There are many causes of shoulder pain, from osteoarthritis, to rheumatoid arthritis, bursitis, to polymyalgia rheumatica. Your provider can help you interpret and manage your pain.

If your shoulder is very painful, many people stop moving the shoulder past the pain point. The fascia becomes locked and you develop a frozen shoulder. This can be healed with physio, massage therapy, chiropractic therapy and/or home exercises.
Sit at your dining or kitchen table. Move your chair so that you face the window or wall and your body is at right angles to the table. You must sit so that the painful shoulder is next to the table. Your arm must be completely at the side of your body. You may have to move the chair away from the table so that you can slide your hand and arm across the table, supporting your arm as you stretch your arm in the direction where it hurts. Sliding motion with your hand and arm stretched at ninety degrees to your body. You can also use a wall for this, sliding up the wall.

The further the pain radiates from the site of injury, the more likely you are to have inflammation of your Fascia  Check out Step 3 

Consult your doctor first before following any program

It can be very painful to break up your fascia that is locking your joint

The Rotator cuff is a group of muscles around your shoulder.

Here is a link to exercises suggested by orthopedic surgeons for a rotator cuff injury that doesn’t require surgery. A physiotherapist can help with shoulder therapy.

For weak Trapezius muscles – big muscle going from the neck to the middle and top part of the shoulder blade, here are some exercises.