Podcast
Questions and Answers
A patient presents with limited shoulder elevation. Advanced imaging reveals a significantly compromised sternoclavicular (SC) disc. Considering the disc's role in SC joint mechanics, which of the following compensatory kinematic adaptations is LEAST likely to occur?
A patient presents with limited shoulder elevation. Advanced imaging reveals a significantly compromised sternoclavicular (SC) disc. Considering the disc's role in SC joint mechanics, which of the following compensatory kinematic adaptations is LEAST likely to occur?
- Augmented translation at the acromioclavicular (AC) joint to maximize scapulothoracic articulation. (correct)
- Premature and excessive posterior rotation of the clavicle during arm elevation to maintain glenohumeral congruity.
- Increased reliance on costoclavicular ligament stabilization, leading to altered clavicular axial rotation.
- Enhanced scapulothoracic upward rotation via accentuated trapezius and serratus anterior activation with consequential AC joint compromise.
A high-level gymnast reports anterior shoulder pain following a landing where she experienced a direct impact to her outstretched arm. Clinical examination reveals hypermobility at the sternoclavicular joint with notable anterior instability. Which ligamentous structure is MOST likely compromised, contributing to this anterior instability?
A high-level gymnast reports anterior shoulder pain following a landing where she experienced a direct impact to her outstretched arm. Clinical examination reveals hypermobility at the sternoclavicular joint with notable anterior instability. Which ligamentous structure is MOST likely compromised, contributing to this anterior instability?
- The costoclavicular ligament's posterior bundle, which resists medial translation of the clavicle.
- The posterior sternoclavicular ligament, the primary restraint against posterior clavicular translations.
- The interclavicular ligament, limiting clavicular depression and protecting the brachial plexus.
- The anterior sternoclavicular ligament, primarily resisting anterior translation of the medial clavicle. (correct)
Elite overhead athletes often exhibit adaptive changes in their shoulder complex kinematics. Considering the interplay between the SC and AC joints, which motion at the AC joint is MOST directly coupled with posterior rotation of the clavicle, facilitating optimal glenohumeral positioning during humeral elevation?
Elite overhead athletes often exhibit adaptive changes in their shoulder complex kinematics. Considering the interplay between the SC and AC joints, which motion at the AC joint is MOST directly coupled with posterior rotation of the clavicle, facilitating optimal glenohumeral positioning during humeral elevation?
- Posterior tilting of the scapula, decreasing the subacromial space during hyperabduction.
- Internal rotation of the scapula, optimizing glenohumeral joint congruency during adduction.
- Anterior tilting of the scapula, allowing greater freedom for humeral extension.
- Upward rotation of the scapula, maximizing the available range for humeral abduction and flexion. (correct)
A researcher is investigating the force transmission through the shoulder complex during weightlifting. If the individual is performing a bench press, at what locations would the greatest compressive forces be expected during the concentric phase, assuming optimal biomechanics?
A researcher is investigating the force transmission through the shoulder complex during weightlifting. If the individual is performing a bench press, at what locations would the greatest compressive forces be expected during the concentric phase, assuming optimal biomechanics?
Following a motor vehicle accident, a patient presents with clinical signs indicative of costoclavicular ligament insufficiency. Which of the following scenarios would MOST likely exacerbate symptoms related to this injury?
Following a motor vehicle accident, a patient presents with clinical signs indicative of costoclavicular ligament insufficiency. Which of the following scenarios would MOST likely exacerbate symptoms related to this injury?
A patient exhibits excessive scapular anterior tilting during shoulder elevation. Which of the following structural adaptations at the acromioclavicular (AC) joint could be a contributing factor to this kinematic impairment?
A patient exhibits excessive scapular anterior tilting during shoulder elevation. Which of the following structural adaptations at the acromioclavicular (AC) joint could be a contributing factor to this kinematic impairment?
A surgeon is planning a complex reconstruction following a complete dislocation of the sternoclavicular (SC) joint with significant ligamentous damage. Which of the following surgical considerations is MOST crucial to restore optimal SC joint kinematics and stability?
A surgeon is planning a complex reconstruction following a complete dislocation of the sternoclavicular (SC) joint with significant ligamentous damage. Which of the following surgical considerations is MOST crucial to restore optimal SC joint kinematics and stability?
Consider a patient presenting with limited shoulder internal rotation. Advanced imaging reveals adaptive remodeling of the glenoid fossa with increased retroversion. Which compensatory motion at the acromioclavicular joint is MOST likely to be observed to maintain optimal glenohumeral alignment?
Consider a patient presenting with limited shoulder internal rotation. Advanced imaging reveals adaptive remodeling of the glenoid fossa with increased retroversion. Which compensatory motion at the acromioclavicular joint is MOST likely to be observed to maintain optimal glenohumeral alignment?
In a cadaveric study examining the effects of sequential ligamentous transection at the sternoclavicular (SC) joint, which order of transection would MOST likely result in the GREATEST degree of clavicular instability during simulated shoulder movements?
In a cadaveric study examining the effects of sequential ligamentous transection at the sternoclavicular (SC) joint, which order of transection would MOST likely result in the GREATEST degree of clavicular instability during simulated shoulder movements?
