Relieving the tension helps return joints to normal mobility.
Yup, subluxation here, too--my shoulders subluxate sometimes, and my hips get pulled out of joint when I'm pregnant by muscle cramps.
A GOOD deep-tissue massage therapist can make all those muscles relax, and a good exercise program can keep them that way so that you only need the therapist once a month or so. This protects joints form injury. MC isn't progressive, but joint damage can be!
And apparently, pregnancy make MC worse in pretty much everyone. Wheee. But it gets better after.