The hip joint is a major ball and socket joint optimally designed to provide low friction motion over a wide range with inherent stability. Mechanical Hip dysfunction comprises of hip problems attributable to morphological variations of the femur and the acetabulum that affect hip function. For normal function, the hip joint requires
1. Healthy articular cartilage
2. Stable femoral head in the acetabulum
3. Adequate impingement free range of motion
4. Neuromuscular control.
Primary cartilage and synovial disorders that degrade the cartilage, neuromuscular conditions that effect hip function, primary trauma and bone conditions like infections, tumors, and metabolic bone disease are non-mechanical causes of hip dysfunction and they need disease specific treatment. Morphological sequelae of these diseases can cause mechanical hip dysfunction.
Interaction of morphological features
Minor variations are common and do not usually cause any problems. Some major variations may also not produce problems when compensated by countering morphological factors.
- Lateral dysplasia by coxa vara or flattening of the sourcil angle.
- Coxa profunda by coxa valga and increased head-neck offset.
- Cam morphology and mild scfe by increased anteversion or shallow acetabulum.
- Anterior dysplasia by femoral retroversion.
- Posterior dysplasia by femoral anteversion.
Morphology, Biology, Activity level
Each morphological variation has a specific effect on the hip and the effects of variations can be additive to cause disease early or they can compensate for others and allow good function. As mechanical hip disease is activity related, more active people are more likely to become symptomatic early. In addition to morphology, biology dictates who becomes more symptomatic from the same activity level. So, the prognosis of each variation is unknown in that particular person. The most effective way to correct morphological variations is with surgery. As surgery has cost, risk of complications, and no guaranteed outcome, we offer surgical treatment only to symptomatic and active patients who understand all the risks and benefits. The exception is a painless condition that has poor prognosis without treatment like dysplasia in a growing child that gets worse without causing pain.