Mechanical capsulitis or metatarsalgia is a common cause of forefoot pain. It can co-exist, and is often confused, with Morton’s neuroma.
Mechanical capsulitis is usually felt as pain under the ball of the foot during walking or running. It may feel as though there is a pebble in the shoe. It is due to inflammation of the lesser metatarsophalangeal joints caused by abnormal architecture or biomechanics of the foot. It is often seen in feet with hallux valgus (bunions) or tight calf muscles.
The treatment of mechanical capsulitis depends upon the cause of the problem, but options include orthotics (insoles), exercises to stretch out tight calf muscles, steroid injections, or surgery to address the structural abnormalities.