By Jodie Humphrey
Jodie Humphrey, PT, ATC, CSCS, is a Physical Therapist for Complete P.T., in Los Angeles and a former Sports Medicine Coordinator for HealthSouth in Warwick, R.I.
Training & Conditioning, 14.3, April 2004, http://www.momentummedia.com/articles/tc/tc1403/rotationshoulder.htm
With baseball season upon us, rotator cuff injuries are on many athletic trainers’ minds. Last year, in the professional ranks alone, we saw Ken Griffey Jr., Troy Glaus, and Mike Remlinger, to name a few, suffer from rotator cuff injuries.
Of course, this injury can affect athletes in almost any sport. The term "rotator cuff injury" has evolved to be a blanket term for shoulder injuries. The rotator cuff is actually four muscles in the shoulder that hold the humerus in place. But the public and some medical practitioners are using the term whenever some portion of the shoulder complex is involved in the athlete’s shoulder dysfunction.
Comprised of the supraspinatus, infraspinatus, teres minor, and subscapularis, the rotator cuff controls fine movement at the glenohumeral joint. It functions primarily to center the humeral head in the glenoid fossa by a suction cup process known as the circle concept. All four of these muscles are engaged in a tug-of-war, and in a healthy, normal shoulder there is net equilibrium to balance these forces in any movement pattern in space. However, if the balance is disrupted, injury and pain occur.
The athlete’s shoulder complex is attached to the entire body, of course, hence looking at the entire kinetic chain is also important. A rotator cuff injury is the end result of a failure somewhere in the kinetic chain throughout the whole body.
Symptoms & Causes
A rotator cuff tear can occur at the muscle belly, the muscle-tendon junction, the tendon, or the insertion of the tendon to one of the bones, scapula, or humerus. The symptoms that commonly occur with rotator cuff injuries are pain, weakness, and loss of motion in the shoulder. Some athletes will feel a pop in their shoulder after which they cannot lift their arm very well. Others will report a gradual onset of shoulder symptoms, like grinding or clicking, but may not experience any loss of motion.
A significant traumatic force is required to tear a healthy rotator cuff. Most often, however, rotator cuff tears result from a combination of trauma and degenerative changes.
Degeneration causes muscles and tendons which should not normally be working to assist in producing the equivalent net force and power that the activity demands. The degenerative process usually starts with swelling and inflammation in the bursa from repetitive motion activities at or above shoulder level. This process causes compensatory muscles to engage during the activity to produce the required forces for the sport. This process continues until the rotator cuff tendons fight for space and develop a tendonitis. Continued overuse due to the tendons’ weakened state leads to further degeneration.
Think of a rope fraying from friction around a sharp edge, and the movement of the rope causing further breakdown of the rope’s strands. Eventually the fibers tear at the surface where the point of excess friction is applied.
Of course, not all rotator cuff injuries occur in isolation. Injury at other muscles, tendons, ligaments, joint surfaces, and other non-contractile supporting soft tissues can occur.
With all these variables assessed for performance deficiencies, the level of rotator cuff dysfunction can be determined and classified in a more appropriate categorization of mild, moderate, or severe shoulder complex dysfunction. That’s why the diagnostic process is so important.
Muscles & Tendons
All the muscles that act at the shoulder joint have one of two purposes, either to stabilize or to mobilize. A football lineman’s rotator cuff functions to produce a greater stabilizing force than a baseball pitcher’s. The baseball pitcher’s rotator cuff, in turn, functions with a greater endurance and aerobic capacity.
The stabilizer muscles are those that primarily hold the joint in place so the larger muscles can produce power and strength. The stabilizers are the rotator cuff and the musculature around the scapula, which keep the scapula anchored to the thoracic wall via the spine. The scapula is stabilized to the spine by muscular actions of the levator scapulae, trapezius, rhomboid major, rhomboid minor, and serratus anterior. The stabilizing force couples at the shoulder complex provide the stable foundation for mobility to occur, particularly at high velocities in the athletic population. The stability is the hinge for all functional strength and power, since the body inherently limits muscle strength gains without a sound foundation to build upon in an automatic self preservation tactic.
