With rheumatoid arthritis (RA), the immune system attacks healthy joints—and those in the feet don't escape the effects. Joint lining becomes inflamed, causing pain, swelling, and redness. Over time, relentless inflammation can damage the cartilage and bones of the feet, leading to foot deformity.
For an estimated 20% of people with RA, the first symptoms they have are in the feet. About 90% of people with this disease will develop foot and ankle problems over the course of their disease.1
Treating foot problems early can help prevent serious, permanent damage and thwart not only foot deformity, but disability
RA's Impact on Foot Structures
The human foot is a complex construction of bones and joints supported by muscles, tendons, and ligaments. Nearly one-fourth of the body’s bones are found in the feet.
The many joints of your foot are enclosed in a fibrous capsule lined with a thin membrane known as synovium, which secretes a fluid that lubricates joints.3
Rheumatoid arthritis attacks synovial tissue in joints, causing pain, inflammation, and damage. It can affect the ankle, heel (hindfoot), arch (midfoot), ball, toes (forefoot), and connective tissue.1
As you walk or run, your foot goes through a cycle of pronation (weight shifts to the inside of the foot) and supination (weight shifts toward the outside of the foot). This allows your foot to adjust to uneven surfaces, absorb shock, and propel you forward.
RA can affect the pronation/supination cycle in your feet, resulting in:
Abnormal foot flattening (overpronation)
Midfoot and forefoot instability
Excessive weight-bearing on the inside of the foot
Foot rolling onto the outer edges (oversupination)2
This can shift weight distribution and cause:
Soft tissue problems
Skin abnormalities (corns and calluses)
All of these issues, together, can lead to foot deformities. While any single deformity can be a problem on its own, RA can cause you to have several at once, which can increase your level of pain and disability.1
Anatomy of the Feet and Ankles
The bones of your forefoot include the phalanges (toes) and metatarsals (five long bones that extend from your ankle to your toes). The joints between the metatarsals and phalanges, located at the base of your toes, are called the metatarsophalangeal (MTP) joints.
RA can cause several problems in the forefoot. An early sign is often dislocation of the MTP joints. As the disease progresses, it can lead to some common deformities involving forefoot bones and joints.
MTP Joint Dislocation
MTP joint dislocation is caused by inflammation of the synovium, which occurs because the immune system attack that occurs with RA.
It causes swelling and pain that's typically felt on the sole of the foot or on the top near the MTP joint. Pain is often exacerbated by wearing shoes.
When an MTP joint—usually of the second, third, or fourth toe—becomes misaligned (and goes untreated), it can take on a claw-like appearance called hammertoe. With this, tissue from the ball of your foot is being pushed forward and under the toes, which moves the joint out of proper alignment.
Hammertoe causes pain in the bent toe and in the ball of the foot (metatarsalgia) underneath the affected joint. Inflammation, stiffness, and redness are also common.
A crossover deformity of the toes is a type of hammertoe. Not only is the MTP joint misaligned, but the next joint up on the toe—the proximal interphalangeal joint—is as well. This problem usually impacts the second toe and causes it to cross over the big toe.
Bunions, also called hallux valgus, are bony protrusions on the outside of the big toe, right at the MTP joint. When they appear on a smaller toe, which is uncommon, they're called bunionettes or tailor's bunions.4 In RA, they typically develop as a result of abnormal pressure on the first MTP joint.
Bunions aren't usually symptomatic until they've been there for a while. Symptoms may include:
Stiffness, swelling, and redness
Calluses under the ball of the foot
Hammertoes, due to the swelling5
Living With Bunions
Your midfoot is the arch of your foot. RA can damage the cartilage in this region and cause pain that may be exacerbated by wearing shoes. It can also cause flatfoot deformity.
Your arch is supported by ligaments that maintain its curved shape. However, with RA, these ligaments can become weak and collapse. That causes your metatarsals and phalanges to point outward while your hindfoot is pointing straight. This condition is known as flatfoot (also called adult-acquired flatfoot to differentiate it from flatfoot in children).
The flatfoot deformity can change the shape of your feet, put pressure on joints and other structures, and cause considerable pain. Some people develop a large, bony lump on their arch. It can become very difficult to tolerate shoes.
Flatfoot may also be caused by RA-related problems in the hindfoot.
Flatfoot and Fallen Arches
Pain in the hindfoot (heel region) and ankle, especially while walking on rough ground, is a common early symptom of RA. Over time, if the disease progresses, this area can become the source of considerable pain.
