Presentations

Abstract

Introduction: Synovial chondromatosis (SC), also known as synovial osteochondromatosis or Reichel syndrome, is characterized by the presence of loose cartilaginous bodies within the joint capsule or surrounding tissue. Patients typically endorse monoarticular pain, swelling, and decreased range of motion that may lead to significant disability or physical limitation. Diagnosis relies heavily on radiological evaluation demonstrating loose bodies within the affected joint, bursae, or rarely, the periarticular tendons. In this report, we present a case of intra-articular SC with migration to the quadriceps tendon following repeated episodes of septic arthritis.

Case Information: The patient is a 44 year old male presenting with severe right knee pain, swelling, erythema, and warmth following a minor trauma. Past medical history was notable for SC of the right knee diagnosed approximately twenty years prior following a traumatic fall from a ladder. Plainfilm evaluation of the right knee demonstrated degenerative joint changes with large suprapatellar joint effusion and similar SC compared to previous studies. He was diagnosed with septic arthritis and received antibiotics followed by parapatellar arthrotomy with drainage, extensive synovectomy, and loose body removal as well as subsequent incision and drainage with lavage. He was discharged with a regimen of antibiotics but returned two days later with similar right knee pain, swelling, warmth, erythema, and serosanguinous drainage at the arthrotomy incision site. Magnetic Resonance Imaging (MRI) of the knee demonstrated diffuse high-grade chondral loss, large joint effusion with enhancing thickening, and several intra-articular calcified bodies. An area of capsular dehiscence was present at the previous incision site superior and medial to the patella with a communicating fluid collection present. The patient received three additional arthrotomies of the knee during this admission with copious purulent fluid removed. He was discharged with antibiotics and recommendations for follow-up. Two weeks after discharge, the patient was evaluated in an outside clinic. He continued to report pain and swelling of the right knee. Radiographs of the knee were obtained and again demonstrated extensive degenerative changes, though now with decreased burden of chondromatosis and small calcific foci within the distal quadriceps tendon. Three months later, the patient presented again with severe right knee pain. Knee radiographs demonstrated interval increase in calcifications along the quadriceps mechanism, as well as similar, but less dense loose bodies compared to prior study. Arthrocentesis was performed under fluoroscopy with approximately 5 cc of unremarkable, non-purulent synovial fluid evacuated. Fluid cultures were negative for infectious organisms. The patient was discharged with recommendations for outpatient follow-up with orthopedics.

Discussion/Clinical Findings: SC affects men approximately four times as often as women and has a predilection for large joints such as the knee and hip. While generally considered benign, rare malignant transformation to chondrosarcoma is possible. Primary forms of SC resulting from synovial hyperplasia have been identified, however the majority of cases are secondary to traumatic or degenerative joint changes. Loose fragments of bone and/or cartilage may implant within the synovium, where they may persist or even grow. These loose bodies show greater variation in size compared to the primary form and have a greater tendency to ossify. Considering our patient's history of trauma, the secondary form of SC is likely. Previous radiographic evaluation of the patient's knee demonstrated multiple loose bodies within the joint. Involvement of the quadriceps tendon was not identified until after the patient's repeated episodes of septic arthritis. Current understanding of the pathophysiology of SC suggests that loose bodies may implant within articular or periarticular tissue. Following implantation, these loose bodies may grow due to nourishment from synovial fluid and local vasculature. Due to this patient's repeated episodes of septic arthritis, he received multiple surgeries of the knee with removal of multiple loose bodies. It is possible that during one of these procedures, small fragments broke off from within the joint capsule and deposited within the quadriceps tendon. It is also possible that loose bodies within the knee migrated to the quadriceps tendon via the area of dehiscence identified on MRI. On the patient's most recent admission, knee radiographs demonstrated increased calcification within the quadriceps tendon, suggesting implantation and growth of these loose bodies. While septic arthritis may necessitate surgical washout, surgeons should be aware that such procedures may lead to extra-articular manifestations of SC in patients with previously identified intra-articular loose bodies.

Conclusion: SC is characterized by the presence of loose cartilaginous bodies within or around the joint space. Secondary chondromatosis is due to traumatic or degenerative changes within a joint, leading to free-floating loose bodies that may implant and grow. Patients with SC may be at risk of extra-articular loose body migration following surgical manipulation of the joint. Such patients should receive post-operative radiological evaluation to assess for loose body migration and subsequent growth of implanted bodies. Surgeons should be aware of this potential outcome and should assess for functional complications at subsequent postoperative visits.