The shoulder (from the lower Latin spathula, meaning spatula) is the joint area connecting the upper limbs to the thorax.

Position. Bringing together the upper limbs of the thorax, the shoulders constitute the most mobile articular surfaces in the human body (1).

Bone structure. The shoulder is made up of three bones:

• The humerus which is the sole bone of the arm.
• The scapula, or shoulder blade, which is the bone located on the posterior and upper part of the thorax.
• The clavicle which is the bone located on the anterior and upper part of the thorax (2).

Joint complex. The articular complex of the shoulder is made up of three joints and two sliding spaces (2):

The scapulo-humeral joint is a spheroid joint and is the main joint of the shoulder. At this joint, the head of the humerus is inserted into the glenoid cavity of the scapula.

• The acromioclavicular joint is a joint with a flat surface uniting the lateral end of the clavicle and the acromion, a bony protrusion starting from the scapula.
• The sternoclavicular joint is the joint between the medial end of the collarbone and the upper part of the sternum, the manubrium. It also unites the first thoracic rib because the latter is attached to the manubrium.
• The scapulothoracic sliding space corresponds to several surfaces between the scapula and the thorax, allowing greater mobility of the shoulder.
• The subacromial sliding space corresponds to the space located under the acromion and above the humerus.

Many ligaments join and strengthen these joints.

Musculature. Many muscles are involved in the shoulder and fall into three groups (3):

• The posterior superficial thoraco-appendicular muscles are extrinsic muscles of the shoulder: the trapezius muscles and the latissimus dorsi muscle.
• The posterior deep thoracoappendicular muscles are also extrinsic muscles of the shoulder: the elevator scapular muscle, as well as the rhomboid large and small muscles.
• The scapulohumeral muscles are intrinsic muscles of the shoulder: the deltoid and teres major, as well as the rotator cuff muscles which are the supraspinatus, infraspinatus, scapularis and teres minor. The latter have an important role since they make it possible to stabilize the humeral head within the articular cavity of the scapula.

Mobility. Joints and sliding spaces provide great mobility to the shoulder and upper limb. The shoulder thus makes it possible to perform many movements, such as (2):

• anti-drive movements, bringing the upper limb up and forward with an amplitude of 180 °;
• feedback movements, bringing the upper limb down and back with an amplitude of 45 °;
• abduction movements, bringing the upper limb laterally with an amplitude of 180 °;
• adduction movements which are achievable only when the upper limb is brought to the front or rear of the thorax, with a low amplitude at the rear and 30-45 ° at the front.

Shoulder pain may occur. The causes are varied and can in particular be related to bones, joints, or muscles.

Bone fractures and pathologies. The various bones present in the shoulder can be fractured as a result of trauma. Certain bone diseases can increase this risk of fracture, such as osteoporosis (4).

Shoulder dislocation. This pathology corresponds to a loss of adhesion at the level of the articular surfaces.

Muscle pain without lesions. (5)

• Cramp. It corresponds to an involuntary, painful and temporary contraction of a muscle.
• Contracture. It is an involuntary, painful and permanent contraction of a muscle.

Muscle injury (5) The muscles of the shoulder may suffer muscle damage, accompanied by pain.

• Elongation. First stage of muscle damage, elongation corresponds to a stretching of the muscle caused by microtears and resulting in muscle disorganization.
• Breakdown. Second stage of muscle damage, the breakdown corresponds to a rupture of muscle fibers.
• Rupture. The last stage of muscle damage, it corresponds to a total rupture of a muscle.

Rotator cuff tendinopathies. They designate all the pathologies that can occur in the tendons of the muscles of the rotator cuff. (6) The causes of these pathologies can be varied. The origin can be intrinsic as well with genetic predispositions, as extrinsic, with for example bad positions during the practice of sport.

• Tendinitis: It is an inflammation of the tendons.

Drug treatments. Depending on the pathology diagnosed, certain drugs may be prescribed to reduce pain and inflammation.

Surgical treatment. Depending on the pathology diagnosed and its evolution, surgery may be necessary.

Physical treatment. Physical therapies, through specific exercise programs, can be prescribed such as physiotherapy or physiotherapy.

Physical examination. First, a clinical examination is performed in order to identify and assess the symptoms perceived by the patient.

Medical imaging exams. Depending on the suspected or proven pathology, additional examinations may be performed such as an X-ray, an ultrasound, a CT scan, an MRI, a scintigraphy or even a bone densitometry.

In the shoulder area, we often talk about rotator cuff injuries in top athletes. They are quite frequent and due to repetitive and sometimes violent movements in the shoulder.