Review Question - QID 103031

A patient with a femoral nerve inury will have a decreased knee jerk (patellar) reflex (Choice 2).

Traumatic femoral nerve injury is uncommon but can occur with injury to the pelvis or anterior thigh. Important signs of femoral nerve injury include an absent or decreased knee jerk, an inability to extend the knee against resistance, and sensory loss over the anterior and medial thigh, medial shin, and foot. Knee jerk (or patellar reflex) examines the motor function of L2-L4, the spinal roots of the femoral nerve.

Stuart et al. review nerve compression syndromes of the lower extremity. They report compression of the peroneal nerve is relatively frequent, while that of the sciatic nerve and femoral nerve are rare. They emphasizes the importance of distinguishing between lumbar spine pathology, peripheral compression, and from systemic conditions such as diabetic, alcoholic or vasculitic neuropathy when evaluating peripheral nerve symptoms.

Kovacevic et al. review hip injuries in adolescent athletes. They write femoral nerve compression injury presents with quadriceps weakness and sensory changes over the anterior thigh and anteromedial leg. Patients may have trouble ambulating due to the injury. Knee jerk may be decreased or absent.

Illustration A shows the patellar reflex arc.

Incorrect answers:
Answer 1: Decreased ankle jerk is typical of injury to the sciatic nerve.
Answer 3: Weakness in leg adduction is typical of injury to the obturator nerve.
Answer 4: Weakness in foot dorsiflexion is typical of injury to the common peroneal nerve.
Answer 5: Numbness to the dorsum of the foot is typical of injury to the common peroneal nerve.