Worked out last Friday, including a 35 min run...everything good. My left knee tightened up that evening...never have had any problems with either knee. Since then, when I get up in the morning, knee feels OK but as the day goes on, it tightens up and is painful. When I sit for a long period, it is painful to stand and strertch out my leg. Eventually it stretches out and feels better but still somewhat painful. I am 63 years old and in excellent health. Never had any problems with my legs.
Hello, If I was your treating doctor for this condition of the knee, it could be of the following possibilities.  First - Mild ACL - Anterior Cruciate Ligament injury. Often we can diagnose with a physical examination.  An ultrasound and an MRI will confirm the diagnosis. If it is, so I suggest providing rest to the joint, use kneecap while moving around and also avoid jerky and quick movements of the knee.  Secondly - mild osteoarthritis - This can be diagnosed with an x-ray. It can be diagnosed with physical examination too.  I suggest consulting a physician and get an X-Ray of the joint done to rule out the other possibility.  Hope I have answered your query. Let me know if I can assist you further. Take care Chat Doctor. 