Shoulder Biomechanics

1. Biomechanics of Shoulder Muscles
Dr. Muhammad Affan Iqbal, PT
Assistant Professor
Riphah International University, Islamabad

2. Muscles of the Shoulder Complex: Action at GH Joint 1
Shoulder Flexors Coracobrachialis Short Head of Biceps
Long Head of Biceps Pectorais Major
Anterior Deltoid
Shoulder Extensors The Triceps Posterior Deltoid
Teres Minor Teres Major
Latissimus Dorsi
Shoulder Abductors Supraspinatus
Deltoid
Shoulder Adductors Subscapularis Pectoralis Major
Latissimus Dorsi Teres Majore
Teres Minor
Shoulder Internal Rotators Pectoralis major Serratus anterior
Subscapularis Pectoralis major
Latissimus dorsi Teres major
Shoulder External Rotators Infraspinatus Supraspinatus
Deltoid Teres minor
Applied Anatomy

3. ClassificationofMusclesofShoulderAccordingtotheirFunction1
I. Scapular Pivoters
II. Humeral Propellers
III. Humeral Positioners
IV. Shoulder Protectors

4. I. Scapular Pivoters 1
• The scapular pivoters comprise
• Trapezius,
• Serratus anterior
• Levator scapulae
• Rhomboid major
• Rhomboid minor
• As a group, these muscles are involved with motions at the scapulothoracic
articulation, and their proper function is vital to the normal biomechanics of
the whole shoulder complex.

5. II. Humeral Propellers 1
• The shoulder’s internal rotators
• Subscapularis
• Anterior deltoid
• Pectoralis major
• Latissimus dorsi
• Teres major
• The external rotators
• Infraspinatus
• Teres minor
• Posterior deltoid
• The total mass of shoulder internal rotators is more than that of external
rotators that’s why internal rotator torque is 1.7 times more than external
rotators.

6. III. Humeral Positioners 1
• Deltoid
• Position the humerus in space.

7. IV. Shoulder Protectors 1
• Rotator Cuff
• Biceps Brachii
• These muscles are referred to as the protectors of the shoulder since, in addition
to actively moving the humerus, they fine-tune the humeral head position during
arm elevation.

8. Stability of the Shoulder
Static & Dynamic

9. Glenohumeral ligament
• 3 parts all attach from upper margin of glenoid cavity and strengthen
anterior portion of capsule
• Superior - over the humeral head to a depression above the lesser tuberosity
• Middle - in front of humerus to lower lesser tuberosity
• Inferior - to lower part of the anatomical neck

14. Simple or Complex?

15. 3phasesofflexion

17. Rotator Muscles of the Arm
• Medial Rotators
1. Latissimus Dorsi
2. Teres Major
3. Subscapularis
4. Pectoralis Major
• Lateral Rotators
5. Infraspinatus (suprascapular N.)
6. Teres Minor (circumlflex N.)
Importants
• For Lateral Rotation
• Adduction of the Scapula
• Rhomboids, Trapezius
• For Medial Rotation
• Abduction of the Scapula
• Seratus Anterior and Pectoralis
Minor
• Clinical Significance

18. Shoulder Adduction
1. Teres major
2. Latismis dorsi
3. Pactoralis major
4. Rhomboids
 Couple Formed by the Rhomboids (1) and Teres Major(2)
 Couple Formed by Long Head of Triceps (4) and Latissimus Dorsi
(3)

19. ContributorsofGlenohumeralAbduction1
00 to 900
 Both Active and Passive Stabilizers should be in a workable position
 Suprapinatus contracts to initiate movement
 RC contracts to pull humeral head into glenoid fossa
 At 200 of the humeral abduction, scapular upward rotation begins with concurrent
calvicular elevation and axial rotation
 At 90 of humeral abduction, clavicular rotation ceases due to costocalvicular
ligament
 Continued abduction of the humerus requires continued upward rotation of the
scapula, which by this point has rotated through a range of approximately 30
degrees
900 to 1500
 As the scapula upwardly rotates on the posterior chest wall, the glenoid fossa faces
upward and laterally, and its inferior angle moves laterally through about 60
degree. The scapular contribution peaks between 90 and 140 degrees.
 The scapular upward rotation is accommodated at both the sternoclavicular and
A-C joints by a posterior axial rotation of the clavicle of 30–40 degrees and a
clavicular elevation of approximately 30–36 degrees
 The muscles producing this movement are the serratus anterior and trapezius,
acting as a couple on the scapulothoracic joint.
 The movement is limited by the acromion and sternoclavicular joints, and by the
scapular and humeral adductors (notably latissimus dorsi and pectoralis major)
1500 to 1800  Requires Adequate motion of Vertebral Joints of Cervical and Upper Thorax

