Causes ofshoulder painand weakness can vary in both younger and older people.
They include shoulder impingement, rotator cuff tears, and shoulder inflammation.
Impingement is often because of the repeated, overhead motion of the arm.

Barry Austin / Getty Images
These structures together help lift the arm and perform overhead tasks.
Arotator cuff tearcan be the result of sudden injury or microabrasions sparked by ongoing inflammation.
If left untreated, a person’s range of motion and strength can be permanently affected.
It can also be triggered by a condition called brachial neuritis, which is inflammation of certain nerves.
While many of the symptoms of these conditions are similar, they have differences, as well.
In shoulder injuries, weakness is not entirely because of the inflammation itself.
The appearance of symptoms tends to be gradual rather than immediate.
The pain is localized around the outside of the shoulder.
There may also be swelling, tenderness, and excessive warmth at the site.
Shoulder clicking is common, often more so when you reach behind your head or back.
Pain can be felt when raising your arm above your shoulder or sleeping on the shoulder itself.
As tendonitis progresses, the pain can become more persistent and severe.
Persons with shoulder tendonitis may also experience weakness, swelling, tenderness, and loss of range of motion.
Mitchell C, Adebajo A, Hay E, Carr A.Shoulder pain: diagnosis and management in primary care.BMJ.
2017;114(45):765776. doi:10.3238/arztebl.2017.0765
MedlinePlus.Rotator cuff injuries.
2015;29(3):405423. doi:10.1016/j.berh.2015.04.001
Johns Hopkins Medicine.Shoulder bursitis.
Johns Hopkins Medicine.Shoulder tendonitis.
National Organization for Rare Disorders.Parsonage Turner syndrome.
American Academy of Orthopedic Surgeons.
OrthoInfo.Shoulder pain and common shoulder problems.