What are all the possible injuries that can occur to the rhomboid muscles?

The rhomboid area is in the upper back and can be injured or strained by poor posture,throwing,pulling,pushups,weight lifting,and repetitive motions.

The basic answer to what possible injuries can occur to a muscle is ... strain or tear. When you get a strain there can be bruising and swelling and possibly protective spasm/partial contraction of the muscle which leads to a painful muscle. The results of the tear are somewhat self-explanatory whereby that portion of the muscle is no longer capable of functioning.