A Baker’s cyst (also known as a popliteal cyst), is a collection of swelling/fluid that accumulates behind the knee. It occurs when there is some kind of jointpathology that results in joint swelling. Different knee conditions that can result in a Baker’s cyst include osteoarthritis, rheumatoid arthritis, meniscal tears and articular cartilage damage.
The synovial fluid and excess inflammation from the joint are pushed out to the posterior aspect of the knee, causing tightness, swelling and pain. The swelling can be noted on ultrasound scans and MRIs, but is also often visible in the popliteal fossa of the knee when compared to the other knee (see picture). The pain is often aggravated by trying to fully flex or extend the knee, so activities such as squatting are painful.
The pain is usually in the posterior knee, and can also refer pain down into the calf muscle. Calf pain associated with tenderness to touch and swelling can also be a sign of a DVT/blood clot, which can be a very serious condition which must be addressed quickly by seeing your local G.P. A Doppler Ultrasound helps to diagnose and differentiate if there is a DVT/clot, muscle tear, Baker’s cyst, or other cause of the pain.
Occasionally a Baker’s cyst can rupture, leading to the release of the inflammation/fluid from the posterior knee down into the calf, ankle and foot. This is usually associated with quite intense pain in the knee and lower leg, which generally resolves over 2-4 weeks as the fluid is reabsorbed by the body. Massage, rest, compression, elevation and medication can all help with pain relief and shorten the recovery period during this stage.
It is important that the underlying cause of the Baker’s cyst is identified. Radiological imaging (such as XRays, CT scans, MRIs) can help to identify any joint damage or arthritis that might be creating the inflammation. In cases where a definite injury is identified, such as a large meniscal tear, surgical intervention to repair the damaged meniscus may be required before the Baker’s cyst will resolve. In other cases such as osteoarthritis, the best management may involve medication (eg. Anti-inflammatories, analgesics), physiotherapy treatment to help maintain knee movement and strength, rest, compression and elevation.
Occasionally the cyst may be drained, however if the underlying cause of the swelling/cyst is not addressed, there is a high likelihood of the cyst
Physiotherapy treatment to relieve pain associated with Baker’s cysts, and their underlying causes, can be very effective. Massage and exercises can help to maintain or restore normal joint movement.
Strengthening the quadriceps, calf, gluteals, adductors and hamstring muscles with a graduated exercise program helps to offload the knee joint, which helps reduce the pain and inflammation.
Hydrotherapy is great way to improve knee movement and strength, as well as reduce swelling without as much weight-bearing on the leg.
Occasionally a Baker’s cyst can develop and be asymptomatic. In this case, there will still be some underlying pathology causing the swelling, so it is worth addressing the cause before the cyst gets larger and becomes symptomatic.
Other causes of posterior knee pain include patello-femoral dysfunction, meniscal tears, hamstring tendinopathy, upper calf strains and
referral from the lumbar spine. Physiotherapists can appropriately assess and diagnose the reason for the posterior knee pain and then develop a treatment plan to help resolve the symptoms.