The glenohumeral joint consists of the joint head, which is part of the humeral head, and the socket, which is located between the shoulder blade and the collarbone. The glenoid cavity is smaller than the articular head and therefore does not provide the necessary stability to keep the upper arm securely in the socket. For this reason, the joint is stabilized on the one hand by muscles that run around the upper arm and shoulder joint, and on the other hand by the so-called labrum.
The labrum is a joint lip that extends around the socket and thus gives the socket the necessary enlargement. The advantage is that the labrum does not have a fixed structure such as a bone, so that the upper arm has sufficient room to move in the socket. A muscle tendon is attached to the upper part of the joint lip, which is counted as a biceps muscle. Both structures are anatomically also called labrum-biceps complex. Injuries and damage to this complex are called slap lesions.
Cause of the SLAP lesion
The reason why a SLAP lesion is triggered can be acute or chronic. One of the chronic causes is overloading in the area of the shoulder joint. If excessive loads are carried or balanced or lifted over a long period of time, the entire shoulder joint, including the labrum-biceps complex, may be under such heavy strain that at some point a tear or tearing results.
In addition to chronic overloading, chronic incorrect loading can also lead to parts of the labrum-biceps complex being subjected to greater stress than other parts. This can also lead to cracks or tears. Some sports are also often mentioned as risk factors for slap lesions.
Usually these are bat-swinging sports, such as baseball, tennis or table tennis, which place a particularly heavy load on the shoulder area due to the constantly repeated arm movements. If acutely very heavy loads are carried (e.g. weight lifting for untrained persons), immediate tears or tears can also occur. The same can also happen in accidents. In this case, so-called high speed traumas, such as those that occur in car accidents or sports accidents, can be the main triggers for an acute slap lesion. If the shoulder is squeezed or twisted without braking, these acute slap lesions can occur.
