Arthrosis is a term used to describe the changes that occur when there is an imbalance and greater degradation (breakdown) compared to synthesis (building) of cartilage in the joint. The cartilage becomes frayed and can crack. Later in the disease process, cartilage can disappear completely so that the two bone ends slide directly on each other. It is not uncommon to feel swelling and increased heat in the joints due to inflammation.

Cartilage does not have pain receptors but bones do, therefore when they become affected we start to feel pain. This can be made worse as the soft tissue, including the ligaments and muscle around the joint, become affected. This may result in too much laxity (looseness of the joint) and the muscles may tighten to compensate, leading to more pain.