National Physical Therapy Examination (NPTE) Practice Exam

What is the primary impairment resulting from a lesion in the femoral nerve?

1. Loss of hip flexion strength

2. Loss of knee extension strength

3. Loss of sensation in the anterior thigh

4. Loss of foot dorsiflexion

The correct answer is: Loss of knee extension strength

A lesion in the femoral nerve primarily results in the loss of knee extension strength. This is because the femoral nerve innervates the quadriceps muscle, which is essential for extending the knee. The quadriceps is a large muscle group at the front of the thigh, and its primary function is to extend the leg at the knee joint, making it crucial for activities such as walking, running, and climbing stairs. While there can be associated functional impairments, such as difficulty with hip flexion (because the iliopsoas also receives some innervation from the femoral nerve) and sensory loss in the anterior thigh, the most significant and direct impact of a femoral nerve injury is on the ability to extend the knee. Loss of foot dorsiflexion, on the other hand, is related to the common peroneal nerve, which innervates the muscles involved in this movement, thus making it irrelevant in the context of a femoral nerve lesion.