So I was running a few times a week in the fall of my sophomore year in college. I did not run very far, but a lot of people who were not active were impressed with my mileage.
One day I was running north on Western Avenue after running to downtown Macomb, and I felt a sharp pain in my left knee. I stopped for a few minutes. Then I restarted, and again I felt a sharp pain. I stopped again and did not restart.
I saw a doctor, and found out that I had chondromalacia patellae. When you put weight on your knee, the kneecap should move vertically. With CP, when you put weight on your knee, it moves horizontally, cutting into cartilage. The doctor said that it was because my left leg was not as strong as my right leg. He told me that I should stop running, and I should look into weight training. I was upset since I liked running, but I did look into weight training. Back then I did not know about the different muscle types.
Image from Wikipedia