The hamstrings primarily perform which action?

• A. Plantarflex the ankle
• B. Dorsiflex the ankle
• C. Extend the knee
• D. Flex the knee

Answer: (D)

The main function of the hamstrings is to bend the knee. These muscles run along the back of the thigh and cross the knee joint, so when they contract they pull the lower leg toward the buttocks, producing knee flexion. They don’t move the ankle through plantarflexion or dorsiflexion—that’s handled by muscles crossing the ankle. Extending the knee is primarily the job of the quadriceps, with the hamstrings acting more as knee flexors (and also helping to extend the hip when the thigh moves). So the primary action they perform is flexing the knee.