Baker cyst

A 47-year-old man presents to the emergency department with left lower extremity pain and swelling. The patient was outside jogging when he suddenly felt a “pop” with associated pain behind the left knee. The left lower extremity has become progressively more swollen and painful over the past few hours. The patient recently traveled to the United States from London. Past medical history is notable for hypertension. Vital signs are within normal limits. Bilateral lower extremity pulses are normal and equal. Physical examination reveals a swollen and tender calf and ecchymosis at the popliteal region. Anterior and posterior drawer tests are negative. An ultrasound of the left calf is shown below. Which of the following is the most likely diagnosis?
 
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