A sesamoid is a bone embedded in a tendon, the largest of which is the kneecap (patella). “Sesamoiditis” most often refers to the 2 tiny bones underneath your big toe that can become irritated and cause pain on the bottom of your foot by the ball of your foot.
Sesamoiditis is most often an overuse condition caused by excess activity on the balls of your feet. Ballet dancers are known for getting this condition. Tendinopathy (dysfunction) of the flexor hallucis brevis, the tendon in which the 2 sesamoid bones are embedded, can precipitate sesamoiditis. An anatomic variant called a bipartite sesamoid may predispose these bones to injury. Certain inflammatory arthritides are associated with sesamoiditis and should be thought of especially when the condition is present in both feet.
Symptoms include pain at the ball of the big toe on the undersurface of your foot, most often made worse with weight bearing and specifically standing on your toes.
Procedural treatment is geared toward the underlying cause. For instance, a dysfunctional tendon (FHB tendon) can be treated with regenerative-type injections (such as platelet-rich plasma [PRP] or orthobiologic injections) that can theoretically provide long lasting pain relief and improved function by stimulating the body’s own natural healing response.