The knee is made up of three bones. The thigh bone or femur, the knee cap or patella and the shin bone or tibia. The surfaces of the bones that move against each other are covered by a layer of tissue called articular cartilage, or the joint surface. In healthy joints this is smooth and the surfaces move freely against each other. In damaged or arthritic joints this layer may be rough or patchy and this can cause pain, swelling and feelings of instability.
The knee is stabilised by various structures. The strongest of these are muscles, that act through tendons to attach to the bone. The best thing about muscles is that they respond to training and this forms the basis for many of the benefits from exercise and physiotherapy programs. Different muscles around the knee do different things and often the physiotherapist or exercise physiologist will give you exercises to target specific muscles to achieve a treatment goal.
Ligaments also play a very important role in stabilising the knee. The collateral ligaments are on either side of the knee and limit sideways movement. The cruciate ligaments form an ‘X’ shape in the centre of the knee and limit front to back movement.
The articular cartilages or meniscal cartilages are important shock-absorbing devices that also play a role in the smooth movement of the knee in bending and straightening. They are very important in protecting the joint surface. They are often torn with trauma and are what people are usually referring to when they say that they have had a ‘torn cartilage’.
Common Knee Conditions
Arthritis is a very common condition affecting knees. There are various causes like injury, whole-body diseases like rheumatoid disease, psoriasis and lupus and the most common – wear and tear. There are many different ways to treat arthritis before surgery is required. These include an exercise program and weight loss, modification of activity, various walking aids and braces, medications (both prescription and non-prescription), physiotherapy, podiatry and injections. Surgery is usually used when another treatment has failed or the disease is too advanced for it to be likely to work. The surgical options broadly can be divided into joint sparing or joint replacing categories. The joint sparing operations include ‘key hole surgery’ or arthroscopy, changing the shape of the bones to move load bearing away from worn out areas and occasionally ligament reconstructions. Joint replacing operations include various partial and types of total knee replacement.
Cartilage or meniscal tears are also very common in knees. These often come from sporting or twisting injuries but can occur almost silently due to wear and tear. They will often appear as sharp exacerbations of pain on a background of a dull ache and can be associated with instability. These can also be treated without surgery on occasion with the same types of treatments as for arthritis. If non-surgical treatment fails, keyhole surgery is usually conducted to repair and stitch the tear or more commonly trim the loose portion of the tearaway.
Ligament injuries are also common. These are usually the result of an accident and often are associated with sporting injuries. The vast majority of ligament injuries will be able to be treated with a good physiotherapist and bracing for a period of time. Building up the muscles around the knee will help with the pain and will make the recovery faster. On occasion, the knee will continue to be troublesome and knee ligament repairs or reconstructions may need to be performed. Repairing usually involves stitching and securing the ligament back down to the bone that they were torn from. In reconstructions, ‘donor’ tissues usually from the same patient if possible will be used to repair, augment or replace the torn ligament.
Knee cap instability is also very common and there is often a wide spectrum of troubles from this issue. This can range from grinding from the front of the knee especially with steps, kneeling or crouching to complete dislocation of the knee cap sideways, which may need an anaesthetic to help put back in place. Again, with this problem, non-operative management with an exercise program, bracing and taping and often correction of biomechanics with orthotics is the first line of treatment. In a small percentage of patients, surgery is required and that can range from simple keyhole day surgery to more advanced realignment and ligament reconstruction procedures.