National Physical Therapy Examination (NPTE) Practice Exam

A patient has a fracture at the fibular head. Weakness in which of the following motions might indicate injury to the common fibular nerve?

1. Ankle plantarflexion and inversion

2. Knee flexion

3. Ankle dorsiflexion and inversion

4. Knee extension

The correct answer is: Ankle dorsiflexion and inversion

In the case of a fracture at the fibular head, weakness in ankle dorsiflexion and inversion is indicative of possible injury to the common fibular nerve. This nerve is primarily responsible for innervating the muscles that perform these actions, which include the tibialis anterior, extensor digitorum longus, and peroneus tertius. When the common fibular nerve is compromised, the patient may experience difficulty with dorsiflexion—lifting the front of the foot up towards the shin—as well as with inversion, which involves turning the sole of the foot inward. Such weakness can lead to complications like foot drop, where the foot drags on the ground during walking. The other options provided refer to actions that are not directly associated with the function of the common fibular nerve. Ankle plantarflexion and inversion primarily involve the tibial nerve. Knee flexion is predominantly controlled by the hamstring muscles, which are innervated by the sciatic nerve, while knee extension is controlled by the quadriceps, which are also innervated by branches of the femoral nerve. Thus, the correct answer focuses on the specific nerve innervation affected by a fracture at the fibular head.