Back of the knee pain can be caused by a range of conditions. An acute injury or slow chronic onset can help determine the cause and treatment of the pain. One of the most common causes of back of the knee pain is due to inflammation of the popliteal bursa. When this occurs, the condition is diagnosed as a Baker’s cyst (popliteal cyst).
- Excessive knee joint fluid (synovial fluid) accumulates in the bursa behind the knee
- The fluid buildup can be caused by an acute injury (for example: meniscal tear)
- Or caused by an joint swelling, most commonly osteoarthritis
- Tightness and stiffness when the leg is fully flexed
- Pain is present behind the knee
- Swelling behind the knee
- In rare cases, the Baker’s cyst can rupture and cause similar symptoms to a deep vein thrombosis (DVT), which is very painful
- Musculoskeletal (MSK) ultrasound and in some cases MRI can aid in developing the diagnosis
- Understand the underlying cause of the Baker’s cyst can help determine the most effective treatment
- If it is arthritis that has caused the inflammation a Cortisone (steroid) injection may be effective
- The excessive fluid buildup can be drained with a needle
- If indicated surgical removal might be required
It is worth noting that back of the knee pain can also be caused by many other conditions. It is essential to first get diagnosed by a medical provider before seeking treatment.
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Croy, T. (2016). IMAGING. Musculoskeletal Ultrasound Imaging Case Study: Knee Baker's Cyst in a Triathlete. Orthopaedic Physical Therapy Practice, 28(3), 210-211.
Herman, A. M., & Marzo, J. M. (2014). Popliteal cysts: a current review. Orthopedics, 37(8), e678-84. doi:10.3928/01477447-20140728-52