The biceps muscle has two attachments around the glenohumeral joint. The so-called short head is attached to the coracoid bone in front of the joint. Ruptures to the short head occur very seldom. The long biceps tendon is much thinner than the short one. It derives from the upper part of the glenohumeral joint and goes through the rotator cuff structure in a complicated manner. It is the long tendon of the biceps muscle which most often encounters various problems such as spontaneous ruptures.

In conjunction with rotator cuff problems, the biceps tendon may be frayed or tendinotic, i.e. it has permanent degenerative changes in its structure. A tendinotic tendon is painful and weak and a spontaneous rupture of the tendon may occur. The biceps tendon may also be unstable and even dislocate. The long tendon may rupture even with the slightest stress and a so-called Popeye shape forms on the biceps muscle. There may be a hematoma on the muscle and it is often prone to cramps. Treatment of a spontaneous biceps rupture is generally conservative, i.e. non-operative. The bruises and cramping disappear with time. The biceps muscle loses some of its strength but this strongly depends on the initial level of strength in the muscle. Later, the degree of strength is more or less a matter of exercise. The disability caused by a rupture in the long head of the biceps is considered minor.