1. Runner's Knee
Self-Diagnosis: Sharp pain underneath your kneecap.
Cause: A weak inner-thigh muscle makes the kneecap grind on cartilage.
Treatment: Gentle hamstring and calf stretches.

2. Achilles Tendinitis
Self-Diagnosis: Tightness in the Achilles tendon.
Cause: Speed work or shoes with too much cushioning.
Treatment: Buy a firm shoe and a quarter-inch heel lift to insert under the insole. Stop stretching for two weeks.

3. Shinsplints
Self-Diagnosis: Sharp pain near the shinbone.
Cause: Overstriding while running down long hills.
Treatment: Stretch your calf muscles, shorten your stride, and avoid downhills.

4. Plantar Fasciitis
Self-Diagnosis: Pain in the heel when you first stand up.
Cause: Overpronation and floppy shoes.
Treatment: Reduce mileage by 50 percent and switch to a firm shoe with a midsole that doesn't bend.