Why is my knee/thigh twitching and pulsing continuously?

Don't know: Really hard to say without more information or examining you. Are you getting enough sleep, is the first question. Have you been exercising heavily, or conversely, not enough? Do you take any medications that could affect your potassium level, like a diuretic? Try some gentle stretching of you leg muscles, get a good night's rest, and if it persists go see your doctor.