“This sharp pain in the front of my shoulder will not go away!” This is a common cry for many who have been diagnosed with shoulder impingement. Impingement can be a nagging injury that drags on for months without the proper treatment. This does not have to be the case; however, since medicine is quite effective at limiting the ill effects of this pathology. It is important to understand how the shoulder, rotator cuff, and scapula work in unison for upper extremity function in order to properly treat impingement.
Shoulder Anatomy 101
The human shoulder is an amazing structure built for mobility but strong enough to lift our bodies and throw a baseball 100 miles per hour. The bony anatomy of the shoulder consists of the head of the humerus (the ball), the scapula or shoulder blade containing the glenoid fossa (the socket), and the clavicle (the collar bone).
Surprisingly, those are the only primary bones that control the shoulder. The only bone to connect the actual shoulder joint to the axial skeleton is the clavicle. That is why when you fracture your collar bone you need to where a sling since, besides the muscles, there is no bony anatomy holding the shoulder to the skeleton.
The Shoulder Muscles
In order to lift, press, pull, and throw we need strong muscles surrounding the shoulder to keep it stable and to produce force. In an effort to keep this simple I will provide brief descriptions and pictures. The infamous rotator cuff is a group of four muscles and tendons that surround the shoulder. These muscles are called the supraspinatus, infraspinatus, subscapularis, and teres minor. The primary role of the rotator cuff is to keep the ball, or head, of the humerus stable within the glenoid. The rotator cuff also functions to lift and rotate the arm. These are not large muscles but they perform a vital role.
The next layer of muscles consist of the deltoid (anterior, middle, and posterior), the upper trapezius, middle trapezius, lower trapezius, pectoralis minor, levator scapulae, and serratus anterior. This is not an exhaustive list but rather a functional list for brevity sake.
The deltoid: A very strong set of muscles that add compression to the shoulder joint but allow heavy lifting, pushing, and pulling
The trapezius: The upper trapezius lifts the shoulder to the ear, the middle trapezius brings your shoulder blades together, and the lower trapezius depresses your shoulder blade.
The serratus anterior: Helps to spin the shoulder blade in order to lift the arm overhead.
The Partnership Between the Scapula and Arm
If you have ever had rotator cuff impingement or shoulder surgery you understand that lifting the arm overhead is something we take for granted. Most of the time when the signal from our brain tells the arm to lift it behaves without any issue. When there is pain or injury everything goes askew. In order to reach the arm overhead there is a very specific pattern of movement that needs to occur for all structures to do their intended job without injury. When we think of our arm going overhead we envision that our arm does 100% of the moving. In reality, it only does 2/3 of the overall moving while your shoulder blade moves the other third. Anatomical range of motion at the shoulder is 180 degrees of flexion. That means your arm is pointing perfectly up towards the ceiling. For most people, the functional range of motion at the shoulder is around 150-170 degrees. Therefore, the shoulder blade needs to provide 50-60 degrees of rotation to achieve full motion.
The rotation of the shoulder blade is essential since it needs to move with the humerus as the arm raises overhead. If the humerus moves but the scapula stays put then the two bones compress resulting in sharp pain (impingement).
What is Rotator Cuff Impingement?
The term impingement refers to the compression of the rotator cuff and subacromial bursa during arm motions. When the timing and partnership between the scapula and humerus is off the two bones come in close contact with one another. Soft tissue gets compressed in the small space. The tissues compressed are the supraspinatus (part of your rotator cuff) and the bursa sac that protects the tendon. A bursa is a fluid filled sac that keeps the tendon from scraping along the bone. When the rotator cuff tendon and the bursa are compressed repeatedly that irritates the tissue causing inflammation and pain. When the tissue is inflamed it takes up more space underneath the acromion (the roof of the shoulder and part of the scapula) causing more difficulty reaching overhead due to limited space to move. As you can see in the cycle of pain and dysfunction below.
The Different Types of Impingement
There are different causes for impingement and therefore slightly different approaches to treatment.
Primary impingement: Occurs when the main cause of the impingement is from anatomical or congenital factors. The acromion, or roof of the shoulder joint, can come in a few different shapes. The optimal shape is a flat sloped acromion which provides the most amount of space. The acromion can also be curved or hooked both which take up valuable space and increase the likelihood that impingement will occur with movement.
Secondary impingement: Occurs when the main cause of impingement is related to poor movement patterns, altered motor control, decreased strength, injury, tissue restriction, or overuse. The outcome of these factors is the adherent movement of the humeral head in the socket. Altered control of the scapula is termed “scapular dyskinesia” and is a likely culprit causing impingement.
Internal impingement: Occurs when the main cause of impingement is the hyperabduction/external rotation of the shoulder causing the under surface of the rotator cuff to compress against the glenoid rim.
How to End the Pain Cycle of Impingement
Eradicating pain and dysfunction from impingement relies on multiple factors. Many clinicians assume that all impingement is “secondary impingement” and prescribe rotator cuff strengthening exercises with an exercise band. This is a faulty assumption and leads to many poor outcomes when treating impingement. Additionally, there are more effective ways to treat impingement.
Once you have correctly identified the type of impingement you need to address the specific causative factors.
Primary impingement:
- Address faulty posture by improving thoracic extension, scapular retraction, and pectorlis minor flexibility
- Education to avoid horizontal adduction and cardinal plane flexion/abduction
- Education to avoid impinging exercises such as dips, upright rows, deep bench press, and lateral raises
Secondary impingement:
- Address faulty posture by improving thoracic extension, scapular retraction, and pectoralis minor flexibility
- Strengthening exercises for lower trapezius, serratus anterior, middle trapezius, infraspinatus, and latissimus dorsi
- Motor control training in prone and standing to correct scapular dyskinesia
- Education for lifting in the “scaption” plane of motion
- Education to avoid impinging exercises such as dips, upright rows, deep bench press, and lateral raises
Internal impingement:
- Treatment here is for the most part identical to secondary impingement except for a couple of additions
- Stretching of the posterior capsule/posterior muscles
- Restoration of normal external to internal rotation range of motion ratio
- Gain full internal rotation range of motion
- Movement education to limit excessive horizontal abduction of the shoulder (typical in overhead throwing athletes)
Conservative Management
It is important to note that treating shoulder impingement conservatively is very successful. The pain may not subside immediately, maybe 6-8 weeks, but it will go away with proper treatment. I recommend that you give physical therapy and movement retraining an honest chance before heading under the knife.
Impingement may be the most common reason for shoulder pain, but it does not have to be difficult to treat.
If you have shoulder impingement be sure to visit a physical therapist with experience treating impingement for the best outcomes. For physical therapists, we can do a much better job treating impingement if we go beyond band exercises and modalities. If you would like to speak with a specialist in shoulder rehabilitation please call Kevin at 408-784-7167 or email kevin@compedgept.com