A rehabilitation specialist is designing an exercise program for a patient with scapular dyskinesis characterized by excessive downward rotation. Focusing on the acromioclavicular (AC) joint's role, which exercise modification would be MOST effective in promoting upward rotation of the scapula?
A rehabilitation specialist is designing an exercise program for a patient with scapular dyskinesis characterized by excessive downward rotation. Focusing on the acromioclavicular (AC) joint's role, which exercise modification would be MOST effective in promoting upward rotation of the scapula?
A researcher is investigating the impact of varying scapular positions on glenohumeral joint range of motion. Which of the following scapular positions would MOST likely result in a DECREASE in passive shoulder external rotation range?
A researcher is investigating the impact of varying scapular positions on glenohumeral joint range of motion. Which of the following scapular positions would MOST likely result in a DECREASE in passive shoulder external rotation range?
An elite swimmer is diagnosed with superior shoulder impingement syndrome. Considering the interplay of forces at the acromioclavicular (AC) joint during the freestyle stroke, which biomechanical factor is MOST likely contributing to this condition?
An elite swimmer is diagnosed with superior shoulder impingement syndrome. Considering the interplay of forces at the acromioclavicular (AC) joint during the freestyle stroke, which biomechanical factor is MOST likely contributing to this condition?
A patient with thoracic outlet syndrome (TOS) exhibits neurovascular compression symptoms exacerbated by specific shoulder movements. Which biomechanical dysfunction at the sternoclavicular (SC) joint is MOST likely contributing to these TOS symptoms?
A patient with thoracic outlet syndrome (TOS) exhibits neurovascular compression symptoms exacerbated by specific shoulder movements. Which biomechanical dysfunction at the sternoclavicular (SC) joint is MOST likely contributing to these TOS symptoms?
A manual therapist is assessing a patient with suspected acromioclavicular (AC) joint pathology. During palpation, they note increased joint play with superior glide of the distal clavicle on the acromion. Which ligamentous structure is MOST likely compromised?
A manual therapist is assessing a patient with suspected acromioclavicular (AC) joint pathology. During palpation, they note increased joint play with superior glide of the distal clavicle on the acromion. Which ligamentous structure is MOST likely compromised?
A patient with adhesive capsulitis ('frozen shoulder') is undergoing rehabilitation. Considering the integrated function of the shoulder complex, which compensatory movement pattern is LEAST advisable during early-stage exercises to regain functional elevation?
A patient with adhesive capsulitis ('frozen shoulder') is undergoing rehabilitation. Considering the integrated function of the shoulder complex, which compensatory movement pattern is LEAST advisable during early-stage exercises to regain functional elevation?
A patient presents with chronic shoulder instability following a traumatic anterior dislocation. Advanced imaging reveals a Bankart lesion and a Hill-Sachs defect. Considering the biomechanics of the glenohumeral joint, which surgical intervention addresses both the osseous and soft tissue pathologies to restore stability and prevent recurrent dislocations, while also optimizing long-term joint kinematics and minimizing the risk of osteoarthritis?
A patient presents with chronic shoulder instability following a traumatic anterior dislocation. Advanced imaging reveals a Bankart lesion and a Hill-Sachs defect. Considering the biomechanics of the glenohumeral joint, which surgical intervention addresses both the osseous and soft tissue pathologies to restore stability and prevent recurrent dislocations, while also optimizing long-term joint kinematics and minimizing the risk of osteoarthritis?
A high-level overhead athlete reports increasing shoulder pain during the late cocking phase of throwing. Clinical examination reveals subtle anterior instability and internal impingement. Which combination of pathokinematics and underlying structural deficiencies is MOST likely contributing to the athlete's symptoms, requiring a nuanced and comprehensive rehabilitation approach to restore optimal function and prevent further injury?
A high-level overhead athlete reports increasing shoulder pain during the late cocking phase of throwing. Clinical examination reveals subtle anterior instability and internal impingement. Which combination of pathokinematics and underlying structural deficiencies is MOST likely contributing to the athlete's symptoms, requiring a nuanced and comprehensive rehabilitation approach to restore optimal function and prevent further injury?
Following a complex proximal humerus fracture treated with open reduction and internal fixation, a patient exhibits persistent limitations in glenohumeral abduction and external rotation, accompanied by signs of adhesive capsulitis. Which intricate interplay of biomechanical factors and soft tissue restrictions MOST significantly impedes the restoration of full range of motion, necessitating advanced manual therapy and mobilization techniques to address the underlying causes?
Following a complex proximal humerus fracture treated with open reduction and internal fixation, a patient exhibits persistent limitations in glenohumeral abduction and external rotation, accompanied by signs of adhesive capsulitis. Which intricate interplay of biomechanical factors and soft tissue restrictions MOST significantly impedes the restoration of full range of motion, necessitating advanced manual therapy and mobilization techniques to address the underlying causes?
A powerlifter presents with anterior shoulder pain during bench press, exacerbated by eccentric loading. Examination reveals a hypermobile glenohumeral joint and a positive apprehension test. Which comprehensive rehabilitation strategy BEST addresses the underlying biomechanical instability and optimizes the force-generating capacity of the prime movers, while minimizing the risk of recurrent subluxation during high-intensity exercises?
