A muscle spasm is a sudden, involuntary muscle contraction that can feel like a cramp, twitch, or tight knot. It often happens without warning and can range from mildly uncomfortable to sharply painful. Common triggers include dehydration, muscle fatigue, nerve irritation, or electrolyte imbalances—particularly low levels of potassium, calcium, or magnesium. Spasms can last anywhere from a few seconds to several minutes. While they’re usually harmless, they can be painful and temporarily limit m