What Causes Sharp Pain In My Knee?

I have a 2 to 3 inch (diameter) osteochondroma on my femur medial to my knee. (left leg) Recently I have been expieriencing pain. It feels similar to when you need to crack your elbow by extending it. The pain is brought on by attempting to raise my left heel and touch it to my right knee. If i move slowly, i can get about 2/3 the way there then I lose strength and feel pain. If I move faster, I can touch my heel to my knee but I feel a sharp pain midway and when I move back. It feels very similar to cracking your elbow. I also feel a similar pain when i attempt to make my femur parallel to the ground while keeping my lower leg perpendicular to the ground. Some everyday activiities that cause pain are walking long distances, walking up or down stairs or an incline, getting in and out of a car and changing clothes. Will the pain subside eventually? Getting the tumor removed is my last option because I am currently working and I am going to college in the fall.