**M79.1 — Myalgia** describes muscle pain without an identified inflammatory or structural cause. It is distinct from myositis (M60.x) which involves inflammation.
Common causes include exercise-induced soreness, viral infections, fibromyalgia (M79.7), statin-related myopathy, and other drug effects. Persistent myalgia warrants laboratory workup (CK, ESR, vitamin D).
Belongs to **Chapter M** — Diseases of the musculoskeletal system.
