Kinesiology Exam 2

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Muscle Forces are the Primary Means For:

Muscle Forces are the Primary Means For:

Securing the Shoulder Girdle to the Thorax

Providing a Stable Base for Upper Extremities and hand use

Shoulder Configuration

Designed to Prioritize Mobility, at the Expense of Stability

Motions of the SternoClavicular (SC) Joint

Clavicle:
Elevation/Depression, Protraction/Retraction, Anterior/Posterior Tilting

Motions of the AcromioClavicular (AC) Joint

Scapula (Glenoid Positioning):
Internal/External Rotation, Anterior/Posterior Tilting, Upward/Downward Rotation

Scapula (Contact with Thorax):
Protraction/Retraction

AC Joint

Joint Orients Glenoid Fossa into Optimal position in relation to the Head of Humerus

AC Joint

Joint allows the Scapula to Rotate in 3 Dimensions to achieve Scapular Stability on the Thorax

Motions of the Scapulothoracic Joint

Scapular:
Upward/Downward Rotation, Elevation/Depression, Protraction/Retraction, Internal/External Rotation, Anterior/Posterior Tilting

Scapular “Winging”

Excessive scapular Internal Rotation; Vertebral Border of scapula comes Off the Thorax

Due to Loss/Weakness of Serratus Anterior

Motions of the GlenoHumeral (GH) Joint

Shoulder:
Flexion/Extension, Abduction/Adduction, Internal/External Rotation

Functions of the Labrum

Deepens Glenoid Fossa, Enhancing articular Surface Area

Resists humeral head Translations

Rotator Cuff Muscles Function

Additional Stability of the glenohumeral joint

Static Stability (At Rest) at GH Joint: Gravity

Exerts Downward Translatory force on Humerus

Static Stability (At Rest) at GH Joint: Joint Stabilization

Result of Passive Tension created by taut Rotator Interval Capsule (RIC)

Static Stability (At Rest) at GH Joint: Resultant Force

Vector Compresses humeral head into lower Glenoid Fossa, Preventing Inferior Translation

Gravity Vector + RIC Vector =

Closed-Pack Position of GH Joint

90 degrees Abduction and Full External Rotation

GH Dynamic Stabilization - Line of Action: Deltoid

Made of 3 Force Vectors which all coincide/match with the fibers of Middle Deltoid

GH Dynamic Stabilization - Deltoid Force Resolution Vectors

F_D → F_x + F_y

Deltoid Force Vector → Parallel Force + Perpendicular Force

GH Dynamic Stabilization: Parallel (F_x) Force of Deltoid

This component is Larger and Superior, causing the humerus to Translate Superiorly

Contributes to Joint Compression

GH Dynamic Stabilization: Perpendicular (F_y) Force of Deltoid

Applied to humerus

Contributes to Rotary Force (Abduction)

GH Dynamic Stabilization: Rotator Cuff

Infraspinatus, Teres Minor, Subscapularis (ITS) all have Similar Lines of Action

Individual and Together, lines of action are Similar

GH Dynamic Stabilization: Parallel (F_x) Force of ITS

Offsets the Superior Translatory force of the Deltoid, with Inferior Translatory Force

GH Dynamic Stabilization: Perpendicular (F_y) Force of ITS

Compresses and Rotates humerus

GH Dynamic Stabilization: Parallel (F_x) Force of Supraspinatus

Superiorly directed Translatory force

GH Dynamic Stabilization: Perpendicular (F_y) Force of Supraspinatus

More Compressive than other rotator cuff muscles

Can Indpendently Abduct the humerus; Rotary Force

Coracoacromial Arch

Created by the coracoid process, acromion and coracoacromial ligament

Forms an arch over the humeral head

Humeral Impingement

During Abduction and Flexion the humeral head will Roll Up on the Coracoacromial Arch

Preventing Humeral Impingement

Must Externally rotate, allowing Downwards sliding of Humeral Head

External rotation moves the humeral Greater Tuberosity out of the way of the Coracoacromial Arch

Scapulohumeral Rhythm: Scapula

Contributes to humeral flexion/abduction by Upward Rotation

50-60 degrees of Scapulohumeral Rhythm

Scapulohumeral Rhythm: Glenohumeral Joint

Flexion: 100-120 degrees of Scapulohumeral Rhythm

Abduction: 90-120 degrees of Scapulohumeral Rhythm

Scapulohumeral Rhythm: Total

150-180 degrees of Scapulohumeral Rhythm

2:1 Ratio (GH:Scapula, 120:60)

Force Couple — Trapezius and Serratus Anterior: Initial Arm Elevation

Action lines of Upper Trapezius and Serratus Anterior Initiate Upward Scapular Rotation

