End of the Line
Over the past dozen years or so, this space has covered just about every part of the body that could conceivably be the site for a running-related injury, from just about the top of the (Article #22) to tips of the toes.
Actually, that last part isn’t exactly true – the farthest down we’ve traveled is to the bottom of the heel and foot (plantar fasciitis and toe flexor tendinitis). Now we’ll go a bit farther and look at a not-uncommon condition known as sesamoiditis.
As usual, the “itis” suffix tips us off that we are talking about an inflammatory condition. In this case, we’re dealing with the sesamoids, two small pebble-like bones found underneath the ball of the foot just before we reach the big toe. The sesamoids sit side-by-side and are embedded in the tendon of a muscle that flexes, or pulls down, the big toe relative to the rest of the foot. The purpose of the sesamoids is to function as a pulley, giving that muscle a greater mechanical advantage in transmitting forces. They also assist in weight-bearing and help elevate the bones of the big toe.
Sesamoiditis is generally found most often in runners and dancers and presents as pain and occasionally swelling under the ball of the foot. Onset is usually gradual, with symptoms worsening with increased activity. (A sudden onset of sharp pain following excessive force to the ball of the foot, such as when jumping from a height and landing directly on the ball of the foot, can be indicative of a fracture of the sesamoids and should be X-rayed immediately.)
The actual source of the pain is not clear; the usual suspects include an actual bruising of the bones, a joint irritation between the sesamoids and the metatarsal head where they articulate, or a tendinitis condition from overuse irritation as the big toe extends and flexes repetitively during push-off. Contributing factors can include worn shoes, hill workouts, and increased speedwork, since this tends to increase the tendency to make contact at foot strike closer to the front of the foot than the heel.
Individuals with high-arched feet also seem to have a greater susceptibility to this injury, again because they naturally place more pressure on the balls of the feet. Runners with bunions and an angulation of the big toe laterally toward the outside of the foot (hallux valgus) are also at an increased risk, as this malalignment may alter the position of the sesamoids and amplify the amount of weight borne by one of the small bones.
Treatment of this problem is always conservative initially. Measures include:
- anti-inflammatory medications
- rest from the precipitating activity until the area is non-tender
- use of stiff-soled shoes (but with good cushioning properties) to minimize the amount of big toe joint extension at push-off. Clogs for everyday use are often helpful
- avoidance of high-heeled, narrow shoes that increase the proportion of weight distribution to the ball of the foot
- use of a pad or orthotic device fabricated to divert or disperse the weight-bearing pressure to other parts of the foot.
- physical therapy intervention (ultrasound, electrical stimulation, etc.) to enhance circulation to the injured tissue
Pain that does not respond to rest within six weeks should be evaluated by a physician or podiatrist to rule-out the possibility of a stress fracture of the sesamoids and to consider more aggressive measures such as corticosteroid injection or casting to eliminate weight-bearing for a few weeks.
Sesamoiditis can be a very disabling injury and should not be taken lightly. These two little bones can sure create some big-time hurting!