A bursa is a fluid filled sack that is found throughout the body. The bursae sit between bones and muscles, ligaments, or tendons, and provide cushioning and allow for easy movement between the structures.
Bursa, like many other tissues of the body, are prone to inflammation under certain conditions. Typically overuse or additional force through activity, biomechanics, or poor footwear is responsible for causing irritation of the bursa. Bursae can also become aggravated through trauma or injury. Finally, other inflammatory conditions such as rheumatoid arthritis, lupus, and gout can also cause bursitis.
In the foot, the common bursae that are prone to injury are found at the insertion of the Achilles tendon, the side of the bunion joint, and under the metatarsal heads in the ball of the foot.
Bursitis in the foot can be located in different areas.
At the back of the foot, where the Achilles tendon inserts into the heel bone (the calcaneus), there is the retrocalcaneal bursa. This point is particularly susceptible to inflammation due to overuse or abnormal mechanics of the Achilles tendon. It is more common in active patients, particularly runners. Hiking, climbing ladders, and general walking up an incline causes the foot to be in a position that is more likely to compress the bursa and cause pain. The biomechanics of a foot, or how the foot functions, can also contribute to friction at this bursa. The retrocalcaneal bursa is associated with Haglund’s syndrome, which is a condition that presents as a firm lump that forms at the side of a patient’s Achilles tendon, at the heel bone.
The 2nd toe and respective metatarsals is also particularly susceptible to bursitis. Usually the pain will occur under the base of the 2nd toe under the foot (at the metatarsophalangeal joint). Again, this typically occurs with repetitive movement or poor biomechanics, such as a tendency for the foot to roll inwards (pronate).
Finally, bursitis can flare up on the lateral side of the big toe joint (the bunion joint, or first metatarsophalangeal joint). This usually comes about through friction against tight shoes. It is often seen in feet that possess a bunion, or if have a joint that tends to press tightly against the side of shoes. A similar bursa that is prone to inflammation is also found at the 5th toe.
Treatment of bursitis
As it is an inflammatory condition, first line treatments of rest and ice are often helpful. Your physiotherapist and podiatrist can assist you with identifying the cause of discomfort, and help to develop a treatment plan that may involve specific footwear, orthotics, or stretching and conditioning of the surrounding muscles and tendons.