Sesamoiditis is a common ailment that affects the forefoot, typically in young people who engage in physical activity. Its most common symptom is pain in the ball of the foot, especially on the medial or inner side. This pain may be constant, or it may occur with, or be aggravated by, movement of the big toe joint. It may be accompanied by edema (swelling) throughout the bottom, or plantar aspect, of the forefoot.
The big toe, is made up of two bones (phalanges) and two joints (interphalangeal joint and metatarsal phalangeal joint); it also features two tiny, round, sesamoid bones that enable it to move up and down. On an x-ray of the foot, they appear as a pair of distinctive oval dots near the first metatarsal head, the front end of the first long bone of the forefoot.
Both sesamoids are embedded in exert pressure from the big toe against the ground and help initiate the act of walking, or as podiatrists call it, "the propulsive phase of the gait cycle." The sesamoid bones have two principal functions. They help absorb impact forces in the forefoot during the gait cycle. They do this through a series of attachments to other structures in the forefoot. Although they are separated by a bony ridge, called the crista, at the bottom of the first metatarsal head, they are connected to one another by an intersesamoid ligament. They also are attached to other tendons and ligaments in the forefoot: the tendons of the abductor and abductor hallucis muscles, the sesamophalangeal ligament and the metatarsosesamoid ligament. This array of attachments enables the sesamoids to disperse some of the impact of the foot striking the ground during the gait cycle. Together with their connecting ligaments and the first metatarsophalangeal joint capsule, known collectively as the sesamoid apparatus, they act as a fulcrum. This wedge gives the flexor tendons a better mechanical advantage as they pull the big toe down against the ground during propulsion.
Sesamoiditis is a painful inflammation of the region surrounding the sesamoid apparatus, usually caused by repetitive excessive pressure on the forefoot. It typically develops when the structures of the first metatarsophalangeal joint are subjected to chronic pressure and tension. The surrounding tissues respond to this abuse by becoming irritated and inflamed. This is a common problem among ballet dancers and persons who play the position of catcher in baseball, although any activity that places constant force on the ball of the foot -- even walking -- can cause sesamoiditis.
Sesamoiditis typically can be distinguished from other conditions causing pain in the forefoot by its gradual onset. The pain usually begins as a mild ache and increases gradually as the aggravating activity is continued. It may build to an intense throbbing. In most cases there is little or no bruising or redness. The pain and swelling that accompany sesamoiditis can limit the ability of the first metatarsophalangeal joint to flex upward (dorsiflexion) or downward (plantarflexion), causing a loss of range of motion in the big toe and resultant problems in walking.
Sesamoiditis also may be the result of damage to the sesamoid bone itself. Stress fractures -- microscopic tears in the structure of the bones themselves due to repetitive abuse -- can produce the same array of symptoms. Whatever the cause, the prescribed treatment is essentially the same.
Treatment for sesamoiditis is almost always noninvasive. Minor cases call for a strict period of rest, along with the use of a modified shoe or a shoe pad with a cutout to reduce pressure on the affected area. This may be accomplished by placing a metatarsal pad away from the joint so that it redistributes the pressure of weight bearing to other parts of the forefoot. In addition, the big toe may be bound with tape or athletic strapping to immobilize the joint as much as possible and allow for healing to occur. Oral anti-inflammatory drugs can be used to reduce swelling. Severe cases of sesamoiditis may require the application of a below-the-knee walking cast for 2 to 4 weeks and the injection of steroids directly into the area of the inflamed first metatarsophalangeal joint.