You can play lighter and raise the volume. Playing at the bridge will lower the output enough to make you have to "Pluck" harder IMO. That may be what is hurting your Knuckles.
So In summary a lighter touch but raise the volume knob. Worth a try, no?
2012 RIC 4003 M-G, 2004 Fender Jaguar, 2011 Fender American Special P-Bass, Hartke LH1000, Carvin BX500, Avatar B210 & B115, Rickenbacker Club # 496, Jaguar club #103