A patient presents with severe pain in the right knee and massive swelling in the left leg after being in an accident. What is the most likely diagnosis?

The most likely diagnosis in this scenario is extensive left femoropopliteal DVT (deep vein thrombosis). After an accident, patients are at an increased risk for blood clots due to factors such as immobility, vascular injury, and potential trauma to the veins.

In the provided scenario, the severe pain in the right knee may indicate an injury, but the massive swelling in the left leg is particularly indicative of DVT. This condition commonly presents with unilateral swelling, warmth, and sometimes pain, especially following a traumatic event. The left leg’s swelling may be a result of the body’s response to the clot forming in the deep veins, which obstructs normal blood flow and leads to the accumulation of fluid in the surrounding tissues.

While other conditions, such as a right knee fracture or Achilles tendon rupture, may show localized swelling and pain, they would typically not cause significant swelling in the contralateral leg. Chronic venous insufficiency usually leads to persistent swelling over time rather than acute, massive swelling, particularly in a post-accident setting.

Thus, given the acute nature of the symptoms after an accident and the swelling in one leg, extensive left femoropopliteal DVT is the diagnosis that best explains