Sesamoiditis refers to irritation to tendons that run under the sole of the foot. These tendons surround small disc-shaped bones called the sesamoids, found in the ball of the foot.
The sesamoid bones help to strengthen the tendons, assisting with running and with keeping the big toe joint stable (1st MTP joint).
Symptoms
The pain of sesamoiditis is felt under the ball of the foot, beneath the big toe. The signs and symptoms include:
- Pain under the big toe joint that builds up gradually
- Pain that is worse when pushing off, and when walking barefoot on hard floors
- Pain on bending the big toe upwards
- Swelling and tenderness under the joint
- Difficulty wearing high heels or thin-soled shoes
The pain usually comes on over weeks rather than suddenly. Pain that starts suddenly, with a snap or a fall, is more likely to be a fracture of a sesamoid.
Causes
The sesamoids sit directly under the big toe joint and take a great deal of load every time you push off. Sesamoiditis develops when the tendons around them become irritated by repeated loading. Running, dancing and jumping are common causes, and it often follows an increase in training or a change of surface or footwear.
A high arch and a big toe joint that sits low in the foot both increase the pressure on the sesamoids.
Risk Factors
Sesamoiditis is most common in runners, dancers and other people who spend long periods on the ball of the foot. Other factors that increase the risk include:
- A recent increase in training or a change of training surface
- Thin-soled shoes, high heels, or dance shoes
- A high arch, which loads the ball of the foot more
- Reduced fat padding under the ball of the foot, which is more common with age
- Previous injury to the big toe or the ball of the foot
Investigations
Your doctor will examine the foot and press over the sesamoids to find the tender spot. Tests that may be used include:
- X-ray, which shows the sesamoid bones and can reveal a fracture
- Bone scan or MRI, used when a stress fracture is suspected or the pain is not settling
Some people are born with a sesamoid in two pieces, which can look like a fracture on X-ray. Comparing both feet usually settles the question.
Complications
Most people recover well, but problems that can follow include:
- Pain that persists for months, particularly where the load is not reduced
- A stress fracture of a sesamoid
- Loss of blood supply to a sesamoid, which is uncommon but slow to recover
- Changing the way you walk to avoid the sore area, causing pain elsewhere in the foot
Treatment
Sesamoiditis usually settles with time and by taking load off the area. Treatment includes:
- Reducing running, dancing and other activity on the ball of the foot
- Cushioned, stiff-soled shoes, and avoiding heels
- A pad or an insole that offloads the sesamoids
- Ice and simple pain relief or anti-inflammatory medication
- Taping the big toe to limit how far it bends
- Physiotherapy to restore movement and strength before returning to sport
Where a sesamoid is fractured, a longer period without weight through the foot is needed, sometimes in a boot or cast, and crutches may be required for several weeks. Surgery to remove a sesamoid is rarely needed, and is considered only when the pain has not settled after a long period of non-surgical treatment.
Prevention
The risk of sesamoiditis can be reduced by:
- Building up running and dancing gradually rather than in one jump
- Wearing shoes with enough cushioning under the ball of the foot
- Using a pad or insole if you have had the problem before
- Dealing with early pain under the big toe rather than training through it