What is behind knee lump?
A swollen area or lump that can be felt behind your knee can be caused by several different conditions. The lump may create an unsightly appearance, limit knee flexibility, or generate discomfort. A Baker’s cyst is a collection of synovial fluid (the fluid that is present within joint spaces) that bulges out through the back of the knee joint and can be felt as a lump behind the knee. Knee injuries, arthritis, damage to the cartilage of the knee, and other problems can all result in the development of a Baker’s cyst.
The majority of individuals with Baker’s cyst experience no symptoms. The cyst may be found during radiologic imaging for other joint complaints.
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A lump behind the knee may be painful or may not produce any other symptoms. In some cases, you may experience tenderness, warmth, difficulties with movement of your knee joint, or bleeding or bruising.
Other possible causes of a lump behind the knee include abscesses (infections); tumors of the skin, soft tissue, or bones; bleeding; or deformity of the joint accompanying a fracture or other injury to your knee.
A lump behind your knee may be associated with injury and may be accompanied by more serious injuries to the joint. Seek immediate medical care (call 911) for serious symptoms, such as paralysis or inability to move a body part, loss of sensation, absent pulses in the feet, uncontrolled or heavy bleeding, or uncontrollable pain.
If your knee lump is persistent or causes you concern, seek prompt medical care.
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- Baker’s cyst. PubMed Health, a service of the NLM from the NIH. http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002202/
- Knee problems. FamilyDoctor.org. http://familydoctor.org/online/famdocen/home/tools/symptom/542.html
- Hayashi D, Roemer FW, Dhina Z, et al. Longitudinal assessment of cyst-like lesions of the knee and their relation to radiographic osteoarthritis and MRI-detected effusion and synovitis in patients with knee pain. Arthritis Res Ther 2010; 12:R172