20. For Extension at Scapulothoracic Joint /
Adduction of Scapula
For Extension at Glenohumeral Joint
1. Teres Major
5. Teres Minor
6. Posterior Fibers of Deltoid
2. Latissimus Dorsi
4. Rhomboids
7. Middle Transverse Fibers of Trapezius
2. Latissimus Dorsi

21. Shoulder Force Couples

22. Shoulder Force Couples

23. Clinical Pearls

24. Clinical Pearls

25. Differential Diagnosis

26. Cont.

27. Cont.

28. DifferentialDiagnosis
of Muscleand Ligament
TissuePathology

29. Examination of Shoulder

30. • Possible causes of pain and/or limitation of movement
• Trauma
• Fracture of the clavicle, humerus or scapula
• Dislocation of one of the above joints
• Ligamentous sprain
• Muscular strain
• Tendinopathy, particularly of the rotator cuff or long head of biceps
• Spontaneous conditions, e.g. Adhesive capsulitis and rupture of the long head of
biceps
• Osteoarthritis

31. • Inflammatory disorders, e.g rheumatoid arthritis
• Infection, e. g. Tuberculosis
• Bursitis
• Muscle imbalance-related problems, e.g. Winged scapula due to weakness of serratus anterior
• Snapping scapula (grinding sensation beneath the scapula on movement due to rib
prominence)
• Neoplasm
• Thoracic outlet syndrome
• Hypermobility and instability syndromes
• Referral of symptoms from:
• Viscera, e.g. Lungs, heart, diaphragm, gallbladder and spleen
• Joints, e.g. Cervical spine, thoracic spine, elbow, wrist or hand.

32. Subjective Examination
• Body Chart
• Area of current symptoms/ mapping
• Area relevant to the region being examined
• Quality of pain
• Intensity of pain
• Depth of pain
• Abnormal sensations
• Constant or intermittent symptoms
• Relationship of symptoms

33. 33

34. Body Chart for Differential Diagnosis
• As per biomechanics section

35. Differential Diagnosis
•Impingement syndrome
• Subacromial bursitis
• Rotator cuff tendinopathy
• Rotator cuff tear
• Biceps tendinopathy
•Adhesive capsulitis
•SC joint arthritis, sprain
•AC joint arthritis, sprain
•Glenohumeral joint OA
•Avascular necrosis
•Neoplastic disease
•Thoracic outlet syndrome
•Myofascial pain
•Referred pain
• Cervical radiculopathy
• Cardiac
• Aortic aneurysm
• Abdominal / Diaphragm
• Other GI
•Instability
• GH dislocation
• GH subluxation
• Labral tear (e.g. Bankart, SLAP,
etc.)
•Fracture
• Clavicle fracture
• Proximal humerus fracture
• Scapular fracture
•Other arthritic disease
• Rheumatoid, Gout, SLE
• Septic, Lyme, etc.

37. • Behavior of symptoms
• Aggravating factors
For each symptomatic area a series of questions can be asked:
• What movements, activities or positions bring on or make the patient's symptoms
worse?
• How long does it take before symptoms are aggravated?
• Is the patient able to maintain this position or movement?
• What happens to other symptoms when this symptom is produced or made worse?
• How do the symptoms affect function, e.g. reaching, dressing, overhead activities,
sport and social activities?
• Does the patient have a feeling of instability in the shoulder?

38. • Easing factors
• Aggravating+easing factors???????
• Twenty-four hour behavior of sumptoms
• Stage of condition
• Better/worse

39. Functional activity Analysis of the activity
Temporomandibular joint
Yawning
Chewing
Talking
Depression of mandible
Elevation/depression of mandible
Elevation/depression of mandible
Headaches
Stress, eye strain, noise, excessive eating,
drinking, smoking, inadequate ventilation,
odours
Cervical spine
Reversing the car Rotation
Sitting reading/writing Sustained flexion
Thoracic spine
Reversing the car Rotation
Deep breath Extension
Shoulder
Tucking shirt in Hand behind back
Fastening bra Hand behind back
Lying on shoulder Joint compression
Reaching up Flexion
Common aggravating factors – for each region or structure, examples of various functional activities and a
basic analysis of the activity are given

