A bursa is a fluid-filled sac situated in areas of the body that are subject to the mechanical forces of pressure and/or friction. The sac is lined with synovial cells that produce the fluid inside the sac to act as a cushion for tendons or joints.
Anatomic bursae are common to all at births and are distinct anatomic features. Adventitious bursae form in other areas due to abnormal forces applied to these areas, causing irritation.
The only anatomic bursa in the foot is between the Achilles tendon and the heel and acts to cushion the fulcrum when the ankle articulates. Common adventitious bursae in the foot occur in the ball of the foot where the long metatarsal bones meet the digits. Intermetatarsal bursae, between the metatarsals, can increase pressure on nerves, causing pain that is associated with a phenomena known in the general public as Morton’s neuroma.
Bursitis is an inflammation of a bursa when the forces applied to it are beyond its ability to handle. This can result in pain, heat and swelling in the area. Bursitis can occur in any of the major joints such as the hip, knee, shoulder or elbow, and also in the foot.
Adventitious bursae that form on the plantar surface of the ball of the foot are subject to inflammation. The first course of action after the diagnosis is made should be to try and alleviate the causative agent. Offloading to relieve pressure and stress with the use of aperture padding and modified orthotic devices works very well in conjunction with icing to the area and avoidance of unshod (barefoot) walking.
Aspiration and administration of anti-inflammatory steroids can be helpful in more severe cases or those that fail to improve with offloading.
Surgical excision of a bursa is the last resort for refractory cases, but is rarely ever needed. Radiographs and MRI can be other conservative diagnostic aids for bursitis. Changing shoe style and massage rarely provide any benefit for bursitis of the foot. In the foot, offloading to relieve the pressure or friction is the key.
David B. Raynor, DPM, is a podiatrist in Inverness and can be reached at 352-726-3668 or at www.AdvancedAnkleAndFootCenters.com with questions or suggestions for future columns.