Subacromial impingement syndrome: Pain and Weakness of the Arm and Shoulder Girdle

Pain and Weakness of the Arm and Shoulder Girdle, thats what the Subacromial impingement syndrome causes in every person. Causes of subacromial impingement. The process of redaptation in subacromial impingement syndrome.

This article intends to perform an exhaustive analysis of what the shoulder joint is, focusing on its anatomy, biomechanics, injury factors that most affect this joint and the most common injuries we can find, focusing on the subacromial impingement injury or impingement , which is one of the main lesions (along with rotator cuff tendinitis), both at sports and work level.

It also provides some basic concepts that should be taken into account when rehabilitating this lesion.

An important aspect when tackling subacromial impingement is the readaptation phase, in which a series of basic criteria must be followed, such as the restoration of force to optimal levels or the search for asymmetry reduction, both in the injured structure and at the global level, in order to achieve a return to the sport activity in the most optimal way possible and with the highest safety that can be sought for the sportsman.

Currently, the process of rehabilitation of injuries is a value to the rise in both the sports world and daily life, because in different centers, they treat this phase of the subacromial impingement injury in greater measure.

Anatomy and biomechanics of the shoulder


The joint complex of the shoulder is composed of 5 joints. Three are considered true:

• Sternoclavicular joint.

• Acromioclavicular joint: held in place by the acromioclavicular, coracoacromial and coracoclavicular ligaments.

• Glenohumeral joint.

And two of the joints are considered false:

• Subacromial (or subcltoidea) joint: slip cavity of synovial sacs between shoulder roof and rotator cuff.

• Scapulothoracic joint..

In figure one, the deepest anotomy of the glenohumeral joint is found. This joint, which is considered of greater importance in subacromial pinch injury, is classified as a diarthrosis, specifically anarthrosis.

The head of the humerus and the glenoid cavity of the scapula articulate in the form of a spheroidal joint.

Because the head of the humerus is round and convex, and the surface of the glenoid fossa is concave and shallow, it is an incongruous joint, for this the labrum or glenoid impost increases the joint surface and concavity of the fossa.

In figure two, the ligamentous anatomy is found. The capsule and ligaments reinforce the glenohumeral joint.

The capsule attaches around the glenoid rim and forms a cuff around the head of the humerus. It is a lax structure, reinforced anteriorly and posteriorly by ligaments and muscles. Coracohumeral ligaments are the strongest supporting ligaments of the glenohumeral joint.

In figure three, the anatomy of the synovial sacs is found. Between the supporting ligaments and the rotator cuff muscles are the synovial, subacromial, and subdeltoid sacs that allow frictionless sliding of the humeral head and rotator cuff tendon insertions under the roof of the shoulder while the abduction and elevation of the arm is performed.

As for musculature, it is named in figure four and later, when speaking of biomechanics, will be specified in which actions intervene.

With regard to musculature, the rotator cuff is given greater importance, which is formed by the supraspinatus, subscapular, infraspinatus and minor round muscles.


Regarding the section of biomechanics, we try to capture the different movements that occur in the shoulder, while analyzing which structures are involved in each movement (mainly musculature, both the different muscles of the shoulder and the muscles of other areas involved in movements), in order to clearly identify which elements should be affected, depending on the type of pathology to be faced.

According to Llinares, Gisbert, & Espa (7) and focusing on the biomechanics of the glenohumeral joint and the rotator cuff: "A remarkable feature of the glenohumeral joint is that it has great mobility on all axes.

The stability of a joint is provided by both bone and soft tissues (ligaments, muscles and tendons) .The shoulder bone stability is very poor because the humeral head is rounded and the almost flat glenoid and much smaller surface area.

The joint stability of the shoulder is almost completely provided by the strength of the muscle-tendon and ligamentous structures

With respect to biomechanics, the movements that we find in the shoulder and the structures that intervene are:

Flexion: 0-180 ° (from 90 ° onwards the cscapulothoracic intervenes).

Extension: 0-90 ° (from 45 ° the cscapulothoracic intervenes).

Abduction (abd): 0-180 ° (from 90 ° onwards acromioclavicular and cscapulothoracic intervenes).

