Suggest Remedy For Knee Pain

I have pain in the front of my knee on the outer side of my kneecap when I kneel. The only other time it hurts is if I put direct pressure in the one specific spot. The pain is intense but does not last for very long and it doesn''t hurt when I am not kneeling or touching it. I am a 40 year old woman, about 5'8" and I am of average weight. What could be the cause of this problem?