Arthritis is a condition that can affect any joint in the body.
A simple joint forms between the ends of 2 bones and is the structure that allows movement – ie The Hip joint is where the Pelvis bone (containing the socket) interfaces with the Femur/Thigh bone (the top end of which forms the ball).
The joint surface is a specialized layer of gristle like tissue 2-3 mm thick that sits on the end of the bone. The scientific name for this layer is articular cartilage. This tissue acts like a shock absorber and reduces load on the bone beneath. It also has a very low friction characteristics which allows the surfaces to glide easily over each other.
Arthritis is where there is loss (partial or complete) of this joint surface layer. This loss is usually progressive and ultimately leads to a situation where the bone is exposed or uncovered resulting in “bone on bone” contact – this is the situation in an advanced or end stage arthritis. A good analogy for arthritis is a car tyre where the tread has worn down.
The main symptom associated with arthritis is pain. The exact cause of pain in arthritis is uncertain and probably multifactorial. Bone is a very sensitive tissue with lots of nerve endings – a broken bone is usually very painful. When the bone is not properly protected by a damaged joint surface, the bone is subject to more load and stress, which can cause pain. The wear debris created by joint surface damage floats around the joint and irritates and inflames the lining tissue of the joint (synovial lining) which also can be a contributory cause for pain.