Am healthy. had slight upper back pain for 2 months. now have slight neck crepitus and occasional numbness of right arm in mornings. posture related?

No: Continue exercising and loosen up your mildly arthritic neck-possible from an old injury. Arm numbness may be from positioning of your arm at night -the exact problem depends on where the numbness is. Carpal tunnel will affect several but not all fingers. elbow nerve entrapment will affect the little finger side, vascular and nerve will affect larger areas.