elbow Flashcards
Elbow joint complex
3 separate articulations within capsule
capsule most lax @ 80˚F - closed packed at full ext.
o stable joint
o good bony congruency
o reinforced by strong ligaments
o valgus alignment predisposes elbow to valgus injuries
HUMEROULNAR JOINT
trochlea of the humerus and the trochlear notch of the ulna
- Synovial hinge
- flexion and extension
RADIOHUMERAL Joint
capitulum of the humerus and the head of the radius
- synovial hinge
- flexion and extension
elbow joint
Synovial hinge joint: elbow flexion / extension - axis through centre of trochlea & capitulum
Greater contact between radius and capitulum in elbow flexion
PROXIMAL RADIOULNAR JOINT
Between the radial notch of the ulna and the articular circumference of the head of the radius.
- Synovial pivot joint
- Pronation and supination
Medial collateral ligament
anterior, posterior, transverse
Resists valgus force
Extension:
valgus restraint = humeroulnar bony stability + anterior band MCL
~ 90˚ flexion:
less bony stability
> anterior band MCL as main restraint against valgus force
- bones provide stability against further valgus stress and
medial colateral ligaments
in full extension = most bony congruency
prone to valgus injuries
Lateral collateral ligament complex
resists varus force
• provides posterolateral stability
Lateral ulnar collateral ligament, Accessory lateral collateral lig, Radial collateral Ligament, annular lig
ANALYSIS of ELBOW FLEXORS:
Moment = Force x moment arm M=Fxd
PCSA
- brachialis
- biceps brachii
- pronator teres
- brachioradialis
MOMENT ARM:
- brachioradialis
- biceps brachii
- brachialis
- pronator teres
A muscle’s moment arm length changes through the range of movement
longer moment arm more efficient conversion of force
- moment arm least in 0 > 90 - 110˚ flexion is when moment
arm is greatest
Muscle length-tension relationship:
Muscle can produce more force as the muscle is lengthened
OPTIMAL POSITION FOR FORCE PRODUCTION - elbow
= 70 to 90˚ flexion
articular capsule
Attachments: Margins of coronoid, radial & olecranon fossae, medial epicondyle & capitulum to border of olecranon & coronoid processes & annular ligament
Resists: minimal (lax)
Anterior capsule may resist valgus in Ext.
radial collateral ligament (RCL)
Attachmments: From lateral epicondyle to annular ligament
Resist: varus & posterolateral instability”
lateral ulnar collateral ligament (LUCL)
Attach: From lateral epicondyle to supinator crest of ulna
Resists: “varus & posterolateral instability”
medial collateral ligament (MCL)
At: “From medial epicondyle to:
Anterior band to coronoid process
Posterior band to olecranon process
transverse band: coronoid > olecranon
annular ligament
A: Anterior & posterior margins of the radial notch
R: Lateral & distal subluxation of the radial head
oblique cord
A: Ulnar tuberosity to radius distal to tuberosity
R: End range supination
interosseous membrane
A: Interosseous border of radius distally to ulna
R: separation of radius / ulna
“close-packed position”
Position with the most amount of joint congruency
•Capsule and supporting ligaments maximally tight
•Accessory motion is minimized
loose/open-packed position
Position with the least amount joint surface congruency
•Capsule and support ligaments are lax
•Accessory motion or joint play is maximized
Which position is the close packed position of the humeroulnar joint?
Which position is the loose packed position of the humeroulnar joint?
loose packed: 70 deg flexion and 10 deg supination
closed packed: full ext and supination
How can the following affect measured elbow flexor strength?
- position of the shoulder
Length of Muscle
If BB is flexed at shoulder, can’t provide as much force at elbow flx.Hypoext. of shoulder - greatest force
How can the following affect measured elbow flexor strength?
degree of elbow flexion
muscle length
70 - 90˚ flx = moment arm greatest
How can the following affect measured elbow flexor strength?
- position of forearm
in pronation = favours brachialis, less BB activity therefore less elbow flx.
in sup = favours BB
in neutral = favours brachioradialis