40. Elbow
Eating Flexion/extension
Carrying Distraction
Gripping Flexion/extension
Leaning on elbow Compression
Forearm Turning key in a lock Pronation/supination
Wrist/hand
Typing/writing Sustained extension
Gripping Extension
Power gripping Extension
Power gripping with twist Ulnar deviation and pronation/supination
Turning a key Thumb adduction with supination
Leaning on hand Compression
Lumbar spine
Sitting Flexion
Standing/walking Extension
Lifting/stooping Flexion

41. Lifting/stooping Flexion
Sacroiliac joint
Standing on one leg
Ipsilateral upward shear, contralateral
downward shear
Turning over in bed Nutation/counternutation of sacrum
Getting out of bed Nutation/counternutation of sacrum
Walking Nutation/counternutation of sacrum
Hip
Squat Flexion
Walking Flexion/extension
Side-lying with painful hip uppermost Adduction and medial rotation
Stairs Flexion/extension
Knee
Squat Flexion
Walking Flexion/extension
Stairs Flexion/extension
Foot and ankle
Walking
Dorsiflexion/plantarflexion,
inversion/eversion
Running
Dorsiflexion/plantarflexion,
inversion/eversion
Muscular tissue
Contraction of muscle
Passive stretch of muscle
Nervous tissue
Passive stretch or compression of

42. • Special questions
• Previous shoulder dislocation.
• Neurological symptoms
• Vascular symptoms
• Vertebrobasilar insufficiency

43. • History of present condition
• Past medical history
• Social history
• Family history
• Expectations and goals

47. • Plan of physical examination
• Re confirm briefly about your understanding
• Reason for examination
• Enlist precautions or contraindications
• Enlist structures involved
• Priorities hypothesis
• Pain mechanismhow tests should be performed
A. severe before onset of symptoms or just to the onset of
symptoms production….no overpressure
B. irritablejust before symptoms production or onset of
provocation

48. Physical Examination
• Observation
• Informal observation
• Formal observation
• Posture
• Muscle form
• Soft tissue
• Patient’s attitude and feelings

49. • Functional testing
• Active physiological movements
• Range of movement
• Quality of movement
• Behaviour of pain through the range of movement
• Resistance through the range of movement and at the end of the range of movement
• Provocation of any muscle spasm.

50. • Passive physiological movements
• Abduction
• Adduction
• Flexion/abduction
• Flexion/adduction
• Extension/abduction
• Extension/adduction.

51. Impairments in Individual Joints and Their Effects
on Shoulder Motion
1. Common pathologies involving the glenohumeral joint include capsular tears,
rheumatoid arthritis, osteoarthritis and inferior subluxations secondary to
stroke.
2. Scapulothoracic joint function can be compromised by trauma such as a
gunshot wound or by scarring resulting from injuries such as burns.
3. The sternoclavicular joint can be affected by rheumatoid arthritis or by
ankylosing spondylitis.
4. The acromioclavicular joint is frequently dislocated and also is susceptible to
osteoarthritis.

52. • Shoulder motion is not lost completely, even with complete glenohumeral joint
immobility.
• The scapulothoracic and sternoclavicular joints with the acromioclavicular joint
combine to provide the remaining one third or more motion.
1. In the absence of glenohumeral movement these joints, if healthy, may become even more
mobile.
2. Complete loss of glenohumeral joint motion, however, results in total loss of shoulder rotation.
3. The loss of scapulothoracic motion results in a loss of at least one third of full shoulder
elevation ROM, although this appears to be roughly true in passive ROM
I, II. LOSS OF GLENOHUMERAL OR SCAPULOTHORACIC JOINT
MOTION
• Inman et al. reported that in the absence of scapulothoracic joint motion, active shoulder
abduction is closer to 90° of abduction rather than the expected 120°
• These authors hypothesized
That upward rotation of the scapula is essential to maintain an adequate contractile
length of the deltoid muscle

