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The scapula, or shoulder blade, can move in many directions, including protraction, retraction, elevation, depression, anterior/posterior tilt, and internal/external and upward/downward rotation. This movement is produced by specific, primary muscles. Scapular dyskinesis, a dysfunction in scapular movement, is characterised by a lack of upward rotation, a lack of posterior tilting, and increased internal or medial rotation of the scapula. This can lead to shoulder dysfunction. The serratus anterior, for example, pulls the scapula into protraction, medial and upwards rotation, as well as posterior tilt. The levator scapulae elevates the scapula and tilts the glenoid cavity inferiorly by rotating the scapula downward. The pectoralis minor is also associated with scapular tilt, as tightness of this muscle can cause increased internal rotation and anterior tilting of the scapula.
| Characteristics | Values |
|---|---|
| Muscles controlling scapular tilt | Levator scapulae, Serratus Anterior, Inferior Trapezius, Middle Trapezius, Upper Trapezius, Pectoralis Minor |
| Scapular movement | Protraction, Retraction, Elevation, Depression, Anterior/Posterior tilt, Internal/External rotation, Upward/Downward rotation |
| Scapular Dyskinesis characteristics | Lack of upward rotation, Lack of posterior tilting, Increased internal or medial rotation |
| Treatment for scapular dyskinesis | Stretching, Manual therapy, Strengthening exercises, Shoulder brace or taping |
| Rounded shoulder posture characteristics | Protraction, Downward rotation, Anterior tilting, Internal rotation |
| Rounded shoulder posture treatment | Stretching, Strengthening exercises, Shoulder brace or taping |
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What You'll Learn
The role of the levator scapulae
The levator scapulae is a long and slender muscle that is a part of the superficial layer of extrinsic muscles of the back. It is one of the muscles within the floor of the posterior triangle of the neck. The superior part of the levator scapulae is covered by the sternocleidomastoid, while its inferior part is covered by the trapezius. The spinal accessory nerve crosses the muscle laterally, and the dorsal scapular nerve may lie deep to or pass through it.
The levator scapulae muscle extends from the transverse processes of vertebrae C1-C4 to the medial border of the scapula. The muscle fibres descend laterally to insert at the superior angle and medial border of the scapula, between the superior angle and base of the spine of the scapula.
The main function of the levator scapulae is to elevate the scapula and tilt the glenoid cavity inferiorly by rotating the scapula downward. When the spine is fixed, the levator scapulae elevates the scapula and rotates its inferior angle medially. It often works in combination with other muscles like the rhomboids and pectoralis minor to produce downward rotation of the scapula. When the scapula is fixed, a contraction of the levator scapulae leads to the lateral flexion of the cervical vertebral column to the side and stabilizes the vertebral column during rotation.
The levator scapulae is innervated by the anterior rami of spinal nerves C3 and C4 and the dorsal scapular nerve (C5), a branch of the brachial plexus. The vertebral portion of the muscle is supplied by the vertebral artery.
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Pectoralis minor and shoulder movement
The pectoralis minor is a muscle that can cause pain in the front of the shoulder and arm, and may also affect posture. It originates from the third, fourth, and fifth ribs near their costal cartilages and inserts at the coracoid process of the scapula. Its main nerve supply is from the medial pectoral nerves (C8, T1). The pectoralis minor muscle pulls the coracoid process anteriorly and downward, producing a protracted shoulder position.
A shortened pectoralis minor restricts flexion of the shoulder joint by limiting scapular rotation and preventing the glenoid cavity from attaining the cranial orientation necessary for complete flexion of the joint. This can result in pain and/or restriction in neck movements, stiffness and pain in the upper back, and an increased risk of rotator cuff pathologies. It can also cause "winging" of the scapula, or prominence of the medial border of the scapula with anterior tilting, together with prominence of the inferior angle and depression of the coracoid process.
Tightness or adaptive shortening of the pectoralis minor can inhibit activation of opposing muscle groups. It is common to find tightness of the pectoralis minor in patients with scapular dyskinesis. Scapular dyskinesis is generally characterized by a lack of upward rotation, a lack of posterior tilting, and increased internal or medial rotation of the scapula. To treat scapular dyskinesis, manual therapy and stretching of tight structures can be employed early in the rehabilitative process.
Specific exercises that target the pectoralis muscle group, such as chest dips and chest press, can help to release and lengthen the pectoralis minor muscle. It is important to have adequate strength to maintain good posture and prevent further injury. Once normal flexibility has been achieved, a conscious motor control-strengthening program can be initiated to help normalize the scapular resting posture.
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Serratus anterior and scapular position
The serratus anterior (SA) is a fan-shaped muscle that originates on the superolateral surfaces of the first to eighth or ninth ribs at the lateral wall of the thorax. Its main part lies deep under the scapula and the pectoral muscles. It is also known as the "boxer's muscle" as it is largely responsible for the protraction of the scapula, which occurs when throwing a punch. The main actions are protraction and upward rotation of the scapulothoracic joint. It is a key scapular stabiliser, keeping the shoulder blades against the ribcage when at rest and during movement.
The contraction of the entire serratus anterior leads to an anterolateral movement of the scapula along the ribs. Due to the pull of the inferior part at the lower scapula, the shoulder joint is shifted superiorly. This shifting now enables the arm to be lifted above 90 degrees (elevation). In contrast, the superior part depresses the scapula and thus acts antagonistically. Another function of the serratus anterior is the active stabilisation of the scapula within the shoulder.
