The L4 myotome refers to a specific segment of the spinal cord that corresponds to the fourth lumbar vertebra. It is responsible for controlling certain muscle movements in the lower body, particularly those related to the knee and ankle. The L4 myotome primarily innervates the muscles that allow for knee extension and ankle dorsiflexion. Testing the L4 myotome can help assess nerve function and identify potential issues in the lumbar region. Common tests include checking the strength of the quadriceps muscle and the ability to lift the foot upward. This information is crucial for diagnosing conditions related to the lumbar spine and associated nerves.