Accessory movements are the small gliding and sliding movements which occur inside a joint during normal movement but which cannot be performed in isolation by a person. They are essential to the function of a joint and if lost can interfere with the ability to perform movements or can contribute to painful conditions. In the hip the accessory movements are not obvious with few gliding and sliding movements due to its deep and stable nature. One accessory movement which does occur is upwards and downwards, i.e. compression into the socket and distraction of the femoral head out of the socket.
The cycles of compression and relaxation which occur with weight bearing and gait are essential to the health and nutrition of cartilage. As the cartilage is compressed it gives to some extent even though it is quite dense and once this is released it reverts to normal shape, squeezing the fluid out of it under pressure and then sucking it back in as force is removed. This sets up a pumping action of fluid up from within the cartilage and underlying bone, providing an essential fluid replacement mechanism to keep cartilage healthy.
When the joints experience normal mechanical stresses they respond with the synthesis of new cartilage, with the cyclical stresses with rest periods important to cope with the levels of force involved just in heel strike in gait. Encouraging growth of cartilage may be possible by using the joints in big movements through their ranges but it may reduce cartilage growth if stresses are removed or it is subjected to static loads over time. These static loads when kept up, using a stick to reduce hip forces and having high bodyweight may all contribute.
While resting a joint may reduce the pain at first it may not be the most successful treatment for a painful joint. The normal processes of cartilage regeneration do not occur when insufficient force is applied to the joint and the joint capsule may shrink to some degree, tightening the joint. This tightness may increase the typical joint compression and so the pain. It is important to take into account any pain in a joint but on average it is better to keep arthritic joints mobile rather than still. A good blood circulation to the areas around the hip is kept up by the rhythms of cyclical gait.
The cyclical nature of gait may have other effects such as creating a pumping effect in the blood vessels of the ligamentum teres, a cord like structure which runs from the inside of the socket to the femoral head. This may increase the blood throughput to the head and so provide better nutrition. Continuing to walk places stresses on the hip which the upper femur needs, to keep the bones dense and healthy, with reduction of this from bed rest or using a stick potentially causing loss of bone minerals and overall density. This can also make the bone less flexible and increase the effects of jarring or other stresses on the area.
Typically in western countries people utilise only a small part of the rather large range of movements available to the hip. Walking is a repetitive movement in only a small range and on sitting we don't often go over ninety degrees flexion. As we get older we are less and less inclined to make our hips go to the ends of the ranges they are capable of. Hips seem to benefit particularly from keeping a variety in their movement available and stressing them to their extremes now and again. In eastern societies squatting, even to iron, is common, and our levels of hip arthritis may be higher than theirs.
An increased tightness in the joint capsule can result from a person not taking advantage of their full joint ranges over a time period, elevating the tendency for the head to be compressed into the socket. If there is a discrepancy in leg length this can primarily affect hip extension as the hip and knee are maintained in slight flexion to keep the eyes and head level. This fixed flexion deformity of the hip limits extension excursion of the joint in walking and changes the pattern of gait.
Author Resource:
Jonathan Blood Smyth is the Superintendent of Physiotherapists at an NHS hospital in the South-West of the UK. He writes articles about back pain, neck pain, and injury management. If you are looking for physiotherapists in Bolton visit his website.
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