What might cause pain behind the knee?

Reviewed by Yoshinori Abe, MD

Internal Medicine

Pain behind the knee has several possible causes. The most common include:

Baker's cyst – a fluid-filled swelling behind the knee, often linked to arthritis or cartilage injury
Ligament or tendon injuries – such as a hamstring strain or posterior cruciate ligament (PCL) tear
Arthritis – osteoarthritis or rheumatoid arthritis can trigger pain, stiffness, and swelling
Nerve irritation or sciatica – referred pain from the lower back or pinched nerves
Blood clot (DVT) – a serious cause requiring urgent medical attention

Because pain behind the knee can range from a minor strain to a medical emergency like a blood clot, identifying the likely cause early is critical. Guessing can delay treatment—or cause unnecessary worry. Take a free, instant, online symptom check to get personalized insight into what may be behind your knee pain and clear guidance on your next steps.

Reviewed for medical accuracy: 07/14/2026

Important Next Steps

Discover causes of your behind-knee pain Learn if behind-knee pain needs care See if it could be a clot Find OTC relief for knee pain Find a doctor for knee pain Discover home remedies for knee pain Understand if your pain is serious

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Explanation

Sometimes pain behind the knee is due to a Baker's cyst. This is when extra fluid builds up in the knee and forms a small balloon-like sac behind it. Baker's cysts can happen because of arthritis, a small tear in the knee's cartilage, or other knee injuries. When the knee becomes irritated or inflamed, extra fluid is produced, and it may collect in the back of the knee, causing swelling and discomfort. Apart from a Baker's cyst, other causes may include injuries to tendons, ligaments (which help hold the knee in place), or even a strain in the muscles like the hamstrings. Nerve problems, such as irritation of the saphenous nerve (which mainly causes pain along the inside of the knee), may sometimes contribute to pain that feels like it is coming from behind the knee. If you're experiencing persistent or worsening knee pain and want to better understand what might be causing it, try Ubie's free AI symptom checker to help identify potential causes and determine whether you should seek medical attention.

(References)

Updated 2023 Aug 4]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK430774/
Morganti CM, McFarland EG, Cosgarea AJ. Saphenous neuritis: a poorly understood cause of medial knee pain. J Am Acad Orthop Surg. 2002 Mar-Apr;10(2):130-7. doi: 10.5435/00124635-200203000-00008. PMID: 11929207.
Dulay GS, Cooper C, Dennison EM. Knee pain, knee injury, knee osteoarthritis & work. Best Pract Res Clin Rheumatol. 2015 Jun;29(3):454-61. doi: 10.1016/j.berh.2015.05.005. Epub 2015 Jun 9. PMID: 26612241.

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