A powerlifter presents with anterior shoulder pain during bench press, exacerbated by eccentric loading. Examination reveals a hypermobile glenohumeral joint and a positive apprehension test. Which comprehensive rehabilitation strategy BEST addresses the underlying biomechanical instability and optimizes the force-generating capacity of the prime movers, while minimizing the risk of recurrent subluxation during high-intensity exercises?
Elite swimmers often develop unique shoulder adaptations due to repetitive overhead movements. Considering the prolonged physiological stresses, what combination of structural adaptations and muscle imbalances is MOST characteristic of a swimmer's shoulder, requiring a highly specialized and individualized training program to maintain optimal performance and prevent chronic pain syndromes.
Elite swimmers often develop unique shoulder adaptations due to repetitive overhead movements. Considering the prolonged physiological stresses, what combination of structural adaptations and muscle imbalances is MOST characteristic of a swimmer's shoulder, requiring a highly specialized and individualized training program to maintain optimal performance and prevent chronic pain syndromes.
A patient with a history of recurrent shoulder dislocations presents with apprehension and pain during resisted external rotation at 90 degrees of abduction. Advanced imaging reveals a subtle lesion of the superior labrum extending anterior to posterior (SLAP lesion), Type II. Which biomechanically-informed surgical approach, incorporating both labral repair and biceps tendon management, is MOST likely to restore native joint kinematics, minimize long-term complications, and optimize return to sport activities at a pre-injury level?
A patient with a history of recurrent shoulder dislocations presents with apprehension and pain during resisted external rotation at 90 degrees of abduction. Advanced imaging reveals a subtle lesion of the superior labrum extending anterior to posterior (SLAP lesion), Type II. Which biomechanically-informed surgical approach, incorporating both labral repair and biceps tendon management, is MOST likely to restore native joint kinematics, minimize long-term complications, and optimize return to sport activities at a pre-injury level?
Following a surgical repair of a massive rotator cuff tear, a patient exhibits persistent weakness in glenohumeral abduction despite adequate healing of the tendon. Considering the intricate interplay of force couples and muscle recruitment patterns, which targeted neuromuscular re-education strategy is MOST critical for restoring optimal shoulder function and compensating for the biomechanical alterations caused by the prior injury and surgical intervention?
Following a surgical repair of a massive rotator cuff tear, a patient exhibits persistent weakness in glenohumeral abduction despite adequate healing of the tendon. Considering the intricate interplay of force couples and muscle recruitment patterns, which targeted neuromuscular re-education strategy is MOST critical for restoring optimal shoulder function and compensating for the biomechanical alterations caused by the prior injury and surgical intervention?
A patient presents with chronic shoulder pain, night pain, and limited range of motion. Radiographic imaging reveals significant glenohumeral joint osteoarthritis with associated bone spurs and joint space narrowing. Considering the complex interplay of biomechanical alterations and inflammatory processes, which surgical intervention is MOST appropriate for pain relief, functional restoration, and long-term joint preservation, while minimizing the risk of complications and optimizing patient-specific outcomes?
A patient presents with chronic shoulder pain, night pain, and limited range of motion. Radiographic imaging reveals significant glenohumeral joint osteoarthritis with associated bone spurs and joint space narrowing. Considering the complex interplay of biomechanical alterations and inflammatory processes, which surgical intervention is MOST appropriate for pain relief, functional restoration, and long-term joint preservation, while minimizing the risk of complications and optimizing patient-specific outcomes?
In the context of glenohumeral joint stabilization, how does the collective action of the rotator cuff muscles contribute to centering the humeral head within the glenoid fossa during dynamic movements, and what potential kinematic alterations arise from imbalances or deficiencies within this musculature?
In the context of glenohumeral joint stabilization, how does the collective action of the rotator cuff muscles contribute to centering the humeral head within the glenoid fossa during dynamic movements, and what potential kinematic alterations arise from imbalances or deficiencies within this musculature?
A baseball pitcher complains of shoulder pain and decreased throwing velocity. Clinical examination reveals scapular dyskinesis and a positive Speed's test. Which of the following biomechanical impairments is MOST likely contributing to the pitcher's symptoms, and what specific interventions should be implemented to address these deficits and restore optimal throwing mechanics?
A baseball pitcher complains of shoulder pain and decreased throwing velocity. Clinical examination reveals scapular dyskinesis and a positive Speed's test. Which of the following biomechanical impairments is MOST likely contributing to the pitcher's symptoms, and what specific interventions should be implemented to address these deficits and restore optimal throwing mechanics?
Considering the biomechanical function of the coracohumeral ligament (CHL), what specific limitations in glenohumeral joint motion are MOST likely observed with CHL contracture, and how does this restriction influence the overall kinematics of the shoulder complex, specifically during activities involving combined abduction and rotation?
Considering the biomechanical function of the coracohumeral ligament (CHL), what specific limitations in glenohumeral joint motion are MOST likely observed with CHL contracture, and how does this restriction influence the overall kinematics of the shoulder complex, specifically during activities involving combined abduction and rotation?
