Function
The deltoid muscle (Musculus deltoideus) becomes the most important lifter of the arm through the middle section coming from the shoulder blade. The deltoid muscle allows the arm to move in all directions (dimensions). Key blade portion (pars clavicularis): Shoulder roof portion (pars acromialis): Rear portion (pars spinalis): Information on all movement forms can be found here in an overview of movement forms
- Lifting (anteversion) from arm
- Spreading (adduction) of the arm
- Internal rotation of the arm
- Abduction (abduction) from the arm
- Abduction (abduction) from the arm
- External rotation of the arm
- Lifting back (retroversion) from the arm
Strain
Strains, also called distensions, are excessive muscle stretches that are usually caused by a sudden overload of a muscle. Typically, jerky movements, such as sudden stops or changes of direction, lead to strain. In this case the muscle tissue is overstretched but remains intact, in contrast to a torn muscle fibre or torn muscle.
Strains can be very painful, but usually heal by themselves. This can take up to several weeks depending on the severity of the injury, but the symptoms usually disappear after a few days. Strains can theoretically be contracted in any muscle, including the deltoid muscle, for example when lifting too much weight, e.g. when pressing on a bench.
Symptoms of strain
The main symptom of a pulled muscle is a sudden, initially stabbing pain in the affected muscle, which persists for several days if the muscle is strained. This leads to oedema formation, which means water leaks from the vessels into the surrounding tissue. This phenomenon is perceived as swelling.
In the case of a severe strain, a bruise can also form in the surrounding tissue, which can cause further pain due to the pressure on neighbouring structures. In addition, pain can also be caused by chronic overloading or incorrect loading, especially in the case of relieving postures taken as a result of other shoulder injuries. The starting point of the deltoid muscle on the humerus is a so-called trigger point. This means that pressure on this point triggers pain in almost all forms of shoulder complaints. This point is therefore unsuitable for diagnosis as it is very unspecific, but it should be taken into account during therapy.
Pain, injuries and their causes
Injuries to the deltoid muscle are very rare and almost always traumatic in nature. Nevertheless, pain can be caused by overloading, for example, the rear part of the muscle is particularly stressed when swimming with dolphins. In addition, pain can manifest itself mainly in the anterior deltoid muscle, the cause of which is not in this muscle itself but in other muscles of the shoulder joint.
The tendon of the supraspinatus muscle, a muscle of the rotator cuff, is often thickened or inflamed. Pain occurs particularly when the arm is abducted between 60 and 120°. This is because the tendon becomes trapped between the acromion and the humerus when the arm is abducted at this angle.
This symptomatology is referred to as “painful arc” or impingement syndrome. The deltoid muscle is not necessarily involved, but its tension is increased by reflection, which can result in pain. Furthermore, there is a potential for injury not only to the muscle but also to its nerve, the axillary nerve.
This can happen, for example, through bicycle or motorcycle accidents or through fracture of the humerus in the area of the Collum Chirurgicum, since the N. axillaris wraps itself around the humerus at this point. Such damage leads to movement restrictions in the affected arm and shoulder girdle as well as to sensory disturbances in these areas. In addition, atrophy of the deltoid muscle occurs over a longer period of time. Atrophy is a perceptible loss of tissue.
