A common complaint among long-distance runners, runner's knee feels like a soreness around and sometimes behind the kneecap. It's usually aggravated by running or climbing stairs. Your knee may feel stiff and sore after sitting down for long periods. You might even hear a clicking sound when you bend or extend your knee.
Runner's knee (also known as patellofemoral pain syndrome) is usually caused by weakness in the middle quadriceps muscles and tight hamstrings or IT bands. You may also be at risk if you overpronate (your feet roll inward) when you run. Running on uneven running surfaces or running in incorrect or worn-out running shoes may also a contributing factor.
First, you can reduce the pain and inflammation by icing your knees immediately after running. Work on strengthening your quad muscles, which will help support and stabilize your kneecap. You can do simple exercises, such as forward lunges or straight leg raises. Stretching your hamstrings and IT bands can also help. Don't run through pain. Take a couple days off from running or cross-train, as long as it's pain-free.
Shortening your stride and striking the ground directly underneath your center of gravity may also help alleviate the problem.
Make sure you have the right kind of running shoes for your foot type. Also, make sure you're not running in worn-out shoes. You should replace your shoes every 300-400 miles. You may also want to consider buying over-the-counter arch supports. If you're still experiencing pain, you may need to see a doctor about getting custom-fitted orthotics or visiting a physical therapist for treatment.