Baker’s or Popliteal Cyst

Definition: A benign swelling involving one or more of the
popliteal bursae.

Causes:  The most common cause of a Baker’s cyst is some sort of articular damage at the knee joint. When fluid accumulates and extravasates as a result of pathology or degeneration, this fluid has the potential to be retained in one of the bursae located behind the knee joint;  commonly the semimembranosus bursa. Baker’s cysts in children do not usually point to underlying joint injury. Other causes include Lyme’s disease.

Examination: It is important to exclude deep vein thrombosis, popliteal artery aneurysm, and space occupying lesions when attempting to diagnose a Baker’s cyst. It is also worth noting that a popliteal cyst may burst and its contained fluid tact down the calf and cause pain distal to its site of origin.

Observation: A patient with a Baker’s cyst will present with swelling of varying proportions over the popliteal region that is most easily viewed from behind with the patient standing.

Palpation: A popliteal cyst is best appreciated with the patient lying supine and the symptomatic leg slightly flexed. If a vascular pathology is suspected: DO NOT PALPATE. Diagnosis of a Baker’s cyst is confirmed via ultrasonography.