Runner’s knee is a “catch-all” term for any pain occurring to the knee. Most commonly this is the result of patellofemoral syndrome or patellar tendonitis. Here are some tips for helping your knee pain.
Patellofemoral pain syndrome got its nickname for an obvious and very unfortunate reason–it’s common among runners. The stress of running can cause irritation where the kneecap (patella) rests on the thighbone. The resulting pain can be sharp and sudden or dull and chronic, and it may disappear while you’re running, only to return again afterward. While biomechanical issues may be to blame, the cause can often be traced back to poorly conditioned quadriceps and tight hamstrings.
Source: Cure Runner’s Knee