Functional Anatomy and Biomechanics of Elbow and Radioulnar Joints

Question 1

Elbow and Radioulnar Joint Intro

Answer 1

• 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

Question 2

Humeroulnar Joint (HU)

Answer 2

• 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

Question 3

Osteokinematics at HU Joint

Answer 3

• 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

Question 4

Arthrokinematics in HU Joint

Answer 4

• 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

Question 5

Humeroradial Joint (HR)

Answer 5

• 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

Question 6

Osteokinematics at HR Joint

Answer 6

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

Question 7

Arthrokinematics in HR Joint

Answer 7

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

Question 8

Proximal Radioulnar Joint (PRU)

Answer 8

• 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

Question 9

Osteokinematics at PRU and DRU Joints

Answer 9

• 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

Question 10

Arthrokinematics in PRU Joint

Answer 10

• 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

Question 11

Distal Radioulnar Joint

Answer 11

• 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

Question 12

Arthrokinematics at DRU Joint

Answer 12

• 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

Question 13

Ligaments

Answer 13

• 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

Question 14

Gross Motion in Elbow Region

Answer 14

• 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

Question 15

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?

Answer 15

• 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?

Question 16

Muscular Actions in Elbow Region

Answer 16

• 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

Question 17

Elbow Flexors

Answer 17

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

Question 18

Brachialis

Answer 18

• 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

Question 19

Biceps Brachii

Answer 19

• 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

Question 20

Brachioradialis

Answer 20

• 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

Question 21

Elbow Extensors

Answer 21

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

Question 22

Triceps Brachii

Answer 22

• 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

Question 23

The Pronators

Answer 23

• 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

Question 24

Supinators

Answer 24

• 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

Question 25

Strength of Forearm Muscles

Answer 25

• 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

Question 26

Therapeutic Exercise in Elbow Region

Answer 26

• 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

Question 27

Lateral Epicondylitis

Answer 27

• 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

Question 28

Medical Epicondylitis

Answer 28

• 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

Question 29

Bursitis

Answer 29

• 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

Question 30

Ulnar Nerve Injuries

Answer 30

• 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