source: PhysioRoom.com

 The Injury

Osteoarthritis is common and usually manifests itself in middle age.

Structure of the Knee

• The knee is a synovial joint enclosed by a synovial capsule that contains synovial fluid. The articular surfaces of the femur and tibia are covered by 'hyaline cartilage', and are coloured light blue in this diagram.

• The semi-circular structures sitting on top of the tibia are the 2 menisci. The knee joint has a medial (inside) and lateral (outside) 'compartment' and one or both of these can be affected by osteoarthritis.

Damage to the Knee

• Damage to the 'articular' or hyaline cartilage can be as a result of sporting trauma, but is more commonly due to repetitive stresses over a long period of time. This is usually associated with habitual overuse of a joint for occupational or sporting purposes.

• In most individuals, the signs and symptoms do not appear until middle age, but the disease process starts much earlier.

• The hyaline cartilage is normally ultra smooth to allow friction free movement, but early damage to the superficial layers produces a frayed appearance. In time, with more stress, this frayed surface evolves into cracks or 'fissures' in the articular cartilage, which can leave the underlying bone exposed.

• With continued wear the underlying bone takes on a polished appearance and eventually micro-fractures appear. The body's natural reaction is to attempt to heal the micro-fractures by laying down more bone. This leads to a thickening of the underlying layer of bone, which can be seen on x-ray.

• Another common feature on x-ray is the formation of bone cysts in the layer of bone beneath the joint surface, together with a flattening of the articular surfaces as the body attempts to spread the surface area over which forces are transmitted.

• As well as changes in the articular cartilage and underlying bone, osteoarthritis produces soft tissue changes. As the joint becomes deformed by bony changes the ligaments which support the joint become stretched. There is also thickening and distension of the capsule that surrounds the joint and both of these features get progressively worse.

 Signs and Symptoms

• Often a person in their thirties or forties will 'over do it' one weekend, either in sport or in the garden, and they will experience a flare up from the degenerate joint. This flare up may last for 48 hours and usually consists of stiffness (particularly in the morning), pain and swelling of the affected joint. The knee may make a creaking or grating sound as the process progresses. Flare ups will settle with rest and the use of NSAID's prescribed by a doctor.

• A substantial time period may pass before there is another flare up, but each flare up will get progressively more intense. Also as time goes by and more stress is put on the affected joint, the time interval between flare ups will decrease to the point where, eventually, the person will have pain even at rest.

• As the disease progresses the symptoms that start off being triggered by over activity, become triggered by immobility. Whereas, in the early stages, rest is essential during a flare up period, disuse in the later stages will exacerbate the problem. This is because the dynamic stability provided by the muscles surrounding the joint is lost if there is muscle wasting due to inactivity. This puts even more strain on the ligaments and ultimately the joint surfaces themselves - producing more pain. In the later stages, if there is pain at rest and during the night, as well as a problems with mobility, then joint replacement surgery is appropriate.

 Treatment

• In summary, the patient must understand that too much activity or too little activity will make the problem worse. Each individual is different but, over time and through experience, each person will learn the optimum level of activity for their affected joint.

• During the early phase flare ups are best treated symptomatically. NSAIDs prescribed by a doctor are effective in relieving pain. An ice pack may be used to relieve a hot painful joint (never apply ice directly to the skin) . Once the condition has been recognized a more long term preventative strategy can be undertaken. This is aimed at reducing pain and stiffness and maintaining range of movement in the affected joint. A sensible approach can prevent excessive degeneration which may eventually lead to disability.

• Each individual case is different and a full assessment will identify factors that may exacerbate the problem. Once identified, your Physiotherapist will formulate a strategy to address these problems. It may be that a work task is putting excessive repetitive stress on the affected joint. It may be possible to modify the task so it can be done in a different position, or specially adapted equipment can be used the reduce the repetitive loads. The main problem may be due to posture or a mal-alignment of the body. If so, this can be remedied through corrective exercise, orthotics or a knee brace.

• Where the knee joint is affected maintenance of full range of motion is encouraged to reduce stiffness. Knee bend can be lost if the person doesn't use the full range of motion because of pain. Pendular exercises (gently swinging the foot back and forward) to encourage knee movement may be helpful. The Physiotherapist can use manual techniques to help maintain the range of movement.

• Pain in the knee joint can lead to an inhibition of the quadriceps muscles. This leads to a vicious circle of further joint instability and more pain, leading to more inhibition and muscle weakness. Exercises to maintain quadriceps and hamstring muscle strength are encouraged to provide support for the affected joint. This strengthening should be done under the supervision of a Chartered Physiotherapist. If there is pain during or following the exercises then the weight used is probably too high.

• If the knee joint is affected then weight bearing activities can make the problem worse. Running on a hard surface increases the stress on the articular surfaces and is not helpful for a person with osteoarthritis. Cycling and swimming, because of their partial weight bearing status, are much more beneficial for the person with osteoarthritis of the knee (note: breaststroke should be avoided, particularly in those with osteoarthritis of the medial compartment of the knee). Kneeling should be avoided, as should sitting in one position for a period of time. Frequent breaks should be taken to stretch and take the knee joint through it's full range of motion, as the articular cartilage draws most of it's nourishment from the synovial fluid within the joint, and this has the effect of providing nutrients to the joint surfaces.