Force Couple — Trapezius and Serratus Anterior: Maximum Arm Elevation

Lower Trapezius and Serratus Anterior Sustain scapular position

This type of elevation Creates the Longest/Greatest Moment Arms/Torque of Lower Trapezius and Serratus Anterior

Rhomboid Muscle Function

Offsets Teres Major’s Upwards Rotary Torque of the humerus, permitting Scapular Stabilization

This stabilization allows humeral Adduction and Extension

Scapular Downward Rotation Muscles

Rhomboids, Levator Scapulae, Latissimus Dorsi, Pectoralis

Trochlea Function

Medial aspect creates a valgus angulation or carrying angle

Carrying Angle

Moves the upper extremities away from the body during arm swinging while walking

Medial (Ulnar) Collateral Ligament

Limits elbow Extension at end of ROM

Resists Longitudinal Distraction of joint surface

Lateral (Radial) Collateral Ligament

Stabilizes Humeroradial Joint in varying positions of the forearm

Resists Longitudinal Distraction of joint surface

Brachialis

Inserts close to elbow

Moment Arm/Torque is Largest at 100 degrees of Elbow Flexion

Biceps Brachii

Moment Arm/Torque is Largest at 90 degrees and Smallest at Full Extension

Brachioradialis

Inserts at radial styloid, Far from Elbow Axis

Creates Compressive forces, leading to Joint Stability

Triceps Brachii Active Insufficiency

Result of Extension of both Elbow and Shoulder, creating a Decrease in Torque

2 Joint Muscle

Pushup: Lowering Into Pushup

Triceps Eccentrically Contract which controls Elbow Flexion

Push Up: Pushing Up

Triceps Concentrically Contract which creates Elbow Extension

Push Up: Kinematic Chain Type

Closed Kinematic Chain

Triceps Brachii

Acts and Synergist during Supination of Biceps Brachii, by preventing Elbow Flexion

Functional Activities

Require a combination of ROMs and motions at the elbow and radioulnar joints

Components of the Radiocarpal Joint

Scaphoid, Lunate, Triquetrum and Radius

Components of Midcarpal Joint

Trapezium, Trapezoid, Capitate, Hamate

Scaphoid, Lunate, Triquetrum

Proximal Joints

Serve to Increase support, positions, and degrees of freedom of the hand

Examples:
Shoulder serves as dynamic base of support for hand tasks
Elbow serves as a mechanism to position the hands closer/farther from the body
Forearm adjusts positioning of hand when approaching object

Main Contributions of the Wrist

Controls Length-Tension Relationship

Controls Prehension/Grasp for the most Optimal Grip Pattern

Importance of Wrist

Ensures Balance/Control with multiarticular hand muscles, rather than focusing on generating maximum torque

Wrist Complexity

Highly Complex, where structure/biomechanics of the wrist can be Highly Variable from person to person

Incongruence/Angulation

Lack of proper Fit or Alignment of the joint surfaces

Incongruence/Angulation of Radiocarpal Joint

Greater ROM in wrist Flexion than extension

Greater ROM in wrist Ulnar Deviation than radial deviation

Midcarpal Joint Articulation

Between Proximal and Distal Carpal Rows

Proximal: Scaphoid, Lunate, Triquetrum
Distal: Trapezium, Trapezoid, Capitate, Hamate

Midcarpal Joint and ROM

Greater wrist Extension than flexion

Greater wrist Radial Deviation than ulnar deviation

Wrist Flexion to Extension Sequence

Start: full Wrist Flexion
Active wrist extension Initiated at Distal Carpal Row and MCPs
Distal carpal row Glides on Fixed Proximal carpal Row
At 45 degrees wrist extension Scaphoid and Lunate are in Close-Packed Position; uniting all carpals into one functional unit
Close-Packed united carpals move on radius and TFCC to achieve full wrist extension
Ligaments are taut and carpals are in Closed-Packed position at Full Extension

Full Radial Deviation

Radiocarpal and Midcarpal joints are in Close-Packed position

Full Wrist Extension

Close-Packed Position, carpals locked

Radial/Ulnar deviation Not Possible

Full Wrist Flexion

Open/Loose-Packed Position

Despite open/loose-packed position Proximal Carpal Row unable to move further, making Radial/Ulnar Deviation Not Possible

Flexor Carpi Radialis

This muscle offsets Wrist Extension created by Extensor Carpi Radialis Longus

This muscle is a synergist of radial deviation, Offsetting wrist extension to allow Radial Deviation

Flexor Carpi Ulnaris

More efficient at Ulnar Deviation than flexor carpi Radialis is at radial deviation

This muscle is More Efficient than flexor carpi Radialis at wrist Deviation

Flexor Carpi Ulnaris

Strongest wrist muscle, creating high tension

Best muscle for actions that require Ulnar deviation (chopping wood)

