Question

a 30 - year - old runner presents with sudden onset sharp pain in the back of his thigh during a sprint. he recalls feeling a pop at the time of injury. on examination, there is tenderness and swelling over the posterior thigh, with a palpable defect in the muscle belly. passive knee extension is painful, and there is weakness during resisted knee flexion. which of the following is the most likely diagnosis? a hamstring strain b quadriceps tendon rupture c achilles tendon rupture d patellar tendon rupture

Explanation:

• Hamstring strain: The hamstrings are located at the posterior thigh. A strain (injury to muscle - tendon unit) can present with sudden - onset pain (often described as a "pop"), tenderness, swelling, a palpable defect (if it's a more severe strain), pain with passive knee extension (which stretches the hamstrings), and weakness with resisted knee flexion (as the hamstrings are responsible for knee flexion).
• Quadriceps tendon rupture: The quadriceps tendon is at the front of the thigh. Rupture would affect knee extension, not flexion.
• Achilles tendon rupture: The Achilles tendon is at the back of the lower leg (ankle area), not the thigh.
• Patellar tendon rupture: The patellar tendon is related to the knee (connects the patella to the tibia) and is involved in knee extension, not the symptoms described here.

Answer:

A. Hamstring strain