During glenohumeral abduction, what arthrokinematic motion MUST occur at the glenohumeral joint to prevent impingement of the greater tubercle against the coracoacromial arch, and what specific soft tissue structures play a pivotal role in facilitating this essential motion?
During glenohumeral abduction, what arthrokinematic motion MUST occur at the glenohumeral joint to prevent impingement of the greater tubercle against the coracoacromial arch, and what specific soft tissue structures play a pivotal role in facilitating this essential motion?
A patient presents with a confirmed full-thickness tear of the supraspinatus tendon. Considering the biomechanical consequences, how does this injury alter the force-couple relationship between the deltoid and rotator cuff muscles during glenohumeral abduction, and what are the predictable compensatory movement patterns observed at the shoulder complex?
A patient presents with a confirmed full-thickness tear of the supraspinatus tendon. Considering the biomechanical consequences, how does this injury alter the force-couple relationship between the deltoid and rotator cuff muscles during glenohumeral abduction, and what are the predictable compensatory movement patterns observed at the shoulder complex?
A patient having a shoulder examination presents with weakness in external rotation and abduction, and imaging reveals damage to the infrasprinatus and teres minor. How is the arthrokinematics of the glenohumeral joint impacted, and what subsequent changes would be expected at the scapulothoracic joint?
A patient having a shoulder examination presents with weakness in external rotation and abduction, and imaging reveals damage to the infrasprinatus and teres minor. How is the arthrokinematics of the glenohumeral joint impacted, and what subsequent changes would be expected at the scapulothoracic joint?
What are the anticipated alterations in scapulohumeral rhythm following a surgical release of a tight pectoralis minor muscle, and how do these changes correlate with improvements in glenohumeral joint range of motion and overall shoulder function?
What are the anticipated alterations in scapulohumeral rhythm following a surgical release of a tight pectoralis minor muscle, and how do these changes correlate with improvements in glenohumeral joint range of motion and overall shoulder function?
Given a patient presenting with scapular winging and confirmed serratus anterior dysfunction via electromyography, but exhibiting no apparent nerve damage pathway, which of the following biomechanical factors would MOST likely exacerbate the patient's condition, assuming compensatory strategies are in play?
Given a patient presenting with scapular winging and confirmed serratus anterior dysfunction via electromyography, but exhibiting no apparent nerve damage pathway, which of the following biomechanical factors would MOST likely exacerbate the patient's condition, assuming compensatory strategies are in play?
A high-level overhead athlete demonstrates excessive glenohumeral external rotation at 90 degrees of abduction. While various factors could contribute, which capsuloligamentous adaptation would MOST likely explain this finding, considering the glenohumeral joint's inherent structural properties?
A high-level overhead athlete demonstrates excessive glenohumeral external rotation at 90 degrees of abduction. While various factors could contribute, which capsuloligamentous adaptation would MOST likely explain this finding, considering the glenohumeral joint's inherent structural properties?
In a patient status post Bankart repair, presenting with limited shoulder internal rotation and persistent apprehension testing at end ranges of external rotation six months post-operatively, which of the following interventions targets the MOST relevant underlying biomechanical impairment contributing to their clinical presentation?
In a patient status post Bankart repair, presenting with limited shoulder internal rotation and persistent apprehension testing at end ranges of external rotation six months post-operatively, which of the following interventions targets the MOST relevant underlying biomechanical impairment contributing to their clinical presentation?
Considering the intricate force couples governing scapulothoracic motion, if an individual exhibits weakness in the lower trapezius, which compensatory muscle recruitment pattern would MOST likely develop to maintain upward rotation of the scapula during arm elevation, potentially leading to secondary impingement?
Considering the intricate force couples governing scapulothoracic motion, if an individual exhibits weakness in the lower trapezius, which compensatory muscle recruitment pattern would MOST likely develop to maintain upward rotation of the scapula during arm elevation, potentially leading to secondary impingement?
In the context of scapulohumeral rhythm and its kinematic chain, if the sternoclavicular joint's elevation range is significantly restricted due to arthritic changes, which compensatory movement pattern would MOST likely manifest at the acromioclavicular and glenohumeral joints to achieve full arm elevation?
In the context of scapulohumeral rhythm and its kinematic chain, if the sternoclavicular joint's elevation range is significantly restricted due to arthritic changes, which compensatory movement pattern would MOST likely manifest at the acromioclavicular and glenohumeral joints to achieve full arm elevation?
Considering the glenoid labrum's role in glenohumeral joint stability and force dissipation, a superior labral tear from anterior to posterior (SLAP lesion) would MOST significantly compromise which specific biomechanical function during forceful overhead activities?
Considering the glenoid labrum's role in glenohumeral joint stability and force dissipation, a superior labral tear from anterior to posterior (SLAP lesion) would MOST significantly compromise which specific biomechanical function during forceful overhead activities?
Given an individual with confirmed pectoralis minor tightness and resultant anterior scapular tilt, what intervention would MOST effectively address the underlying biomechanical cause of associated shoulder impingement symptoms during forward flexion?
