I had some knee surgery done last year. I went through rehab and completed that. My leg was feeling good up until today. The weather has been damp and foggy today and I think this weather is bad for my leg. During my lifting session I stretched, I did stationary bike, I did everything possible to loosen up my leg. However, my hamstrings were really really tight. I could not get them to loosen up. It got so bad that I had to end my workout early. What can I do to loosen the hamstrings up?