Sesamoiditis is a foot condition that affects the sesamoid bone. The sesamoid is a small bone embedded in the tendon, one of them being located in your first toe. The sesamoid bone is supposed to provide protection and shock absorption but can become irritated and lead to pain. The pain you feel with Sesamoiditis is located in the ball of the foot of the big toe. It is often tender to touch and can be swollen. Causes can include arthritis, high heels, high arches, flat feet, running on the balls of your feet, and high impact sports. Your therapist will assess your foot and create a treatment plan to address your symptoms.