The rheumatoid foot and ankle: pathology and treatment

Abstract

Rheumatoid arthritis (RA) is a systemic disease which frequently involves the foot. Since there are many synovial-lined joints within the foot, active rheumatoid disease can produce widespread foot pain. Joint swelling can probably be best seen in the forefoot in the metatarsophalangeal (MTP) joints. Swelling can also be seen surrounding the tendon sheaths across the dorsum of the ankle, along the posterior tibialis tendon, and occasionally, the peroneal tendons. Swelling of the hindfoot is best seen at the talonavicular joint medially, and over the sinus tarsi laterally. The classic findings of rheumatoid arthritis in the forefoot include hallux valgus with intra-articular degeneration of the MTP joints. Synovitis of the MTP joints usually occurs early in the disease.’ The toes drift laterally with dorsal subluxation or dislocation. As this occurs, the metatarsal heads are directed more plantarward, the toes develop a clawtoe deformity, and the weightbearing plantar fat pad is drawn further forward losing its normal location underneath the metatarsal heads. Large bursae with overlying calluses are frequent under the middle metatarsal heads, and at times, under the hallux. Web space pathology,2 usually an intermetatarsal bursa, gives neuroma-like symptoms as an early sign of forefoot involvement,3s4 and may be an early sign of RA. Pathology of the hindfoot is more subtle, can progress rapidly, and frequently affects the forefoot. Synovitis of the hindfoot joints and subsequent loss of articular cartilage and erosion of the talonavicular and subtalar joints lead to a persistent valgus deformity of the hindfoot. The talonavicular joint becomes unstable with the head of the talus drifting medially and plantarward.’ The remainder of the midfoot and forefoot drifts into abduction. The calcaneus may also abut against the distal fibula producing pain at the lateral malleolus.6 The posterior tibia1 tendon may rupture,7 or if intact may not function effectively as the medial stabilizer of the hindfoot due to the altered hindfoot mechanics. Only 8% of patients with disease of less than 5 years had moderate to severe hindfoot deformities.’ However, in patients with disease of more than 5 years, 25% had abnormal hindfoot valgus on weightbearing. Ankle pathology gives far fewer symptoms, and when patients complain of ankle pain, most are actually experiencing hindfoot pain. Ankle instability can occur from erosions of the dome of the talus and ligament instability so that a valgus deformity may result from pathology within the tibio-talar joint rather than the hindfoot. It is essential to make this distinction between hindfoot and ankle pathology.* A standard set of radiographs should be obtained when evaluating any rheumatoid patient with significant involvement of the foot. These should include a weight-bearing anteroposterior (A-P) and lateral view of the foot. Also a weight-bearing A-P view of the ankles is important, especially if there is any ankle or hindfoot pathology. The most important aspect of nonoperative care is proper shoewear in patients with rheumatoid disease.‘,” Usually a shoe must be selected or modified to fit the patient’s deformity. Shoes do not correct deformities, rather they accommodate the deformities and thus reduce pain. Since the forefoot is the most common area of symptoms and pathology, a shoe with a wider and deeper toebox is important in patients with rheumatoid arthritis. The most common shoe modification is a metatarsal pad, which should be placed with the apex of the pad just proximal to the area of maximum tenderness or callus formation, usually between the second and third metatarsal heads.