There are three tests of function used by physical therapists that may help you chart your own progress. The first is the hand-to-neck test. Using a mirror, reach up with both hands and touch the back of your neck as if you were lying out under the stars with your hands behind your head.
Can you reach the neck? Touch the neck? Reach the middle of the back of the neck? Does the motion look the same on the ‘good’ side compared to your ‘bad’ side?
Next reach your good hand behind your back. Slide the hand as far up your spine as you can toward the shoulder blade. Do the same test with your involved side. Compare how far you can reach on the good side compared to the injured side.
For the last test, use your good hand to reach across the front of the body and place your hand on top of your opposite shoulder. Now slide the hand as far down the back as you can toward the shoulder blade. Switch hands and do the same thing with the other hand. Again, compare how far you can reach using your ‘good’ hand versus the hand on the side of your frozen shoulder.
You can measure progress in small increments using these tests. If you have a camera, have someone take photos of all three tests on both sides to help you compare.