I have severe pain in my right knee with stiffness. Please suggest a solution.

Hi doctor,

I am a 56-year-old male and I do not have any other medical conditions. My right knee is very painful. I have had pain in my knees for a while but it has been fine to live with. But recently, the pain in my right knee is starting to affect my everyday life. There is no swelling or redness and it was not caused by an injury or accident. I have been using over the counter painkillers to help but they do not always work. Now the pain is at its worse. I can straighten my knee but I cannot bend it fully. It feels very stiff when I try to do so. I played football and worked as an industrial painter when I was young which ment a lot of kneeling. Please help.