There are several types of arthritis that can afflict dogs of all breeds and sizes. The most common forms of canine arthritis are:

Osteoarthritis is a chronic, slowly progressing condition that is caused by the breakdown and destruction of your pet's cartilage. As that occurs, the bony structures begin to rub against one another causing pain and discomfort.

Degenerative Joint Disease involves some kind of a breakdown or destruction in portions of the joint, usually cartilage. Just as in the case of osteoarthritis, this condition does not necessarily mean that your pet is experiencing any inflammation.

Hip Dysplasia is characterized by a malformed 'ball and joint' socket in your animal. As you might expect, this ill-fitting combination causes a series of complications. Here, chronic inflammation is common; calcium build-ups occur; there is muscle pain; and the tissue in the surrounding areas begin to break down. More information on hip dysplasia.

Elbow Dysplasia is a like condition that is typically hereditary and most generally found in larger breeds of dogs. Bones become malformed and usually results in 'bone chips' that are very painful. Typically, your pet will exhibit some lameness when suffering from this condition.

Knee (dysplasia) is also characterized by malformed bones and bone 'chips.' It is painful and often obviates itself since the pet is lame and/or limping as the condition progresses.

Knee (stifle) joint typically involves torn ligaments which cause instability in the joint. Dislocation of the (knee) joint is also a problem. Inflammation is common since this is a joint that is subjected to a lot of stress and strain. In most cases it is a result of poor breeding.

Osteochondrosis is a condition where you are contending with a medical condition that results from poor breeding. Improper or inadequate diet can also cause this condition (both factors may be at play). It is characterized by cartilage deterioration and tissue is generally both inflamed and painful.

Hypertrophic arthritis involves excessive bone growth and/or 'spurs' on the joints themselves. In such situations, the pet is typically experiencing a lot of pain.

Shoulder (degeneration) is usually a multi-factorial situation making a clear-cut cause difficult to isolate. An unstable joint, osteochondrosis or even trauma may be the cause.

(Or, a combination of factors).

Wrist arthritis (carpi) might be compared to 'carpal tunnel syndrome' seen in humans. Usually, this area of the pet's body is affected more frequently with pets who are very active.

Kneecap (dislocation) is usually caused by poorly formed leg bones which secondarily, allows the kneecap to move or 'pop' out of its normal position. Usually, this is either an inherited condition or results from poor breeding.

The ultimate outcome of these factors is a joint that simply isn't working properly and where the sensory nerve endings in the supporting joint structures are irritated. These irritated nerve endings in the stressed joint tissues send pain and discomfort signals to the brain. The result is a dog that limps, rests often and is reluctant to move in a normal fashion. And since there is no nerve cells in articular cartilage, when pain is present it is coming from the joint capsule, ligaments and supporting tissues.

These changes in a joint can occur rapidly, such as after a fracture and unsatisfactory healing, or progress with subtle but long term damage as with moderate forms of hip dysplasia. Gradual degeneration of the spine such as in the image above is very common and takes years to develop. Since there are no blood vessels or sensory nerves in joint cartilage, damage to cartilage can be quite advanced before the surrounding supportive tissues become inflamed and sore.