Rheumatoid arthritis can have significant effects on the feet and the ankle. These effects range from swelling of the toe joints to severe destruction of the joints of the foot and the ankle.
The process of joint inflammation begins with an inflammation of the lining of the joints called the capsule. As the capsule becomes inflamed, the joint fills with fluid and becomes painful. The cartilage lining of the joint may wear out.
The joint space becomes narrow and bone begins to rub on bone, leading to painful arthritis. In addition, deformities may occur as a result of loosening of the ligaments and capsule lining of the joint. If the housing of the joint (the capsule) loosens up significantly, the joints (particularly in front of the foot) may dislocate.
This can cause painful swelling on the bottom of the ball of the foot that can make walking terribly uncomfortable. In addition to the dislocation of the joints, the big toe begins to deviate and bunions may form on the inside of the big toe.