Surprise on Popping the Popliteal Swelling: A Case Report.

Popliteal swelling is a common complaint seen in the practice of orthopaedics. Although imaging is useful to aid in the diagnosis of popliteal swelling pre-operatively, definitive diagnosis is often obtained post-operatively through histopathological report of the swelling. Baker's cyst arises medially and hence usually spares the posterolaterally located neurovascular bundle until it becomes larger in size. A thrombosed aneurysm can mimic that of Baker's cyst on computed tomography (CT) imaging in view of its location and the absence of contrast within the lesion. Diagnosis of a popliteal swelling with neural or vascular compression is not as straightforward and surgeons should be well aware that intra-operative findings may differ from diagnosis made pre-operatively. Meticulous exploration is pertinent in identifying the origin of the swelling and structures related to it. MRI imaging of the swelling should be done pre-operatively whenever possible.