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 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.
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.
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.
The symptoms of an osteoarthritic knee are typically pain, increased temperature, range of motion limitation, oedema, enlargement, joint crepitus and inability to do functional tasks. As the joint deteriorates it can go through cycles of pain and swelling, with walking become more restricted. Due to the difficulty of finding a comfortable resting position sleeping may become a challenge. Tenderness of the medial joint line means that pressure from another knee is not well tolerated in sleeping on the side, meaning a pillow is often required to allow comfortable resting.