When rheumatoid arthritis affects the joints of the foot and ankle, inflammation can make it painful to walk and difficult to wear shoes.
The foot and ankle contain 30 joints, and those joints are particularly susceptible to inflammation in people who have rheumatoid arthritis (RA). At least 90% of people with RA experience inflammation of the foot and ankle joints at some point in their lives,1 and most (65%) experience it within the first few years of diagnosis.2-4
Even though rheumatoid arthritis may cause only intermittent inflammation in the feet and ankles, resulting damage to the joints can be permanent. The damage can change the biomechanics of the foot and ankle joints as a person stands and walks. This change may set the stage for further joint destruction, even when RA is not active in the body.
This article describes how RA can affect the feet and ankles; symptoms, including possible foot deformities; and treatments that can help lessen both pain and future joint damage.
Foot and Ankle Joints Affected by RA
In patients with foot and ankle involvement, symptoms may appear in one or more of the following joints:
- The metatarsophalangeal (MTP) joints, where the long metatarsal bones of the foot meet the toes, are frequently affected by RA. The MTP joints help form the ball of the foot.
- The interphalangeal joints are located where the small phalange bones of the toes meet with each other. (Some people refer to these as knuckles of the toes.)
- The joints connecting the heel and mid-foot’s seven tarsal bones to each other as well as to the long metatarsal bones and the shin’s tibia and fibula. Some of these joints comprise the ankle.
Rheumatoid arthritis inflammation in these joints causes pain in the toes, feet and ankles.
How RA Causes Foot and Ankle Pain
The joints in the foot and ankle are called synovial joints. Each flexible joint is surrounded by a thin membrane called a synovium. This membrane produces a clear, viscous substance called synovial fluid, which normally nourishes and lubricates the joint.
In a person with rheumatoid arthritis, the body’s autoimmune system malfunctions, attacking healthy tissue in the feet and ankles.
- The immune system sends white blood cells, called leukocytes, to invade foot and ankle joints.
- The white blood cells initiate a cascade of biochemical changes that cause inflammation of the joints’ synovium. Inflammation of synovium is called synovitis.
- As the immune system attack continues, the inflamed synovium adds layers of new cells at a rapid pace. The abnormal layer of synovial cells is called pannus.
- Pannus squeezes into the joint space between bones and releases proteins that degrade articular cartilage and bone at the foot and ankle joints.
- The pannus may create excess fluid that contributes to foot and ankle swelling.
See What Is Pannus?
In addition to causing changes to a foot or ankle joint’s synovium, cartilage, and bone, changes can also occur in other soft tissue, such as the tendons and ligaments.
Tendon and ligament damage in the foot and ankle
Synovial tissue also surrounds most tendons, which connect muscles to bones. In RA, the synovial tissue covering tendons can become inflamed, a condition called tenosynovitis. While not always painful, over time this condition can lead to tendon degeneration.
Damage can also occur to ligaments, which connect bones to other bones. Ligaments are like strong rubber bands, offering a limited amount of stretch. Ligaments in the feet may become overstretched and injured as joints deteriorate. Ligaments may also degenerate because of the damaging proteins in the synovial fluid.
Damage to tendons and ligaments can eventually lead to misalignment of the bones in the foot and ankle.