Baker’s Cyst ( 2 фото )

A 63-year-old woman with psoriatic arthritis involving her knees presented to the rheumatology clinic with a 9-month history of pain in the left knee. The patient’s psoriatic arthritis had recently been well controlled with leflunomide and monthly golimumab injections. The physical examination was notable for a nontender, palpable mass in the left popliteal fossa that was more prominent when the patient was standing with the knee in full extension (Panel A). Point-of-care musculoskeletal ultrasonography (Panel B) showed a well-defined, anechoic, fluid-filled structure resembling a “speech bubble,” with a neck extending into the joint space between the medial head of the gastrocnemius muscle (blue outline) and the semimembranosus tendon (red outline). A diagnosis of a Baker’s cyst was made. A Baker’s cyst — also known as a popliteal synovial cyst — results when synovial fluid from the knee joint flows into and accumulates in the gastrocnemius–semimembranosus bursa. Baker’s cysts are associated with underlying joint disorders, including osteoarthritis, traumatic injury, or inflammatory arthritis (as in this case). Imaging is not always required to make the diagnosis but may help rule out other conditions. Ultrasound-guided aspiration of the cyst was performed, and an intracystic glucocorticoid injection was given. The patient’s knee pain abated shortly after treatment, and she had remained pain-free as of the 2-month follow-up.
Burak Karakaya, M.D. , and Ertugrul Cagri Bolek, M.D.
Published January 28, 2026
N Engl J Med 2026;394:497
DOI: 10.1056/NEJMicm2513847
VOL. 394 NO. 5


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