The mobilizers generate strength, power, and speed. These are the larger muscles traditionally involved in weight training circuits. Those that exert force over the shoulder joint are the rhomboids, levator scapulae, pectoralis major and minor, and latissimus dorsi, which are trained in the seated row, shoulder shrugs, chest press, and lat pull downs, respectively. Other combined contractile forces to consider at the shoulder complex include:
• Deltoid (anterior, middle, and posterior heads)
• Infraspinatus, Teres Minor, and Subscapularis
• Teres major, coracobrachialis
• Biceps Brachii and Triceps.
The shoulder complex musculature needs to be assessed considering force production requirements of the sport (strength, endurance, and flexibility), and work-rest intervals specific to the shoulder complex.
To assess scapulohumeral rhythm, look for muscular forces that are in line with the following:
• Upper trapezius should be most active in coronal plane, with abduction less than 60 degrees.
• Lower trapezius abduction should be most active when greater than 90 degrees.
• Serratus anterior should be most active in forward flexion.
• Middle trapezius should be most active during abduction at 90 degrees, and scaption less than 90 degrees.
• Rhomboids should be most active at flexion and abduction at end range.
The process of assessing mobility in the rotator cuff muscles is depicted well in Muscle Stretching in Manual Therapy, by O. Evjenth, MS, and J. Hamberg, MD. They describe the best stretches in these positions:
Supraspinatus: Athlete lies on his or her side with wedge in axillary, and force is applied while the shoulder is in a slight extension as the arm is adducted across the back.
Subscapularis: Athlete lies supine with elbow flexed 80 degrees, abducted 30 degrees, and force is applied to externally rotate the shoulder with forearm supinated.
Teres minor: Athlete sits with shoulder in full flexion with elbow flexed 90 degrees, and force is applied into internal rotation.
Infraspinatus: Athlete is supine with shoulder abducted 80 degrees and elbow flexed 90 degrees, and force is applied into internal rotation.
When muscles and tendons are involved, we need to incorporate a gradual progressive resistive exercise program. With injury, the muscle’s cellular system is disrupted, partly due to nerve disruption. Some portion of communication with the tissue is temporarily out of order. It is difficult to speak of muscles’ healing properties without acknowledging this relationship, which is critical in the healing process.
As the axon approaches the muscle fiber for innervation, it loses its myelin sheath and branches into an array of terminal fibers, called motor end plates. Essentially, healing of the muscle injury is strongly dependent on the amount of shearing to these motor end plates and the axon.
The supraspinatus tendon is most often involved in rotator cuff injury, because its position makes it most susceptible to impingement. For tendon tears, the connective tissue re-establishes its firm attachment of myofiber ends with scars. But excessive connective tissue scar formation between stumps may impede regeneration of myofibrils and re-innervation of abjunctional stumps. This means the tendon will heal with a lesser percentage of ROM than normal, and a weak link will occur. The balance at the tug-of-war will be disrupted, setting the stage for further pain and degeneration.
Joints & Non-Contractile Soft Tissues
When diagnosing an athlete with shoulder pain, first examine the tissues and joints involved. Particular to the shoulder complex, the sternoclavicular (SC), acromioclavicular (AC), glenohumeral (GH), and scapulothoracic (ST) are the direct articulations that need thorough evaluation. Another primary cause of painful arc is the subacromial joint (SAJ), which defines the space between the coracoacromial roof and the humeral head that houses the deep portion of the subdeltoid bursa.
Sternoclavicular: This intra-articular disk and fibrous capsule provide stability to the shoulder. They hold the clavicle in a normal resting position with a 10-degree upward angle in the coronal plane. In arthrokinematic terms, it should have:
• 45 degrees of movement with elevation.
• Five degrees with depression.
• 15 to 35 degrees of movement with protraction/retraction.
