Flashcards in Joints of the elbow Deck (17):
Describe the elbow joint.
- Compound joint between humerus, radius and ulna (more than 2 articular surfaces)
- Hinge joint
- Capsule houses two distinct joints: Elbow and proximal radioulnar
- No meniscus
- Supplied by branches of the brachial artery
- Innervated by musculocutaneous, radial and ulnar nerves.
What are the ligaments of the elbow joint?
1. Ulnar collateral ligaments: Anterior, posterior, oblique
2. Radial collateral ligaments: Blends with annular ligament
The strongest support comes from the medial collateral ligament
Articular capsule is lax anteriorly and posteriorly.
What is the purpose of the fat pads in the fossa?
They are in the olecranon, radial and coronoid fossa - they cushion movement and help spread synovial fluid
What are the movements at the elbow?
1. Flexion: This usually occurs between humerus and ulna. There is radial contact in a close-packed position (90 degree flexion and mid-way between pronation/supination)
2. Extension: Occurs at an oblique angle of the trochlea. There is no hyperextension because of the olecranon.
Carrying angle: Elbow extension, forearm supination. It is greater in adults than children and is greater in females than males.
Which muscles allow flexion at the elbow joint?
- Biceps brachii
Which muscles allow extension at the elbow joint?
- Triceps brachii
Describe the radioulnar joints.
- They occur at each end of the radius, thus proximal and distal radioulnar joints.
- Between radial notch on ulna and ulnar notch on radius
- Fracture at one end may lead to dislocation at the other
What is the purpose of the interosseous membrane?
It transmits forces from radius to ulna and eventually to the humerus. At the proximal end, only 20% through radius and at the distal end 80% thorough the radius.
It tightens as the joint undergoes pronation.
Describe the proximal radioulnar joint.
- It is between the head of radius and radial notch of ulna.
- It is a pivot, synovial joint.
- it is within the elbow joint capsule
- It has a sacciform recess in which the synovial membrane extends downwards.
- It is innervated by the median, musculocutaneous and radial nerves
- It is supplied by the branches of deep radial and radial arteries.
What are the ligaments of the proximal radioulnar joint?
- Annular ligament
- Quadrate ligament
- Interosseous membrane
Describe the distal radioulnar joint.
- It is between the head of ulna and ulnar notch on radius
- It is a pivot type synovial joint
- It is supported by anterior and posterior ligaments
- An articular disc sits between the bones and progresses to distalmost face of ulna
- Innervated by Median and rdial interosseous nerves
- Supplied by anterior and posterior interosseous arteries
What are the movements at the radioulnar joints?
- Pronation/supination, working with flexion/extension
- Midprone position most stable
What are the muscles moving the radioulnar joints?
- Pronation: Pronator teres, pronator quadratus. Assisted by FCR, PL, Brachioradialis
-Supination: Supinator, biceps brachii. Assisted by EPL, ECRL
Dislocaiton of the proximal radioulnar joint
- May cause annular ligament laxity in children
- Radial head is displaced as muscles pull radial head superiorly.
- There will be reduced capacity to carry out some movements e.g - supinate forearm, push proximally and flex joint.
What are the clinical considerations at the H-U and R-U joints?
- Avulsion fractures: Medial epicondyle of humerus; olecranon/coronoid process/styloid process of ulna.
- Supracondylar fracture of humerus - Volkmann's ishchemic contracture.
What is a valgus deformity?
In terms of dislocation at the elbow, it is when the distal joint is lateral to the proximal joint.