Right knee: pain bottom left of knee cap; no pain kneeling, pain 1st 4-5 times down stairs and when walking on hard surface store floors for 3+ hours?

Chondromalacia: Very likely this represents roughened/damaged cartilage behind the kneecap termed patellar chondromalacia. 1st line treatment can include quadriceps, gluteal and hamstring strengthening; it band stretching and a knee brace that stabilizes the kneecap. Many other treatment options exist based on age, severity, activity level, etc.