• 25-50 degrees axial rotation.
Note that the sternoclavicular joint is the foundation of the shoulder complex, since it is the last hinge that keeps the arm in neutral alignment. Once dysfunction affects this joint, the structural alignment for the whole shoulder complex and the entire kinetic chain must be considered. If the shoulder complex was a house, the sternoclavicular would be the foundation and its integrity would affect the integrity of the whole house.
Acromioclavicular: This intra-articular disk and fibrocartilage is primarily stabilized by coracoacromial, coracoclavicular, and acromioclavicular ligaments. It has an inferiormedial oblique orientation. Its arthrokinematics around a vertical axis consist of the following features:
• 15 degrees of scapular winging by clavicle rotation.
• Flexion/extension tilt is restricted by thorax-scapula space.
• Abduction and adduction rotate scapula upward and downward.
Subacromial: This provides a functional articulation between the coracoacromial arch and the head of the humerus. The costocoracoid fascia lies superiomedial to the pectoralis minor muscle and when contracture occurs, it causes loss of elevation of the arm. Soft tissue is often a culprit in the diagnosis of "subacromial bursitis."
Glenohumeral: This is a synovial, multiaxial ball-and-socket joint. The glenohumeral index, calculated by dividing the maximal transverse diameter of the glenoid by the maximal transverse diameter of the humeral head, is 57.5 in normal shoulders. Articular cartilage of the glenoid is thicker peripherally than centrally, whereas the cartilage on the humeral head is slightly thicker centrally. The anterior, superior, and posterior aspects of the capsule are reinforced by the tendons of the rotator cuff, coracohumeral, and superior glenohumeral ligaments.
The glenoid labrum is a flexible structure allowing adaptation of its shape to accommodate rotation of the humeral head. This deepens the glenoid cavity. If removed, there is a 20 percent reduction in resistance to superioinferior and anteroposterior translatory forces.
Its arthrokinematics vary in two different research studies. The concave-convex rule says the humeral head slides inferiorly during abduction, anteriorly during external rotation, and posteriorly during internal rotation. More recent research has shown that during the initial 30-60 degrees of elevation in the scapular plane, the humeral head moves superiorly three millimeters then stays centered within one millimenter; and during horizontal plane movement, the humeral head stays centered until maximal extension and external rotation (such as the cocking phase of pitching) when four millimeters of posterior translation occurs. These studies suggest that movement of the humeral head is related to tightness in the joint capsule.
Scapulothoracic: This area relies on force couples for orientation and movement patterns—trapezius, rhomboid major and minor, and levator scapulae. It sits 30 to 45 degrees obliquely in the coronal plane with a forward tilt of nine degrees. The medial border of the scapula is oriented vertically. In a normal position, the glenoid fossa faces anterior, lateral, and five degrees downward.
The scapulothoracic allows three rotatory motions (elevation/depression, abduction/adduction, upward rotation/downward rotation) and two translatory motions (protraction/retraction). Fifty degrees of scapular movement with protraction arise from translation of the scapula as 35 degrees of anterior clavicle movement occurs at the sternoclavicular joint when 15 degrees of rotation occurs at the acromioclavicular joint.
In regards to the joint surfaces, the SC, AC, and GH all function as ball and socket joints. When joint degeneration is present, there is low recoverability, whereas capsular restricted patterns mean high recoverability (in the sense of restoring normal joint mechanics, not necessarily equating to functional restoration). When cartilage is damaged, the reparative work is entirely earmarked for the chondrocytes in the matrix surrounding the defect area, since cartilage is avascular and cannot respond with inflammation.
Consequently, no fibrin clot is created and no inflammatory cells can invade the defect area to clean it and differentiate into cells with a reparative capacity. Articular cartilage lacks neural elements, but pain can be felt by subchondral bone, soft tissue, and free nerve endings.
