A 60-yeаr-оld pаtient presents with pоsteriоr knee pаin. They describe pain that travels into their calf. Onset was 2 days ago, and pain began after a 6-hour plane flight for business travel. The patient notes pain with ambulation, and calf tenderness and pitting edema are present. Medical history includes a lumbar spine disc herniation, congestive heart failure, and current treatment for prostate cancer. What is the MOST likely cause of the patient's clinical presentation?