Elbow (functional exam 2)

Joints of the elbow

Humeroulnar (true elbow)

Humeroradial

Proximal radioulnar

What kind of joint is elbow + DOF

Synovial

1 (flexion, extension)

Trochlea structure and function

Anterior articulating surface for ulna

Hyaline cartilage

For WB surfaces

Coronoid process enters coronoid fossa during

Flexion

Olecranon process enters olecranon fossa during

Extension

Carrying angle of HU joint at rest

Slight valgus

Cubitus valgus

Larger carrying angle

Cubitus varus

Smaller carrying angle

Where does HU joint have good bony stability

End ranges of flexion and extension

HU loose pack

70 degrees of flexion

HR loose pack

Full extension (no contact between the two, can feel the space in extension)

Describe fibrous joint capsule

3 joints in capsule

Loose and redundant anteriorly to allow for extension

Blends with annular ligament and collateral ligaments

Describe synovial joint capsule

Nutrition: synovial fluid

Hyaline cartilage

Medial and lateral epicondyles of humerus and olecranon of ulnar outside of capsule

What makes up the MCL

Anterior bundle

Posterior bundle

Transverse bundle

Describe anterior band of MCL

Restrains valgus forces from 20-120 degrees of elbow flexion

Why doesn’t anterior band of MCL work at full extension

Other structures such as bony congruency and anterior joint capsule takes the load

At full extension olecranon process is locked into the fossa of humerus, taking the majority of stress

Describe the posterior band of MCL

Restrains valgus forces at greater than 90 degrees of flexion

Primary mode of injury of MCL

Repetitive overhead use

Components of LCL

Lateral radial collateral ligament

Lateral ulnar collateral ligament

Lateral radial collateral ligament function

Restraint to varus forces and supination

Lateral ulnar collateral ligament function

Restraint to varus forces and supination

Maintains posterolateral rotary stability of elbow (so forearm doesn’t roll of humerus aka elbow dislocation)

Annular ligament role

Helps stabilize radial head

What happens at LCL when we forcefully over-supinate

We supinate the ulna as well, creating tensile load that strains the LCL

What causes posterolateral rotary instability

Combined supination and axial load

Lateral ulnar collateral ligament is most likely to fail

HU joint concave or convex

Concave trochlear notch of ulna on convex humerus

HU flexion arthrokinematics OPEN CHAIN

Anterior roll, anterior glide

HU flexion arthrokinematics CLOSED CHAIN

Convex on concave

Anterior roll, posterior glide

HU extension arthrokinematics OPEN CHAIN

Posterior roll, posterior glide

HU flexion arthrokinematics CLOSED CHAIN

Convex on concave

Posterior roll, anterior glide

Which muscle, when passively insufficient, will restrict the available passive range of motion into elbow flexion

Triceps (long head)

Which muscle, when passively insufficient, will restrict the available passive ROM into elbow extension

Biceps

In elbow flexion which part of the elbow enters the fossa

Coronoid process and radius head

In elbow extension which part of the elbow enters the fossa

olecranon process

As elbow flexion contracture (degrees) increases, percent loss in area of forward reach ____

Increases

Proximal radio ulnar joint concave or convex

Convex radial head on concave radial notch of ulna

Describe proximal radio ulnar joint ligaments

Annular ligament: stabilizer to hold radius in place against ulna; lined with hyaline cartilage

Quadrate ligament: limits pronation/supination

Oblique cord: holds bones together

Distal radio ulnar joint concave or convex

Concave ulnar notch of radius on convex ulnar head (opposite to proximal end)

Describe triangular fibrocartilagenous complex (TFCC)

At distal radioulnar joint

Made up of palmar and dorsal ligaments (dynamic stabilizers)

Describe dorsal and palmar radioulnar ligaments

Pronate: dorsal ligament tight

Supinate: palmar ligament tight; pulls ulnar styloid towards palm

Describe interosseus membrane and its fiber orientation

Approximates radius and ulna

Fiber orientation allows for transfer of loads from bigger distal radius to bigger proximal ulna during UE weight bearing activities

At proximal joint pronation is a ___ glide

Posterior

During pronation and supination the ___ is moving on a relatively fixed ___

Radius, ulna

What movement occurs at the shoulder to compensate for lack of supination

ABD

IR

What movement occurs at the shoulder to compensate for lack of pronation

ADD

ER

Proximal stabilizer of radio ulnar and humero ulnar joints

Pronator teres

Active stabilizer of distal radio ulnar joint

Pronator quadratus

Ligamentous contributions to proximal radio ulnar joint

Annular and quadrate ligaments

Oblique cord (limits supination)

Interosseous membrane

Muscular contributions to proximal radio ulnar joint

Passive tension in the biceps brachii in the fully extended elbow position

Pronator teres (maintains contact of radial head and capituulum)

Ligamentous contributions to distal radio ulnar joint

Interroseous membrane

Dorsal and palmar radio ulnar ligaments

Triangular fibrocartilage

Joint capsule

Muscular contributions to distal radio ulnar joint

Pronator quadratus

Extensor carpi ulnaris

Pronator teres

Primary elbow flexor

Brachialis

Energy efficient

No passive insufficiency bc it’s a one joint muscle

Force generation doesn’t depend on position of shoulder or forearm

3 elbow flexors

Brachialis

Biceps brachii

Brachioradialis

Describe role of biceps brachii in elbow flexion

Forearm supinators

Supinator

Biceps brachii

Role of Supinator in forearm supination

Can function alone in unresisted, slow supination or in fast supination with the elbow extended

Crosses elbow; can produce small amount of torque into elbow flexion

Doesn’t need a partner to supinate

Role of biceps brachii in forearm supination

Always involved in resisted supination

Involved in fast unresisted supination

Helps supinator if demands are too high

Muscles involved in foreceful pronation

Pronator quadratus

Pronator teres

Triceps (not including long head)

Muscles involved in forceful supination

Supinator

Biceps brachii

Triceps (including long head)

Muscles involved in bicep curl

Biceps brachii

Brachialis

Brachioradialis

Shoulder extensors (delts, lats, teres major) (since biceps want to flex the shoulder)