[1] The bursae rest at the points where internal functionaries, such as muscles and tendons, slide across bone.

Healthy bursae create a smooth, almost frictionless functional gliding surface making normal movement painless.

Moreover, movement of tendons and muscles over the inflamed bursa aggravates its inflammation, perpetuating the problem.

These include the subacromial, prepatellar, retrocalcaneal, and pes anserinus bursae of the shoulder, knee, heel and shin, etc.

Inflammation of the bursae may also be caused by other inflammatory conditions such as rheumatoid arthritis, scleroderma, systemic lupus erythematosus, and gout.

The inflammation irritates because the bursa no longer fits in the original small area between the bone and the functionary muscle or tendon.

[1] Bursae that are not infected can be treated symptomatically with rest, ice, elevation, physiotherapy, anti-inflammatory drugs and pain medication.