Bursitis is the irritation or inflammation of a synovial bursa. Bursae are located at mechanically stressed sites and reduce friction between bone, tendons, muscles and skin.
Common locations are the subacromial bursa at the shoulder, the olecranon bursa at the elbow, and bursae at the greater trochanter of the hip and around the knee. Clinically there is local pain, tenderness to pressure and occasionally visible swelling. Frequent causes are repeated mechanical irritation or prolonged unfavourable loading.