Acetabulum: The socket part of the hip joint.

Arthrogram: Anarthrogram is a radiology procedure in which special X-ray medicine is placed into the hip joint. This X-ray exam shows and evaluates the shape of the ball part of hip joint (femoral head). It also assesses whether the femoral head is covered (contained) by the socket part of the hip joint (acetabulum). Most patients tolerate this procedure very well. A nurse will monitor your child for pain management needs. Sedation is available if needed.

Femoral head: The ball part of the hip joint.

Leg length discrepancy: A difference in length between the two legs.In some patients with Perthes disease, the affected leg can be shorter.

Necrosis: Refers to cell death in general; osteonecrosis refers to bone cell death.

Ossification:This is a process of new bone formation.

Range of motion: Movement of a joint in all its directions. For example, hip abduction is to move the leg out, away from the body.

Referred pain: This is pain starting from somewhere else but is perceived to begin at that site. In Perthes disease, some patients complain of knee or thigh pain instead of hip pain.

Resorption: Removal of dead bone by the body.

Tenotomy: Surgically lengthening or releasing a tendon that is tight to improve hip joint motion. In some patients with Perthes disease, hip adductors or muscles that bring the leg in (adduction), can get tight and prebent the leg from being abducted (bring the leg out). If the abduction movement is lost, the hip adductors may need a tenotomy.