What causes neck , sholder and back pain on left side?

Many causes: There are many things that can cause left neck, shoulder, and back pain including myofascial pain, muscle strain, whiplash, poor posture, muscle imbalances, rotator cuff strain/tears, arthritis of the neck, disc rupture in the neck, a pinched nerve, or even lung or heart problems. See a physiatrist or pain specialist to find the cause, and then you can customize an appropriate treatment.

Left side neck,shoul: left side neck, shoulder & back pain may be caused by cervical arthritis,disc or radiculopathy,coronary artery disease with angina,bursitis or rupture of biceps tendon, pe,subclavian artery blockage,injury of neck or left shoulder. Diagnosed by EKG,X-ray cervical spine & shoulder,MRIof nech & shoulder,cbcwith sed rate & arthritis profile,echocardiogram,stress echo,thallium stress test,cardiac cath