Rheumatoid nodules and soft-tissue disorders are common.
Rheumatoid nodules on the Achilles' tendon, which runs from the back of your heel up to your calf, are a common problem.2
These are small masses of inflammatory tissue that appear either alone or in clusters. They can appear in several places throughout the body and may feel rubbery, though they are more likely to feel firm when on a tendon, such as the Achilles' tendon. Rheumatoid nodules usually move around when you push on them.
Often, nodules aren't painful except for possibly during rheumatoid arthritis flares.6 They're most likely to develop in people with severe or long-standing RA, and in those with high levels of rheumatoid factor or who test positive for anti-CCP.7
Understanding Rheumatoid Nodules
While not deformities, soft tissue problems can contribute to foot and ankle pain, especially when they're alongside the issues discussed here. What's more, foot inflammation and deformities may contribute to their development.
Common soft-tissue foot disorders faced by people with RA include:
Plantar fasciitis: The plantar fascia is a connective tissue in the foot that can become inflamed and irritated, causing pain in your heel.8
Peroneal tendonitis: The peroneal tendon connects your outer calf to your foot and can be quite painful when tendonitis (inflammation of the tendon) develops.
Bursitis: Inside your joints are cushions called bursa. Bursitis, inflammation of the bursa, can cause pain and stiffness, especially during and after activity.9
If you have RA and are experiencing foot problems—or even if you're not diagnosed with RA, but foot pain has you concerned about it—let your doctor know. Early diagnosis and treatment can help you limit disease progression and keep deformities from becoming severe or permanent.
A simple physical/visual exam may be all that's needed in some cases of hammertoe, bunions, flatfoot, and nodules.
Such an exam may involve:2
Checking for swelling and tenderness
Looking for signs of deformity (e.g., bunions are fairly obvious to the naked eye)
Feeling the foot for nodules
Having you spread your toes or move your feet and ankles in various ways while sitting, standing, and/or walking (e.g., you may be asked to stand on your toes or heels to reveal if you have an arch)
Checking range of motion of the ankle and hindfoot
But the source of foot pain is not always clear right away, especially if deformities are in the early stages.
Other diagnostics—such as X-rays, computed tomography (CT) scan, and magnetic resonance imaging (MRI), as well as biopsy—may be used to confirm the type and nature of the podiatric issue (i.e., whether it is due to rheumatoid arthritis or another cause of foot pain).
An X-ray or MRI is needed in addition to an exam to diagnose MTP joint deformity.
An X-ray can also show what's happening inside the joint and help determine if hammertoe is an early sign of undiagnosed RA.
A biopsy may be done to confirm that suspected rheumatoid nodules are just that and not something more serious.
Possible Diagnoses for Foot Pain
Standard RA medications are likely to help any foot issue related to your disease. RA is typically treated with disease-modifying anti-rheumatic drugs (DMARDs), which address the underlying causes of inflammation, slow disease progression, and help prevent future damage and deformity.10
Beyond that, what else may help you depends on the type of foot concern you have, although there is a lot of overlap.
Issue Treatment Options
MTP joint dislocation • Over-the-counter anti-inflammatory drugs
• Strapping or taping the toes to realign them
• Toe sleeves to prevent pain when wearing shoes
• Footwear with stiff soles
• Orthotic shoe inserts or insoles
• Surgery (if conservative options fail)
Hammertoe • Stretching and strengthening exercises
• Loose-fitting shoes with roomy toes
• Hammertoe pads
• Icing the affected area
• Surgery (severe cases)
Bunions If no symptoms:
If symptoms occur:
• Elevating your foot
• Icing the bunion
• Soaking your foot in cool water
• Simple foot exercises
• Anti-inflammatory drugs
• Bunion pads or toe spacers
• Soft, low shoes with roomy toe boxes
• Night splints
• Physical therapy and/or surgery (if other approaches fail or pain is severe)
Flatfoot • Arch supports or inserts
• Taking and strapping
• Foot insoles
• Proper footwear
• Anti-inflammatory drugs
• Physical therapy or surgery (depending on severity)
Rheumatoid nodules If no symptoms:
If bothersome or infected:
• Rituxan (rituximab) or another RA medication
• Steroid injections or surgery (though often discouraged because nodules tend to come back quickly)
The importance of appropriate footwear cannot be overstated. While therapeutic footwear can reduce pain and improve function, a lot of people end up not wearing it because they don't like the fit and style. Your foot health should be your number one priority when selecting shoes.