Hip impingement is also called femoroacetabular impingement and is an important cause of hip pain in childhood and early adolescence.
It is the result of an abnormal connection between the hemispherical femoral head and the cup-shaped hip socket or acetabulum in which it rotates. This leads to increased surfaces of contact between the two, especially when the hip is flexed. This causes injury to the cartilage protecting the rim of the acetabulum and the head of the femur, resulting in pain.
It is almost always seen in athletically active adolescents, especially girls, and the sport or activity is associated with the symptoms. It may occur at more advanced ages too.
Hip impingement may manifest as stiffness of muscles in the thigh, hip or even the groin. There is groin pain after hip flexion, especially after the individual has been running or sitting down for a long period. The hip is painful to flexion beyond 90 degrees. Rest pain may also occur in the groin, hip or lower back.
Its clinical features include:
Pain over the anterior aspect of the hip, which becomes worse with flexion
Reduced internal rotation of the hip
Positive impingement sign
It may result in osteoarthritis of the hip with time.
There are different types, including pincer impingement and cam impingement. Both may coexist. Cam impingement refers to the abnormality of the shape of the femoral head, while pincer impingement is related to the excessively deep acetabular cup, which limits movement.
Causes of Hip Impingement
Any change in the shape of the femoral head, femoral neck, or hip socket can lead to the signs and symptoms associated with hip impingement.
This may be due to a congenital structural abnormality or it may be one that is acquired by repetitive movement of the hips exceeding their normal range of motion.
This may be seen, for instance, in sports such as baseball or soccer, dancing and in golfers. In a few cases, the hip impingement may be due to hip injury, Perthe’s disease, or a slipped capital femoral epiphysis (SCFE).
Diagnosis and Treatment
The occurrence of osteoarthritis due to damaged cartilage makes the accurate diagnosis and treatment of this condition necessary. This is based upon a complete history and physical examination, as well as the assessment of the involved hip.
Imaging tests may be ordered, including X-rays, as well as CT or MRI scans to visualize the soft tissues, including labral cartilage, and to better show the joint structure.
Treatment may be conservative, such as limiting the offending activity and physical therapy. Pain management may play a role in recovery. However, surgical intervention is recommended in severe impingement.
Arthroscopic surgery is now offered as the less invasive option. In the case of severe deformity, or if the impingement is part of a more complicated process, open surgical correction is preferred.
Correction involves realignment of the hip joint, or reshaping the bones so that they fit each other properly. Recovery involves rehabilitation that may last for up to four months.