Replying to Which Bindings for bad knees

Hey guys. I recently took advantage of JSkis selling some blemished skis, and snagged a pair of whipits. Now I'm deciding on a pair of bindings, and I'm looking at some FKS's. I've knocked out the 180's, as I'm low on cash and I don't need my din that high. But, I'm deciding between 120 and 140. My knees are shit, and ive dislocated both kneecaps, so I don't think my DIN should be too high. Should I save some money and get the 120? I'm 6'2 and 160 lbs. Thanks NS