The largest joints of the hand are called the metacarpophalangeal joints (MP joints). A joint is where two bones meet and move. The different joints of the hand are shown in Fig. 1. MP joints are important for both power grip and pinch activities.

Hand bones are called metacarpals. The finger bones are called phalanges. The metacarpophalangeal joint (MCP joint), or knuckle, is where the finger bones meet the hand bones. At the MCP joint, the fingers can move in multiple directions. They can bend, straighten, spread apart and move together. MCP joints are important for both pinching and gripping.

Causes

The MP joints are often affected by arthritis either from routine wear and tear, an injury, or medical conditions.

The most common medical condition causing arthritis at the joint is termed rheumatoid arthritis. Rheumatoid arthritis affects the inner coating of the joint, called the synovium, and can result in the loss of the cartilage between the joints. The cause of rheumatoid arthritis is not known.

Other conditions that can cause loss of the cartilage include previous injuries and other medical conditions such as gout, psoriasis, or infection.

Diagnosis

Arthritis may cause pain, loss of motion, swelling, and a joint that appears larger than normal. Also, especially in MP joint arthritis, the fingers can shift. Pain in the joint is made worse by hard use of the hand in gripping and grasping activities. People with arthritis may notice weakness when trying to use their hands.

The diagnosis of arthritis is confirmed by taking x-rays. Fig. 3 is an x-ray of a hand with arthritis: the x-ray shows narrowing of the space between the bones, which is a sign that cartilage has been lost.

Treatment

There are many treatments available depending on the amount of pain and loss of function. Medication (prescribed by an arthritis doctor or rheumatologist) can be very helpful in relieving pain and preventing worsening joint destruction. Sometimes joint injections of a steroid medication can also help.

If medical treatment fails, then surgery can be considered. There are many surgical options. One option is synovectomy, which is the removal of destructive tissue. Also, since this disease can cause loosening of the tissues around the joint, these tissues can sometimes be tightened to provide relief.