Knee Lump

What is a knee lump?

A knee lump can represent a joint deformity due to a chronic inflammatory condition such as arthritis or a deformity that arises following any kind of injury to the joint. Knee lumps can be caused by a number of other conditions as well, including infections or tumors of the bone or soft tissues. Depending on the cause, lumps may be single or multiple, soft or firm, painful or painless. They may grow rapidly or may not change in size.

Lumps due to local infectious causes may appear as boils or abscesses. Traumatic causes of knee lumps range from bug bites to severe injuries, such as fractures of bone, that can produce a localized collection of blood in the tissues (hematoma).

Both benign and malignant tumors of the skin, soft tissues, or bones of the knee joint can sometimes feel like lumps. In these cases, either a biopsy or surgical removal of the lump can determine whether cancer is present. Cysts, which are fluid-filled, sac-like structures that can form in various parts of the body, often feel like lumps. A Baker’s cyst is a collection of fluid from the knee joint that appears at the back of the knee.

A knee lump can be a sign of injury and require emergency care. It may be accompanied by serious injuries to the joint. Seek immediate medical care (call 911) for serious symptoms, such as paralysis, loss of sensation, absent pulses in the feet, the inability to move the knee joint, severe bleeding, or uncontrollable pain.

If your knee lump is persistent or causes you concern, seek prompt medical care.