The serratus anterior is associated with painful shoulder conditions. Lack of control, strength, or activation of this important muscle is believed to be associated with several painful conditions involving the shoulder complex. Weakness of the serratus anterior leads to an altered line of pull of the rotator cuff muscle, which could increase the risk of subacromial impingement syndrome.
Tests for serratus anterior weakness include the shoulder abduction test, where the examiner simultaneously resists maximal-effort scapular plane abduction and upward rotation of the scapula. A second method of testing the strength of the SA applies manual resistance against protraction of the scapula and the entire upper extremity. This test can be performed with the patient supine or sitting, with the shoulder flexed to about 90-100 degrees and the elbow held in full extension. In cases of a weakened SA, the scapula is unnaturally "pushed" by the examiner into a position of retraction and internal rotation, causing the medial border of the scapula to flare away from the rib cage. The resulting distorted position of the scapula is often referred to generically as scapular "winging".
Exercises that target the activation of the serratus anterior include the towel-wall slide, serratus punches, and push-up plus performed on hands and toes.
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Trapezius and scapular posterior tilt
The scapula, or shoulder blade, is the bone that sits above the rib cage in the upper back. It facilitates the shoulder joint where it meets the head of the humerus, the bone of the upper arm. The scapula can move in six directions, each produced by specific primary muscles.
The levator scapulae, serratus anterior, and trapezius muscles all play a role in scapular tilt. The levator scapulae elevates the scapula and tilts the glenoid cavity by rotating the scapula downward. The serratus anterior and trapezius muscles work in tandem to produce scapular posterior tilt and upward rotation. If these muscles are not properly co-activated, the scapula will be pulled into downward and/or anterior rotations.
The trapezius muscle has three parts: upper, middle, and lower. The lower trapezius (LT) is responsible for scapular adduction and depression, along with other scapular muscles such as the middle trapezius (MT), rhomboid, levator scapulae, and latissimus dorsi. The LT and serratus anterior are the primary muscles responsible for scapular posterior tilt.
Few studies have explored the effects of scapular posterior tilt on LT activation. One study examined the EMG activity of the UT, MT, and LT during prone shoulder horizontal abduction (PSHA) with and without the intended scapular posterior tilt. The results indicated that LT muscle activity increased when scapular posterior tilt was applied, with and without trunk extension, compared to the preferred condition. This suggests that scapular posterior tilt may be a useful strategy for selective LT muscle activation.
Scapular posterior tilting exercises have been proposed as a method for rehabilitating and correcting round-shoulder posture (RSP), a common postural condition characterized by scapular protraction, downward rotation, and anterior tilting. These exercises have been studied in both men and women with RSP, comparing EMG activities of the lower trapezius and serratus anterior muscles during SPT exercises on different support surfaces.
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Dyskinesia and scapular stabilisation
Scapular dyskinesia (SD) is a physical impairment that affects the position and motion of the scapula. It is characterised by a loss of normal range of motion in the shoulder blades, causing them to stick out abnormally during rest or activity. This condition is also called winging because the shoulder blades stick out like wings on the back. While the condition itself may not be painful, it can increase the risk of injury.
The serratus anterior and trapezius muscles play a key role in scapular stabilisation. They act as a force couple during upper extremity movements and are particularly important in the overhead position. These muscles are also the main ones that cause dyskinesia, so they should be considered during rehabilitation.
The levator scapulae function to elevate the scapula and tilt the glenoid cavity inferiorly by rotating the scapula downward. Exercises used to strengthen the rotator cuff and scapulothoracic musculature are also effective in eliciting activity of the levator scapulae.
The treatment of SD aims at the restoration of scapular retraction, posterior tilt, and external rotation. Specific exercises for scapular rehabilitation include flexibility exercises to increase the flexibility of the pectoralis minor and the external rotation and posterior tilt of the scapula, such as shoulder horizontal abduction at 90 degrees and 150 degrees of elevation.
To determine the role of scapular position in shoulder pain, two tests that apply manual assistance to the scapula are The Scapular Assistance Test (SAT) and The Scapular Reposition (Retraction) Test (SRT). In the SAT, the patient is asked to do arm flexion or abduction and rate their pain on a scale. The examiner then facilitates upward rotation by pushing upward and laterally on the inferior angle, and pulls the superior aspect of the scapula to produce posterior tilt. If two or more points of pain decrease after assisted movement, the test is positive, suggesting that scapular dyskinesia influences the patient's pain.
Most cases of scapular dyskinesia are improved through physical therapy or rehabilitation with a qualified physical therapist or athletic trainer. Therapy typically lasts 4 to 8 weeks and includes exercises to restore range of motion and strengthen the surrounding muscles.
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Frequently asked questions
Scapular dyskinesis is a condition characterised by a lack of upward rotation, a lack of posterior tilting, and increased internal or medial rotation of the scapula.
The levator scapulae, serratus anterior, and trapezius muscles all play a role in scapular tilt.
The levator scapulae elevates the scapula and tilts the glenoid cavity by rotating the scapula downward.
The serratus anterior pulls the scapula into protraction, medial and upward rotation, as well as posterior tilt.
The trapezius muscle is involved in scapular posterior tilt exercises, with the lower trapezius playing a major role in SPT exercises.
