Facts About Hip Disease
What causes hip disease?
The vast majority of hip disease diagnosed in adults is attributable to a poorly understood developmental abnormality that leaves the hip ball slightly disproportionate compared with the hip socket. Osteoarthritis (wear and tear arthritis) is the most common diagnosis and represents a primary problem with the joint cartilage or cushion in the joint. Rheumatoid arthritis, on the other hand, is an inflammatory arthritis with the primary disorder arising in the lining of the joint and the cartilage is secondarily damaged from this process. It is much less common than osteoarthritis.
Injury to the adult hip is also a common cause of eventual hip arthritis. Fracture of the hip socket or dislocation of the ball from the socket is a common injury sustained when the knee of the driver or front seat passenger strikes the dashboard of the car in an accident. Despite our best efforts to repair the broken bones, cartilage is not capable of repairing itself and sometimes arthritis is a late result of this kind of high-energy hip injury. Childhood or adolescent hip disease is also occasionally responsible for problems with the hip in adult life.
A small percentage of adult hip disease can be attributable to what has previously been known as congenital hip dysplasia, which is a condition where the socket does not develop normally in the first year of life and remains shallow relative to the ball. Over time, the ball tends to slip out of the shallow socket and the cartilage surface wears abnormally, often with the involved leg begin short. Hip replacement is often the solution during young adulthood for many of these patients. In addition, the upper end of the femur bone, which makes up the hip joint, contains a growth center and changes rapidly during the teenage growth spurt. Because of this, the adolescent hip is prone to problems peculiar to children aged five to 15 years.
How do I know that the hip is the problem?
As the cartilage wears in the hip joint it creates an irritation or inflammation of the lining of the joint and fluid is produced within the joint in response to the irritation. The hip joint capsule can hold the largest amount of fluid when the hip is flexed and the leg rotated outward. Since most of the nerve endings that sense pain are concentrated in the lining (synovium) of the joint, a person will automatically hold the hip flexed and rotated outward when there is fluid or irritation in the joint in order to relieve the stretch of the capsule and lessen the pain. If the fluid stays in the hip joint for a long period of time, the capsule and ligaments of the hip become stiff and it becomes difficult to straighten the hip out or turn the toes inward. This leads to a crouched or stooped walking posture with the foot turned outward. The stiffness and inability of the hip to rotate also makes it difficult to put on shoes and socks.
Pain caused by hip arthritis or irritation is most commonly felt in the front of the hip in the groin region. Occasionally, pain from hip disease is felt entirely in the thigh or knee and the patient incorrectly suspects a problem in the knee. This pain pattern is called referred pain, because the pain from the hip is referred to another location and it is due to the pattern of the nerves in the lower limb that are responsible for the sensation of pain. Similarly, pain in the buttock or hip is usually referred pain from the low back and not due to hip disease at all. The concept of referred pain is important to recognize as hip disease, especially in children and adolescents, and will often be felt as knee pain. Failure to recognize this as referred pain from the hip can lead to a delay in making the proper diagnosis and therefore a delay in treating the real problem in the hip.
How is hip disease treated?
The hip joint experiences forces that are typically two to three times body weight during usual walking and activities of daily life. Excess body weight and vigorous activity both tend to increase strain on the hip and worsen symptoms of hip irritation. Weight loss and restriction of activity are therefore the initial treatment for hip disease.
Use of a cane can be extremely helpful in reducing pain in the hip by decreasing the load across the hip joint. It is important to hold the cane on the side opposite the painful hip to get the most benefit from it. By using the cane in the hand on the side opposite the painful hip, you are forced to lean away from the bad hip, which decreases the load on the bad hip and lessens the pain. Often with proper use of the cane a painful limp will magically disappear! However, holding the cane on the same side as the bad hip can actually cause more pain by forcing one to lean onto the bad hip, which further aggravates the symptoms.
What about total hip replacement?
Total hip replacement is often the definitive treatment for advanced arthritis of the hip, but is usually the last resort among treatment options because the artificial parts have a limited lifetime and all will eventually wear out. Therefore, hip replacement was initially reserved for the senior citizens with limited activity expectations. Modern technology has provided considerable improvement in total hip replacement over the past two decades so that it is now available to younger patients and is one of the most successful of all operations performed in hospitals today.
Nearly 300,000 hip replacements are performed each year and most now employ techniques to have the bone attach directly to the artificial parts such that loosening is a relatively uncommon reason for failure at this time. Wear of the bearing surfaces is the usual cause for eventual failure and considerable research is being conducted to increase the durability of the presently used parts as well as searching for better materials to help create a lifetime hip. Nonetheless, with current devices a well performed hip replacement in a patient with moderate activity expectations can produce complete relief from the pain of hip disease and be expected to last ten to 20 years in more than 90% of patients.