Pistol grip deformity describes the abnormal shape of the hip joint. It was first described by Dr. S. D. Stulberg and associates back in 1975. The head and neck of the femur takes on the shape of a pistol grip when viewed on X-ray.
It’s an early sign of osteoarthritis (OA). The edge of the acetabulum (hip socket) is prominent. The head of the femur butts up against the edge of the acetabulum instead of sliding and gliding down smoothly in the socket. It gives the joint the look of a pistol grip shape when seen on X-rays.
The result is that the wrong part of the head of the femur is in contact with the acetabulum. The abnormal part of the head is forced into the socket during hip flexion and internal rotation.
This creates shear forces against the cartilage. This stress produces abrasion and then tearing or shredding of the cartilage. The rim of cartilage around the socket called the labrum is often involved, too.
All of these changes can lead to degenerative joint disease known as osteoarthritis.