I think that specific soft tissue work can change the ROM of a shoulder almost instantly. I agree that a lot of problems are primairaly mechanical but secondairy problems maintain or make things worse. As to Origens of it. I think that we have to pay dearly for the most flexible joint we have and often are unable to stabilise sufficiently with our muscles. I also think that a small problem quickly triggers others. A mild supraspinatus irritation can cause bursa and capsular problems (coz' there so close together?)