A rare case report of tenosynovial chondromatosis of the semimembranosus-medial collateral ligament bursa

Abstract

Background: Synovial chondromatosis is an uncommon metaplastic process of the synovial lining that results in the formation of cartilaginous nodules within joints or their associated bursae or tendon sheaths. Radiologic evidence of mineralized bodies within these structures is typically pathognomonic for this condition. Extraarticular chondromatosis is rarer than intraarticular chondromatosis, and the knee is affected less frequently than the smaller joints of the hands and feet. To our knowledge, no reports describing this condition in the semimembranosus-medial collateral ligament (SM-MCL) bursa have been published.

Case presentation: We describe a case of tenosynovial chondromatosis in a 37-year-old woman. The case was atypical for both the location within the SM-MCL bursa and the paucity of radiodense or hypointense changes to support a clinical suspicion of chondroid metaplasia on radiographs and T2-weighted MRI, respectively. Recreational weightlifting and swimming by the patient were impaired by chronic pain, and restricted range of motion of the ipsilateral knee persisted despite extensive skilled physical therapy and injections of both corticosteroids and platelet-rich plasma. Thirteen months after a diagnostic and therapeutic knee arthroscopy, open surgical excision of the SM-MCL bursal body was performed, and knee pain and range of motion improved by the 6-week postoperative reevaluation. Pathologic evaluation of the excised tissue was consistent with tenosynovial chondromatosis.

Conclusions: Synovial chondromatosis should be considered in the differential diagnosis for recalcitrant bursitis, even in the absence of classic imaging findings.

Keywords: Knee; Semimembranosus-medial collateral ligament bursa; Tenosynovial chondromatosis.

Fig. 1

Diagnostic arthroscopic images of the right knee 7 months before presentation. A chondral flap (arrow) was present at the far medial aspect of the medial facet of the patella (A). The intercondylar notch demonstrated hypertrophic synovitis with some tearing of the ligamentum mucosum (B). There was very mild fraying (arrow) at the far posterior root of the lateral meniscus (C)

Fig. 2

Unenhanced 3-T MRI of the right knee. Focal fluid signal (asterisk) surrounded the distal semimembranosus tendon. The ill-defined margin of the bursa was atypical for simple semimembranosus-medial collateral ligament bursitis (A), and there was mild tendinosis of the semimembranosus tendon, which was otherwise intact (B)

Fig. 3

Semimembranosus tendon and bursa visualized with a 12-MHz ultrasonography transducer. Short axis view of the posteromedial knee showing substantial semimembranosus bursitis and hypoechoic swelling surrounding the tendon (arrow) (A) and ultrasound-guided corticosteroid injection of the semimembranosus bursa in long axis view with both proximal and distal extents of the needle indicated (arrows) (B)

Fig. 4

Pathologic appearance of the excised semimembranosus-medial collateral ligament bursal body. The intraoperative ex situ gross appearance of the bursa demonstrated multiple fragments of firm, white, nodular and fatty soft tissue. On cut sections, the fragments were either pale, white, and firm or lobulated and yellow (A). Histologically, the tissue was composed primarily of coalescing nodules of mature hyaline cartilage surrounding foci of mineralization (B: hematoxylin and eosin stain, 40× magnification). Higher magnification showing mature chondrocytes chondrocytes within lacunae (arrowheads) surrounded by cartilaginous matrix (blue-green) (C: Alcian blue stain, 200× magnification). The chondroid matrix multifocally surrounded regions of dystrophic mineralization (brown staining; arrows) (D: Von Kossa stain, 100× magnification). The remaining surface synovium consisted of mildly hypertrophied synoviocytes and lymphoplasmacytic inflammation (asterisks) in concert with reactive neovascularization (arrows) (E: hematoxylin and eosin stain, 200× magnification). Mature fibrillar collagen (blue), often in association with small blood vessels, was observed at the periphery of the cartilaginous nodules (asterisk) (F: Masson’s trichrome stain, 40× magnification)

Fig. 5

Timeline summarizing diagnostic (blue) and therapeutic (red) details relevant to the clinical course of chronic, progressive semimembranosus-medial collateral ligament bursitis and tenosynovial chondromatosis in our patient. AROM: active range of motion; R: right; MRI: magnetic resonance imaging; PMR: physical medicine and rehabilitation; PRP: platelet-rich plasma; US: ultrasound