What is osteoarthritis?

The most common cause of chronic knee pain is arthritis, with osteoarthritis (OA) being the most common form. Arthritis generally refers to damage to the joints, while osteoarthritis particularly describes damaged caused by degeneration of the knee’s protective cartilage or menisci. Degeneration is caused simply by stresses, damage, and general wear and tear on the joints over a person’s lifetime. Other parts of our body heal back to their original state after an injury, however cartilage does not. This means cartilage damage can accumulate over time. The more stress and injury a person’s joints are subjected to, the more likely they are to develop OA. It makes sense then, that the joints most commonly affected by OA are those that carry the most bodyweight; your hips, knees, feet and lower spine.

What does osteoarthritis look like?

The articular cartilage and meniscus cannot be seen on an X-ray image. An X-ray of a healthy knee with good cartilage should show a gap between the bones, such as the knee on the right of the image below. You can see that there is no gap between the bones of the knee on the left of the image. This indicates the articular cartilage and meniscus have completely worn away causing arthritis and the ends of the bones to rub. This is a painful condition.

X-ray 1

Osteoarthritis between the patella (knee cap) and femur (thigh bone) is also common. The lateral (side-on) X-ray below shows a healthy gap between the patella and femur, meaning the articular cartilage still has a healthy thickness. A narrowing of this gap would indicate cartilage wear and osteoarthritis of the patella-femoral joint.

X-ray 2

In the last X-ray below, you can see uneven wear in the medial (inside) compartment of the knee only. Such degeneration can give the patient the appearance of being ‘bow-legged’ over time as the medial joint space collapses. Similarly, wear on the lateral (outside) compartment only can bring about the reverse appearance of having ‘knock-knees’.

X-ray 3


Impact of Osteoarthritis

The pain and other symptoms from knee OA can come and go over time. Certain conditions may trigger painful ‘flare-ups’, such as cold weather, small traumas to the joint, being inactive for a prolonged period of time, or biochemical changes in the body or joint.


It is common for OA sufferers to reduce their physical activity in response to their pain. However, literature and ongoing studies have consistently demonstrated that doing so begins a vicious cycle of degradation and reduced quality of life. Maintaining good physical activity levels is key to managing knee OA, as it offers benefits such as:

  • Maintaining or reducing body weight, which in turn decreases stress on your joint.
  • Improving synovial fluid flow, sustaining the protective and lubricative aspects of knee cartilage.
  • Maintaining muscle strength and tone around your joint, and hence reducing the risk of injury.
  • Improving mental state and your ability to cope.


What can I do?

There remains no cure for OA at the current time, and although a huge amount of research is devoted to this, it seems unlikely that a cure will be forthcoming in the near future. Nonetheless, OA can be effectively managed with a multidisciplinary approach.


Surgical treatment of OA can be very successful for carefully selected patients. But if performed for a patient for whom it is inappropriate, surgery can be an inconvenient and expensive waste of time, or in some situations can actually make matters worse. However, OA is a slow-onset joint disease. As such, sufferers will inevitably reach a point where symptoms can become unbearable. It is as this stage that your surgeon may make an informed decision to perform a partial or total knee replacement on you.

tka illustration


Intensivekneeclinic.com.au. (2019). Sydney Intensive Knee Clinic | About Knee Osteoarthritis (OA). [online] Available at: https://intensivekneeclinic.com.au/about-knee-osteoarthritis-oa/ [Accessed 2 Aug. 2019].

Orthoinfo.aaos.org. (2019). Arthritis of the Knee - OrthoInfo - AAOS. [online] Available at: https://orthoinfo.aaos.org/en/diseases--conditions/arthritis-of-the-knee/ [Accessed 2 Aug. 2019].