ZocdocAnswersWhat is a small lump on back of knee?

Question

What is a small lump on back of knee?

I'm 14 and I stretch and run and dance a lot. Yesterday when I was stretching and straightened my knee and lifted my leg to my head I found it. It's not as noticeable when i'm just standing. I'm scared it's cancer!! Please help! Thanks in advance.

Answer

Thank you for your question. In order to determine the exact cause of your knee lump, you will need to have a physician complete a thorough review of your medical history as well as a physical exam. Once this is complete, they can make recommendations regarding the possible causes of this finding as well as whether you need any additional testing to determine its cause. A common cause of a lump on the posterior knee joint is a Baker's cyst. This is basically a fluid-filled sac that typically does not cause a problem. It can become quite enlarged and in some cases can rupture, and this may require surgical excision. There are also other potential explanations for this lump. It may be a normal variant of your anatomy with no clinical significance. Damage to one of the muscles or tendons in this area could cause swelling. Rarely, a blood vessel that develops abnormally can cause a superficial lump. As you mentioned, although rare, this could be a tumor involving the bone, muscle, or nerve in this area. In order to investigate these potential causes, I recommend you see a primary care doctor. After examining you, the doctor will decide whether you need additional testing.

This answer is for general informational purposes only and is not a substitute for professional medical advice.

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