Munky is right about later in life. I tore the cartilage in my left knee playing rugby when I was 22. Had it repaired, and then suffered a partial ligament tear in the same knee six years later, which I did not have repaired for various reasons. I now have back and foot problems because I have been favoring that knee (unknowingly) for 40-plus years. I still ride, but I ride very carefully because the knee is unstable. Get it checked out and get it fixed now it will save you pain and aggravation later.