Ortho - Shoulder

Glenohumeral Joint

• The glenohumeral joint is a synovial ball and socket joint.
• The head of the humerus sits medially, slightly posteriorly, and superiorly.
• The glenoid fossa of the scapula is lateral, forward, and pear-shaped, narrow superiorly and wider inferiorly.
• Capsular strength is weak and lax, especially inferiorly at the inferior axillary pouch.
• Ligaments include the superior, middle, and inferior glenohumeral ligaments that check for external rotation.
• Mid limits lateral rotation up to 90° abduction and is important for anterior stabilization.
• The inferior portion is thickest and strengthens the anterior-inferior part to prevent anterior subluxation and dislocation.
• The coracohumeral ligament strengthens the superior capsule and checks gravity.
• The transverse humeral ligament holds the long biceps tendon in the groove; rupture leads to biceps tendon instability.
• Dynamic ligaments are tendons from the rotator cuff muscles that blend with fibers of the joint capsule.
• The glenoid labrum surrounds and deepens the glenoid cavity of the scapula, supporting articulation.
• Movements include 3 degrees of freedom: Flexion-Extension, Abduction-Adduction, External Rotation-Internal Rotation.
• The head of the humerus is convex, and the glenoid fossa is concave.
• The resting position is 55-70° abduction and 30° horizontal adduction.
• The closed packed position is full abduction and external rotation.
• The capsular pattern of restriction is external rotation > abduction > internal rotation.
• Flexion range is 180° (0-60° GH, 60-180° GH, scapula, trunk) with a firm end feel.
• Extension range is 60° with a firm end feel.
• External rotation range is 90° with a firm end feel.
• Internal rotation range is 70° with a firm end feel.
• Abduction range is 180° (0-30° GH, 30-180° GH, scapula, trunk) with a firm/hard end feel.
• Horizontal abduction range is 45° with a firm end feel.
• Horizontal adduction range is 135° with a firm/soft end feel.

Acromioclavicular Joint

• The acromioclavicular joint is a synovial, modified gliding joint.
• The articulating surfaces include the medial surface of the acromion, an incomplete articular disc, and the acromion facet of the clavicle.
• The joint orientation results in a strong compression force, potentially leading to clavicle override of the acromion, resulting in an AC separation.
• The capsular strength is weak and lax.
• The superior and inferior acromioclavicular ligaments prevent AC separation.
• The coracoclavicular complex consists of the trapezoid and conoid ligaments.
• The trapezoid ligament (horizontal) checks excessive lateral movement.
• The conoid ligament (vertical) checks excessive superior movement and widening of the scapuloclavicular angle.
• The incomplete intra-articular disc dangles from the superior part of the synovial joint capsule.
• Movements include 3 degrees of freedom: Elevation-Depression, Protraction-Retraction, Anterior Rotation-Posterior Rotation.
• The acromion is concave, and the acromial end of the clavicle is convex.
• The resting position is arm by side.
• The closed packed position is with the arm abducted to 90°.
• Full elevation is associated with pain.
• Elevation/Depression range is 30°.
• Protraction/Retraction range is 50°.
• Rotation range is 50°.
• All motions have a capsular firm end feel.

Sternoclavicular Joint

• The sternoclavicular joint is a synovial, modified gliding joint.
• Articulating surfaces include the clavicular notch of the manubrium and the sternal end of the clavicle.
• Capsular strength is weak and lax inferiorly.
• Ligaments include the anterior and posterior sternoclavicular ligaments, the interclavicular ligament, and the costoclavicular ligament.
• The interclavicular ligament checks excessive medial movement.
• The costoclavicular ligament checks elevation with medial movement and elevation with lateral movement.
• Movements include 3 degrees of freedom: Elevation-Depression, Protraction-Retraction, Anterior Rotation-Posterior Rotation.
• The clavicular notch of the manubrium is anterior/posterior convex and superior/inferior concave.
• The sternal end of the clavicle is anterior/posterior concave and superior/inferior convex.
• The resting position is arm by side.
• The closed packed position is with the arm maximally elevated.
• Full elevation is associated with pain.
• Elevation/Depression range: 15°.
• Protraction/Retraction range: 10°.
• Rotation range is 50°.
• All motions have a capsular firm end feel.

