When i do push ups on the ground, above my knee starts to become painful. am i doing it incorrect or is there possibly something wrong?

May be locking out: Try using a slight flexion in both knees.

Pain: Hard to access if you are doing you push up right or wrong. However, pain could be from conditioning if you are just getting started. However, I would expect this in both knees. If this is only one side I would be more suspicious of a problem.

Wrong technique: In addition to the push ups, do you practice any spor or exercise that involves constant use of the legs? It is possibe that the pain is due to a wrong training technique when you are doing push ups. Take care of the technique and if the pain persists, go with a Dr. to evaluate your knee.