The inward rotation of the femur which occurs as the knee comes close to its locking position of extension is not large but very important to knee function, making the knee much more complex than a simple hinge joint. The small internal movements of the knee are limited in the knee joint and the joint cannot afford any losses of these motions without losing some of its function. These small movements are called accessory movements and are small gliding and sliding movements which occur within the joint during functional activity but which cannot be performed in isolation.
The knee's function is to complete two contradictory demands, the ability to move the body quickly into a newly desired position and the ability to keep the body stable and controlled in a chosen position. In the walking cycle the knee has to be a mobile limb for moving into the next position at one moment then at the next function as a reliably stable support. In the gait cycle the knees go through a repeated process of unlocking to move and locking to bear weight, permitting a human to walk significant distances with safety and effectiveness. Loss of the accessory movements may be involved in early knee problems.
The knee has very strong muscles but can also respond to changes such as an uneven surface by finer controlled reactions. The knee is strong enough to achieve full squatting and then stand our body weight up again without pause. The knee's accessory movements are small in distance with side to side more limited than front to back, both however contributing to coping with uneven ground. The inside of the knee joint can gap open more than the outside due to the natural angle of the lower leg to the knee.
As reviewed in the article which precedes this one, the knee functions typically only in one plane, that of forwards and backwards. If a sideways stress is introduced so movement occurs in another plane also, as with knock-knee or bow leg, the patello-femoral joint and the knee compartments can suffers degenerative consequences. The compartments of the knee are the division into the outside half and the inside half of the joint, with each consisting of a tibial and femoral condyle, a meniscus and the ligament. The amount of sideways angulation alters the way that stresses pass across the knee compartments.
If the knee becomes bow-legged to some degree the quadriceps pulling on the patella levers it towards the inside and can cause the patella to be compressed against the inside of the femoral groove, with painful results. The lateral knee compartment then suffers increased forces and is subject to accelerated wear changes on that side. Typically people have a small degree of knock knee, and any exaggeration of this can make kneecap pain more likely on the outside and cause increased wear of the inside compartment.
If the knee is not capable of full extension then the kneecap can develop problems due to the persistent flexion which makes the quadriceps overactive to hold the knee in place, increasing patellar compression. This increased compression can cause a very common condition known as anterior knee pain or patellofemoral pain. To correct the lateral misalignment a small wedge can be placed under the outer edge of the heel to correct alignment of the shin and so influence the stresses which are passing through the knee joint above.
Difficulties with other joints can cause changes in the patella stresses also. The arches of the foot suffer from time and body weight and so reduce as they get weaker, moving towards a flatter foot. On weight bearing the foot turns inward as it flattens, bringing the ankle and the shin towards the centre with it, exaggerating any knock knee amount. Patello-femoral pain can then occur as the kneecap is pressed more forcefully towards the lateral side of the knee. Prescribing individual orthotics for the shoes can be an effective management, both providing an amount of medial heel wedging plus correcting the collapse of the foot arches. - 29957
The knee's function is to complete two contradictory demands, the ability to move the body quickly into a newly desired position and the ability to keep the body stable and controlled in a chosen position. In the walking cycle the knee has to be a mobile limb for moving into the next position at one moment then at the next function as a reliably stable support. In the gait cycle the knees go through a repeated process of unlocking to move and locking to bear weight, permitting a human to walk significant distances with safety and effectiveness. Loss of the accessory movements may be involved in early knee problems.
The knee has very strong muscles but can also respond to changes such as an uneven surface by finer controlled reactions. The knee is strong enough to achieve full squatting and then stand our body weight up again without pause. The knee's accessory movements are small in distance with side to side more limited than front to back, both however contributing to coping with uneven ground. The inside of the knee joint can gap open more than the outside due to the natural angle of the lower leg to the knee.
As reviewed in the article which precedes this one, the knee functions typically only in one plane, that of forwards and backwards. If a sideways stress is introduced so movement occurs in another plane also, as with knock-knee or bow leg, the patello-femoral joint and the knee compartments can suffers degenerative consequences. The compartments of the knee are the division into the outside half and the inside half of the joint, with each consisting of a tibial and femoral condyle, a meniscus and the ligament. The amount of sideways angulation alters the way that stresses pass across the knee compartments.
If the knee becomes bow-legged to some degree the quadriceps pulling on the patella levers it towards the inside and can cause the patella to be compressed against the inside of the femoral groove, with painful results. The lateral knee compartment then suffers increased forces and is subject to accelerated wear changes on that side. Typically people have a small degree of knock knee, and any exaggeration of this can make kneecap pain more likely on the outside and cause increased wear of the inside compartment.
If the knee is not capable of full extension then the kneecap can develop problems due to the persistent flexion which makes the quadriceps overactive to hold the knee in place, increasing patellar compression. This increased compression can cause a very common condition known as anterior knee pain or patellofemoral pain. To correct the lateral misalignment a small wedge can be placed under the outer edge of the heel to correct alignment of the shin and so influence the stresses which are passing through the knee joint above.
Difficulties with other joints can cause changes in the patella stresses also. The arches of the foot suffer from time and body weight and so reduce as they get weaker, moving towards a flatter foot. On weight bearing the foot turns inward as it flattens, bringing the ankle and the shin towards the centre with it, exaggerating any knock knee amount. Patello-femoral pain can then occur as the kneecap is pressed more forcefully towards the lateral side of the knee. Prescribing individual orthotics for the shoes can be an effective management, both providing an amount of medial heel wedging plus correcting the collapse of the foot arches. - 29957
About the Author:
Jonathan Blood Smyth, editor of the Physiotherapy Site, writes articles about Physiotherapy, back pain, orthopaedic conditions, neck pain, injury management and Physiotherapists in Coventry. Jonathan is a superintendant physiotherapist at an NHS hospital in the South-West of the UK.