Given an individual with confirmed pectoralis minor tightness and resultant anterior scapular tilt, what intervention would MOST effectively address the underlying biomechanical cause of associated shoulder impingement symptoms during forward flexion?
If a patient presents with limited shoulder flexion and internal rotation following a prolonged period of immobilization post-fracture, which specific combination of glenohumeral joint mobilizations would BEST address the capsular restrictions MOST likely contributing to these limitations?
If a patient presents with limited shoulder flexion and internal rotation following a prolonged period of immobilization post-fracture, which specific combination of glenohumeral joint mobilizations would BEST address the capsular restrictions MOST likely contributing to these limitations?
In a throwing athlete with scapular dyskinesis, demonstrating early and excessive protraction of the scapula during the acceleration phase, which neuromuscular re-education strategy would be MOST effective in optimizing scapulothoracic control and reducing strain on the glenohumeral joint?
In a throwing athlete with scapular dyskinesis, demonstrating early and excessive protraction of the scapula during the acceleration phase, which neuromuscular re-education strategy would be MOST effective in optimizing scapulothoracic control and reducing strain on the glenohumeral joint?
Considering the complex interplay between humeral torsion and glenohumeral joint kinematics, an individual presenting with excessive humeral retroversion would MOST likely exhibit which compensatory adaptation during internal rotation to maintain optimal joint congruency?
Considering the complex interplay between humeral torsion and glenohumeral joint kinematics, an individual presenting with excessive humeral retroversion would MOST likely exhibit which compensatory adaptation during internal rotation to maintain optimal joint congruency?
If the coracohumeral ligament is significantly compromised due to a chronic tear, which specific pattern of glenohumeral instability would MOST likely manifest, considering the ligament's primary biomechanical role?
If the coracohumeral ligament is significantly compromised due to a chronic tear, which specific pattern of glenohumeral instability would MOST likely manifest, considering the ligament's primary biomechanical role?
In a patient with confirmed anterior glenohumeral instability, what specific scapular orientation would MOST likely exacerbate the instability during resisted external rotation at 90 degrees of abduction, given the scapula's influence on glenohumeral joint mechanics?
In a patient with confirmed anterior glenohumeral instability, what specific scapular orientation would MOST likely exacerbate the instability during resisted external rotation at 90 degrees of abduction, given the scapula's influence on glenohumeral joint mechanics?
Considering the impact of scapulothoracic joint dysfunction on glenohumeral joint biomechanics, which specific pattern of scapular malposition would MOST likely contribute to internal impingement in an overhead athlete during the late cocking phase of throwing?
Considering the impact of scapulothoracic joint dysfunction on glenohumeral joint biomechanics, which specific pattern of scapular malposition would MOST likely contribute to internal impingement in an overhead athlete during the late cocking phase of throwing?
During a comprehensive shoulder evaluation, you observe a patient with restricted shoulder abduction and note the arm elevates primarily via scapulothoracic motion with minimal glenohumeral contribution. Which of the following glenohumeral accessory motion restrictions would MOST likely explain this aberrant movement pattern?
During a comprehensive shoulder evaluation, you observe a patient with restricted shoulder abduction and note the arm elevates primarily via scapulothoracic motion with minimal glenohumeral contribution. Which of the following glenohumeral accessory motion restrictions would MOST likely explain this aberrant movement pattern?
A patient presents with chronic anterior shoulder pain and reports a history of repetitive overhead activities. Upon examination, you identify increased anterior humeral head translation and a positive apprehension test. Which combination of structural impairments is MOST likely contributing to this patient’s anterior instability?
A patient presents with chronic anterior shoulder pain and reports a history of repetitive overhead activities. Upon examination, you identify increased anterior humeral head translation and a positive apprehension test. Which combination of structural impairments is MOST likely contributing to this patient’s anterior instability?
Flashcards
Clavicle Rotation
Clavicle Rotation
Rotation of the clavicle reduces tension on these ligaments, which effectively "opens" the AC joint, allowing for upward rotation of the scapula.
Scapulothoracic "Joint"
Scapulothoracic "Joint"
Formed by the anterior surface of the scapula and the thorax, it is not a true anatomical joint but relies on the AC and SC joints for movement.
Scapular Upward Rotation
Scapular Upward Rotation
Upward rotation is the primary motion of the scapula during arm elevation, requiring coordinated movement at the SC and AC joints.
