What Causes Muscle Pain, also called myalgia, is experienced by many. The most common cause of localized muscle pain is overuse or injury of a muscle (strain). On the other hand, viral infections like influenza may cause systemic muscle pain, as can taking certain medications or having a disease like fibromyalgia or hypothyroidism.
Muscle pain can feel different—aching, cramping, stabbing, or burning—depending on what's behind it. In the end, diagnosing the reason for your muscle pain requires a medical history, physical examination, and sometimes, blood and/or imaging tests. Rarely, a muscle biopsy is required.