External rotation (re): 0-50 ° (the scapular intervenes).

Internal Rotation (Rl): 0-90 ° (the scapulohumeral and cscapulothoracic intervenes). Flexion: Participate in the anterior fascia of the Deltoid, Pectoralis major. Serrato major, Subcyscapular and Pectoralis minor.

Extension: Participate posterior Deltoid Fasciculus, Infraspinatus, Lesser Round, Trapezius, Supraspinatus, Greater Round and Rhomboids.

Internal Rotation (Rl): They act Wide Dorsal, Infraspinous, Round Greater, Pcctoral major and Subcapular.

External rotation (re): They act Infraspinous and Redondo minor.

Abduction (abd) 0-90 °: Scapulohumeral joint. Deltoid and Supraspinous Muscles. The supraspinatus is not indispensable for ABD, not even for the beginning of it.

or 60-120 °: Escapulohumeral and cscapulothoracic articulation. Trapccio and Serrato major muscles.

Do not forget that the scapula fixations are due to this antagonistic partner. So the trapccio is responsible for the bindings in ADD and the serratus of the bindings in ABD.

Both the wide dorsal and the major dorsal can limit ABD movement. or 120-180 °: Scapulohumeral, cscapulothoracic or trunk inclination to the opposite side. Trapccio and Serrato major muscles.

• Adduction (add): Always with slight flexion. 20-40Â °. Muscles Dorsal width, Pcctoral major, Round Greater.

• Circunduction: This movement encompasses all previously seen, so the muscles involved, are the same as those of previous actions.

Risk factors for subacromial impingement

When reviewing the different bibliographic sources, referring to the concept of sports injury, one can find that there is a classification that predominates over all others, which differentiates between intrinsic risk factors and extrinsic risk factors, which is found in figure six.

Meeuwisse (1994) developed a model that considers all the factors involved. As summarized in the following figure (2), although an injury can occur from a single cause, it can result from a complex interaction between internal and external risk factors.

However, in observing this model, it is appropriate to affirm that the readapter, where it can mainly affect, is mainly in the intrinsic risk factors since, hardly, it can have some control to everything that is external to the athlete.

Causes of subacromial impingement

With regard to the causes of subacromial impingement. Gil, Cañadas, & Antón (3) make a more generic relation of the different factors that favor the appearance of an injury, emphasizing as the most frequent the following:

• Lack of basic knowledge about the sport being practiced.

• Lack of training.

• Inequality and / or lack of mastery of the technique.

• Insufficient or improper heating.

• Overconfidence.

• Age for sports.

• Poor postural hygiene.

• Unsuitable sports gestures.

• The weather (extreme temperatures).

• Poor nutrition and / or nutrition.

• Lack of sleep or fatigue.

• Inadequate training.

• Lack of respect for the rules of the game.

• Return to sports practice without recovering from a previous injury.

But it is necessary to specify something more about the causes that produce a tendon injury.

The tendons are structures that transmit and absorb forces, have a direct insertion in the bone and in turn a great resistance that hinders its pulling in this insertion and its fibers are mostly collagenous, although we can also find elastic fibers.

Among the causes of tendon injury (which can be seen in Figure 7), a normal tendon or pathological tendon should be differentiated (3):

• Normal Tendon: It is produced mainly by an excess of eccentric-centric traction.

Aging increases stiffness of the tendons, precarious vascularization also helps in certain areas.

• Pathological Tendon: With respect to the most common pathologies, the syndrome of overload, ie, excessive overuse of tendons, can be found, from which the different causes can be deduced, as shown in the previous figure.

Types of Shoulder Injuries: Subacromial Impingement as One of the Major Lesions

After reading several authors (Bahr & Maehlum, 2007, Gil et al., 2006, Guerrero & Pérez, 2005, Pastrana, 2007, Pérez Ares, Saínz, & Varas, 2004) types of classifications, the first focusing on a more general concept of the types of injuries to the shoulder, while in the second classification we see how lesions are more specifically established, referring to specific sports, for example , swimming, where the swimmer's shoulder injury is located.

But, in this case, we will use the classification of shoulder injuries performed by Rodríguez & Gusí (2002), but eliminating some of the injuries that they include:

• Shoulder dislocation.

