Cartilage Pain, I Think

I set off to do a short local walk this morning to see how I'm reacting to the new tablets I've been prescribed for high blood pressure; I think they make me a bit drowsy. Well, I didn't get to find out because after only a couple of hundred yards after getting off the bus I felt a sharp pain in my right knee and was struggling to walk. I had to abandon the walk and cross over the road and catch a bus going back into town. I've not had pain all the time, but it keeps flaring up. I fear this is going to be another long term problem that will be limiting my walking capabilities.