i'd second the post above me in terms of variety. An instructor at my gym teaches both cycle and RPM (she teaches a lot) and unfortunately, the effect has gotten to her knees (she says it burns when she teaches pump as well).
Im an RPM participant and when i first started out i just did RPM / Cycle (4-5 times) and NOW i limit to 2-3 times a week for RPM and the rest of my weekly workout is floor based classes like BA (2 times), BS (Once atm, but thinking of adding another class), BP (2 times a week) and BB whenever i can. Its also very important to stretch (hence the BB/yoga/pilates suggestion). Now, my muscles aint tight anymore compared to a year ago.
Since BA, BC, BS are out for you, i wander if your gym offers BV (Bodyvive?)..this is another great alternative for an overall body workout. Low impact as well....
I hope this helps...
RPM + Attack + Pump + Balance...I breathe on les mills baby!!!!!