• Unstable shoulder (subluxation).

• Acromioclavicular dislocation.

• Cstcrnoclavicular luxation.

• Supraspinous tendon rupture.

• Supraspinatus tendinitis.

• Subacromial compression or pinch syndrome.

Regarding the types that can be observed in this classification, this article is mainly focused on the well-known subacromial compression-impingement syndrome (figure eight). After consulting different authors (6,7,12,13,14) we can affirm that impingement or subacromial impingement can occur in two ways:

• Primary: Subacromial impingement is caused by a narrowing of the subacromial space or coracoacromial arch due to multiple causes such as: combination of repeated activities above the humeral head, vicious consolidation or pseudoarthrosis after a fracture of the acromion, and acromioclavicular separation or degeneration with the appearance of inferior osteophytes.

This narrowing, which generates the mechanical compression between the tendon and the arch.

• Secondary: In this case the narrowing is relative and can be due to glenohumeral instability, congenital laxity, impotent rupture, rupture of the rotator cuff, glenohumeral capsular rigidity.

Stages by Noer (1972)

In the clinic there are three phases called "Stages of Neer" (1972):

Stage 1: edema and inflammation of the supraspinatus tendon. It is a recurrent lesion that presents pain on the front and side of the shoulder, and increases at night.

Tendinopathy of one or more tendons of the rotator cuff of the shoulder is observed, the tendon of the supraspinatus muscle being the most affected after a beginning.

There is a painful arch between the 70-120 ° of abduction, in these cases there is no thickening and there are no signs of rupture in radiological tests (> 25 years, with overuse of the joint).

Stage 2: fibrosis and thickening of tendons and bursa. In this phase the thickened subacromial serous pouch can be found, which increases the compression of the rotator cuff and reduces its friction index with the acromial roof (acromion floor and eoraeo-acromial ligament).

We find crepitation, limiting the mobility signs of microroturas of the fibrous cuff. The most intense pain that occurs mainly at night, but I can appear during the day sporadically and conditioned by movements of lifting and abduction of the shoulder (25-40 years).

Stage 3: rupture of the cuff. In this phase, partial fractures of the rotator cuff are found.

A partial or total tear of one of the deliveries that make up the rotator cuff is observed at the radiological level.

The supraspinatus tendon (the tendon most commonly affected within this tendon complex) is usually the most affected. Two breaks are distinguished: acute and chronic.

Acute breaks are caused by trauma (such as a fall on the shoulder) or lifting a specific weight.

These ruptures are sudden, they are preceded by a sharp, intense and persistent pain and do not have to be preceded by a previous tendinopathy nor by the previous phases.

The chronic or slow evolutionary breaks are micro breaks that are generated with the passage of time and that are gradually tearing; is usually preceded by chronic pain that the subject tolerates with analgesics and anti-inflammatory.

In both cases, the subject will feel weak or impotent when flexing or abducting the shoulder. Chronic ruptures are caused by degeneration and micro-trauma of the cuff (> 40 years).

The process of redaptation in subacromial impingement syndrome

The process of rehabilitation of the subacromial impingement injury is established after the rehabilitation phase, and aims to restore the optimal conditions for the athlete to return to the sport practice in the safest possible way, ensuring that the pathology or other different. This process is divided into different points:

• Working motor control: Seeking the athlete to purify different aspects of coordination of movement and sports gesture.

• Search for optimal levels of strength: These levels, not only refer to high values ​​of strength, but to look for strength and strength to become applicable in sports gesture or work activity.

In addition, not only should I seek improvement of strength, but I must establish what type of work to use depending on the phase of rehabilitation in which we are and taking into account the state of the athlete.

• Elimination of asymmetries: Asymmetry should be sought at the local level (asymmetry between concentric and eccentric contraction) and at the global level (asymmetry between one body hemisphere and another) as both types of asymmetry are determinants of recovery and possible occurrence of different pathologies.

• Proprioception work: At present, the term propiocopción has been divided into several concepts, encompassing the work of sensitization of the affected area, proximal stability, rebalancing of the damaged structure, and coordination of the specific sports gesture.


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