Osteoarthritis is one of the oldest-described and most common types of arthritis. It is characterised by the breakdown of the joint's cartilage. 

It occurs when the cartilage covering the ends of the bone wears away, leaving bone rubbing on bone (known as crepitus) causing the joints involved to gradually become stiff, painful and difficult to move.

The condition can range from mild to severe.  It generally affects the hands and in particular joints under considerable strain such as weight-bearing joints like the knees, hips, feet and back.

As the cartilage breaks down, the body attempts to repair the damage by making new bone and this in turn may cause the joint to lose its normal shape.  The bone ends may thicken and grow outward, forming obvious bony spurs or nodules.  This is common on the ends of finger bones and causes the fingers to appear gnarled and disfigured. 

It is these bony spurs that can be responsible for restricting movement in the fingers and are therefore the direct cause of many of the problems experienced by osteoarthritis sufferers, such as an inability to use the fingers to grip and perform daily activities. These bony nodules also add to the pain and inflammation experienced.
 
In some cases, fluid-filled cysts may form in the bone near the joint and bits of bone cartilage may float loosely in the joint space.

What causes osteoarthritis?

The exact cause of the cartilage breakdown seen in osteoarthritis is not known.  However, scientists currently believe that the production of mechanical stress is a key component.  Any sort of mechanical stress may cause the cells in the joint to release large amounts of enzymes and other chemicals that usually play a role in regulating the natural balance between cartilage breakdown and buildup.  It is thought that if too many enzymes are released, this could accelerate joint cartilage breakdown.

Written by Dr. Anna Tilley 

23/04/2009