Small movements which allow a glide and a slide inside a joint are essential for the normal use of the joint but cannot be done in isolation, occurring with other movements. These are called accessory movements and their presence is vital to joint function, a reduction in available range or a pain problem resulting if they are lost or reduced. The hip is a deep joint with significant stability so the accessory movements are rather subtle, with the main one being compression and distraction, the pushing in to and pulling out of the ball from the socket.
The health and well-being of the articular cartilage are related to the repeated cycles of compression and relaxation applied to the joint such as with weight bearing and walking. The cartilage is pressed downwards to a degree when pressure is applied and this indentation returns to normal once the pressure is relieved. This engages a fluid pumping system where it is squashed out of the cartilage under compression and pulled back in on relief of the pressure. This pumping of fluid from the deeper cartilage and underlying bone keeps the surface 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.
Resting a joint when it is painful is not a clearly positive strategy. Pain may be reduced when resting but the mechanisms which encourage regrowth of cartilage are not stimulated and the joint capsule may stiffen and reduce the available range of movement at the joint. This may increase the compressive forces in the joint and produce more pain. Whilst painful joints do need respect, in general arthritic joints are worse being still and better being kept moving about. The ability to achieve a rhythmical cycle of gait is very beneficial for the movements and the blood supply of the upper femoral structures.
In the inside of the hip, leading from the acetabulum to the femoral head, is the band like ligamentum teres which carries blood vessels that can be stimulated by the typical cycle of gait and allow a fluid pump. The may give an improved blood supply to the femoral head and maintain bone health. The normal forces which walking places on the upper femoral region are vital to keeping the bone composition and density within normal ranges. Resting in bed or using a walking aid can both contribute to a reduction in mineralisation and density in bone, making it less flexible and so less able to counter strains and jars.
Western individuals normally take advantage of only a small proportion of the large ranges of movement which the hip possesses. The repeated nature of walking only occurs in small ranges and we rarely go over 90 degrees flexion when we are sitting. As time goes on we push our hips less and less towards the ends of their movement, allowing loss of motion. Keeping the full ranges of movement available is beneficial to hips as is pushing them as far as they will go from time to time. In the east many people squat, even for ironing, and may have lower incidence of hip arthritis than western populations.
If the ranges of movement are not routinely used the capsule of the joint will tend to tighten to a degree, increasing the forces which compress the head into the socket. A discrepancy in the length of leg can have a subtle effect on the hip range of movement, particularly of extension. When standing the longer leg will tend to shorten itself slightly to compensate for its length and keep the head and eyes at a normal angle. This means it is held forward by a slight flexion of the hip and knee and so some of the range of hip extension is lost as a hip flexion contracture develops.
The health and well-being of the articular cartilage are related to the repeated cycles of compression and relaxation applied to the joint such as with weight bearing and walking. The cartilage is pressed downwards to a degree when pressure is applied and this indentation returns to normal once the pressure is relieved. This engages a fluid pumping system where it is squashed out of the cartilage under compression and pulled back in on relief of the pressure. This pumping of fluid from the deeper cartilage and underlying bone keeps the surface 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.
Resting a joint when it is painful is not a clearly positive strategy. Pain may be reduced when resting but the mechanisms which encourage regrowth of cartilage are not stimulated and the joint capsule may stiffen and reduce the available range of movement at the joint. This may increase the compressive forces in the joint and produce more pain. Whilst painful joints do need respect, in general arthritic joints are worse being still and better being kept moving about. The ability to achieve a rhythmical cycle of gait is very beneficial for the movements and the blood supply of the upper femoral structures.
In the inside of the hip, leading from the acetabulum to the femoral head, is the band like ligamentum teres which carries blood vessels that can be stimulated by the typical cycle of gait and allow a fluid pump. The may give an improved blood supply to the femoral head and maintain bone health. The normal forces which walking places on the upper femoral region are vital to keeping the bone composition and density within normal ranges. Resting in bed or using a walking aid can both contribute to a reduction in mineralisation and density in bone, making it less flexible and so less able to counter strains and jars.
Western individuals normally take advantage of only a small proportion of the large ranges of movement which the hip possesses. The repeated nature of walking only occurs in small ranges and we rarely go over 90 degrees flexion when we are sitting. As time goes on we push our hips less and less towards the ends of their movement, allowing loss of motion. Keeping the full ranges of movement available is beneficial to hips as is pushing them as far as they will go from time to time. In the east many people squat, even for ironing, and may have lower incidence of hip arthritis than western populations.
If the ranges of movement are not routinely used the capsule of the joint will tend to tighten to a degree, increasing the forces which compress the head into the socket. A discrepancy in the length of leg can have a subtle effect on the hip range of movement, particularly of extension. When standing the longer leg will tend to shorten itself slightly to compensate for its length and keep the head and eyes at a normal angle. This means it is held forward by a slight flexion of the hip and knee and so some of the range of hip extension is lost as a hip flexion contracture develops.
About the Author:
Jonathan Blood Smyth, editor of the Physiotherapy Site, writes articles about Physiotherapy, back pain, orthopaedic conditions, neck pain, injury management and physiotherapist in hartlepool. Jonathan is a superintendant physiotherapist at an NHS hospital in the South-West of the UK.
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