Swelling on the Lateral Side of the Knee

A bump directly beside the knee can involve a bursa, tendon, or the tissues around the joint. Pain after twisting may occur with a meniscus tear or ACL tear, while gradual stiffness can accompany knee osteoarthritis. Sudden warmth and marked tenderness can occur with gout. A Baker's cyst is usually felt behind the knee, but fluid can make the area feel full around the joint. The swelling itself does not identify one condition.

Reduce running, squatting, and kneeling while the knee is swollen. Rest with the leg supported, and use a wrapped cold pack for brief periods if that feels helpful. Keep gentle, comfortable movement rather than forcing a deep bend. A clinician may compare both knees, assess stability and the meniscus, and consider imaging or joint aspiration when the cause or fluid needs clarification.

Get urgent care for a hot red knee with fever, inability to bear weight, a deformed joint, severe pain after injury, or a cold, numb, or unusually pale foot. Seek an appointment if swelling returns, limits walking, follows a twist, or does not improve with reduced activity.

Ask which structure seems swollen, whether the knee is stable, and whether imaging is appropriate. Ask how much activity is safe, whether a brace or physiotherapy could help, and what symptoms would change the urgency.