A rare finding of suspected synovial chondromatosis

Human gross anatomy laboratory dissections provide a rich learning environment, sometimes including rare anatomical variation or pathological findings. Here we describe a rare knee joint abnormality, which provided an opportunity to review pathological processes unique to this region and expand the learning experience beyond the standard curriculum. Findings During a routine lower limb dissection of an 88‐year‐old formalin‐fixed Caucasian male donor, first‐year medical students discovered an enlarged semimembranosus bursa in the superomedial corner of the right popliteal fossa. Opening of the bursa revealed nine irregular‐shaped osteochondral bodies bathed in synovial fluid, with an average length of 1.76 cm and an average width of 1.25 cm. The donor exhibited no obvious trauma, however bilateral knee joint dissections revealed advanced osteoarthritis. Glenohumeral and acetabulofemoral joint cavities and their surrounding bursae were explored bilaterally, with the only significant finding being bilateral glenohumeral osteoarthritis. Histological studies supplemented by a review of the literature suggests a diagnosis of secondary synovial chondromatosis. Discussion Synovial chondromatosis outlines a rare, benign process characterized by the metaplasia of synovial tissue into chondrocytes within joint cavities, tendinous sheaths, or bursae. It can be further classified into one of two categories: primary, where the proliferation of hyaline cartilage in synovial membranes is seemingly spontaneous, or secondary, in which osteocartilaginous bodies are generated as a result of trauma or inflammatory joint pathologies. The condition most often affects males, has a monoarticular presentation, with a proclivity for the knee joint, followed by the shoulder and hip. Cases in the ankle, elbow, wrist, and temporomandibular joints have also been described. Although it is classified as benign and non‐metastatic, pain, swelling, and functional deficits have been reported. Treatment most often consists of surgical excavation of loose bodies with open arthrotomy and synovectomy. Conclusion Anomalies discovered through anatomical dissection provide unique opportunities to research pathological processes that may not otherwise be covered in standard anatomical curricula.