A 25-year-old man complains of a sharp pain in the lower back. He has difficulty walking on his heels and has associated weakness in the extensors of the big toes. Which of the lumbar nerves is possibly associated with these symptoms?

Choice A reason: The L1 nerve root primarily innervates the groin and upper thigh region. Damage to L1 may cause pain or sensory changes in these areas but does not typically affect heel walking or toe extension, which are controlled by more distal nerve roots. Choice B reason: The L3 nerve root contributes to thigh adduction and knee extension. Symptoms of L3 involvement include anterior thigh pain and weakness in quadriceps muscles, not the dorsiflexion of the foot or toe extension. Choice C reason: The L5 nerve root innervates muscles responsible for dorsiflexion of the foot and extension of the big toe, such as the extensor hallucis longus and tibialis anterior. Difficulty walking on heels and weakness in toe extension are hallmark signs of L5 radiculopathy. This nerve also contributes to sensation on the dorsum of the foot, aligning with the patient's symptoms. Choice D reason: There is no L7 nerve root in the human lumbar spine. The lumbar spine consists of five vertebrae (L1–L5), followed by the sacral region. Therefore, this option is anatomically incorrect.