Scapulothoracic Elevation
Scapulothoracic Elevation
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Scapular Protraction
Scapular Protraction
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Muscles for Scapular Protraction
Muscles for Scapular Protraction
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Muscles for Scapular Retraction
Muscles for Scapular Retraction
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Muscles for Scapular Elevation
Muscles for Scapular Elevation
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Muscles for Scapular Depression
Muscles for Scapular Depression
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Muscles for Scapular Downward Rotation
Muscles for Scapular Downward Rotation
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Muscles for Scapular Upward Rotation
Muscles for Scapular Upward Rotation
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Glenohumeral Joint
Glenohumeral Joint
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Glenoid Labrum
Glenoid Labrum
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Glenohumeral Capsule & Ligaments
Glenohumeral Capsule & Ligaments
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Rotator Interval Capsule
Rotator Interval Capsule
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Shoulder Complex
Shoulder Complex
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Sternoclavicular (SC) Joint
Sternoclavicular (SC) Joint
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Osteokinematics of SC Joint
Osteokinematics of SC Joint
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SC Disc
SC Disc
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Interclavicular Ligament
Interclavicular Ligament
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Clavicular Elevation (SC Joint)
Clavicular Elevation (SC Joint)
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Acromioclavicular (AC) Joint
Acromioclavicular (AC) Joint
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Superior Acromioclavicular Ligament
Superior Acromioclavicular Ligament
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Conoid Ligament
Conoid Ligament
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Trapezoid Ligament
Trapezoid Ligament
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Motions at the AC Joint
Motions at the AC Joint
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Internal Rotation of Scapula (AC Joint)
Internal Rotation of Scapula (AC Joint)
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Anterior Tilting of Scapula (AC Joint)
Anterior Tilting of Scapula (AC Joint)
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Upward Rotation of Scapula (AC Joint)
Upward Rotation of Scapula (AC Joint)
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Clavicular Rotation
Clavicular Rotation
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Labrum Function
Labrum Function
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IGHLC Function
IGHLC Function
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Coracohumeral Ligament Function
Coracohumeral Ligament Function
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Coracoacromial Arch
Coracoacromial Arch
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Contents of Subacromial Space
Contents of Subacromial Space
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Scaption
Scaption
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GH Abduction Arthrokinematics
GH Abduction Arthrokinematics
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GH Flexion Arthrokinematics
GH Flexion Arthrokinematics
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GH Lateral Rotation Arthrokinematics
GH Lateral Rotation Arthrokinematics
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Stabilization of Dependent Arm
Stabilization of Dependent Arm
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Dynamic Stabilization Factors
Dynamic Stabilization Factors
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Rotator Cuff Function
Rotator Cuff Function
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Offsets Deltoid Translation
Offsets Deltoid Translation
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Scapulothoracic Upward Rotation Contribution
Scapulothoracic Upward Rotation Contribution
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Scapulohumeral Rhythm Ratio
Scapulohumeral Rhythm Ratio
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Study Notes
Introduction to the Shoulder Complex
- Focuses on the joints of the shoulder complex, their structure, components, kinematics, and integrated functions.
- It includes the Acromioclavicular joint, Sternoclavicular joint, Glenohumeral joint, Scapulo-thoracic joint
The Shoulder Complex
- Four mechanically interrelated articulations involve the sternum, clavicle, ribs, scapula, and humerus, allowing for a wide range of motion.
- Dynamic stability via muscular control is crucial, with muscle forces acting as the primary mechanism to secure the shoulder girdle to the thorax.
- Passive structures do not provide major stability.
Joints of the Shoulder Complex
- The joints include Sternoclavicular (SC), Acromioclavicular (AC), Scapulothoracic (ST), and Glenohumeral (GH) joints.
Sternoclavicular Joint
- This joint's the only structural articulation between the axial skeleton and the shoulder/upper extremity (UE).
- Articulation occurs between the medial clavicle and the manubrium of the sternum, plus the 1st costal cartilage.
- The SC joint's a synovial, saddle joint that, at rest, has a wedge-shaped joint space open superiorly.
Osteokinematics of SC Joint
- The sternoclavicular (SC) joint has 3 rotational degrees of freedom (dof), including elevation/depression, protraction/retraction, and anterior/posterior rotation of the clavicle.
- Elevation/depression and protraction/retraction are based on lateral clavicle motion.
- The joint has 3 translatory dof but small in magnitude in a healthy joint.
- Elevation and depression occur near the frontal plane.
- Protraction and retraction occur near the transverse plane.
- Rotation occurs around the longitudinal axis.
- Elevation range of motion (ROM) is up to 48°.
- Depression ROM from neutral is less than 15°.
- Protraction ROM ranges from 15° to 20°.
- Retraction ROM is around 30°.
- Anterior rotation past neutral is less than 10°.
- Posterior rotation reaches up to 50°.
Sternoclavicular Joint: SC disc
- The SC disc acts as pivot point for medial end of clavicle during movements.
- The disc transects the joint into 2 cavities and limits medial translation of the clavicle.
- The SC disc improves joint stability, increases congruence, and absorbs forces.
- The disc's upper attachment is at the posterosuperior clavicle, while the lower attachment is at the manubrium, first costal cartilage, and joint capsule.
Sternoclavicular Capsule & Ligaments
- A relatively strong fibrous capsule is supported by 3 ligament complexes including anterior & posterior sternoclavicular, bilaminar costoclavicular, and the interclavicular ligaments.
- A thick posterior capsule serves as the primary restraint to both anterior and posterior clavicular translations.
- Anterior and posterior sternoclavicular ligaments reinforce capsule & limit anterior & posterior translation of the medial clavicle.
Sternoclavicular Capsule & Ligaments: Costoclavicular & Interclavicularligaments
- The costoclavicular is a strong ligament composed of 2 bundles that limit clavicle elevation, with the posterior bundle resisting the medial translation of clavicle.
