Lost community and motivation .... And full use of a knee

over the last two years I turned into a little bit of a gym rat and I loved it I was there every day mostly group fitness. I didn't lose a lot but I started to get fit but I over did it and hurt my knee and had to back off the more strenuous stuff. I tried to switch to slower less intense stuff but it's a different kind of people different kind of vibe. I never want to go anymore. It has become so hard for me to work out by myself I have no competition no one to correct my form no one to challenge me. I know I should be able to do this myself but everything just seems boring to me now. I have to do something though. Any suggestions?