Can I take tramadol daily for joint pain so that I am able to exercise?

Yes. I have many patients who do so. I am assuming it was prescribed to you for that reason. If not see an orthopedic specialist to assess your joint issues.
Sure! Exercise like walking increases your metabolism helping you to lose weight which will decrease your knee pain. It also increases your bodies own endorphins which helps the pain. Be aware that tramadol has interactions with certain antidepresants and in the elderly can cause tremors or even seizures. Tramadol does avoid some of problems of nsaids like BP increase and GI bleeding, too.