The Knee-Part 4



Posted: Thursday, November 12, 2009

by Jonathan Blood Smyth

If knee control is not precise and the knee moves in unplanned ways such as laterally when it shouldn't, then the menisci (cartilages) within the knee will suffer increased stresses. The menisci have as one of their roles the guiding of the large femoral condyles into particular movement patterns and if the condyles move abnormally this can be damaging. During the movements the large femoral condyles can roll over the edges of the menisci which are trapped between them and the flat upper surface of the tibial condyles.

The types of damage pattern which can occur in the menisci vary and include the development of tears, splits and bites out of the edge. A "bucket handle tear" can develop if the condyle causes a circumferential split in the meniscus whilst the ends of the tear remain attached to the rest of the meniscus. An unplanned movement such as twisting and turning can damage a meniscus and dislodge a part of it into the joint as a loose body. This can move around inside the knee and jam between the surfaces of the joint, causing sharp pain and a giving way of the knee when it is weight bearing.

Ongoing degenerative changes in the menisci mean the condyles of the femur are less controlled and this heightens the stresses which are placed across the knee between the condyles. The articular cartilage surfaces can also degenerate in response to the increased stresses and this may lead to the development of osteoarthritis. If the meniscus was troublesome in the past the usual technique, before arthroscopy developed, was to remove the entire meniscus, which commonly lead to arthritic changes later in life. Knee problems lead to medial quadriceps wasting and a lot of treatments are prescribed to counteract this.

It is important to look at the accessory movements and the ranges of motion of the knee if strengthening is going to be effective for the inside quadriceps. The knee can be improved functionally by restoring the joint's accessory movements and the ability of the medial quadriceps to function will be greatly enhanced by restoring knee extension. Muscle strengthening exercises will not be effective without the joint's range being restored. The introduction of slim modern arthroscopes for knee surgery has meant easy visualisation of the knee interior and the ability to do the surgical minimum to achieve the desired goal.

Hundreds of millions of people in the world suffer some degree of osteoarthritis, making it the most prevalent degenerative joint condition in the world, affecting almost all the elderly in some way. It is more likely that osteoarthritis will develop if there has been damage to the joint or ligaments, surgery to the menisci or a family history. If the lateral, medial or cruciate ligaments are damaged the knee may develop unwanted extra movement and so generate excessive forces within the joint which can facilitate breakdown of the joint surfaces. The lateral stresses caused by shearing movements in the joint can be of a high level.

The knee can start to develop a grating or clicking as it ages with small degrees of degeneration and is only painful if kept in one position for excessive periods. The joint capsule can become tighter if we do not perform the strong movements any longer which stress the joint to the ends of its ranges. This can increase joint compression which increases the stresses across the joint surfaces and make the joint more likely to be injured during stressful movements. As the process continues the cartilage wears down and the underlying bone, which normally has some elasticity, becomes denser and harder.

An arthritic knee can be enlarged, swollen, hot and painful with limited range of movement, crepitus on motion and a degree of disability. Pain and swelling can go through repeated cycles and gradually become worse as the joint deteriorates. Walking may be limited and the knee pain can disturb sleep due to the difficult in maintaining a position. As the inside of the joint can become very tender it does not tolerate pressure from another knee or the gapping pressure which can occur when we lie on our sides. A pillow between the knees is typically required.

Jonathan Blood Smyth, editor of the Physiotherapy Site, writes articles about Physiotherapy, back pain, orthopaedic conditions, neck pain, injury management and physiotherapists in Rugby. Jonathan is a superintendant physiotherapist at an NHS hospital in the South-West of the UK.

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