had some bad things happen to my left knee in the past but it has been just fine for years. But now, it is twitching a lot. Almost all of the time. Is it from the old injuries? What else makes a knee twitch?
Knee injuries can cause problems later in life, most often because they can lead to stiffness and pain from arthritis. They can also cause chronic trouble with knee weakness if there has been damage to the ligaments. However, old knee injuries would be unlikely to cause 'twitching' at the knee, unless by twitching you mean that, when you stand or move, you feel like the knee is 'giving out' or 'catching', in which case these could be a symptom of weakness of the ligaments in the knee.
On the other hand, if what you are experiencing is true 'twitching' then this is more likely related to the activity of the muscles in your thigh. Twitching of muscles is most commonly the result of muscle strain or fatigue, for example from heavy exercise such as running long distances. However, rarely, muscle twitching can be a sign of a more serious medical problem (although this is unlikely if the twitching is confined just to this one knee).
I would suggest that you set up an office visit with your primary care doctor as a first step. They can examine your knee and help you figure out whether anything is going on that might require treatment.
This answer is for general informational purposes only and is not a substitute for professional medical advice.
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