When assessing the motor function of the lower extremities in a patient with a sprained ankle, what should you ask the patient to do?

Asking the patient to wiggle their toes is the most effective way to assess motor function in the lower extremities, particularly in the context of a sprained ankle. This action specifically evaluates the ability of the muscles and nerves in the foot and toes to function properly. Wiggling the toes requires the activation of several muscle groups that are innervated by nerves originating in the lumbar and sacral regions of the spinal cord, allowing you to determine if there are any deficits in motor control or neurological function.

In contrast, having the patient bend their knees, while it may provide some information about overall motor function, is not specific to the lower extremity, particularly the ankle. Lightly touching the skin of the patient's foot focuses more on sensory function rather than motor function. Palpating around the patient’s ankle can help with understanding the injury and assessing for tenderness or swelling, but does not provide direct insight into the motor capabilities of the foot and toes. Thus, the most relevant and direct method for assessing motor function in this scenario is to ask the patient to wiggle their toes.