Knee Pain maybe a link to fractured hip over ten years ago?

Patient: I fractured the right side of my hip when I was 10 years old and had a six inch pin put in place. I am now 25 years old. A couple of months ago my right knee cap started to seize up whenever I saw on my legs (which I have done all my life) but it would only happen after being on my knees for about 20 minutes of more. In December I fell down (top to bottom) stairs and I was fine but since then my knee cap has seized up even worse. I can now sit on my knees and it will seize up after a few seconds and it is painful to stretch out. I am also finding lately when I sit crozz legged at my desk as work my knee cap aches and so does my right thigh. My right thigh is also starting to ache when I walk. What does this mean?