- It serves as functional axis of rotation, absorbing & transmitting forces applied to clavicle via sternocleidomastoid (SCM) and sternohyoid muscles.
- The interclavicular ligament limits excessive depression of clavicle & prevents superior gliding of medial clavicle on manubrium and protects brachial plexus & subclavian artery.
Arthrokinematics of SC Joint
- For clavicular elevation, the lateral end of clavicle moves superiorly.
- The medial clavicle surface rolls superiorly & slides inferiorly on the sternum and 1st rib during clavicular elevation.
- For clavicular depression, the lateral clavicle moves inferiorly, while the medial clavicle surface rolls inferiorly & slides superiorly.
- During clavicular retraction, the lateral clavicle moves posteriorly while its medial surface rolls and slides posteriorly on the sternum and first costal cartilage.
- During clavicular protraction, the lateral clavicle moves anteriorly in the transverse plane.
- The medial clavicle rolls & slides anteriorly.
- Clavicular rotation occurs as a spin between surfaces and disc with clavicle primarily rotating posteriorly from neutral position.
Acromioclavicular Joint
- The AC joint is an articulation b/w the lateral clavicle & acromion of scapula characterized by an incongruent, synovial joint with 3 rotational and 3 translational degrees of freedom.
- It allows scapula movement in 3 dimensions during arm movement, increases UE motion, positions glenoid beneath humeral head and helps maximize scapula contact with thorax.
- It assists in force transmission from UE to clavicle.
AC Joints: Articular Surfaces & Union Structure
- The shape of articular surfaces can vary from flat to concave/convex.
- Relatively vertical orientation of joint surfaces makes it more susceptible to shear forces leading to degenerative effects.
- Initially, it's a fibrocartilaginous union between clavicle & acromion.
- With use, joint space develops that may leave a "meniscal homologue," or fibrocartilage remnant, in the joint.
Acromioclavicular Capsule and Ligaments
- The AC joint capsule is relatively weak but is reinforced by superior, inferior acromioclavicular, and coracoclavicular ligaments.
- Superior acromioclavicular ligament resists anteriorly directed forces applied to lateral clavicle and reinforced by the the trapezius & deltoid muscles but is stronger than the inferior capsule and ligament.
- The coracoclavicular ligament has two parts: conoid (triangular & vertical orientation) and trapezoid (quadrilateral & horizontal orientation).
- Coniod's primary role is to restraint inferior translation of the acromion, while the trapezoid resists to posterior translations of lateral clavicle relative to acromion.
- Both coniod and trapezoid limit upward rotation of the scapula at the AC joint.
- It plays a role in coupling posterior clavicle rotation & scapula upward rotation during UE elevation
Acromioclavicular Joint Kinematics
- Axes of motion are difficult to define due to variability in joint surfaces among individuals.
- Motions occur around axes oriented to plane of scapula, including internal/external rotation, anterior/posterior tilting, and upward/downward rotation.
- AC motion influences, and is influenced by, rotation of the clavicle, and small translations also occur, including anterior/posterior, superior/inferior, and medial/lateral.
Resting Position of Scapula
- The scapula rests in an internally rotated position 35°-45° anterior to the coronal plane, has an anterior tilt ~10°-15° from vertical, and is upwardly rotated 5°-10° from vertical.
- The scapula generally rests on posterior thorax ~5 cm from the midline, between the 2nd and 7th ribs.
- Significant variability occurs in scapular rest position.
AC Joint: Scapula Resting Position & Motion
- Internal/external rotation in AC joint occurs around a nearly vertical axis.
- Ant/post tilting occurs around an oblique "coronal" access.
- Upward/downward rotation occurs around an oblique “A-P” axis
- Small translations occur: anterior/posterior, superior/inferior, and medial/lateral.
- Internal rotation orients the glenoid fossa anteromedially, while external rotation orients glenoid fossa posterolaterally.
- IR & ER help maintain contact of the scapula with the curvature of the thorax, position of the glenoid fossa toward plane of humeral elevation, and maximize the function of the GH muscles.
- Anterior tilting: Acromion moves forward causing the inferior angle to move posteriorly
- Posterior tilting: Acromion moves backward causing the inferior angle to move anteriorly
- Anterior tilting occurs with scapular elevation and posterior tilting with scapular depression.
- Upward & downward rotation occurs around the "A-P" axis. The glenoid fossa tilts upward & inferior angle moves laterally during upward rotation. The glenoid fossa tilts downward & inferior angle moves medially during downward rotation.
- Passive upward/downward rotation in AC joint is limited by coracoclavicular ligament; with active movement, Post. clavicle rotation reduces tension on ligament opening the joint to allow upward rotation to occur.
- This joint is not inherently stable and susceptible to trauma & degenerative changes.
- Trauma-related dysfunction is more common in first 3 decades; degenerative changes later in life. This can occur from contact sports or fall on shoulder with arm adducted.
Scapulothoracic Joint
- It is formed by anterior surface of scapula and the thorax/not a true anatomic j, and SC & AC joints are interdependent with scapulothoracic motion.
- Any movement of the scapula on the thorax must result in movement at AC joint, SC joint, or both.
