There are several reasons you might have knee pain. Arthritis in the knee or the knee cap, cartilage problems or a ligament strain/tear.
There are two areas where arthritis can develop in the knee. The back of the knee cap can become arthritic and cause pain when you go up and down stairs. Arthritis in the knee joint can cause discomfort with standing and long-term walking.
Another type of headache is a migraine. Migraine headaches are usually caused by genetic or environmental factors. Often, they can be set off by hormones, food, stress and or physical exertion.
A stretch or tear of the one of the major ligaments can making walking or a higher-level activity difficult because the knee will feel like it is giving way.