If mris and ultrasounds can't show wear and tear of testicle muscle, what can?

The cremaster: muscle is an involuntary muscle whose main function is to help regulate the temperature of the testes by contraction/relaxation, and wouldn't normally be subject to "wear and tear" or injury unless there is direct trauma. It is a thin muscle and under normal circumstances difficult to image, but if focal pathology is suspected, ultrasound or MRI would be best, albeit limited.