, 55), permanent histology or microbiological study; (6). Although up to 40% of patients with synovial haemangioma and, in most patients, definitive treatment. We indicate it in the may have cutaneous haemangioma (4), we appreciate that it is event of persistent knee pain and normal imaging examinations. less frequent, probably because patients are often not carefully However, as in case 2, it is not always possible to visualize examined for such haemangiomas, or, if so, they are not reported. the tumor (17, 20, 28, 31, 57, 59, 60) or show the complete Cutaneous haemangioma has been described in patients with extent of the lesion (8), either because it is not localized (59) diffuse extra-articular KSH (6, 29, 31, 49) or with systemic or misdiagnosed (28) or because the lesion is subjacent to the angiodysplasia (Klippel-Trénaunay) (22, 23). synovial lining and cannot be seen (20). No clinical test or imaging procedures provide a definitive Histological examination is essential to establish a definitive diagnosis, nor is there a clear algorithm for diagnosis. Plain diagnosis, although it was not reported in 8.3% of reviewed radiographs are typically normal (4, 8, 11, 13, 16, 17, 21, 27, cases. Haemangiomata are tumors derived from endothelial cells, 28, 35, 38, 39, 41, 44, 47, 49, 50, 53, 55–57), and only a few and four types have been described (51). Although three of cases show non-specific abnormalities (2, 4–10, 33, 36, 45, 53) our cases were of the arteriovenous type, we showed that the such as periosteal reaction, osteolysis, osteopenia, intra-articular most common was the cavernous type, followed by the venous phleboliths, trochlear dysplasia or osteoarthritis. Even if there is vascular malformation, capillary, arteriovenous and cavernous- a small region of bone erosion, as in our cases, plain radiographs capillary types. In 19.8% of the cases, the histological type was not can appear normal. Formerly, it was the first imaging test ordered described. It is considered a vascular venous malformation more because it is fast and inexpensive and permits a general evaluation than a tumor, often associated with a lymphatic hamartomatous of the joint, although it is not useful in the diagnosis of KSH. component (8). MRI appears to be the examination of choice (1, 2, 5– We advise treating these lesions because they can cause joint 11, 16–18, 21–24, 26, 27, 33, 35–40, 42, 43, 46, 48, 50, 53– destruction either by direct invasion of the surrounding tissues 57). It is non-invasive and non-irradiating and usually allows or by repeated haemarthrosis (5, 10, 31). Embolization may be three-dimensional localization, although occasionally, as in our indicated in cases of diffuse lesions, when complete surgical series, a tumor mass may not be identified (3, 47). However, the resection is difficult or impossible, or when the tumor mass is features of low or intermediate intensity compared to muscles nourished by a large blood vessel (7, 36). Non-surgical treatment on T1-weighted sequences and high intensity on T2-weighted and observation have been recommended by some authors in or fat-suppressed sequences are not specific to haemangioma diffuse cases (6, 32, 49). (28, 58). Fatty fibrous septa can be seen within the lesion in As KSH appears as a synovial tumor mass with benign some cases (57). Large venous haemangiomata can cause high characteristics in imaging studies, an excisional biopsy and signal intensity on T1 due to slow blood flow (58). Two reports regional synovectomy can be performed until free resection suggested that only 22% of the cases had a correct suspected margins are obtained for diagnosis and treatment purposes diagnosis before surgery (2, 10). MRI is useful for demonstrating before diagnostic confirmation. Biopsy prior to treatment is extension into the periarticular tissues (7), for detecting bone rarely reported (9.4%) but should be indicated if there is erosion in our cases, for surgical planning, and for following doubt regarding the benignity of the tumor based on imaging Frontiers in Surgery | www.frontiersin.org 12 December 2021 | Volume 8 | Article 792380 Hernández-Hermoso et al. Knee Synovial Haemangioma Literature Review examinations. There is controversy as to whether open or which the papers were published and the large number of cases arthroscopic surgery is better. Most patients have been treated by identified, the included studies are likely representative of the open surgery because it has been argued that it allows a better literature. We are unaware of any other such reviews at this level view of the full extent of the lesion, mainly when it is located of detail. within the Hoffa fat pad, and therefore leads to a lower recurrence It is clinically relevant to know the frequent and unusual rate (4, 8–10, 18, 20, 36, 50, 55). However, recurrence can occur locations of KSH, its multiple clinical presentations, the real value despite complete resection by open surgery (4, 10). Our study of image examinations and the