Bone marrow edema is excess collection of fluid that usually occurs in response to infection, inflammation or
injury. Thus it is seen in fractures, ligament injuries, bone bruises (
injury to bone without a fracture), synovitis (inflammation of the synovial membrane that lines the joints), osteoarthritis, osteoporosis, ischemia (decreased blood flow) and tumors.
If you had a MRI of the shoulder joint, then probably ligament injuries and fractures are ruled out.