A Rare Case Report of Infected Baker’s (Popliteal) Cyst
A popliteal cyst, otherwise known as a Baker’s cyst, is a fluid-filled sac that forms behind the knee between the medial head of the gastrocnemius and the semimembranosus muscles. These cysts have a high prevalence in the adult population and are frequently associated with a variety of degenerative conditions of the knee, which complicates the diagnosis. Our patient is an elderly male initially evaluated for a deep venous thrombosis. Further evaluation revealed a baker’s cyst abscess, which was diagnosed on imaging and confirmed post-operatively. A culture growth of the abscess was obtained that grew Streptococcus anginosus. The patient presented with right leg swelling, erythema and knee pain. His physical exam showed significant effusion of the right knee, with tenderness to palpation of the right posterior knee and a limited range of motion with flexion. The venous duplex was negative for deep venous thrombosis (DVT) and the patient continued to experience significant pain with ambulation. A knee aspiration was done with purulent joint fluid sent for culture. A computed tomography (CT) scan without contrast of his right leg revealed a Baker’s cyst abscess within a collection of fluid. The patient was taken to the operating room (OR) with a diagnosis of right septic knee and popliteal cyst abscess where arthroscopic irrigation and debridement with extensive synovectomy of the right knee was performed. Aspiration cultures were positive for Streptococcus anginosus, which has a unique ability to promote abscesses formation. Patient tolerated the procedure well and was discharged from the hospital in good condition with instructions to take Rocephin IV for six weeks. The patient ambulated without difficulty and showed significant improvement after 2 months.