You need a plan with training goals. Not sure who your team leader/coach is but I am pretty sure I would not 100 mile test someone who is new on the bike and has knee issues. Because of your newness and knee problem you need to increase time on the bike gradually and get in some moderately paced long base miles. Is it a requirement to train with the team? I would think seriously about skipping their rides and doing your own ride as dictated by your training goals which seems to be a long ride ... century? If your ride is in late summer - with consistency you can do it. If you don't want to shell out for a coach the LAF site has training plans for things like centuries. TrainingPeaks.com has good info too. I would share your training plan with your Dr to make sure it is okay and see if you can add in strength training too.