I've been playing soccer and tennis, and I've been running for many years.
I started playing indoor soccer about 9½ years ago, and in the past 5 years I started having problems with my left knee. I started wearing a knee brace thinking it was my knee. I never went to see a doctor about my knee. Then, I started "Train to End Stroke" to do a marathon. At one of the training sessions, I started talking to Dr. Cragg. He had informed me that runners don't wear knee braces.
Dr. Cragg asked me to come into his office to take some x-rays and check what was wrong with my knee. The x-rays came back and there wasn't anything wrong with my knee. The problem was in my back. The lower part of my spine was turned wrong. Also, I had a fallen arch, and my hamstrings were tight which caused stress on my knee.
Dr. Cragg started with physical therapy and stretching exercises. I was also fitted for orthotics. I was able to complete a marathon and I didn't have to wear a knee brace.
Now, I'm training for another marathon, and my knee doesn't affect my running or any other activity.