- Stability is related to AC joint integrity, SC joint integrity, muscle strength and control, and dynamic stabilization.
- The scapula rests on the posterior thorax ~5 cm from midline between the 2nd and 7th ribs, internally rotated (35°-45°), anteriorly tilted (10°-15°),. There is significant variability.
Scapulothoracic Kinematics
- The rotational movements are: upward/downward rotation, internal/external rotation, anterior/posterior tilting
- Scapulothoracic elevation/depression and protraction/retraction are considered translatory motions.
- Upward rotation of scapula along with elevation at the sternoclavicular joint, clavicular posterior rotation and AC joint upward rotation are needed in active arm elevation.
Scapulothoracic Kinematics: Elevation-Depression & Scapular Protraction-Retraction
- Scapulothroacic elevation couples clavicular movement with small adjustments at the AC jt for IR/ER or ant/post tilting for contact to the thorax
- Scapular protraction is caused by protraction at the clavicle as well as internal rotation at the AC joint; full protraction leads to an anterior facing glenoid and retraction does the opposite.
- Excessive IR can increase the prominence of medial border (scapular wingin) and is a sign of pathology.
- Anterior and Posterior Tilting primarily occur at the AC joint and cause could cause prominence.
Scapulothoracic Joint : Kinetics
- Muscles that contribute scapular protraction are: Serratus anterior, Pectoralis major, Pectoralis minor
- Muscles that contribute scapular retraction are: Middle trapezius, Rhomboids
- Muscles that contribute scapular elevation are: Upper trapezius, Levator scapulae, Rhomboids
- Muscles that contribute scapular depression are: Lower trapezius, Latissimus dorsi, Pectoralis minor
- A group of muscles facilitate Scapular upward rotation
- Another group of muscles facilitate Scapular downward rotation
Glenohumeral Joint
- This classical ball and socket joint comprised of 3 degrees of rotation and 3 transitional degrees of freedom, allowing it to articulate between between the humeral head and glenoid fossa.
- Its designed for mobility at the cost of stability leading to increased possibility of instanility.
- The Gleniod fossa of the joint has shallow concave features, with its orientation to respect to the position of scapular. The fossa is often slightly tilted upward but is not perpendicular relative to the scapular.
- Its faces slightly anterior with respect to the plane of scapular (anteversion) but can face slightly posterior (retroversion).
- The Humeral head makes up 1/3 to 1/2 of a sphere.
GH Joint - Inclination & Torsion Angles
- The angle of inclination formed by an axis through humeral head & neck in relation to a longitudinal axis through the humeral shaft normally is between 130°- 150°.
- Angle of torsion: Formed by an axis through the humeral head and neck in relation to an axis through the humeral condyles which runs 30°.
- A normal but slightly retroverted angle of humeral torsion centers humeral head on glenoid fossa when scapula is in resting position & arm is at the side.
- Excessive retroversion or anteversion alters the the position of humeral head which may predispose you to injury.
Glenohumeral Joint: Accessory Structures - Glenoid Labrum
- The Accessory structure is and is attached to glenoid fossa where its improves the articular surface.
- By increasing the depth/ concavity of fossa, it protects the bony edges and makes the joint stronger.
- It functions to minimize GH friction, improve Translations, and dissipate forces.
- The labrum serves as an attachment site for the glenohumeral ligament.
Glenohumeral Capsule & Ligaments
- Characterized by it's loose make up, its taut superiorly when at rest and is stabilized with rotator cuff ligament.
- The GH is further reinformced with the superior, middle and inferior GH ligaments as well as Coracohumeral ligament.
- With the arm to the side and uo to 60 degs of abbduction, the glenohumeral liigament limits the anterior Humeral.
Key elements Of glenohumeral ligament complex
- With the complex having has 3 parts/components: anterior & posterior ligament bands, with axillary pouch in between, variability changes depending at each position.
- Has a Major role of jt stabilization with abd > 45° or rotation, the inferior capsule slack is taken up, and resists inferior humeral head translation
- When in ER, bands of function out anterior to provide joint stability resisting head Translations and posterior joint stability.
Other Stabalzing Feature and Mechanics
- The joint has a "Rotator interval" that forms between the joint capsule comprised of of superior GH capsule/ligament together with the coracohumeral ligament, this bridges a gap between the key rotator cuff features.
- Coracoacromial Arch is comprised of the coaracoid process, undersurface of the acromionand acromioclavicular ligament, a vault over the humeral. the space above has subacromial space.
- As shoulder extends a set of range of motion like Flexion is (120°), Extension (50°), and rotation varies depending with arm abducted.
Arthrokinematics
- A critical range of motion for an adequate movement requires for the Humerous to have full inferior side force, with forces by cuff also allow for the upper force that compresses to push the gleniod
- Movement such as Flexion/extension has heads largely spins that require joint to have adequate side force for stabilization.
- During shoulder stabilization. rotator cuff facilitates for rotation, however the Suprasinatus does not offset for upward pressure
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Description
Overview of the shoulder complex, including joints (SC, AC, ST, GH) and their functions. Focuses on the kinematics, structure, and components of each joint. The shoulder complex enables a wide range of upper extremity motion.
