Numbness, tingling lower leg

Some years back I had a bucket handle tear of my lateral meniscus. I had arthroscopic surgery, and a the torn piece was removed. Since then, whenever I subject my knee to more-than-normal load bearing (such as lunges, stairmaster, etc.)I experience tingling and numbness in my lower leg, down to my ankle. It feels like a nerve is being irritated. Does anyone have any ideas as to what is actually going on?