Functional Anatomy and Biomechanics of Elbow and Radioulnar Joints Flashcards Preview

DPT 726: Orthopaedic Foundations > Functional Anatomy and Biomechanics of Elbow and Radioulnar Joints > Flashcards

Flashcards in Functional Anatomy and Biomechanics of Elbow and Radioulnar Joints Deck (30)
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Elbow and Radioulnar Joint Intro

-elbow has 3 joints between 3 bones
-movements between arm and forearm occurs at humeroulnar and humeroradial joints
-movement within forearm occurs within proximal radioulnar joint and distal radioulnar joint


Humeroulnar Joint (HU)

-articulation between humerus and ulna
-major articulation in elbow
-joint is composed of trochlea on distal humerus, trochlear notch on proximal ulna
-flexion is limited by approximation of coronoid fossa on anterior humerus, coronoid process on front of ulna
-extension is limited by approximation of olecranon fossa on humerus, and olecranon process on
-motion: flexion/extension (hinge jt)
-trochlea covered with articular cartilage: asymmetrical joint surface, asymmetry creates lateral angulation (valgus) of ulna when joint is extended
-carrying angle describes this angulation: ranges from ~10-15* in males, and ~20-25* in females
-valgus position lessens with elbow flexion
-articular cartilage also covers anterior, inferior, and posterior surfaces of trochlear notch


Osteokinematics at HU Joint

-flexion ROM ~145*: limited by soft tissue, posterior capsule, extensor mm, terminally restrained by bone on bone contact of coronoid process and fossa
-extension ROM 0*: 5-10* hyperextension more common in females, typically limited by joint capsule and flexor mm, terminally restrained by bone on bone contact
-flexion/extension ROM needed for ADL ranges from 30-130* of flexion


Arthrokinematics in HU Joint

-joint orientation: humerus-inferior, posterior; ulna-superior, anterior
-concave surface: ulna
-loose-pack position: 70* flexion, 10* supination
-close-pack position: full extension and supination


Humeroradial Joint (HR)

-2nd joint participating in elbow flexion/extension
-capitulum is distal articulation of humerus: articular cartilage on anterior and inferior surfaces, provides support against lateral compression in high velocity activities: eg throwing etc
-pivot joint exists between capitulum and radial head


Osteokinematics at HR Joint

-motion: flexion/extension, supination/pronation
-pivot joint
-same as osteokinematics in HU joint


Arthrokinematics in HR Joint

-joint orientation: humerus inferior, radius superior
-concave joint surface: radius
-loose-pack position: full extension and supination
-close-pack position: 90* flexion, 5* supination


Proximal Radioulnar Joint (PRU)

-establishes motion in pronation and supination
-articulation exists between: radial head, radial fossa on side of ulna
-radial head rotates within fibrous osseous ring and annular ligament
-radius and ulna lie parallel in neutral position
-in full pronation radius crosses ulna diagonally, ulna moves laterally slightly
-opposite happens in supination
-interosseous membrane runs between ulna/radius and maintains specific relationship between bones-transmits force


Osteokinematics at PRU and DRU Joints

-motion: pronation/supination
-pronation ROM ~70*: limited by ligaments, joint capsule, and soft tissue compression as radius and ulna cross
-supination ROM ~85*: limited by ligaments, capsule, and pronator mm
-~50* pronation and ~50* supination needed for most ADL


Arthrokinematics in PRU Joint

-joint orientation: ulna-lateral, anterior; radius-medial, posterior
-concave surface is ulna
-loose-pack position is 35* flexion, 70* supination
-close-pack position: full supination or pronation


Distal Radioulnar Joint

-located at distal radius and ulna
-adjacent to wrist joint
-ulna separated from carpals by fibrocartilage disc: allows ulna to pronate/supinate without influencing wrist or carpal movements


Arthrokinematics at DRU Joint

-joint orientation: ulna-lateral; radius-medial
-concave joint surface is radius
-loose-pack position is 10* of supination
-close pack is full supination or pronation



-collateral ligaments support medial and lateral elbow
-medial (ulnar) collateral ligament connects ulna to humerus: resists valgus stress upon elbow, most forces directly medially in elbow
-lateral (radial) collateral ligament provide support against rarer varus forces
-annular ligament wraps around radial head, attaches to ulna, holds radius in elbow but allows rotation
-quadrate ligament and interosseous membrane provide additional support to radioulnar joint


Gross Motion in Elbow Region

-close pack position for 3 joints are at different points in ROM
-radio-humeral joint at 90* and in semi-pronated position
-ulnar-humeral joint is full extension
-proximal radio-ulnar joint when in slightly flexed, semi-pronated position: complements HRJ
-approximate ROM values for flexion/extension: ~145* active flexion, 160* passive, ~0-10* hyperextension
-flexion limited by soft tissue, posterior capsule, extensor tightness; bone-to-bone restriction at coronoid process
-extension limited by anterior capsule, flexor tightness; bone-to-bone restriction at olecranon at end range
-most ADL require 100-140* flexion/extension ROM: ranges from 30-120* for many activities
-pronation ROM ~70* limited by ligaments, joint capsule, soft tissue compression as radius and ulna cross
-supination ROM ~85* limited by ligaments, joint capsule and pronator muscle
-most ADL require ~50* pronation to ~50* supination


Case Study-Jenny works in purse factory and quits and has tennis elbow. How might we deduce whether the lateral elbow pain is truly coming from structures in elbow or somewhere else?

