ELBOW JOINT

The elbow joint is a loose hinge type joint that provides shoulder and hand movement with the help of muscles. Because there is rotational movement of the ulna when the elbow is in flexion/extension. The medial collateral and lateral collateral ligaments are directly connected, and at the same time, there are 5 muscles directly affecting the joint, namely the flexor muscles in the anterior and the extensor muscle groups in the posterior.

HUMEROULNAR AND HUMERORADIAL JOINT SURFACES

1)HUMERUS:

On the anterior side;

• Distally articulating surfaces are medially trochlea and laterally capitulum. These two structures are between medial and lateral epicondyle.
• The coronoid fossa is located just above the trochlea. The coronoid protrusion of the proximal ulna fits here while the elbow is flexed.
• The radial fossa is located just above the capitulum. The radius head sits here while the elbow is flexed.
• The capitulotrochlear groove separates the capitulum and the trochlea from each other.

On the posterior side;

• Olecronon fossa is located distal. At the end of the elbow extension movement, the olecranon of the ulna settles in this fossa. It restricts/locks the elbow extension.

2) RADIUS AND ULNA:

• In the humeroradial joint, the articular surface of the radial head is concave, while the capitulum humeri is convex. The fovea is surrounded by the cup-like structure of the radius head.
• In the humeroulnar joint, the ulna has a concave articular surface while the humerus is convex.

JOINTS

1) Humeroradial Joint

• The radial surface of the joint consists of the radial head.
• The finca-shaped concave structure surrounding the sides of the radial head is called the fovea.
• Radius head is concave, capitulum is convex.
• Joint closed pack position》90 degrees flexion +5 degrees supination
• Joint open pack position》full extension + supination

2) Humeroulnar Joint

• Primarily, the trochlear notch slides over the trochlear groove.
• There is an angulation medially in the frontal plane of the elbow. The angulation originates from the articular surfaces of the humeroulnar joint. The medial structure of the trochlea is more distal than its lateral structure and the medial structure pushes the trochlear notchu distally and laterally, resulting in angulation. The normal value of this angle is 15 degrees. As the angle increases, cubitus valgus, and as it decreases, cubitis varus occurs.
• Joint closed pack position》full extension
• Joint open package position》70 degrees flexion+10 degrees supination

3) Proximal Radioulnar Joint

• The articular surfaces consist of the ulnar/radial notch, the anular ligament, and the radial head.
• The radial notch is lateral to the proximal ulna and also below the trochlear notch and has a concave articular surface.
• The annular ligament attaches to the posterior-anterior part of the radial notch and surrounds the radial head.

LIGAMENTS TAKING ACTION IN ELBOW STABILITY

1) Medial(Ulnar)Collateral Ligament/MCL

*It is the major structure that resists high VALGUS STRESS in events such as golf and throwing.
*MCL is more affected in golfer’s elbow/medial epicondylitis.
*Ligament has three parts as anterior, transverse and posterior;

》Anterior band:

It starts from the anterior surface of the medial epicondyle and inserts into the ulnar coronoid procces. This band of MCL is most tense in the elbow 20-70 degrees flexion. (It primarily restricts the valgus stress at 20-120 degrees flexion.)

》Transverse band:

It starts from the coronoideus and ends in the olecranon. It connects the anterior and posterior bands to each other. It is the structure that contributes the least to resisting valgus stress.

》 Posterior band:

It starts from the posterior face of the medial epicondyle and inserts into the olecranon+ulnar coronoid proc.. Although it is not as effective as the anterior band against valgus stress, it limits the elbow extension. It also contributes to the formation of cubital tunnel.
*If we are to compare the contribution of the bands to the valgus stress of MCL;

anterior>posterior>transverse

2) Lateral Collateral Ligament Complex

》Lateral Collateral Ligament/Radial Collateral Ligament/LCL

• Starts from the lateral epicondyle of the humerus and inserts into the annular ligament and olecronon.
• Contributes to the humeroradial joint.
• Prevents longitudinal distraction of joint surfaces.
• It resists VARUS STRESS of the elbow joint.

》Lateral Ulnar Collateral Ligament

• It starts from the lateral epicondyle of the humerus and inserts into the lateral ulna+supinator muscle.
• Primary lateral stabilizer that provides humeroulnar joint stability.

》Anular Ligament

• It starts from the radius head and inserts into the radial notch in the ulna.
• Provides proximal radioulnar joint stability and prevents the radial head from moving away from the ulna.
• As soon as it allows supination and pronation movement, it is stretched.
• The accessory ligament supports the anular ligament.

》Accessory Collateral Ligament

• It starts from the proximal annular ligament and inserts into the ulna lateral.
• Supports the anular ligament against varus tension at the elbow.

