The low back, sacroiliac joint, and hip joints can all cause pain in a similar anatomic distribution, and each must be considered in the evaluation of a patient with complaints of pain in the region of the lower back, buttock, groin, or knee. Pain from the hip joint is poorly localized and may be felt in the groin, inner thigh, trochanteric area, buttock, anterior thigh, and/or knee.
Patients with true hip joint disease will classically complain of pain in the groin region, although this varies depending on the type of hip pathology. Pain typically radiates down toward the anterior aspect of the knee. Individuals who are experiencing pain on the lateral aspect of the hip, in the region of the greater trochanter, or pain in the lower back or in the buttock area may also complain of hip pain. To determine what the patient’s complaint of “hip pain” really means, it is essential to ask the patient to describe exactly where the pain is primarily located and where it radiates.
The hip joint is a ball-and-socket, weight-bearing articulation that combines a wide range of motion (ROM) with considerable stability. The stability of the joint depends on the deep insertion of the femoral head into the acetabular socket, the strong capsule and ligaments, the powerful muscles surrounding the joints, and the circular fibrocartilaginous acetabular labrum.
On anteroposterior radiographs of the hip, the normal femoral neck–shaft angle in an adult is 120° to 135°. In coxa vara the angle is less than 120°; in coxa valga, the angle is greater than 135°.
Common Painful Disorders of the Hip Region:
- Osteoarthritis and Inflammatory Hip Arthritis
Hip arthritis typically causes pain in the groin or low buttock area, with possible radiation into the knee. The pain in osteoarthritis is generally worse with activity and is relieved by rest. In inflammatory arthritis, the patient may experience stiffness with inactivity and some improvement of this symptom with movement of the hip joint.
- Trochanteric Bursitis
This condition is extremely common. The greater trochanteric bursa may become inflamed due to direct trauma or overuse with strenuous physical activity, such as running or jumping.
- Snapping Hip (Coxa Saltans)
Young patients may present with complaints of snapping or clicking about the hip. Intraarticular causes: loose bodies (synovial chondromatosis, fracture fragments, broken-off osteophytes), labrum tears, and, rarely, a true subluxing hip joint, especially after total hip replacement surgery. Extraarticular causes are far more common: sliding of the iliotibial band or fibers of the gluteus maximus muscle over the greater trochanter and, less commonly, snapping of the iliopsoas tendon over the femoral head. Generalized ligamentous laxity is a common finding in these individuals.
- Periarticular Fracture
A displaced hip fracture through the subcapital or intertrochanteric region is a dramatic event that results in sudden severe pain and inability to bear weight or to move the affected hip. Most acetabular or pelvic fractures are the result of high-energy trauma with an equally dramatic presentation that allows ready diagnosis of the problem.
- Sacroiliac Joint Pain
Inflammation of the SI joint (sacroiliitis) can be the source of buttock and upper thigh pain. This is seen classically as ankylosing spondylitis and the other seronegative spondyloarthropathies.
- Osteitis Pubis
Pain in the region of the anterior pelvis due to inflammation and erosive lesions of the symphysis pubis, or osteitis pubis, is an uncommon disorder of diverse causes that include spondyloarthropathies, trauma, infection, distance running, and multiple deliveries.