Hips with synovial chondromatosis may display the features of femoroacetabular impingement.

Background: Both synovial chondromatosis and femoroacetabular impingement present with hip pain and may lead to hip osteoarthritis. We present a small case series and describe the clinical presentation, investigation, and treatment of patients with synovial chondromatosis who also had cam-type femoroacetabular impingement involving the same hip.

Methods: Five patients (four men and one woman with a mean age of thirty-four years [range, thirty to thirty-seven years]) with unilateral synovial chondromatosis of the hip presented with clinical and radiographic features of ipsilateral cam-type femoroacetabular impingement. The diagnosis of associated synovial chondromatosis was made on the basis of preoperative imaging in four of the cases. All patients were treated with surgical hip dislocation, excision of the synovial chondromatosis loose bodies, and reshaping of the femoral head-neck junction.

Results: These hips exhibited radiographic features that are not typically seen with idiopathic cam-type femoroacetabular impingement, including femoral head hypertrophy, lateralization of the femoral head, and haziness in the acetabular fossa. None of the hips showed signs of advanced osteoarthritis intraoperatively. The alpha angle improved from a mean of 72.4° preoperatively to 42.6° postoperatively. At a mean of twenty-two months of follow-up, the patients had a mean Harris hip score of 80.6, substantially improved from the preoperative value of 39.

Conclusions: Hips with synovial chondromatosis may present with clinical and radiographic features resembling those of cam-type femoroacetabular impingement. As simultaneous treatment of both conditions is best accomplished with surgical hip dislocation rather than other, less-extensive surgical approaches, we recommend preoperative consideration of synovial chondromatosis in patients presenting with unilateral cam-type femoroacetabular impingement.