As for ligaments, they heal with scar similar to scarring elsewhere, but are mechanically inferior to normal tissue. During scarring, normal large-diameter collagen fibrils in soft tissues are replaced with relatively small collagen fibrils.
If the nerve is traumatized, an extended time to fully recover is warranted due to its slow rate of repairing itself. When a nerve regenerating sprout does find an appropriate end organ (muscle cell or receptor), these regenerated and re-myelinated fibers have internodal distances, diameters, and conduction velocities around 80 percent of normal. Involvement of the nerve portion of the neuromuscular connection presents as muscle weakness, but overloading the muscle with resistance training to strengthen the muscle is similar to shooting the messenger.
Denervation hypersensitivity is a symptom of nerve injury, and an example is a brachial plexus injury in which the athlete complains of alternating warm and cold sensations. At times the arm is warm (no vasomotor tone) and at other times cold and cyanotic (vasospasm), as a result of hypersensitivity to circulating epinephrine.
Neuromuscular re-education involves working muscles and the nervous system together, with precise regard to timing, speed, power, strength, and rest-to-work ratio. The nerves and corresponding muscles that appear with a dysfunctional scapulohumeral rhythm include:
Long thoracic --> serratus anterior
Dorsal scapular --> rhomboids
Suprascapular --> supraspinatus and infraspinatus
Axillary --> deltoid and teres minor
Another variable is kinesthesia, or eye-hand coordination. Poor coordination results in inefficient movement patterns, which strain the rotator cuff. The work that the muscles perform in the arc of movement, considering millimeters of inaccuracy, will cumulatively affect the strain at the rotator cuff.
To associate the effects of this to an identifiable situation, consider walking with a small pebble in your shoe under the ball of your foot. The pressure over time will alter the way your foot position conforms to the ground to maintain the speed of walking. Eventually, pain occurs at stressed points that were not designed to bear weight in that fashion. Similarly, the kinesthesia at the shoulder complex adapts until pain sets in upon soft tissue destruction. As stated earlier, the body is designed to be self-guided in all of its systems, so this process of abnormal compensatory movement must be consciously re-trained to revert back to more efficient mechanics.
Obviously, proper prognosis gets the treatment on the right track. Here is a list of questions to consider while diagnosing and coming up with a treatment plan:
• What is the degree of movement dysfunction?
• What are the diagnostic work-up results?
• Does the patient want or need surgery?
• Is the athlete willing to allot time for recovery?
• How long has the problem been present?
• Is there a prior injury to this area?
• Is the cervical spine involved?
Once damage to the tissue is determined through an evaluative process, and an understanding of the tissue’s healing capacity in a conservative treatment regime is appreciated, the treatment modalities and exercise prescription can be focused at the bull’s-eye. A complete biomechanical understanding is necessary for efficient implementation of treatment interventions. Ultrasound, in particular, can only be effective if it is directed at the target tissue.
Prognosis helps the clinician achieve the desired outcome and helps the athlete know what to expect. If the hands feel what is going on during the physical examination, diagnostic testing provides the eyes to see more clearly.
Sidebar: In the Weightroom
The following are some do’s and don’ts for an athlete lifting weights with shoulder pain:
• Deltoid work and military press beyond elevation range.
• Hyperextension beyond the plane of the body.
• Sacrificing proper mechanics to lift heavier weights.
• Allowing poor mechanics and asymmetries in posture to follow the conditioning regime.
• Seek medical attention early in the onset of shoulder pain, particularly if it’s gradual, since the microtrauma has been hiding for some time before pain is felt.
• Perform two sets of pulling exercise for every one set of pushing.
• Stabilize the core by blocking: Contract the abdominal and pelvic muscles so no spinal movement occurs as another adjacent joint performs the exercise.
• Isolate the rotator cuff with exercises at 8-10 percent max bench press weight.
• I’s, T’s, Y’s, external rotation at 90 percent, and serratus punches for scapular stabilization.
• Functional total body patterns to facilitate kinetic chain biomechanics.
• Chin ups, chin ups, and more chin ups.