**Core Concept**
The common peroneal nerve is a branch of the sciatic nerve that innervates the muscles of the lateral compartment of the leg, including the peroneus longus and peroneus brevis. It also provides sensory innervation to the lateral aspect of the leg and the dorsum of the foot.

**Why the Correct Answer is Right**
The patient's injury to the lateral aspect of the right knee suggests that the common peroneal nerve may have been compressed or damaged. The common peroneal nerve wraps around the lateral aspect of the knee, making it vulnerable to injury in this area. Compression or injury to this nerve can result in weakness or paralysis of the muscles it innervates, leading to difficulties with foot eversion and ankle stabilization.

**Why Each Wrong Option is Incorrect**

**Option A:** The femoral nerve is primarily responsible for innervating the muscles of the anterior compartment of the thigh, including the quadriceps and sartorius. Injury to the femoral nerve would more likely result in weakness of the knee extensors.

**Option B:** The radial nerve is responsible for innervating the muscles of the posterior arm and forearm, including the triceps and extensor muscles of the wrist and fingers. Injury to the radial nerve would more likely result in weakness of the elbow and wrist extensors.

**Option D:** The trigeminal nerve is responsible for sensory innervation of the face and motor innervation of the muscles of mastication. Injury to the trigeminal nerve would more likely result in facial pain or numbness, rather than weakness or paralysis of the lower limb.

**Clinical Pearl / High-Yield Fact**
Injury to the common peroneal nerve can result in a foot drop, characterized by a gait disturbance and difficulty with foot eversion. This can be a classic presentation of common peroneal nerve injury, and should be suspected in patients with lateral knee injuries or compression of the nerve.

**✓ Correct Answer: C. Common peroneal nerve**