Arm Pain after Breast Augmentation under arm scar? I am in week 4 post op and can barely stretch my arm, lots of pain.

As you recover, this may resolve itself. However, you should probably ask your surgeon if you can massage the area or do something else that will help expedite the process. 

This is one of the disadvantages of doing axillary incisions for augmentation - scar contracture in the axilla. In most cases this can be corrected or improves or time like 3 months.. But in other cases only a surgical release or steroidal injection can improve. Worse case there was entrapment of the nerves from the brachial plexus. Best to be followed closely til resolution.//

Scar tissue can develop between the incision and the chest tendons. Massaging the area and an-inflammatories (if okay with your surgeon) help to decrease this process as much as possible. Time is also the best medicine. Numbness or pain can radiate on the undersurface of the arm if the local nerves are pinched or swollen as well. Practicing range of motion in the arm will also be helpful. Hope that helps.