There are actually a series of exercises that really do help. I do believe it depends on your surgeon and what they do, but I too couldn't lift my arm past my waist. Now I really do have full range of motion, and that is after rads too. I was told to do passive exercises first. Using a broom just to get the arm used to that movement again then slowly I gained strength and could do it on my own. I did them twice to three times daily while walking my dog (I used his chuck it instead of a broom if I was at the park with him)

Don't give up. Some people do have a more difficult time of it but you'll never know the most you're capable of if you don't try.

Hugs.