What is the elbow joint?
The elbow consists of 3 different articulations (synovial hinge joint):
-Humeroulnar (has more bony stability) = between trochlea of humerus and trochlear notch of ulnar. Transmits 43% of the longitudinal forces; coronoid process bears 60% total compressive stress when elbow joint is extended
-Humeroradial (has more ligamentous support) = between capitulum of humerus and head of radius. Transmits 57% of the longitudinal forces; force transmission is greater in pronation than in supination.
(The forces are decreased with the elbow at 90 degrees flexion).
- Proximal radioulnar (allows supination-pronation – this is transverse plane)
- Lateral and medial collateral ligaments strengthen the capsule
How is the elbow important?
It can be subjected to high loads, especially in sports. Ligamentous complexes are involved in the pathoanatomy of elbow dislocations and instability. There are important vessels and nerves that cross the elbow. The elbow is the origin of flexor-pronator and extensor-supinator musculatures of the forearm.
What are the movements of the elbow?
- extension (triceps brachii and anconeus):
- flexion (brachialis, biceps brachii and brachioradialis)
- (moves in sagittal plane): 0-146 degrees
What does the coronoid process do?
The coronoid process prevents posterior ulna displacement (prevents posterior dislocation of elbow)
What are the elbow stabilisers?
Primary:
-Ulnohumeral articulation
- Anterior medial collateral ligament (extends from the medial epicondyle of the humerus to the coronoid process of the ulna): primary resistance to valgus stress. The anterior band resists valgus force and tightens in extension; if disrupted, radial head becomes primary restraint to valgus stress. Posterior band tightens in flexion. There’s also an inferior band.
- Lateral (ulna) collateral ligament: main stabiliser of whole elbow. Holds the ulna up to the humerus. primary resistance to varus stress. However, can be damaged on valgus stress and allow the radial head to dislocate posteriorly. It damaged, the ulna sags and instability can be seen
Secondary:
-Radial collateral ligament (has a low attachment to the lateral epicondyle of the humerus. The distal fibres blend with the annular ligament that encloses the head of the radius, as well as with the fibres of the supinator and the extensor carpi radialis brevis muscles): Resists posterolateral rotation instability; stabilises radial head.
- Annular ligament resists subluxation of radial head
- Common flexor-pronator tendon: On the medial epicondyle. The common flexor tendon is the convergence of 5 muscles: pronator teres, flexor carpi radialis, palmaris longus, flexor digitorum superficialis, and flexor carpi ulnaris.
- Common extensor tendon: On the lateral epicondyle. The extensor carpi radialis brevis (ECRB) and longus, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris come together to form the common extensor tendon.
- Joint capsule.
What are the elbow flexors and extensors?
Elbow flexors:
- biceps brachii: active in flexion when supinated
- brachialis: primary elbow flexor
- brachioradialis: active in both rapid and slow flexion
- extensor carpi radialis longus/brevis
Elbow extensors:
- Triceps brachii: primary extensor (the medial head is primary; lateral and long heads act in reserve). The 3 heads form one tendon inserting into olecranon process.
- Anconeus: active in extension
- Flexor carpi ulnaris: active in elbow extension due to posterior origin placement
What is supination and pronation for the elbow?
Pronation-Supination primarily occurs at humeroradial and proximal radioulnar joints
- Normal range 71 degrees pronation to 81 degrees supination- 152 degrees arc
- Most activities require 50degrees pronation to 50degrees supination
-Forearm rotates about a longitudinal axis passing through centre of capitulum.
Muscles in Supination:
• Supinator
• Biceps brachii
• - 20-30% greater strength than pronation. Males 40% stronger than females.
Muscles in Pronation:
• Pronator quadratus : Primary pronator of forearm
• Pronator teres: Secondary pronator when rapid pronation required
What nerves cross the elbow?
Ulnar nerve, median nerve and radial nerve
What is valgus elbow oreintation?
• Flexed Supinated arm
– Valgus orientation places elbow (fulcrum of the lever) next to trunk for increased stability.
• Extended Arm
– Carrying angle (10-15 degrees)
– Less in children than adults, greater in females than males.
– Allows arm swinging without contacting hips.
– Greater resistance to valgus stress than to varus (Medial ulnar collateral ligament).
• Valgus stress places joint into valgus, varus stress places joint into varus
What is lateral epicondylitis (Tennis elbow)?
-Swelling of common extensor tendon, making it hard to extend the forearm and grip. There is tearing of microfibres of extensor tendons of the forearm.
Normally, the extensor carpi radialis brevis is involved but can also include extensor digitorum, extensor carpi radialis longus and extensor carpi ulnaris.
-Pain is located in lateral epicondyle of elbow and can radiate into forearm
- Caused by excessive/repetitive use of the posterior forearm muscles e.g in sports, computer use, heavy lifting, forceful pronation, and supination
- Treatment is with rest, NSAIDs and physical therapy. If they don’t work then corticosteroid injections and surgery may be required.
What is medial epicondylitis (golfer’s elbow)?
- Inflammation of flexor pronator tendon at medial epicondyle of the elbow
- It’s caused by any activity that places valgus force on the elbow or that involves forcefully flexing the volar forearm muscles e.g golfing
- Treatment is NSAIDs, rest and ice and then exercises and gradual return to activity
What is elbow instability?
Elbow instability
- Stability is determined by bony constraints and soft tissue restraints (static)
- Increased constraint = increased stability + decreased range of movement
- Main stabilisers are: Ulno-humeral articulation - MCL – LUCL
Elbow stability – medial ligament complex (the anterior band of the medial collateral ligament of the elbow is the most important stabilizer of the elbow valgus instability)
Elbow stability – lateral ligament complex
- Fracture to coronoid process can lead to elbow instability.
- LCL tear and fracture of anteromedial coronoid process will lead to posteromedial elbow instability. Posteromedial instability is usually caused by varus deforming force. Delayed treatment can lead to varus and posteromedial instability
Valgus instability is due to problems with MCL
What is valgus instability?
Valgus instability arises through injuries to the MCL, specifically the AMCL.
Medial collateral ligament injuries may occur after trauma, such as an elbow dislocation, or as a repetitive overuse injury, commonly seen in overhead-throwing athletes.
The typical history includes a “pop” and medial elbow pain following throwing activities, or patients may present with recurrent medial elbow pain, classically during the late cocking to early acceleration phase of throwing.
What is posterolateral instability?
Posterolateral rotatory instability is the most common recurrent instability of the elbow; it occurs secondary to a traumatic or iatrogenic injury to the LCL.
