This radiology review highlights a relatively common radiological finding, a Bakers cyst. It is important to remember that these are a common radiological finding in asymptomatic people and are not always symptomatic. It is also important to understand that they are not generally a primary pathology and almost always occur in association with other knee pathology.

A 20-year-old male elite player with a three-month history of posterior knee pain and swelling. He reported a history of an ACL reconstruction (hamstring autograft) four years previously. The knee discomfort was made worse by activity and improved by rest. On examination, he was found to have palpable mass in the medial aspect of the popliteal fossa without redness or warmth. He had a full range of motion and no tenderness upon palpation.

An x-ray series of the knee was largely normal. A subsequent MRI scan showed a well-tensioned ACL graft on the sagittal images. The image shown above demonstrates a large cyst (measuring 3.5 x 1 x 4.8 cm) extending posteriorly between the medial gastrocnemius muscle and the semimembranosus tendon. The communication between the popliteal cyst and the subgastrocnemius bursa was noted.

The player was initially managed with a period of rest, activity modification, ice, NSAID and physiotherapy. Unfortunately, due to the congestion of match fixture, his pain persisted, and he eventually underwent an aspiration of the cyst. This was done without complication. Within one month there was a definite improvement in his pain and discomfort. He was able to complete 90 minutes of football.

In contemporary literature, popliteal cysts are classified into two categories, primary and secondary. Primary cysts are idiopathic and often do not have a discernible communication with the joint. Secondary cysts are associated with knee joint pathology and may or may not have a discernible communication with the joint. The management of popliteal cysts depends on the underlying mechanism of cyst formation. A critical component of treatment is to manage the primary pathology that has led to the development of swelling. Cyst aspiration and steroid injections have been shown to be effective in some cases. Surgical cyst removal is associated with high recurrence rates and is reserved for large symptomatic cysts.

By Dr Mark Fulcher on