The Knee – Part Four

The menisci (often called cartilages) and the main joint surfaces of the knee can be made more vulnerable to injury and damage if knee control is not good enough to prevent unplanned joint movements. Meniscal function is partly to control movement of the femoral condyles into particular paths, centring them on the upper shin bone plateau. Without the guiding help the large and strong condyles can catch the edges of the menisci as they roll across the tibial plateau and so cause tears or other damage to the menisci.

The menisci can be damaged in a variety of ways with the body of the cartilage suffering pieces out of the edge, splitting and developing tears. An example is a “bucket handle tear” which develops in the substance of the meniscus, along its circumference with the two ends remaining connected to the rest of the meniscus. Twisting or turning in a sudden action can cause meniscal damage and detach a small section which then travels about inside the joint and can jam in between the condyles of the joint. Jamming is very painful, can limit full extension, and can cause a weight bearing knee to give way suddenly.

If the menisci become damaged with the ongoing wear process there is less precise condylar control of the femur and this can generate increased forces across the joint surface to the tibia. Degeneration can also occur of the articular surfaces themselves in response to the abnormal joint forces and osteoarthritis can be the result. Prior to modern arthroscopy the surgical management of meniscal problems was to remove the whole structure which typically caused knee arthritis later in life. The medial quadriceps muscle typically wastes with any knee problem and commonly many exercises are given for this.

However, strengthening of the medial lower quadriceps will not be very effective if no attention is paid to the knee’s range of motion and its accessory movements. Restoring the accessory movements can help the knee’s overall function and if full extension is restored then the function of the medial quadriceps muscle will gradually return towards normal naturally. Without full extension then no amount of exercise will restore the muscle function. Modern arthroscopic operative techniques involve slim probes to view the interior of the knee, and the minimum is done internally to remove the troublesome parts, leaving the vast majority of structures intact.

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.

Early stages of knee change with age can include some clicking and grating with the knee only feeling uncomfortable if it is held in one posture for too long. If we lack the stresses at the end ranges of the joint because we do not perform vigorous activities any longer then the joint capsule can become tight. This can make it more vulnerable to injury during movement and can compress the joint to some degree, increasing the forces across the weight bearing surfaces. The cartilage can wear down and the bone underneath, which usually has some pliability, increases in density in a process known as sclerosis.

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 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 London visit his website.

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