Hello, if it is a 6 weeks post operative, you can start lateral rotation gradually, but if you have stiffness, consult a physiotherapist and get mobilization technique done and start exercises. You'll have weakness around the shoulder joint. Need to be strengthened.

6 weeks post op shoulder needs to have a passive mobilisation done by a therapist.  you may start with active and assisted movements using the other arm for now to begin with.  use the arm for smaller activities, to ensure stiffness doesn't set in.  start with shoulder elbow and wrist movement to maintain range of motion in the other associated joints of the arm.