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What is Sesamoiditis?
Most bones in the human body are connected to each other at joints. But there are a few bones that are not connected to any other bone. Instead, they are connected only to tendons or are embedded in muscle. These are the sesamoids. The kneecap (patella) is the largest sesamoid. Two other very small sesamoids (about the size of a kernel of corn) are found in the underside of the forefoot near the great toe, one on the outer side of the foot and the other closer to the middle of the foot.
Sesamoids act like pulleys. They provide a smooth surface over which the tendons slide, thus increasing the ability of the tendons to transmit muscle forces. The sesamoids in the forefoot also assist with weightbearing and help elevate the bones of the great toe. Like other bones, sesamoids can break (fracture). Additionally, the tendons surrounding the sesamoids can become irritated or inflamed. This is called sesamoiditis and is a form of tendinitis. It is common among ballet dancers, runners and baseball catchers.
Causes of Sesamoiditis
Sesamoiditis typically can be distinguished from other forefoot conditions 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. One of the major causes of sesamoiditis is increased activity. You’ve probably stepped up your activity level lately, which has forced you to put more pressure on the balls of your feet. Speedwork, hillwork, or even increased mileage can cause this. If you have a bony foot, you simply may not have enough fat on your foot to protect your tender sesamoids. Also, if you have a high arched foot, you will naturally run on the balls-of-your-feet, adding even more pressure.
Symptoms and Signs of Sesamoiditis
The pain of sesamoiditis is beneath the head of the 1st metatarsal; the pain is usually made worse by ambulation and may be worse when wearing flexible thin-soled or high-heeled shoes. Occasionally, inflammation occurs, causing mild warmth and swelling or occasionally redness that may extend medially and appear to involve the 1st metatarsophalangeal joint. Sesamoid fracture can also cause pain, moderate swelling, and possibly inflammation.
Types of Sesamoiditis Injuries in the Foot
There are three types of sesamoid injuries in the foot:
- Turf toe. This is an injury of the soft tissue surrounding the big toe joint. It usually occurs when the big toe joint is extended beyond its normal range. Turf toe causes immediate, sharp pain and swelling. It usually affects the entire big toe joint and limits the motion of the toe. Turf toe may result in an injury to the soft tissue attached to the sesamoid or a fracture of the sesamoid. Sometimes a “pop” is felt at the moment of injury.
- Fracture. A fracture (break) in a sesamoid bone can be either acute or chronic.
- An acute fracture is caused by trauma – a direct blow or impact to the bone. An acute sesamoid fracture produces immediate pain and swelling at the site of the break, but usually does not affect the entire big toe joint. A chronic fracture is a stress fracture (a hairline break usually caused by repetitive stress or overuse).
- A chronic sesamoid fracture produces longstanding pain in the ball of the foot beneath the big toe joint. The pain, which tends to come and go, generally is aggravated with activity and relieved with rest.
- Sesamoiditis. This is an overuse injury involving chronic inflammation of the sesamoid bones and the tendons involved with those bones. Sesamoiditis is caused by increased pressure to the sesamoids. Often, sesamoiditis is associated with a dull, longstanding pain beneath the big toe joint. The pain comes and goes, usually occurring with certain shoes or certain activities.
Treatment of Sesamoiditis
Treatment will vary between patients and will typically involve a period of rest from any activities likely to aggravate the problem. Immobilization strapping, ice and oral anti-inflammatory drugs may also be utilized to settle inflammation and pain and aid in the healing process. A soft full length functional orthotic is commonly used to offload the sesamoids and deflect pressure away from the painful area. Orthotics are essential in treating an underlying causative foot condition, such as flat feet (pes planus), high arched feet (pes cavus), bunions or those with reduced plantar fatty padding. In the case of persistent severe sesamoiditis or stress fractures of the sesamoids, the use of short leg Pneumatic walker with rocker sole (walking cast) for 2 to 6 weeks may be required. Failing this an injection of steroids or surgery may be considered.
In severe cases or following a true fracture of the sesamoids, surgery may be required to remove the damaged or fragmented sesamoid bone. Also in some cases, due to reduced blood supply there may be delayed or absent healing and a surgical review is warranted.
Most individuals will have immediate improvement is symptoms with conservative care, with total resolution achieved within months. Ongoing management may be recommended in those with an underlying foot condition.