The knee can be catapulted into a painful condition by a traumatic event or injury, often minor, which sets off the process. It does not take a large injury to start up swelling within the joint and the knee is sensitive to the presence of any amounts of fluid within it. The lining of the joint capsule is made up of synovial membrane, the tissue which secretes the lubricating fluid vital to a joint. However, this swelling is maintained within the capsule and irritates the capsule as the joint is repetitively moved. Thirty degrees is the usual angle injures knees are held at.
A flexion contracture, a semi permanent loss of extension of the joint, can develop once the knee is kept in flexion for a long period. The locking function of the last few degrees of knee extension is powered by part of the quadriceps muscle and when it is blocked from this by a bent knee it can weaken and lose size. The knee is more and more difficult to straighten as the muscle becomes weaker and it suffers abnormal forces across the joint.
The cartilage underneath the patella can develop pathology, which is a common problem, and the diagnosis of chondromalacia patellae is a typical one. The kneecap lies gently against the femoral surface, with significant pressure only developing if we have to go down stairs, a slope or get up from sitting. A tightening and loss of the accessory movement can make the kneecap press more strongly against the femur. If friction forces develop across the two bony zones this can be worse with rotation of the shin bone, increased leg length or the development of knock knee or bow leg.
The joint surface of the kneecap can develop increased irritability and this limits the willingness to keep a bent knee for any time, preferring to straighten it to reduce the force. As increased forces bear on the kneecap, the articular cartilage lining it changes and becomes lined and fluffy instead of hard and smooth. Further irritation is provided by increased swelling in response to the joint surface changes, with grooves developing in the cartilage as it worsens. Subluxation of the patella, where it moves out of its groove to some degree, can occur with sudden movements such as turning and twisting.
A patellar subluxation is of sudden onset and often exceptionally painful for the short time it occurs, damaging the joint surfaces and bringing on swelling and pain in the knee. Dislocation or subluxation of the patella mostly occurs towards the outside of the knee and subjects the inner knee tissues to a stretch. This slackness permits the pathological movements to recur more easily. Recurrent dislocation of the patella is common and can cause significant disability, with several orthopaedic procedures typically employed, such as medial reefing, where the inside tissues of the knee are tightened up to draw the kneecap more firmly in towards the middle.
After an attempt at minor interventions has not been successful then the surgeon can progress to tibial tubercle transposition, the moving of the bony prominence on the upper shin bone towards the inner side of the knee. This brings the line of pull of the quadriceps muscles into a more inwards line and draws the kneecap in away from the side where the pressure is greatest. Investigation by arthroscopy can show an appearance of fissures and softened cartilage in worse cases of damage. Wasting of the quadriceps muscle can occur in response to the inflammation and pain of this process.
The knee become gradually less supported as the main thigh muscle weakens and wastes, with going down slopes and stairs more difficult as these activities involve the imposition of greater forces across the patello-femoral joints. When we go downhill the quadriceps has to lengthen as it controls the body weight and this is a more stressful process than activities which involve muscle shortening.
A surgeon can debride the back of the joint via arthroscopy, surgically cleaning up rough areas and debris, but results of this procedure are not predictable. Manual pressures or exercises to press the surfaces together in an attempt at smoothing them can be performed by physiotherapists but this is a therapeutic technique with little support from evidence. - 14130
A flexion contracture, a semi permanent loss of extension of the joint, can develop once the knee is kept in flexion for a long period. The locking function of the last few degrees of knee extension is powered by part of the quadriceps muscle and when it is blocked from this by a bent knee it can weaken and lose size. The knee is more and more difficult to straighten as the muscle becomes weaker and it suffers abnormal forces across the joint.
The cartilage underneath the patella can develop pathology, which is a common problem, and the diagnosis of chondromalacia patellae is a typical one. The kneecap lies gently against the femoral surface, with significant pressure only developing if we have to go down stairs, a slope or get up from sitting. A tightening and loss of the accessory movement can make the kneecap press more strongly against the femur. If friction forces develop across the two bony zones this can be worse with rotation of the shin bone, increased leg length or the development of knock knee or bow leg.
The joint surface of the kneecap can develop increased irritability and this limits the willingness to keep a bent knee for any time, preferring to straighten it to reduce the force. As increased forces bear on the kneecap, the articular cartilage lining it changes and becomes lined and fluffy instead of hard and smooth. Further irritation is provided by increased swelling in response to the joint surface changes, with grooves developing in the cartilage as it worsens. Subluxation of the patella, where it moves out of its groove to some degree, can occur with sudden movements such as turning and twisting.
A patellar subluxation is of sudden onset and often exceptionally painful for the short time it occurs, damaging the joint surfaces and bringing on swelling and pain in the knee. Dislocation or subluxation of the patella mostly occurs towards the outside of the knee and subjects the inner knee tissues to a stretch. This slackness permits the pathological movements to recur more easily. Recurrent dislocation of the patella is common and can cause significant disability, with several orthopaedic procedures typically employed, such as medial reefing, where the inside tissues of the knee are tightened up to draw the kneecap more firmly in towards the middle.
After an attempt at minor interventions has not been successful then the surgeon can progress to tibial tubercle transposition, the moving of the bony prominence on the upper shin bone towards the inner side of the knee. This brings the line of pull of the quadriceps muscles into a more inwards line and draws the kneecap in away from the side where the pressure is greatest. Investigation by arthroscopy can show an appearance of fissures and softened cartilage in worse cases of damage. Wasting of the quadriceps muscle can occur in response to the inflammation and pain of this process.
The knee become gradually less supported as the main thigh muscle weakens and wastes, with going down slopes and stairs more difficult as these activities involve the imposition of greater forces across the patello-femoral joints. When we go downhill the quadriceps has to lengthen as it controls the body weight and this is a more stressful process than activities which involve muscle shortening.
A surgeon can debride the back of the joint via arthroscopy, surgically cleaning up rough areas and debris, but results of this procedure are not predictable. Manual pressures or exercises to press the surfaces together in an attempt at smoothing them can be performed by physiotherapists but this is a therapeutic technique with little support from evidence. - 14130
About the Author:
Jonathan Blood Smyth is the Superintendent of Physiotherapy 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 Oxford visit his website.
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