The shoulder is a ball and socket type of joint and anatomically referred to as gleno humeral joint, the two bony structures involved. The socket is the glenoid cavity, a cup-shaped piece of bone that juts out from a corner of the shoulder blade (scapula).

The rim of the glenoid is formed by cartilage called the labrum. The ball that fits into the socket is the head of the humerus. The upper (superior) part of the labrum anchors one of the two tendons of the biceps muscle.

The feature that makes SLAP possible is the way the upper biceps tendon hooks over the head of the humerus. If the arm is forcefully bent inward and twists at the shoulder, the humeral head acts as a lever and tears the biceps tendon and labrum cartilage from the glenoid bone in a front-to-back (anterior-posterior) direction. And that is how the name SLAP is derived – Superior Labrum Anterior-Posterior or, in plain English, Upper Rim Front-Back

Causes
Often an initial forceful movement of the labrum attached to the biceps tendon to be torn away from the bone (glenoid). This may be associated with a dislocation of the joint, but commonly occurs in sportsmen with a pull on the arm, weightlifting, throwing injury or tackle. If the initial condition does not heal properly, pain will result and worsen over time.

The typical symptoms are pain at the top of the shoulder, clicking and pain with overhead activities. These may be confused with Acromioclavicular Joint problems, but athletes with SLAP tears have pain with biceps loading (such as going down in a bench press). Acromioclavicular Joint pain is usually felt when pressing out at the end of a shoulder or bench press.

Prevention
Strong shoulder muscles remain the best defence against shoulder injuries. Exercises that build up these muscles around the shoulder should be done. Adequate warm-up before activity and avoidance of high-contact sports will help prevent of an instability-causing injury.
Taking painkillers and/or anti-inflammatory tablets may help and also you may try physiotherapy.