Myalgia
Myalgia is pain or aching in one or more muscles. It can arise from local injury or disease, systemic illness, medication effects, or other causes.
Delayed-onset muscle soreness: Muscle soreness and stiffness that develop hours after unfamiliar or strenuous exercise. A common exertional pattern, usually resolving without specific treatment.
Nociception: The nervous system’s detection and transmission of signals associated with actual or potential tissue damage. Muscle pain begins when sensory pathways detect injury or chemical signals in muscle.
Myopathy: A disorder of skeletal muscle that can cause weakness, pain, or abnormal muscle enzymes. Some myopathies cause myalgia, while others produce weakness with little or no pain.
Differential diagnosis: The process of comparing possible causes of a patient’s signs and symptoms. Muscle pain has many possible causes, so its pattern and accompanying symptoms shape the evaluation.
Fibromyalgia: A chronic disorder characterized by widespread pain, fatigue, sleep disturbance, and heightened pain sensitivity. It causes widespread pain that includes muscles, though it is not simply muscle disease.
Muscle strain: An injury involving overstretched or torn muscle fibers, often caused by sudden force or overuse. Fiber damage can trigger localized pain, tenderness, and pain with movement.
Muscle weakness: Reduced ability to generate muscle force, distinct from pain-related reluctance to move. Separating true weakness from movement limited by pain guides clinical assessment.
Rhabdomyolysis: A syndrome in which damaged skeletal muscle releases intracellular contents into the bloodstream. Severe muscle pain with weakness or dark urine can signal this urgent complication.
Polymyalgia rheumatica: An inflammatory disorder causing pain and stiffness around the shoulders and hips, primarily in adults over 50. Its name suggests muscle pain, but stiffness and inflammation around joints and bursae predominate.
Inflammation: A coordinated tissue response to injury or infection involving immune cells, signaling molecules, and changes in blood flow. Inflammatory signals can sensitize pain-sensing nerves in affected muscles.