Observation

• Step deformity at the distal end of the clavicle indicates a separation.
• A sulcus sign, or sagging/flattening below the acromion process, indicates a dislocation or deltoid paralysis/atrophy.
• Mal-alignment of the clavicle is often due to fractures.
• Scapular winging occurs when the medial border moves away from the posterior chest wall.
• Dynamic winging indicates serratus anterior injury or a compromised long thoracic nerve and is possibly due to muscle imbalance or strain in to the rhomboids or upper trapezius.
• Static winging indicates structural deformity of the scapula, clavicle, spine, or ribs.
• Scapular tilting is when the superior or inferior angles tilt away from the chest wall and represents weakness and instability (posterior muscles) or tightness of pec minor.
• Painful arc is pain during a specific range of motion.
• Painless arc is the first 45-60° of abduction is painless because there is no pinching under the acromial arch.
• Pain during abduction of 60-120° may indicates structures becoming pinched, resulting in the cessation of abduction or the onset of pain.
• Pain diminishes after 120° of abduction because the pinched structures have passed under the acromion process
• The pain may return in the last 10-20° of abduction, which indicates possible impingement or AC/SC joint involvement.

Force Couples in Biomechanics

• The deltoid wants to pull up and out, but the rotator cuff pulls down and in, properly aligning the humeral head in the glenoid fossa.
• Serratus anterior and upper traps work together to upwardly rotate the scapula during abduction and other arm movements.
• The long head of the biceps tendon, when the arm is laterally rotated, acts as a pulley that depresses the humeral head to keep it centered in the glenoid fossa.

Abduction - Scapulohumeral Rhythm

• Phase 1 (0-30° abduction): Also known as the "Scapular Setting," is performed primarily by the glenohumeral joint.
• The scapula is stabilized against the thorax with minimal movement.
• Clavicular elevation: 0-5°.
• Phase 2 (30-90° abduction): Involves the next approximately 60° of elevation.
• At roughly 40° of humeral angulation, the scapula begins to rotate (approximately 20°), establishing a 2:1 scapulohumeral rhythm.
• Clavicular elevation: Continuing up to 15°.
• Phase 3 (90-180° abduction): Constitutes the last 90° of elevation.
• 2:1 ratio of scapulohumeral movement persists.
• The clavicle elevates further and rotates posteriorly (approximately 15°) due to the pull on the conoid ligament.
• The humerus laterally rotates to clear the acromial arch.
• Full 180° abduction requires movements from upper and lower thoracic vertebrae, the manubrium, and the first rib, in addition to scapula, humerus, and clavicle movements.

Reverse Scapulohumeral Rhythm

• Occurs when the scapula moves more than the humerus with abduction; often indicative of frozen shoulder.
• Individuals tend to hike the shoulder upward to compensate for limited movement.

Passive Stability

• The glenoid cavity faces lateral, forward, and superior, creating a lip for the humeral head.
• The superior joint capsule and coracohumeral ligament resist the force of gravity on the arm.

Active Stability

• Rotator cuff muscles, also known as 'dynamic ligaments', actively stabilize the shoulder joint.

Compromised Stability

• Arises with thoracic hyperkyphosis, change to glenoid > loss of passive stability > increased muscle tone/compensation in rotator cuff> tendonitis/impingement.
• Arises in cases of muscle paresis > compromised dynamic stability > also causes postural changes which have the same effect as hyperkyphosis above

Clavicle Arthrokinematics

• Joint Location: The SC joint is between the sternal facet of the clavicle and the clavicular notch of the manubrium.
• Movement: The clavicle moves on the manubrium.
• Shape: The sternal facet of the clavicle has an 'apple core' shape with the anterior and posterior aspects concave.
• Protraction/Retraction: Occurs as the clavicle (concave) moves on the manubrium (convex), the arthrokinematic movement (glide) is in the same direction as the osteokinematic movement
• Protraction requires anterior glide.
• Retraction requires posterior glide.
• Abduction/Adduction: Occurs as the clavicle (convex) moves on the manubrium (concave), the arthrokinematic movement (glide) is in the opposite direction as the osteokinematic movement.
• Abduction requires inferior glide.
• Adduction requires superior glide.

Tendonitis (Tendinopathy)

• Tendonitis is inflammation of a tendon due to overuse; tendinopathy is a degenerative condition of the tendon due to overuse.
• Both conditions result from overuse and treatment focuses on offloading the tendon to allow it to recover, followed by strengthening to improve load handling.
• Offload tendon is achieved by reducing provocative movements and massaging the muscle belly.
• Strengthen a tendon with eccentric resistance exercises, which are more effective than stretching.
• Common in the shoulder, especially in sports requiring repetitive upper limb movement and maximal muscle contraction.
• Can also occur in occupations involving repetitive movements.
• Cortisone injections may relieve inflammation, but multiple injections in the same area can lead to long-term breakdown of connective tissues.

