Shoulder
Shoulder Impingement - Subacromial Impingement Syndrome
Five different joints contribute to the movements of your shoulder girdle: the glenohumeral joint, the acromioclavicular joint, the sternoclavicular joint, the subacromial gliding space, and the scapulothoracic gliding plane. This anatomical structure provides your shoulder girdle with a tremendous amount of mobility—though it also makes it much more susceptible to injuries and shoulder pain. To ensure that your biomechanical movements function optimally, your thoracic spine must also be freely movable in addition to the mechanics of your 5 shoulder joints.
Braus, Hermann, Braus 1921 148, marked as public domain, details on Wikimedia Commons
The anatomical structure of your shoulder joint
The glenohumeral joint (commonly referred to simply as the shoulder joint) consists of the humeral head (caput humeri) of the upper arm and the glenoid cavity (cavitas glenoidalis) on your shoulder blade. As a classic ball-and-socket joint, the glenohumeral joint is primarily responsible for the vast range of motion in your shoulder girdle.
The articular surface of the humeral head is three to four times larger than the surface of the glenoid cavity, which contributes to your shoulder's extensive mobility—though at the expense of stability. The fibrocartilaginous glenoid labrum on the edge of the socket works together with your entire capsuloligamentous apparatus to compensate for this incongruence and improve the stability of your shoulder joint. However, that stability is mainly provided by your strong shoulder muscles.
The acromion and the clavicle (collarbone) form the acromioclavicular joint. When you move your arm above shoulder height, your clavicle rotates around its own axis. Ligaments (the acromioclavicular, coracoacromial, and coracoclavicular ligaments) keep your acromioclavicular joint in position during the longitudinal and craniocaudal rotation of the clavicle.
The same applies to the sternoclavicular joint — formed by your clavicle and breastbone (sternum) — at the other end of your collarbone. In the sternoclavicular joint, there is an articular disc (similar to an intervertebral disc) to compensate for the incongruence between the joint surfaces of the clavicle and sternum.
After keeping your arm in a protective, resting posture for an extended period, adhesions can develop in the capsuloligamentous apparatus—affecting the ligaments of the acromioclavicular joint, the sternoclavicular joint, and the glenohumeral joint alike. This restricts your mobility and biomechanical movement. In the worst-case scenario, capsule adhesions or contracture over time can develop complications leading to a frozen shoulder, sometimes resulting in massive restrictions in your range of motion.
The scapulothoracic gliding plane and the subacromial gliding space are not true anatomical joints, but they play a crucial role in your shoulder biomechanics. The scapulothoracic gliding plane describes the movement of your shoulder blade (scapula) across your rib cage. Situated in between are your subscapularis and serratus anterior muscles. When shoulder problems occur, it often turns out that your scapula cannot be stabilized adequately against the rib cage, causing it to move prematurely during your arm movements.
The subacromial gliding space is the area between the acromion and the humeral head, containing two bursae between the acromion and your rotator cuff. Here, the rotator cuff—consisting of your infraspinatus, supraspinatus, subscapularis, and teres minor muscles—plays a central role. The rotator cuff is primarily responsible for centering your humeral head within the glenoid cavity. If one of these muscles becomes too weak, overloaded after an injury, or strained from repetitive movements, proper centering and natural biomechanics in your shoulder can no longer be maintained. Similar problems arise if you have calcification or thickening of your supraspinatus tendon, which runs directly through the subacromial space.
The supraspinatus muscle runs beneath your acromion, from the supraspinous fossa of your scapula to the humeral head. If the function of your supraspinatus is impaired, you will experience disruption during the initial phase of raising your arm to the side (abduction). Even more importantly, because of the external rotation function of your supraspinatus, it centers your humeral head posteriorly in the glenoid cavity. If this centering is lost, impingement occurs in the subacromial space, especially when lifting your arm out to the side: the humeral head slides upward (cranially) too quickly, and the greater tubercle of the humerus fails to rotate posteriorly in time, colliding with the acromion and pinching the structures within the subacromial space. Whenever you move your arm overhead, this faulty mechanic irritates the supraspinatus tendon, frequently causing the bursae and corresponding joint capsule to display signs of inflammation. Swelling then further narrows the already tight subacromial space, which understandably leads to additional trouble and pain. This clinical picture is known as shoulder impingement or subacromial impingement syndrome.
Braus, Hermann, Braus 1921 147, marked as public domain, details on Wikimedia Commons
Treating subacromial impingement syndrome – subacromial decompression: yes or no?
Subacromial decompression (acromioplasty) is a common minimally invasive surgical technique used for shoulder impingement syndrome.
The procedure usually takes about an hour and is performed under general anesthesia. Surgical instruments are inserted through small incisions in your skin (usually 3 incisions requiring about 2 stitches each). During the surgery, bone is shaved away from the underside of the acromion, and the bursa may be removed (bursectomy) to create more space in your subacromial gliding area and relieve the bottleneck. The surgeon will also repair any damage found on your tendons.
As we discussed in the article Meniscus injuries in the arthritic knee: arthroscopy yes or no?, here at BodyLab | Osteopathy and Physiotherapy | Rehabilitation and Training | Zurich, we always ask ourselves what real added value surgery offers you as a patient.
In a recently published review [1], 9 studies with a total of 1,014 patients aged 43 to 57 were examined regarding pain, joint function, Global Perceived Effect (GPE), and quality of life at 6 and 12 months postoperatively. The control groups in these studies consisted of active Physiotherapy (6 studies), placebo surgery (2 studies), laser therapy (1 study), bursectomy alone (1 study), and watchful waiting (1 study).
The following results were found for the evaluated outcomes:
*moderate evidence due to imprecise measurements
Acromioplasty has long been known as a widespread standard procedure for subacromial impingement. However, clear advantages over conservative therapy (exercise/training, Physiotherapy) have never been convincingly demonstrated in clinical studies.
What is new is that when comparing acromioplasty directly to placebo surgery, there is no significant difference in pain, joint function, or quality of life at 6 to 12–24 months postoperatively. Compared to active Physiotherapy, there is only a small, clinically insignificant difference in pain relief (moderate evidence) and slightly fewer persistent limitations in mobility/joint function (low evidence).
In conclusion, doctors, healthcare professionals, hospitals, and health insurers should reconsider using subacromial decompression as the default standard solution for shoulder impingement.
As physiotherapists and osteopaths, we advise you to weigh the pros and cons of surgery carefully and, whenever possible, start with a conservative approach first.
Conservative treatment options for shoulder impingement
The goal of conservative treatment in Physiotherapy or osteopathy is to restore the biomechanics of your shoulder girdle in subacromial or shoulder impingement syndrome, as well as to stabilize and strengthen your shoulder. Particularly in osteopathy, manual mobilization and manipulation techniques along with fascial and soft-tissue techniques are used to release the joints and muscles of your thoracic spine and shoulder girdle to relieve any pain you have and restore your mobility.
In Physiotherapy, following anti-inflammatory measures, the primary focus is on activating your rotator cuff to stabilize and center your glenohumeral joint. Moving forward, active exercises will help you relearn your scapulothoracic rhythm and actively stabilize your scapula against your rib cage.
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Find out more on our shoulder impingement page.
References
Lähdeoja T, Karjalainen T, Jokihaara J, et al.
British Journal of Sports Medicine Published Online First: 15 January 2019. doi: 10.1136/bjsports-2018-100486
Cover image credits
Henry Vandyke Carter creator QS:P170,Q955620 Henry Gray author QS:P170,Q40319, Gray326, marked as public domain, details on Wikimedia Commons
