<p>Your muscles help you move and help your body work. Different types of muscles have different jobs. There are many problems that can affect muscles. Muscle disorders can cause weakness, pain or even paralysis. </p> <p>Causes of muscle disorders include:</p><ul> <li>Injury or overuse, such as <a href="https://medlineplus.gov/sprainsandstrains.html">sprains or strains</a>, <a href="https://medlineplus.gov/musclecramps.html">cramps</a> or <a href="https://medlineplus.gov/tendinitis.html">tendinitis </a></li> <li>A genetic disorder, such as <a href="https://medlineplus.gov/musculardystrophy.html">muscular dystrophy</a></li> <li>Some <a href="https://medlineplus.gov/softtissuesarcoma.html">cancers</a></li> <li>Inflammation, such as <a href="https://medlineplus.gov/myositis.html">myositis</a></li> <li>Diseases of <a href="https://medlineplus.gov/neuromusculardisorders.html">nerves</a> that affect muscles</li> <li>Infections</li> <li>Certain medicines</li> </ul> <p>Sometimes the cause of muscle disorders is unknown.</p>