Hip arthritis

After the knee, the hip joint is the second most common joint to be affected by osteo-arthritis (OA). The Australian Orthopaedic Association reports that in 2013 over 410,000 hip replacements were performed in Australia, a jump of around 50% over the previous 10 years. Over 88% of these were for severe hip arthritis.

Your hip is a ball and cup type joint, and, after the knee, is the second largest joint in your body. The cup is formed within the outer part of your large pelvic bone and the ball is formed by the upper end of your femur, the longest bone in your body. Both the ball and cup surfaces are coated with thick layers of cartilage, a material ideally suited to absorb compressive forces. Breaking down of this cartilage is a key feature of hip OA.

Prevention and treatment of hip OA is based on an understanding of the primary role of mechanical forces acting on the hip. Your hip joint is surrounded and acted upon by seventeen muscles, many of which are the most powerful muscles in your body. 

Of all these muscles, biomechanical studies have found that three muscles are most important for stabilising your hip - your gluteal, tensor fascia late and hip flexor muscles. At the same time these muscles place the most load on your hip joint.

When these muscles are used in balance with other muscles, the forces acting on the hip joint are evenly spread out over the largest possible surface area of the joint with each bit sharing the load.

But many people have a propensity to unnecessarily overwork these muscles, leading to a relatively small area at the upper front of the hip joint, the area most commonly and severely affected by OA, taking on the brunt of the load. At the same time other parts of the joint tend to become under-loaded, which can also lead to weakening and breaking down of joint tissue. 

Prevention and treatment of hip OA is based on an understanding of the primary role of mechanical forces acting on the hip.