Septic bursitis of the knee is one of those conditions that looks deceptively simple on the surface. A swollen, red, painful bursa caused by a bacterial infection — the treatment seems obvious: drain it, give antibiotics, rest.

A lymphatic malformation near the knee doesn't behave like a bruise or a cyst that quietly resolves. It swells with activity, sometimes flares after a minor infection, and rarely follows the tidy timeline that a general pediatric or orthopedic handout describes.