-check dermatomes or myotomes try to recreate pain-if able to recreate more likely to be within our scope of practice; non-reproducible means a metabolic problem outside the scope of our practice
-dx by exclusion: ask questions to rule options out
-medical hx: any prior elbow issues
-pain rating at beginning of work vs end
-anything you do to relieve the pain?


Muscular Actions in Elbow Region

-24 muscles cross elbow
-some act exclusively at elbow (brachialis)
-most are capable of contributing to three movements at elbow, wrist, and fingers
-yet one mm is usually dominant: it is the movement for which mm or muscle group is associated


Elbow Flexors

-biceps, brachialis, brachioradialis, pronator teres, extensor carpi radialis
-collectively become more effective as elbow flexion increases: increase mechanical advantage with increase in moment arm



-deep to biceps
-strongest flexor
-secondary to its role as only pure elbow flexor
-does more work than the other muscles
-output not influenced by pronation or supination of forearm
-maximum output at ~120* elbow flexion
-active at all positions, speeds, with or without resistance


Biceps Brachii

-proximal attachment: long head originates at supraglenoid fossa of scapula; short head to coracoid process
-distal to radial tuberosity of radius
-contribution to flexion depends on position of arm: most active during middle 90* of flexion (between 30* and 120*)
-contribution to flexion also depends on position of forearm in pronation and supination: most effective flexor within forearm in supination; attachment twisted under radius when pronated
-activity drops in semi-pronated position-in prone position contributes minimally, even against resistance
-its contribution can be affected if arm is extended or hyperextended
-maximal output occurs at ~120* of flexion



-between distal humerus and styloid process of radius
-small volume and very long fibers
-efficient muscle used with rapid elbow flexion and against resistance
-produces greatest activity at ~120* of flexion with forearm in supinated position
-does not increase its activity when arm is semi-pronated or pronated


Elbow Extensors

-functional antagonist of elbow flexors
-located on posterior humerus
-triceps and anconeus (4th head of triceps)


Triceps Brachii

-strongest arm muscle: secondary to greatest mm volume in upper arm
-output not affected by position of forearm supination/pronation
-has 3 portions: long head (least active), medial, and short heads
-long head only portion to cross shoulder joint, makes its action and effectiveness partially dependent upon shoulder position, least active of 3 heads


The Pronators

-pronation the 3rd motion produced at radioulnar articulations
-pronator quadratus: between distal ulna and radius, activity and production greater of 2 pronator mm, more active regardless of elbow position, fast or slow activity, or with or without resistance
-pronator teres: contribution increases with rapid pronation or against high load; most active at 60* forearm flexion



-produced primarily by biceps brachii and supinator mm
-supinator: between humerus, ulna on one side and radius
-only muscle contributing to slow unresisted supination in all elbow positions
-biceps: active when elbow is flexed, very effective supinator at 90* of elbow flexion, increased effectiveness with rapid or resisted supination


Strength of Forearm Muscles

-flexors nearly 2x stronger than extensors in all positions
-makes us more effective at pulling than pushing
-flexion force production: semi-pronated > supinated > pronated; semi-pronated most common in ADL, include semi-pronated strengthening to take advantage of forearm strength


Therapeutic Exercise in Elbow Region

-complete isolation of specific muscle very difficult
-because arm and forearm mm work in combination functionally
-stretching exercise, manual resistance, isotonic resistance commonly used in rehab
-therapeutic exercise best prescribed with an eye on return to function
-eccentric resistance exercise very important for conditions such as lateral epicondylitis
-typically need to modify exercise prescription for individual patient


Lateral Epicondylitis

-aka tennis elbow
-onset may be slow/insidious or linked to trauma
-usually involves inflammation of tendinous attachment into periosteum
-irritation of forearm extensors-ECRB, ECRL, ECU, extensor communis, supinator
-repetitive activities a common trigger
-palpation to lateral humeral condyle is typically painful


Medical Epicondylitis

-aka golfer's elbow
-common in any repetitive gripping activity
-irritation of flexors and pronators-teres, FCR
-patient hx and intervention conceptually as with lateral epicondylitis



-olecranon bursa most commonly affected
-may be caused by variety of irritants: trauma, gout, RA, etc
-most common symptom is edema
-intervention: anti-inflammatories, remove/change irritating stimulus, strengthen/stretch muscles in area


Ulnar Nerve Injuries

-often develop secondary to entrapment at cubital tunnel
-also irritated by OA, spurs, fracture, soft tissue lesions
-patient hx: numbness/tingling 4th and 5th fingers, elbow/forearm pain
-PT often focuses on change in biomechanics, change in motor programs, neural glides
-address ROM at neighboring joints
-radial and median nerves are also injured too