Anterior dislocation is the most common dislocation and usually happens when the patient falls or is hit on the shoulder when the arm is in overhead position as well as rotated outside. In this case the patient may feel a bony lump in the shoulder associated with pain. A posterior dislocation is an uncommon condition and may happen in patients who may fall over an inside rotated. Posterior dislocation is also common in patients with epileptic seizures and electric shock.