The Hip - Part Three
The effect on the function of the hip joint of a difference in the length of the legs has been mentioned previously in an article in this series. The longer of the two legs will attempt to keep the head level by flexing slightly at the hip and knee, leading to a lack of movement into extension of the hip as we walk. Rotation of the hip and pelvis is required to achieve a more normal gait pattern if extension is not fully achievable. This may be a small change in joint movement, but on repetition thousands of times per day this can set up difficulties in joint movement and over time a painful joint condition.
The hip can give problems and deteriorate into a severely painful joint very quickly after a traumatic event such as a fall, strain or jar. However, this is less common on average as hip problems usually come on slowly over a long period. A small event can set off a painful process which starts with some muscle spasm and a reduction in the extension range typically used in walking. The hip joint is at its tightest and most pressured when it is put into extension, and when we have a painful joint we avoid this kind of joint position in order to avoid pain.
A typical reaction to a painful hip is the development of a limp, a common finding in hip and knee pain problems. Whilst possible to eradicate a limp, once practiced for a while, is very difficult. A limp changes the mechanical stresses through the hip radically, alters the muscle function to different angles and allows the joint to restrict its ranges of motion. This can encourage the hip capsule to tighten up further and perpetuate the cycle. This is why physiotherapists encourage people with hip problems to perform as normal a gait as possible.
The major weight bearing joints of the knee and hip are mostly affected by osteoarthritic changes, osteoarthritis being the most common degenerative joint condition in the world. Many factors contribute to the incidence and severity of arthritis, with a family history being important to some degree. Osteoarthritis becomes much more prevalent with increasing age and is almost universal in some joints in older people. As the arthritis worsens the joint can gradually lose movement as the capsule tightens, with a slow healing due to the lack of good blood supply.
Gradual destruction of the cartilaginous joint lining continues, with some muscle spasm and increasing limp. At some point some arthritic joints deteriorate quickly, perhaps after a trivial traumatic event, and the exact reason for this is not clear, but increased pain and consequent increased muscle spasm may be responsible. Typically hip pain is felt in the lower buttock, the side of the hip, the groin and the front of the thigh. Some patients go to the doctor thinking that they have a thigh or knee problem and end up being diagnosed with hip arthritis.
Little useful information may come from x-rays of the hip in the early stages of osteoarthritis and the patients disability or pain is not easily connected with x-ray findings overall. A worsening joint will show clear x-ray changes such as narrowing of the joint space caused by loss of thickness of the articular cartilage. Abnormal shaping of the femoral head and the formation of marginal joint bone outgrowths called osteophytes will occur in severe cases. On bearing weight or movement a severely osteoarthritic joint will shudder and grate audibly.
There is a particular order in which the restrictions of joint movement develop in the hip joint. The first movement lost is extension, followed by moving the hip outwards (abduction) and finally of the ability to turn the thigh inwards (internal rotation). On examination by a physiotherapist the hip will present turned outwards, close to the midline as moving it away is difficult and held in slight flexion due to the loss of extension. As the leg cannot be extended in walking and the leg is shorter than the other side each step of gait necessitates a trunk twist and a small toe raise to allow for the abnormalities.