Osteoarthritis (OA) of the knee is a degenerative condition where the cartilages of the knee wear away. Pain, stiffness and swelling are common symptoms of an OA knee. In this article, we look at the three factors that lead to the development of OA knee - Aging, Physical Attributes and Muscular Causes. Of which two of these factors, Physical Attributes and Muscular Causes, can be addressed with physiotherapy management. We will focus more in detail on the exercises and treatment for OA knee in a follow-up article.
OA knee usually afflicts the older population as our cartilage thin naturally as we age. If you have a past history of knee injury or 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.
The three key physical attributes are:
- Obesity - A heavier person will load their knee joints more, wearing out their cartilages faster than a lighter person.
- Knee alignment - 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.
- Foot type -
- 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.
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.
The management of these factors are summarised in the following table. In our upcoming article, we will further discuss the specific exercises and treatment for OA knee.
|Weight||Weight loss programme|
|knee alignment||- training of muscles - orthotics|
|foot type||- orthotics|
|Tightness||Stretch Quadriceps, Hamstring and Calves|
|Weak||Strengthen Quadriceps and Gluteus Medius|