Hi daphne, how's the pilates?
Trembling/shaking are normal - small muscles working. we do experience these esp during leg raises, and if u gym, try lifting the weights while lying on yr back or simply lifting weights up and down behind yr head, u will oso noticed, our trembling triceps. becos of the resistance (weights) pushing our muscles to work harder. Overtime, the shake will be lesser.
For us, u, me and kat, with knee problem, strengthening our quads and hamstrings is essential. if u are lazy and don't like the gym, u can do squats. but always remember when u squat, your knees must be behind your toes and not over the toes. Or at your office desk, just sit properly and do leg lift underneath the desk. I do at the same time, is taking glucosamine since my knee/ankle injury last year.
and hi angelin, we don't advise u not to join, becos exercise is good for you. Unlike the bigger fitness centres, amore is very small, no swimming pool, no tea/coffee corner, no free bathing towels, no body combat classes, no Julian, its a place where u really go and exercise and mingle with sports-passioned-ladies. If you are uncomfortable with guys watching you or exercising with you, consider amore which only has 2-3 male instructors watching you.