Which joint among the following is not a true synovial joint?

• A. Glenohumeral Joint
• B. Acromioclavicular Joint
• C. Scapulothoracic Joint
• D. Sternoclavicular Joint

Answer: (C)

The main idea is recognizing the difference between a true synovial joint and a functional articulation. A true synovial joint has a joint capsule with a synovial membrane and fluid, a space (synovial cavity) between articulating surfaces, articular cartilage on those surfaces, and reinforcing ligaments.

The shoulder ball-and-socket joint is a classic synovial joint with a capsule and synovial fluid, so it fits. The joint where the clavicle meets the acromion is a true synovial plane joint with a capsule and ligaments. The sternoclavicular joint is also a true synovial joint, typically described as saddle-shaped with a disc and capsule.

The scapulothoracic articulation is not a true synovial joint. There is no joint capsule or synovial cavity between the scapula and the thoracic wall; movement occurs as the scapula glides over the rib cage due to surrounding muscles and chest wall dynamics. Because it lacks a synovial lining and capsule, it’s considered a functional articulation rather than a true synovial joint.