Sesamoiditis affects the small sesamoid bones under the base of the big toe. It is an overuse injury causing gradual pain in the forefoot. You are particularly at risk if you have had a sudden increase in forefoot weight-bearing activities.
Medically reviewed by Dr. Chaminda Goonetilleke, 20th Jan. 2022
Symptoms of Sesamoiditis include:
- Gradual onset pain in the forefoot, especially when weight-bearing.
- There will be tenderness over the undersurface of the joint.
- You may limp or shift your weight onto the outside of the foot when walking.
- There is likely to be swelling and inflammation.
- Symptoms are reproduced if you move the big toe against resistance.
If you suspect a stress fracture then an MRI or bone scan may be needed.
What is Sesamoiditis?
Sesamoiditis is inflammation of the Sesamoid bones. These are two small bones that are embedded in the tendon of the Flexor Hallucis Brevis muscle just under the base of the big toe.
The purpose of the Sesamoid bones is to protect the tendon of the flexor hallucis longus muscle. They also increase the strength of the muscle by giving it a mechanical advantage by acting as the fulcrum of a level system. They also take most of the weight-bearing load on the inside of the foot.
In 30% of athletes, one of the Sesamoid bones is split in two, called a bipartite sesamoid.
What causes Sesamoiditis?
Sesamoid bones can be injured in a number of ways including a stress fracture, traumatic fracture, a sprain or damage between a bipartite sesamoid bone as well as injury caused by the movement between the Sesamoid bone and the metatarsals bones in the foot.
Sesamoiditis refers to an overuse injury that develops over time due to repetitive impact. An increase in forefoot weight-bearing activities such as dancing is often a contributing factor.
Stress fractures of the Sesamoid bones are more common in sport, especially those involving acute changes of direction. For example, basketball, dancing, tennis, and badminton.
An X-ray rules out acute (sudden onset) fractures of the Sesamoid bones.
An MRI or bone scan is required to identify the early stages of a stress fracture. This is because they are unlikely to show up on an X-ray.
Overpronation should also be considered as a factor that can increase the risk of Sesamoid injury as over pronation may cause sideways displacement or movement of the Sesamoid bones which can cause wear and tear under the first metatarsal bone in the foot.
Treatment is based on reducing painful symptoms and protecting your foot from future injury.
Treatment of Sesamoiditis will initially be rest and applying cold therapy treatment to ease pain and inflammation.
A doctor may prescribe anti-inflammatory medications such as ibuprofen to help reduce inflammation and pain.
Electrotherapy treatment such as ultrasound therapy helps reduce inflammation.
Padding under the foot may help take the pressure off the painful area on the bones. Likewise, a shock-absorbing or cushioning insole takes the pressure off the painful area.
If you overpronate, where your foot rolls in or flattens as you walk, then correct with orthotic insoles.
Your doctor may give a corticosteroid injection if the more conservative methods above are ineffective.
If an MRI or bone scan confirms a stress fracture then you need a period of 6 weeks complete, non-weight bearing rest in a cast. Then scanned again.
Stress fractures are prone to not healing properly. If it fails to heal, then you may require surgery. Your surgeon may pin the bones together, or remove the Sesamoid bones.
However, this is a very last resort. Loss of a Sesamoid bone and the lever function it provides will also result in muscle imbalance which can result in further complications.