Primary Synovial Chondromatosis Displacing Popliteal Neurovascular Structures: A Case Report

The purpose of this case report is to raise awareness among clinicians about primary synovial chondromatosis (PSC), including its pathology, imaging findings, and potential complications. Our patient experienced a slip and fall during icy conditions, prompting radiographs that revealed an incidental left knee lesion. A biopsy confirmed synovial chondromatosis, but the patient did not seek treatment at that time. Months later, he noticed a decrease in his range of motion, along with discomfort and swelling in the left knee. Over one year after the fall, the patient presented to our facility with a newly developing limp. Radiographs and diagnostic ultrasound of the left knee revealed a moderate-sized knee joint effusion and numerous small calcific densities of similar size, located both anterior and posterior to the knee joint. There was also slight internal color Doppler flow within the knee lesion. Follow-up MRI with and without intravenous contrast further showed contrast enhancement and significant mass effect with displacement of the popliteal neurovascular bundle. Due to the complex nature of this lesion, the patient was evaluated by an orthopedic oncologist and treated with a complex limb salvage procedure performed in conjunction with a vascular surgeon. Patients with knee pain and imaging findings suggestive of PSC warrant further investigation due to the potential for progression and adverse outcomes when diagnosis or treatment is delayed.