thanks for writng to HCM,
your problem seems to be a combination of many factors firstly cervical spondylosis
as mentioned that you have arthritis
of your neck (if not yet medically diagnosed go for an X-ray cervical spine
- AP& LAT view), repetitive strain of traps and SCM and thus spasm of the same muscles which could be impinging on the nerves coming down in the arms, excessive stretching can also be a factor, bad posture, weakness of neck and scapular muscles and core muscles, stiffness
in scapular movements.
all of this can be diagnosed and ruled out by doing a detailed clinical examination and a X ray
for the treatment-
firstly relax your neck and scapular muscles by using heat therapy
, followed by intermittent cervical traction and then based on your clinical examination stretch only those muscles which are tight and strengthen the weak muscles. include all the muscles of neck and scapula. i would also suggest you to work on your abdominals and back extensors they will help you main good posture.
for the above take the help of a physical therapist.
if you have history of recurrent shoulder dislocation kindly find out the cause for that - either weak muscles or some lesion in the joint. (for this take the help of your orthopedic specialist)
i hope this helps
wish you speedy recovery