What condition results from an injury to the common peroneal nerve?

The common peroneal nerve is crucial for controlling movements at the ankle and providing sensation to parts of the lower leg and foot. An injury to this nerve typically results in foot drop, which is characterized by a significant weakness in ankle dorsiflexion. This means the person will struggle to lift the front of the foot during activities like walking, leading to a characteristic dragging of the toes and a tendency to trip.

In addition to foot drop, individuals may also experience diminished sensation over the dorsum of the foot and the lateral aspect of the lower leg due to the involvement of sensory branches of the common peroneal nerve. This condition clearly illustrates the specific functional loss associated with an injury to this nerve.

The other options describe symptoms that are not typical for a common peroneal nerve injury; for example, foot inversion and plantar flexion would suggest a problem with the tibial nerve or anterior compartment muscles, while loss of sensation in the plantar surface pertains to the tibial nerve as well. The inability to flex the knee generally indicates issues with the femoral or sciatic nerve, which are not involved in common peroneal nerve injury. Hence, the scenario depicted in the question aligns directly with the correct outcome of a common peroneal nerve