Hindfoot (Heel Region of the Foot)
The main function of the hindfoot is to perform the side-to-side motion of the foot. Difficulty walking on uneven ground, grass, or gravel are the initial signs. Pain is common just beneath the fibula (the smaller lower leg bone) on the outside of the foot.
As the disease progresses, the alignment of the foot may shift as the bones move out of their normal positions. This can result in a flatfoot deformity. Pain and discomfort may be felt along the posterior tibial tendon (main tendon that supports the arch) on the inside of the ankle, or on the outside of the ankle beneath the fibula.
Midfoot (Top of the Foot)
With RA, the ligaments that support the midfoot become weakened and the arch collapses. With loss of the arch, the foot commonly collapses and the front of the foot points outward. RA also damages the cartilage, causing arthritic pain that is present with or without shoes. Over time, the shape of the foot can change because the structures that support it degenerate. This can create a large bony prominence (bump) on the arch. All of these changes in the shape of the foot can make it very difficult to wear shoes.
Forefoot (Toes and Ball of the Foot)
The changes that occur to the front of the foot are unique to patients with RA. These problems include bunions, claw toes, and pain under the ball of the foot (metatarsalgia). Although, each individual deformity is common, it is the combination of deformities that compounds the problem.