The symptom of sesamoiditis is pain directly beneath the base of the big toe that begins gradually as a dull ache and intensifies over time until it becomes an intense throbbing.
The sesamoid bones are the two tiny bones located within the hallucis longus tendon, the flexor tendon attached to the big toes. These bones rotate forward and backward about two grooves in the first metatarsal head, acting as levers to increase the tension of the flexor tendon.
Because of their location and function, the sesamoids are subject to intense pressure during walking or running.
All direct pressure upon this site is painful. Normal walking becomes so painful that gait is altered so that the heel and/or the outer margin of the foot bears the body’s weight. Over time, this can lead to a cascade of compensatory maladapted gait behaviors.
What causes sesamoiditis?
Sesamoiditis occurs when the feet exhibit maladaptive neuromuscular function. The sesamoids become situated so that they are subject to greater impact forces or the surrounding tendon is subject to excessive tension.
There are three primary causes that, individually or collectively, contribute to sesamoiditis-related maladaptive neuromuscular function:
- One, inadequate firing of the flexor hallucis longus muscle
- Two, improper timing for firing of the flexor hallucis longus muscle
- Three, wearing restrictive footwear that inhibits the required raising of the great toe and corresponding raising of the arch system.
Each can result in less-than-optimal sesamoid positioning – side to side, front to back, or both — contributing the excessive sesamoiditis-related loading and tension forces.
Over time, the stresses created by the excessive pressures result in local tissue damage, and inflammation surrounding the sesamoid bones.
At rest, the sesamoid bones are usually positioned slightly behind the first metatarsal head. Ideally, during walking or running:
- the sesamoids move forward, gliding in the groove around the first metatarsal head as the great toe rises
- the great toe rises higher with increased activity levels, causing the sesamoids to rotate to a position in front of the first metatarsal head and
- the great toe rises before the foot contacts the ground, in anticipation of the expected forces.
In this forward position, the sesamoids are subjected to significantly lower impact and tension forces.