I am 42, no history of knee injury. recently i get a burning sensation just beneath my knee cap when kneeling. no knee pain otherwise. any ideas?

Knee sensation: How recently? Please tell me it's been more than a week at least. There are some people who are overly sensitive to their body. Give it a few days at least. U would be surprised how many people don't give tincture of time to work.

Early wear and tear: Pain coud be due to irritated/early wear of the patella cartilage or the surface cartilage of the thigh bone that rubs against the patella (try knee sleeve with a cutout for knee cap). Other causes could include patellar tendonitis (try knee strap) or a plica and osgood schlatters. For starters avoid kneeling, stairs, knee extension machines, deep squats, lunges etc. Try therapy, ice, advil/alleve.