bursitis

Wherever a tendon or skin has to slide over a bony bump, the body builds a tiny fluid-filled cushion called a bursa — a slippery little sac that lets the parts glide instead of grinding. There are dozens around the body, at the shoulder, hip, knee, and elbow especially. Bursitis is when one of these cushions becomes irritated, swollen, and painful, so the smooth gliding turns into a sore, achy catch.

A bursa is normally a flat, almost empty sac with a slick lining. Overuse (repeated kneeling, leaning on an elbow, a shoulder doing overhead work all day), a direct blow, or a nearby problem like an arthritic joint can inflame it; it fills with extra fluid, thickens, and hurts — classically tender, sometimes visibly swollen, and worse with the movement or pressure that compresses it. Less often a bursa gets infected (septic bursitis), which is hot, red, and genuinely urgent because it needs antibiotics rather than ordinary rehabilitation. Common named examples are subacromial bursitis at the shoulder, trochanteric bursitis at the outer hip, and prepatellar bursitis ('housemaid's knee') at the front of the kneecap.

In rehabilitation, the key insight is that bursitis is usually a symptom of how a part is being loaded, not a disease in its own right. So beyond settling the acute flare (relative rest, reducing the offending pressure, sometimes a corticosteroid injection into the bursa), the lasting fix is changing the mechanics — cushioning the pressure point, correcting the movement pattern, strengthening the muscles around the joint — so the bursa stops getting pinched. Treating only the inflamed sac while ignoring why it got irritated invites it straight back.