Frozen shoulder can happen also in case of
diabetes if he is diabetic u need to work on controlling his diabetes through medications and diet modification.
As it is a frozen shoulder it will take around 3-6 months to gain shoulder mobility and pain reduction
Also along with frozen shoulder there can be other factors also like tendinitis or bursitis or any kind of impingement and in some cases cervical radiculopathy can also be associated with this
Next Steps
For pain reduction take hot packs painkillers Tens and ultrasound
To reduce pain and to gain mobility first work on pendulum exercise posterior capsule stretch and joint mobilization, shoulder ladder exercises alongwith neck and upper back exercises
Health Tips
avoid sleeping on the affected side
avoid heavy weights lifting
avoid forward bending of the neck