The Knee Joint-Part 4

Uncontrolled movements of the knee due to a lack of muscular control expose the knee to increased stresses and the knee and its cartilages (menisci) may suffer damage. One of the functions of the menisci is to control the large condyles of the femur as they move across the flat upper tibial surface and without this guidance there can be meniscal damage. The powerful condyles can move over the edges of the menisci, trapping them against the upper tibia and causing damage to their cartilaginous structure.

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.

The ranges of movement of the joint and normal accessory movements need to be restored for the medial quadriceps to respond to strengthening work. Knee extension needs to be full for the medial quadriceps to exert their full and functional force and the accessory movements contribute to the necessary play within the joint. If the full extension is not returned then the exercise to strengthen the muscles will likely be in vain. The development of modern arthroscopy techniques has allowed internal inspection of the joint and the ability to do the minimal intervention to achieve the required treatment goal.

The most common joint degenerative disease is the world is osteoarthritis, affecting many hundreds of millions of people and almost universally prevalent in old people to some extent. The likelihood of developing osteoarthritis is increased if there has been meniscal surgery, ligament or joint damage or a history in the family. With damage to the cruciate, medial or lateral ligaments there may be excessive internal joint movement which can lead to abnormally high joint forces and consequent joint surface degeneration. There can be high levels of force generated by the shearing forces acting laterally across a joint.

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.