Assessing for Tendonitis

• Pain when AROM of the antagonist direction (lengthening).
• Pain during RROM (or MMT) of the affected muscle, especially when held and with an eccentric component.
• Pain with Palpation.

Most Commonly Affected Tendons of the Shoulder

• Supraspinatus: Overuse from overhead activities, postural stress, poor biomechanics (impingement).
• Poorly vascularized, which reduces its capacity to recover and heal.
• Calcific tendonitis is a common condition where fibroblasts are replaced by chondrocytes, leading to calcium deposition.
• Biceps Brachii Long Head: Acts as a humeral stabilizer and elbow decelerator, often affected by throwing and overhead movements.
• Injury to the transverse humeral ligament can cause friction of the biceps tendon, leading to tendonitis.

Bursitis

• The shoulder has many bursae, with the subacromial bursa being the most commonly affected.
• Subacromial (aka subdeltoid): This bursa overlies the supraspinatus muscle (tendon and belly) and sits underneath the acromion and deltoid muscle.
• It is susceptible to impingement by the acromial arch when inflamed or affected by calcified supraspinatus tendon.
• Subscapular: This bursa lies over the anterior joint capsule and under the subscapularis tendon, where joint effusion may be apparent due to inflammation.
• MOI includes trauma to the shoulder, infection, conditions like tendonitis or calcific tendonitis, and overuse of the surrounding structures.
• Overuse with poor biomechanics is a common underlying problem for both bursitis and tendonitis.

How to differentiate from tendonitis

• Pain over the lateral brachial region and referred below the elbow.
• Pain may affect sleep, especially if the bursa is compressed.
• Pain with compression that does not worsen with load, especially eccentric load.
• PROM empty end-feel.

Impingement Syndrome

• Impingement is the pinching of structures in the subacromial space, typically occurring with tendonitis and/or bursitis.
• Rotator cuff tendons, biceps tendon, and subacromial bursa undergo trauma when the head of the humerus is repeatedly pushed up into the coracoacromial arch.
• Caused by hyperkyphosis posture or imbalances in force coupling, especially if rotator cuff muscles are not depressing the humeral head and there is poor serratus anterior activation and scapula rotation.

Shoulder Dislocation:

• Dislocation (luxation) & subluxation occur in three directions.
• Mechanism of Injury: Often with excessive abduction and external rotation of the humerus or with direct/indirect impact
• Posterior Dislocation Mechanism of Injury: Usually flexion, adduction and internal rotation of the humerus when breaking a fall with an outstretched hand or elbow.
• Inferior Dislocation: Least common and occurs with forced abduction with a fixed hand.
• Observation is a sulcus sign; in other words, sagging/flattening below the acromion process; indicates a dislocation or deltoid paralysis/atrophy
• Apprehension indicates unstable joint capsule

Shoulder Apprehension Sign

• Instruct the patient to slowly move the arm and joint into the position in which the dislocation took place
• Precautions and Contraindications: As per general orthopedic treatment
• Before restoring ROM in the direction of dislocation, ensure the majority of strength is regained in the muscles crossing the joint

Shoulder Separation (AC Separation)

• AC Joint Capsule and Ligaments
• Coracoclavicular Complex- Trapezoid and Conoid ligaments.
• Grade 1: No clavicular displacement; Damage to AC joint capsule; Intact coracoclavicular complex
• Grade 2: Subluxation of clavicle; AC Joint capsule disruption; Complete tear of acromioclavicular ligaments; Intact coracoclavicular complex
• Grade 3: Severe step deformity; Disrupted AC Joint Capsule; Complete tear of acromioclavicular ligaments; Ruptured coracoclavicular complex

Adhesive Capsulitis

• Self-limiting inflammation with fibrosis of the joint capsule, with significant pain early on, decreasing ROM
• Ranges affected (usually): ER > ABD> IR;
• Severe conditions show pain radiating below elbow.
• Idiopathic
• Secondary is following additional conditions: previous shoulder injury, disuse systemic disease, other diseases Some texts mention TrPs surrounding muscle especially subscap.
• Gradual onset of pain
• Severe pain at night; unable to lie on affected side.
• Lateral Brachial pain is the main complaint here
• Blends with Acute or Frozen phases
• Motion and function are regained, FULL ROM isn't always regained
• Supposed to be spontaneously reolved over 2 years, symptoms can last for 5-10 years

Explores shoulder abduction phases, scapulohumeral rhythm, and movement limitations. It covers clavicular elevation, glenoid cavity orientation, and shoulder stiffness impact on ADLs. Also, it discusses movement of the humerus to prevent impingement.