The Knee Joint – Part Four

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 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.

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.

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.

Osteoarthritis is one of the commonest joint conditions in the world, affecting hundreds of millions of people and occurring almost universally to some degree in elderly people. A family history, meniscal surgery, joint trauma or ligament injury can all predispose the joint to later osteoarthritis. Damage to and stretching of either the medial or lateral ligaments can cause some sloppiness of the control of movement in the knee, causing increased forces to be generated across the joint and contribute towards articular surface breakdown. Shearing movements, causing a lateral stress as the joints are in contact, exert high forces on the surfaces.

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.

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.

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

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