To reveal the causes of the intra-articular type snapping hip and their frequency.
Case series.
We studied 2 hip joints of 2 male patients and 30 hip joints of 28 female patients with snapping hip syndrome, in which the accompanying pain was transiently relieved by intra-articular injection of local anesthetic. The mean age at diagnosis was 26 years. Plain radiography, hip arthrography, magnetic resonance imaging (MRI), and arthroscopy were performed in these patients and the findings were compared.
Plain radiography findings showed no abnormality in 11 joints, hip osteoarthritis in 19 joints, and femoral head deformation caused by Perthes disease and synovial osteochondromatosis in 1 joint each. Excluding the case of synovial osteochondromatosis, 31 joints were examined by MRI, which failed to identify the cause of snapping hip in all cases. Hip arthrography revealed an intra-articular loose body in 2 joints with osteoarthritis. Arthroscopy revealed acetabular labral tears in all 11 joints with no abnormalities and 15 of 19 joints with osteoarthritis on plain radiography films, and incompatibility between acetabular labrum and deformed femoral head in 2 joints with osteoarthritis. In the case of femoral head deformation after Perthes disease, arthroscopy revealed detachment of the femoral head cartilage as a result of impingement of the acetabulum on the femoral head. Arthroscopic surgeries were conducted: partial limbectomy for acetabular labral tears, surgical removal of loose bodies, partial femoral head excision for incompatibility between acetabular labrum and deformed femoral head, and shaving or articular cartilage detachment. The surgeries resolved the snapping in all cases.
Level IV, case series.
Acetabular labral tear was the cause of 80% of cases of intra-articular type snapping hip. Incompatibility between the acetabular labrum and a deformed femoral head was found to be a cause of intra-articular type snapping hip.