Knee Arthritis

Arthritis is a word of Latin origin.  “Arthro” means joint and “itis” means inflammation.

The “joint” part of the word is clear for all to understand.  The “inflammation” part is a little more difficult.  Inflammation is a specific pathological process that the body uses typically in a pattern of defence.  There are many causes of inflammation.  They include trauma, chemical insults, burns, infection and even cancers.

Most forms of arthritis are of a degenerative nature.  This is so-called osteoarthritis.  Other forms include rheumatoid arthritis, psoriatic arthritis and even ankylosing spondylitis. 

The joint is made up of several important tissues.  There is a bony skeleton that forms the base.  The part of the bone that rubs against the neighbouring bone (the joint surface) is covered by cartilage.  This is a white, smooth, low friction material made up of molecules and cells.  It is called hyaline cartilage.  The joint is surrounded by a capsule which is lined with synovium.  This is a soft, fluffy type of material that secretes nutrients and enzymes into the joint space.  The joint also has a small volume of fluid.

When the arthritic process starts and progresses, the synovium becomes swollen and reddened, the volume of fluid is increased, the enzymatic distribution is changed and the whole joint becomes swollen, hot, painful and stiff.

Whilst the cause of the inflammation can vary, the pathological process is the same, albeit to a greater or lesser extent. 

As the process progresses (if it does), the joint surfaces (and their cartilage coverings) are gradually worn and deformed.  Ultimately, with osteoarthritis, the cartilage is lost completely and a so-called bone on bone joint surface results.  This is the end stage and is usually associated with quite marked pain, stiffness and deformity.