Knee pain following sprint workouts

Question
Hello! Question about a problem I'm having with my knee. I am an ultrarunner, and 5 weeks ago, I ran a 100 mile race. I rested for a week, then light running for a week, then started doing some sprint workouts for a short race I had coming up. Somewhere during the high intensity track workouts, my left knee started hurting, but pretty much only when running (any surface) or walking downhill/downstairs. The pain is in the front of the knee, under and on the inside of the kneecap. It does not hurt when doing cycle, elliptical, or anything without impact. I rested it a week, then ran on it. I did a 30 mile run, and it was perfect for 20 miles, and the last 10 I could barely walk. I'm pretty confident this is not an overuse injury, but more of an injury related to the sprint workouts I did when I shouldn't have. What do you think??? I'm 31 years old, male, great shape, never had any other training/racing related injuries. Thanks!!!

Answer
Ron, congratulations on doing an ultra! I'm very sorry to hear about your knee pain. I would be surprised if it's not patella femoral pain (aka anterior knee pain). The location of the pain and the types of exercises that cause it make this probable. The way to fix this is by performing these 4 exercises in the following order.

Slow calf raises- 2-5 sets each leg https://www.youtube.com/watch?v=Rf-AKupMPNk&feature=relmfu
Side lying hip abduction- 2-6 sets of 10-15 reps each side.https://www.youtube.com/watch?v=YiesZvSVa7c
Towel eater exercise: 2-4 sets of 1-2 minutes each foothttps://www.youtube.com/watch?v=dGsBVoYNGac
Sit to stand- 4-8 sets of 4-6 reps repshttps://www.youtube.com/watch?v=MEtrqCu8Ne8&feature=relmfu

The key to all of these exercises is quality. Don't jog (ephasis on jog) farther than 5 miles a day for the next 7 days. Perform the above exercises 1-2 times a day. Then after the 7 days continue to do the above exercises once per day and increase your mileage. Don't go fro 5 miles to 30 miles, but you could increase to 30 miles again by day 14.

If the above plan doesn't work then let me know and I'll have more suggestions, but this is a relatively easy and quick fix and I'm 85-90% confident it will work. Further, it definitely can't hurt which is another reason why I like this approach.