Answer to Question 1
The anterior, superior, and posterior surfaces of the shoulder joint are reinforced by ligaments, muscles, and tendons, but the inferior capsule is poorly reinforced. As a result, a dislocation caused by an impact or a violent muscle contraction is most likely to occur at this site. Such a dislocation can tear the inferior capsular wall and the glenoid labrum.
Answer to Question 2
The triceps brachii attaches to the olecranon process. Contraction of the triceps brachii muscle causes the ulna to rotate around the distal humerus, causing extension of the forearm.