I have knee pain when I walk up and down stairs, when I've been squatting, or when my legs are bent. Straightening my legs seems to relieve what feels like a build up of pain/pressure on the top and sides of my kneecap. I had this in my teens and was told it was growing pain, then also when i was in the Royal Air force but was told it was probably arthritis. I've never gotten a good answer. It's definitely worse pain in the cold or damp, but seems to be any time of year now,.