Hello, Thanks for your query. You might be suffering from patellar tendinitis or chondromalacia patellae, which causes pain in your knee when you try to climb the stairs. This type of knee pain related to overuse or physical activity. Slight modifications in your life style can help. - Do regular knee exercises (quadriceps and hamstrings). - Always warm up before exercising and cool down afterwards. Stretch your quadriceps and hamstrings. - Lose weight if you are overweight. Every pound that you are overweight puts about 5 extra pounds of pressure on your knee cap when you go up and down stairs. - If you have flat feet, try special shoe inserts and arch supports (orthotics). - Make sure your running shoes are made well, fit well, and have good cushioning I do hope that you have found something helpful and I will be glad to answer any further query. Take care