Osteoarthritis (OA) of the knee is a degenerative condition where the cartilage between the end of the thigh bone and the top of the calf bone wear away, forcing the bones to rub painfully against each other. Pain, stiffness and swelling are common symptoms of an OA knee.
There are three key factors that lead to the development of knee OA.
Knee OA usually affects the older population as our cartilage naturally thinas we age. If you have a previousknee injury or a long history of activities that overloads the knee joint, degeneration may set in much earlier. Unfortunately, these events are irreversible, so it is important that we look after our knees during our early adult life.
There are several physical attributes that increase your chance of knee OA:
A heavier person will load their knee joints more, wearing out their cartilages faster than a lighter person. For every 10 pounds of extra weight you carry, an additional 30 to 60 pounds of force is placed on the knees with each step, according to the Johns Hopkins Arthritis Center.
A bow legged or knock-knee appearance will cause an uneven compression of the knee. Either the outer or inner compartment knee respectively will take up most of the load upon weight bearing and cause more wear and tear.
People with flat feet or whose feet over pronate tend to roll their knee inwards upon weight bearing similar to a knock-knee above.
A person with high foot arch or whose feet under-pronate absorbs less impact with each foot fall. More impact goes up through the leg and the knee will have to work harder to cushion the impact.
When the muscles around the knee do not contract strong and fast enough in a coordinated fashion to absorb the impact of walking or running, the knee joint takes up the remaining forces of the impact.
Tight muscles pull joints closer to each other. In an OA knee where the joint space is already reduced, tight muscles will increase the compression of the joint space. Muscles with reduced flexibility are also less coordinated and slower in reaction time. The muscles that tend to be tight are the quadriceps, hamstrings and calves.
Weak muscles. The quadriceps muscles is the main muscle group that help to support the weight of the body and off loads the knee joint. It is very common for this muscle to atrophy because of disuse. The knee pain deters the patient from loading the knee and this will gradually lead to weakness of the knee which will affect the ability to cushion the impact. This pain, disuse, weakness cycle will continue without treatment.
A weak gluteus medius muscle can aggravate the degeneration of knee cartilage because its function is to keep the hip joint stable, especially in walking. This is often seen as a waddling gait where the hip sway with big movements side to side. The thigh muscle have to work a lot harder to stabilise the wobbly hip and if they are unstable, the knee joints will have to bear the weight.