Flexor Digitorum Synergist Stabilization

FDP+FDS efficiency depends on Extensor muscles

Need to avoid Active Insufficiency/Torque Loss of FDP + FDS

Flexor Digitorum Superficialis Comparison

This muscle is the Stronger Wrist Flexor of the flexor digitorum muscles

Flexor Digitorum Profundus Comparison

This flexor digitorum muscle is more likely to become Actively Insufficient

Due to this muscle Crossing More Joints

Extensor Carpi Radialis Brevis

This muscle is the more Active during Grasp/Release and wrist Extension of the extensor carpi muscles

Extensor Carpi Radialis Longus

This muscle has Increased Tension during Forceful Finger Flexion and Forceful Radial deviation against ulnar deviation

Colles Fracture

Distal fragment of radius displaces radially and dorsally

When healed incorrectly, creates “dinner fork” or “bayonet” deformity

Scaphoid Fracture

Common fracture when falling on outstretched hand

Due to this carpal’s rigid connection with unstable lunate

Deep Transverse Metacarpal Ligament

Runs across Head of Metacarpals 2, 3, 4

Limits Abduction at the CMC joints, creating CMC Joint Stability

Proximal Transverse Metacarpal Ligament

Creates Volar Concavity, which is maintained by the Transverse Carpal Ligament

Proximal Transverse Metacarpal Ligament

Forms tunnel of the Carpal Tunnel, where median nerve and finger flexor tendons go through

Proximal Transverse Metacarpal Ligament

Restricts “Bowing” of finger flexor tendons during wrist flexion

Palmar Arches Function

Increase Conformity between Hand and Objects

Allows hand to fit better around objects

Palmar Arches Function

Allows Increased Somatosensory Feedback

Increased Somatosensory feedback leads to Increased Stability with functional grasp

Proximal Transverse Arch

Runs underneath the Concavity of Carpal Bones;

Along the underside of the carpal bones

Distal Transverse Arch

Across/Level of the Metacarpal Heads;

Along the Heads of the Metacarpals

Longitudinal Arch

Runs along the length of each finger from base (proximal) to the tip (distal);

Along the base of the wrist (proximal) to the tip of the fingers(distal)

Stability of Arches During Functional Grasp/Grip

Created from Deep Transverse Metacarpal Ligament

Volar Plate at MCP Joint

Attaches from the Head of Metacarpal/Phalanx to the Base of the Phalanx

Incongruent Joint

Joint where Bone Surfaces Don’t fit together Evenly (Instable joint)

Volar Plate Definition

Accessory Joint Stabilizer of incongruent PIP and DIP joints

Stabilizes IP joints

Longitudinal Arch

Volar plate Limits Hyperextension, Supporting this structure

Compressive Force

Volar Plate resists this force when Holding objects;

Volar Plate Protects Volar surfaces of Metacarpal Heads when holding objects from this force

Distractive/Tensile Force

Volar plate resists this force during MCP hyperextension

Volar Plate Functions

Reinforces IP Joint Capsule
Provides Stability
Limits Hyperextension

Collateral Ligament

During Full MCP Flexion (close-packed), this ligament Limits Abduction/Adduction

Dorsal Hood / Extensor Hood / Extensor Expansion

Joint Capsule Reinforcement

MCP Flexion ROM

Higher Ulnarly compared to radially

(Radial) Digit 2: 90 degrees → (Ulnar) Digit 5: 110 degrees

MCP Abduction/Adduction ROM

Maximum ROM with MCP Extension

(Ulnar) Long Finger Flexors

Greater ROM in these fingers allows for Tighter Grip

Extrinsic Finger Muscles

Muscles that Originate from the Forearm and attach in the hand

External from the hand (Forearm)

Intrinsic Finger Muscles

Muscles that Originate and attach in the Hand

Internal hand muscles

Thenar/Hypothenar, Lumbricals, Interossei

Flexor Digitorum Superficialis Muscle Function

MCP and PIP Flexion:
Primarily flexes PIP joint, but contributes to MCP Flexion

Extrinsic Finger Flexor

Flexor Digitorum Profundus Muscle Function

MCP, PIP, DIP Flexion

Can act alone for gentle pinching and grasping activities (doesn’t need other muscles)

Extrinsic Finger Flexor

Optimal Length-Tension

FDP and FDS achieve this based on Wrist Position

Extensors need to Counterbalance Flexors to allow for Optimal Grasp

Active Insufficiency

FDP/FDS combined Finger flexion and Wrist flexion causes this Insufficiency

Impossible to fully Flex Fingers during full Wrist Flexion

Passive Insufficiency

Full Wrist Flexion creates this type of Insufficiency on the Finger Extensors

This pulls on the finger Extensors, which prevents full Finger Flexion