What is osteoarthritis 

Osteoarthritis (OA) is a condition that can cause a painful joint. It is the most common form of arthritis. OA is commonly thought to be “wear and tear” associated with aging that affects the cartilage in a joint. However, this commonly held belief isn’t entirely accurate.     

​

Cartilage “degeneration” is certainly a feature of OA, although it is not the only one. Cartilage is not innervated – that is, it doesn’t have nerve supply. So in the early stages of OA it is not capable of producing pain. The pain often comes in part from other structures that are also affected by OA such as the muscles around the joint, the ligaments, the bone underneath the cartilage and the synovium (a membrane that lines the joint). Inflammation of the synovium is a critical feature of OA.

​

While increasing age is a risk factor for OA, there can be numerous contributing factors such as systemic inflammation, trauma (such as from a significant knee injury or knee surgery), biochemical reactions and changes in metabolism.  

 

Wear and tear – The body is not a machine

OA is not a disease that will necessarily get worse over time and it is not caused due to the body wearing out with use. The human body is adaptable and your joint cartilage is no different. It is capable of growing thicker and stronger in response to mechanical stimulus. Similar to getting bigger muscles by lifting weights, any activity that loads your joints can help them adapt. Cartilage also gets its nutrition from synovial fluids that is within a joint and moving your joints helps to maintain the quality of this fluid. A lack of activity is shown to worsen joint health.   

​

There are circumstances though that impair your body’s ability to adapt and can worsen OA. People with “metabolic syndrome” have been shown to have reduced capacity for their joints to adapt and higher levels of disability from OA. Metabolic syndrome relates to high blood pressure, high blood sugars and high cholesterol. These can all worsen systemic inflammation which can worsen inflammation associated with OA and increase your pain. Other things that can contribute to systemic inflammation and OA pain are obesity and smoking.

 

Bone on bone – X-rays for OA

People with “severe” osteoarthritis are often told that their X-rays showed their knee joint is “bone on bone”. What they tend to mean is that there is no more cartilage on the surfaces of your bone, between your femur and tibia. No wonder it hurts so much right? But again this isn’t entirely accurate.

​

X-rays of many peoples knees will often show changes within their joints, some more than others. But many people with these joint changes don’t have any pain at all. Again the X-rays are only part of the picture – they don’t show anything to do with the muscles, ligaments, or synovium.

​

Maybe some of these changes on imaging make your knees a bit less tolerant of activity or more prone to overload. But not for everyone.

Some things to think about when being told you have “bone on bone”

• There are still other things between your tibia and femur bones – your meniscus and synovial fluid

• Your knees might not hurt all the time, or

• Your knee pain might be worse at night when in bed (your knee joint is unloaded)    

 

Pain and OA

If activity is good for OA, why does it often increase your knee pain?

Pain associated with OA is often something that waxes and wanes. It comes and goes or has good and bad patches.

Often people present to me with an onset of knee pain after they have had an increase in their activity levels, or have done an activity they don’t normally do. Doing too much too soon is a good way to make any joint cranky and painful, and your knee is letting you know. But this doesn’t mean you have done any damage to your knee. It is simply been overloaded or not tolerating that amount of activity.

​

As mentioned your joint changes might make it easier to overload. But there might be a combination of factors that have contributed to an increased pain episode.

​

These might be times of stress, other health issues that have affected the overall levels of inflammation in your body, a few poor nights of sleep or even simply it was just time for a bad patch.

​

You can be reassured then, that this current episode of pain will pass. It is a flare up of symptoms. In the short term you might need to modify your activity until it settles, but you don’t need to stop doing the activities you love.

 

In the next post I will discuss exercises for knee OA and how you can manage your pain without the need for surgery.