Could my muscle have slipped off the angle and if so how do I correct this?

What you re describing is known as masseter muscle dehiscence, a not uncommon adverse aesthetic sequelae from jaw angle implants where the muscle now rides up higher than the angle of the implant. The correct anatomic procedure is to try and reposition the muscle back over it which requites an external neck incision to do so. While it is not a complex procedure it is also one that is not 100% effective. Alternative approaches are to augment the now deficient soft tissue over the exposed angle portion of the implant.

Talk to your surgeon who did the procedure. It’s possible that the implant was placed in the subperiosteal plane in which case the muscle was peeled off the bone surface to make room for the implant.Best, Mats Hagstrom MD