What do the quadriceps do?

What do the quadriceps do?

• A. Knee flexion
• B. Knee extension & hip flexion
• C. Hip extension
• D. Plantarflex the foot

Answer: (B)

The quadriceps' main job is to straighten the knee—knee extension—by pulling on the patella and tibia. One member of this group, the rectus femoris, crosses both the hip and knee joints, so it can also assist with hip flexion. This means the quadriceps as a group primarily extend the knee, with a contributing hip-flexion action from the biarticular rectus femoris. The other options describe actions produced by different muscles (knee flexion by the hamstrings, hip extension by glutes/hamstrings, plantarflexion by the calves), so they don’t fit as the main functions of the quadriceps.

The quadriceps' main job is to straighten the knee—knee extension—by pulling on the patella and tibia. One member of this group, the rectus femoris, crosses both the hip and knee joints, so it can also assist with hip flexion. This means the quadriceps as a group primarily extend the knee, with a contributing hip-flexion action from the biarticular rectus femoris. The other options describe actions produced by different muscles (knee flexion by the hamstrings, hip extension by glutes/hamstrings, plantarflexion by the calves), so they don’t fit as the main functions of the quadriceps.