Baker’s Cyst

A Baker’s cyst (also known as a popliteal cyst) is swelling in the popliteal fossa (region at the back of the knee) which can lead to pain and stiffness in the knee ⁽²⁾. The terminology is somewhat misleading as technically it is not a true cyst. It originates from knee joint effusion (swelling) where fluid distends from the gastrocnemio-semimembranosus bursa (a fluid-filled sac between calf and hamstring muscles). It is more common in older people as part of a chronic knee condition, where there may be general swelling of the knee secondary to age-related degenerative changes ⁽²⁾.

There are both primary and secondary cysts. Primary cysts are usually asymptomatic (do not cause pain) and occur in younger patients. These cysts do not directly involve the knee joint. Secondary cysts are more common and directly involve the knee joint. They are more common in older people and are thought to be caused by muscular weakness around the knee and changes within the joint.

Any condition of the knee which causes degenerative changes or inflammation can contribute to the development of a Baker’s cyst. It is a common finding with intra-articular (within a joint) conditions including ⁽³⁾:

• Meniscal tears (most common).
• Anterior cruciate ligament deficiencies.
• Cartilage degeneration.

Approximately 5% of the population may have a Baker’s cyst ⁽³⁾ and up to 25% of those with knee pain may have a Baker’s cyst on an ultrasound scan although this does not mean symptoms will exist ⁽¹⁾. Men and women are nearly equally affected ⁽¹⁰⁾.

Musculoskeletal physiotherapists or other suitably qualified musculoskeletal specialists can provide you with an accurate and timely diagnosis by obtaining a detailed history of your symptoms. A series of physical tests might be performed as part of your assessment to rule out other potentially involved structures and gain a greater understanding of your physical abilities to help facilitate an accurate working diagnosis.

Imaging is not usually required to make a Baker’s cyst diagnosis, but your treating clinician may request further imaging if deep vein thrombosis or significant intra-articular pathology needs to be excluded. Patients with a Baker’s cyst and calf swelling should be referred urgently for appropriate imaging studies to exclude deep vein thrombosis ^(8,9).

As part of your treatment, your treating clinician will help you understand the condition and what needs to be implemented to effectively manage your symptoms. On-going treatment might not be necessary if you have an isolated, asymptomatic Baker’s cyst.

If you have an underlying condition that is causing the Baker’s cyst and it is painful, this may require further management. Over-the-counter pain relief and the application of ice may be used to reduce swelling and manage any pain. Activity modification strategies and regular adherence to a condition-specific rehabilitation programme should also form part of the management. It should be noted that rehabilitation exercises are not always a quick fix but, if adhered to on a consistent basis (weeks to months), over time they have been shown to yield positive outcomes.

For patients wanting to achieve a high level of function or return to sport, we would encourage a consultation with a musculoskeletal physiotherapist as you will likely require further progression beyond the intermediate rehabilitation stage. Before returning to sport, a rehabilitation programme should incorporate plyometric-based exercises; this might include things like bounding, cutting, and sprinting exercises ^(5,7).

As part of a multi-modal treatment approach, your treating clinician may also use a variety of other pain-relieving treatments to support symptom relief and recovery. Whilst recovering you might benefit from a further assessment to ensure you are making progress and establish the appropriate progression of treatment.  Ongoing support and advice will allow you to self-manage and prevent future reoccurrence.

• Deteriorating and symptomatic Baker’s cysts which do not improve with conservative management may require surgical interventions. The main aim of surgery is to resolve any underlying conditions such as meniscal tears or ligament damage. Surgery aimed at treating underlying conditions can result in the resolution of the cyst. Interestingly, cyst excision (removal) is associated with a high rate of recurrence.
• Deteriorating and symptomatic Baker’s cysts which do not improve with self-management may require aspiration (needle being inserted into the cyst and the fluid is drained out). This would require a referral to a medical specialist.

Baker’s cyst – NHS (www.nhs.uk)