Is widening of AC shoulder joint dangerous?

Not dangerous but. May point 2 a separated shoulder of low grade. Was this compared 2 the opposite side? They may both b the same. Injury? A lot missing here as far as info is concerned. C an ortho if it is painful, was injury, and b sure the other side is on the same film plain ; holding weights in each hand, both taken while standing.
AC SEPARATION. Typically an AC JOINT separation can be treated conservatively when it is only a type 2 or 3. Treatment consists of therapy to regain motion after a short period in a sling. If pain persists or you have pain with activities then sometimes surgical intervention is warranted. Consult an Orthopaedic surgeon for a complete work up. Hope this information is helpful. Take care. Wilsonshoulder.com.