53. I, II. LOSS OF GLENOHUMERAL OR SCAPULOTHORACIC JOINT
MOTION

54. MEASUREMENT OF MEDIAL ROTATION ROM OF THE SHOULDER: Goniometry manuals
describe measurement of medial rotation of the shoulder with the subject lying supine and
the shoulder abducted to 90°. In this position the shoulder is palpated to identify anterior
tilting of the scapula as the shoulder is medially rotated. Firm manual stabilization is usually
necessary to prevent the scapula from tilting anteriorly to substitute for medial rotation
I, II. LOSS OF GLENOHUMERAL OR SCAPULOTHORACIC JOINT
MOTION

55. • In addition to the overall loss of passive and active excursion, decreased
scapulothoracic joint motion impairs the synergistic rhythm between the
scapulothoracic and glenohumeral joints. This may contribute directly to abnormal
glenohumeral joint motion and result in an impingement syndrome
I, II. LOSS OF GLENOHUMERAL OR SCAPULOTHORACIC JOINT
MOTION

56. • Shoulder impingement syndrome is the most common source of shoulder complaints, and
the complicated and finely coordinated mechanics of the shoulder complex help explain
the frequency of complaints.
• The possible contributions to impingement syndromes are
1. Dysfunction within individual components of the shoulder complex
1. Abnormal humeral axial rotation
2. Abnormal scapular positions.
2. Abnormal scapulothoracic rhythm, although it is unclear whether the abnormal rhythm is a
cause or an effect of the impingement.
• A thorough and accurate evaluation of movements and alignments of the individual parts
of the shoulder as well as the coordinated function of the entire complex is needed to
develop a sound strategy for intervention.
I, II. LOSS OF GLENOHUMERAL OR SCAPULOTHORACIC JOINT
MOTION

57. • For the scapulothoracic joint to rotate upwardly 60°, the sternoclavicular joint
must elevate, and the acromioclavicular joint must glide or rotate slightly.
• If the clavicle is unable to elevate but the acromioclavicular joint can still move, the
scapulothoracic joint may still be able to contribute slightly to total shoulder
motion but is likely to have a significant reduction in movement.
• If acromioclavicular joint motion is lost, disruption of scapulothoracic joint motion
again occurs, although perhaps to a lesser degree than with sternoclavicular joint
restriction.
III, IV. LOSS OF STERNOCLAVICULAR OR ACROMIOCLAVICULAR JOINT
MOTION
Decreased motion at the acromioclavicular joint appears to result in increased
sternoclavicular motions, and decreased motion at the sternoclavicular joint
results in increased motion at the acromioclavicular joint.

58. • A 60-year-old male patient came to physical therapy with complaints of shoulder pain. He reported a
history of a severe “shoulder” fracture from a motorcycle accident 30 years earlier. He had never regained
normal shoulder mobility however he had good functional use of his shoulder. He owned a gas station and
was an auto mechanic and was able to function fully in those capacities, but he reported increasing
discomfort in his shoulder during and after activity. He noted that the pain was primarily on the “top” of his
shoulder.
• Active and passive ROM were equally limited in the symptomatic shoulder: 0–80° of flexion, 0–70° of
abduction, 0° medial and lateral rotation. Palpation during ROM revealed that all of the arm–trunk motion
was coming from the scapulothoracic joint. Palpation revealed tenderness and crepitus at the
acromioclavicular joint during shoulder movement.
• These findings suggested that in the absence of glenohumeral joint motion, the sternoclavicular and
acromioclavicular joints developed hypermobility as the patient maximized shoulder function, ultimately
resulting in pain at the acromioclavicular joint. This impression was later confirmed with radiological
findings of complete fusion of the glenohumeral joint and osteoarthritis of the acromioclavicular joint.
• Since there was no chance of increasing glenohumeral joint mobility, treatment was directed toward
decreasing the pain at the acromioclavicular joint.
III, IV. LOSS OF STERNOCLAVICULAR OR ACROMIOCLAVICULAR JOINT
MOTION

59. • SHOULDER MOTION IN ACTIVITIES OF DAILY LIVING:
• Magermans et al. report the shoulder mobility required in diverse activities of
daily living (ADL).
• Combing one’s hair use an average of 90º of glenohumeral flexion or
abduction, 70º of lateral rotation of the shoulder, and approximately 35º of
concomitant scapular upward rotation.
• To regain or maintain functional independence, the clinician must work all
four components of the shoulder complex.
*Shoulder Range of Motion

60. • Muscle tests
• Strength
• Length
• Isometric muscle testing

64. 1.Mark Dutton
2.Kapandji
3.Ola Grimsby
4.Magee
5.Nicola J. Petty