We propose that anterior hip pain (AHP) is due to excessive anterior hip joint forces. The overall purpose of this dissertation is to investigate the forces at the hip joint which may be excessive, and explore how muscle activation and movement may affect the hip joint forces.

Excessive forces at the hip joint may result in a tear of the acetabular labrum and AHP. Chapter 2 is devoted to a review of the anatomy and function of the labrum, and presents the current concepts on the etiology, clinical characteristics, diagnosis and treatment of labral tears.

In Chapter 3, using a musculoskeletal model, we explore how muscle force contribution affects hip joint forces during 2 exercises. We find that the anterior hip joint force increases with increasing hip extension and with reducing force contribution from the gluteal muscles during hip extension or the iliacus and psoas muscles during hip flexion.

In Chapter 4, we investigate the muscle activation patterns in people with and without AHP when extending the hip in prone. We find that females with and without AHP use a consistent order of muscle activation. Cues to use the gluteal muscles results in increased activation of the gluteus maximus muscle, and decreased and delayed activation of the hamstring muscles.

In Chapter 5, we use both a musculoskeletal model and clinical gait data to study the effects of hip angle and posture on hip joint forces and moments. We find that increasing the hip extension angle during gait results in an increase in the anterior hip joint force. We also find that when walking in a swayback posture, the hip extension angle, hip flexor muscle moment and hip flexion angular impulse were higher than when walking in a natural or a forward flexed posture.

The results of these studies provide evidence to support instructing patients with AHP to increase the muscle force contribution from the gluteal muscles and the iliacus and psoas muscles, and to avoid both hip extension beyond neutral and a swayback posture. These modifications may reduce the excessive anterior hip joint force and thereby reduce the AHP.