pros and cons of arthroscopic vs. found a 3.1% reported recurrence rate with a 11.4% persistence of open surgery to be able to make informed decisions on the need symptoms rate. We found no large studies reporting recurrence for invasive image examinations, previous biopsy or arthroscopic after open vs. arthroscopic resections of localized or diffuse SH, vs. open surgery in light of the evidence. and the reported follow-up times were short or not reported, In conclusion, KSH is a rare tumor. The superior pole but PVNS recurrence rates were reportedly comparable between of the patella is the most frequent location and only five open and arthroscopic surgery (62). We believe open surgery is intra-articular reported cases (including ours) in the posterior warranted with juxta-articular or intermediate tumors (50), that knee compartment. SH should be considered in the differential is when the tumor extents to the tendons, muscle or bone. diagnosis of long-term knee pain in adults, particularly if there Some authors recommend arthroscopic resection for localized is no history of previous trauma. Plain radiography is usually intra-articular KSH (6, 14, 15, 20–22, 33, 36, 38–40, 42, 43, normal. MRI is the imaging test of choice to localize a synovial 47, 56, 57, 59, 60). Hoffa fat pad SH can be arthroscopically mass, but the images are diagnostically inconclusive. MRA may resected using suprapatellar accessory portals (11, 20, 59). In be useful in diffuse or extended cases. The rare phenomenon the past, posterior knee compartment SH was typically treated of bone erosion, first time described in the patella, have to be by open surgery (1, 5, 12, 16, 17) or non-surgically due to bear in mind. Histological examination is necessary for definitive predicted difficulty in surgical resection (13); only one case, diagnosis. Biopsy prior to treatment should only be indicated if reported twice, was treated by arthroscopic surgery (14, 15). We there is doubt regarding the benignity of the tumor. We believe performed arthroscopic resection of a posterior compartment SH arthroscopic resection should be the surgical technique of choice with resection instruments in the posteromedial and arthroscope for treating localized intra-articular lesions or those in difficult in the anterolateral or anteromedial portal (15, 63). This areas such as the posterior compartment. We recommend open technique avoids possible complications related to an accessory surgery for diffuse tumors and those that are localized in juxta- posterolateral portal but has a limited field of view (64). An articular and intermediate regions with tendon, muscle or bone arthroscopic trans-septal technique using posteromedial and extension. Complete resection of the synovial lesion and the lateral portals may be useful when more working room is needed surrounding affected tissues is important to relieve symptoms in the posterior compartment (14, 15, 64). Arthroscopic surgery and prevent recurrence. is advantageous in that it is a minimally invasive technique allowing good assessment of all the joint compartments; it DATA AVAILABILITY STATEMENT can be used to rule out and treat associated lesions or tumors in the joint; it promotes rapid recovery and superior The raw data supporting the conclusions of this article will be cosmesis; and it reduces the incidence of postoperative stiffness, made available by the authors, without undue reservation. infection, thromboembolic events and joint pain (15, 63). An open posterior approach requires a large incision, preventing AUTHOR CONTRIBUTIONS examination of other parts of the joint, and is associated with relatively poor cosmesis and slow recovery. With the JH-H participated in the design of the study, participated in haemostasis achieved by the use of electrocoagulation during revision of clinical cases and search and revision of bibliography, arthroscopic tumor resection and synovectomy, open surgery has and interpretation of the data and in drafting the manuscript. no advantage in bleeding control (60). JM-B participated in revision of clinical cases and revision We note several limitations of our study. First, some clinical of bibliography. EG-O has participated in search and revision of data were missing in our retrospective clinical review, although bibliography. FC-S has been involved in search and revision key data were available in the records. Second, the literature of bibliography. SL-M has participated in search and revision search was performed only in PubMed and was limited to of bibliography, interpretation of data, and drafting the English, French or Spanish; thus, there is likely additional manuscript. 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(2011) 18:509–11. is cited, in accordance with accepted academic practice. No use, distribution or doi: 10.1016/j.knee.2010.10.004 reproduction is permitted which does not comply with these terms. Frontiers in Surgery | www.frontiersin.org 15 December 2021 | Volume 8 | Article 792380