Rheumatoid Arthritis and Foot Deformity

Rheumatoid Foot Deformity Is Not Uncommon

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It is not uncommon for people with rheumatoid arthritis to develop deformities of the upper and lower extremities. According to the AAOS (American Association of Orthopaedic Surgeons), more than 90% of people with rheumatoid arthritis develop foot and ankle symptoms over the course of the disease. Despite the high prevalence, foot problems tend to be ignored or neglected.

Normal and Abnormal Foot Functionality

Each foot has 26 bones, divided into three regions: the hindfoot (talus and calcaneus), the midfoot (navicular, cuneiforms, and cuboid), and the forefoot (metatarsals and corresponding digit bones or phalanges). With normal functionality (e.g., walking and running), the regions of the foot are interdependent. As you walk or run, your foot goes through a cycle of pronation (foot rolls inward) and supination (foot rolls outward) which allows the foot to adjust to uneven surfaces and absorb shock, followed by propelling forward movement. But, in some diseases and conditions that affect the feet (e.g., rheumatoid arthritis), the pronation/supination cycle can be affected, resulting in abnormal foot flattening (overpronation), midfoot and forefoot instability, excessive weight bearing medially (to the inside of the foot) or over supination (to the outside of the foot). These abnormalities can shift the weight distribution and cause joint pain, soft tissue problems (tendon sheaths, bursae, or entheses), or skin abnormalities (corns and calluses).

Soft tissue problems typically occur around the hindfoot, such as plantar fasciitis, peroneal tendinitis, or bursitis. Rheumatoid nodules can form at the Achilles' tendon.

Rheumatoid Arthritis and Foot Abnormalities

With rheumatoid arthritis, abnormalities most often involve the forefoot, especially dislocation of the metatarsophalangeal (MTP) joints, clawing of the toes (hammertoes), and bunion (hallux valgus).

Such deformities often occur together, especially in advanced rheumatoid arthritis, causing pain and other symptoms that may be more related to the mechanical deformity than the disease itself. Involvement of the ankle joint (the talotibial joint) is relatively uncommon, affecting 10-20% of people with rheumatoid arthritis. The subtalar joint is more commonly involved with rheumatoid arthritis, affecting 33-75% of people with the disease.

The dislocation of the toes, with contracture of the extensor tendons causing the clawing, forces metatarsal heads down into the plantar surface, virtually eliminating the metatarsal arch. Severe, painful calluses can form as the metatarsal heads are pushed down to the sole of the foot.

Diagnosing Foot Abnormalities

A doctor can observe valgus deformity of the ankle and hindfoot (foot twisted outward) from behind when the patient is standing. Palpation for swelling and tenderness around the ankle is indicative of synovitis. The ankle and hindfoot should also be examined for the range of motion.

The patient can be examined for tenderness by the Achilles tendon and heel as well.

Abnormalities of the arch and forefoot can also be detected by observing the patient in the standing position. There will be evidence of pes planus (collapsed arch or flat foot) or pes cavus (high arch) if it exists.

Swelling of the metatarsophalangeal joints causes a visible spreading of the toes, commonly referred to as the daylight sign. Applying direct pressure to the metatarsophalangeal joints will also reveal tenderness if it exists.

Treatment Options

Foot orthotics may help reduce pain and improve function in people with rheumatoid arthritis foot deformity. The importance of appropriate footwear cannot be overstated. While therapeutic footwear can reduce pain and improve function, there is often poor compliance because of dissatisfaction with fit and style.   

For severe cases, when conservative approaches that focus on footwear or orthotics fail, surgery may be an option. Forefoot resection and fusion are considered potentially satisfactory surgical options.

Sources:

The Foot and Ankle in Rheumatology. Philip Helliwell et al. Arthritis Research UK. Issue 8. Spring 2011.
http://www.arthritisresearchuk.org/health-professionals-and-students/reports/topical-reviews/topical-reviews-spring-2011.aspx

Rheumatoid Deformity of the Foot. Leonard Marmor. Arthritis and Rheumatism. Vol. 6. No. 6. December 1963. (First published online November 21, 2005.)
http://onlinelibrary.wiley.com/doi/10.1002/art.1780060610/pdf

Rheumatoid Arthritis of the Foot and Ankle. OrthoInfo. AAOS. December 2011.
http://orthoinfo.aaos.org/topic.cfm?topic=a00163

Primer on the Rheumatic Diseases. Arthritis Foundation. Thirteenth edition. Chapter 2. Evaluation of the Patient. P.13-14.

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