A joint is a point where two or more bones come together. The shoulder joint is the body's most movable joint. Because this is the most likely thing to come off. Dislocation occurs when the top of the joint (the rounded top of the humerus) is pulled out of its socket There are two types of slippage. Non-accidental and non-accidental types, which often occur in teenagers with loose joints. The accidental type is usually a sports injury or in combination with overwork.