Conversation: The conversation between human and AI assistant.
[|Human|] I am a 56 yo male, that runs marathons and does yoga. I have pain in the back of my knee, it is sore and stiff after I sit a bit and move from sitting to walking. After I walk a bit the soreness deceases. The pain started as a weird feeling behind my knee cap after a yoga class. Then the next am I ran 3 miles and had to stop due to the pain.
[|AI|]  Hi, Pain and stiffness in the knees can be due to developing arthritis (RA or OA). Pain and stiffness behind the knee are usually due to Bakers cyst. Bakers cyst can also cause swelling behind the knee and also stiffness and discomfort while flexing the knee. There are times when Bakes cyst goes away by itself but at times it needs to be treated.  Visit ER, get all tests for RA done and get diagnosed. RA or any injury to the knee commonly triggers Bakers cyst formation due to excess secretion of synovial fluid. Physical therapy, steroid injections or Chat Doctor.  Get evaluated and treated at the earliest. In the meantime, for relief from pain, you can take NSAID (Naproxen.) Hope I have answered your query. Let me know if I can assist you further.