It can be. Besides the place where the bones meet to form the shoulder joint, there are ligaments, tendons, and cartilage that could be injured. Sometimes the rim around the socket side of the joint gets torn. This is called a labral tear. They are very hard to diagnose accurately.
Above the shoulder is the acromioclavicular (AC) joint where the collarbone (clavicle) meets the acromion from the shoulder blade. The coracoacromial ligament passes from the acromion to the coracoid process and crosses in front of the shoulder joint. Injury to this ligament can also seem like a true shoulder problem.
Each part of the soft tissue structures has one or more tests that are positive when an injury occurs. A physical exam helps narrow down the choices. This can save money when it comes time to decide if imaging studies are needed and which one(s) is best.
A recent study of tests for the AC joint report two tests are 99 percent accurate for AC injury when positive. These are the Paxinos test (pressing the acromion and clavicle together) and a bone scan. More studies will help us narrow down testing choices and streamline future exams.