3)PROXIMAL RADIOULNAR JOINT LIGAMENTS

》Quadrate Ligament

• Provides inferior support to the joint capsule.
• Restricts supination and pronation. (Prevents rotation of radius head.)
• The anterior part is stretched in supination and the posterior part is stretched in pronation.

》Oblique Cord

• Contributes to the integrity of the radius and ulna.

》Introessous Membrane

• The central band consists of the membranous membrane and the dorsal oblique cord.
• Provides proximal and distal joint stabilization.
• The center band is the most resistant to tension.
• It is also the attachment site of the anterior and posterior muscles of the forearm.

CLINICAL INFORMATION=IF MEDIAL FROM LATERALE STRESS IS APPLIED LCL, IF LATERAL FROM MEDIALE STRESS IS APPLIED, MCL INJURY IS DETECTED!!!

JOINT CAPSULE

• It is loose and convoluted so as not to restrict the ROM.
• While the capsule is weak anteriorly and posteriorly, it is strong thanks to the ligament structures in the lateral and medial.
• Contributes to valgus and varus stability.
• Provides slight resistance to distraction in the humeroulnar and humeroradial joints in elbow flexion.
• The medial part merges with the MCL, and the lateral part merges with the LCL.

MUSCLES

1.Brachialis:

It starts from the anterior aspect of the humerus》Tub.Ulna and Proc.Coronoideus ends in Ulna. The nerve level is C5-C6 and innervated by N.Musculocutaneous. It is the muscle of the elbow that makes PM FLEXION.

2.Biceps Brachii:

As its name suggests, it is a two-headed muscle. Its short head starts from Proc.Corocoideus; its long head starts from Tub.Supraglenodale》Inserts into Tub.Radii. Its nerve level is C5-C6 and it is innervated by N.Mussculocutaneous. Its main function is to the elbow while the forearm is supinated. It makes flexion. In addition, it helps arm flexion.

3.Brachioradialis:

It starts from the crista supraepicondilis lateralis structure in the humerus and ends in the Proc.Styloideus. The nerve level is C5-C6, as in the biceps brachii and brachialis, but they are not innervated by the same nerve. The brachioradialis is innervated by the N.Radialis.

4.Supinator:

It starts from the lateral of the epiconylus and lig.collaterale radiale of the humerus, and ends outside the anterior surface of the radius. The nerve level is C5-C6 and innervated by the N.Radialis. The PM task supinates the forearm.

5.Pronator Teres:

Humeral head starts from epiconylus medialis, ulnar head starts from proc.coronoideus》It ends on outer lateral surface of Radius. Its nerve level is C5-C8/T1 and innervated by N.Medianus. PM task is pronation to forearm. It helps forearm flexion.

6.Flexor Carpi Radialis:

All wrist flexors start from the Medial Epicondyle and end at the base of the 2nd and 3rd metacarpal. The task of PM is to flex the wrist. It also makes the wrist abduct and the forearm weakly flexed. The nerve level is C5-C8/T1 and innervated by the N.Medianus.

7.Flexor Carpi Ulnaris:

All wrist flexors start from the Medial Epicondyle, and intersect the pisiform, hamatum, and the base of the 5th metacarp. The nerve level is C8-T1 and innervated by N. Ulnaris. The task of PM is to flex the wrist. It makes the wrist adduct and weak flexion.

8.Extensor Carpi Radialis Longus:

All wrist extensors start from the Lateral Epicondyle and insertion into the base of the 2nd metacarp. The nerve level is C5-C6 and innervated by the N. Radialis. It extends the wrist.

9.Extensor Carpi Radialis Brevis:

All wrist extensors start from the Lateral Epicondyle and end by inserting into the base of the 3rd metacarp. The nerve level is C5-C6 and innervated by the N. Radialis. It extends the wrist.

10.Anconeus:

It starts from the Lateral Epicondyle, makes the olecranon insertio. The nerve level is C5-C6 and is innervated by the N. Radialis. It extends the elbow.

11.Palmaris Longus:

It starts from the medial epicondyle and inserts into the palmar aponeurosis. The nerve level is C6-C7 and innervated by the N.Medianus. It stretches the palmar fascia and makes the wrist and elbow flexion.

12.Triceps Brachii:

As it can be understood, it is a 3-headed muscle. Its long head, Tub. Infraglenoidale, starts from the humerus section with its lateral head above the Radial Sulcus, and its medial head starts from the section below the Radial Sulcus, ends at the Olecronom Ulna with the common tendon. It is innervated. The task of PM is to extend the forearm. Its long head also adducts and extends the arm.
(The nerve levels of the muscles may differ according to the sources!!!)

TO SUMMARY;

☆Major flexors of the elbow joint;
Brachialis,Brachioradialis and Biceps Brachii
☆Weak flexors of the elbow;
Flexor carpi radialis,flexor carpi ulnaris,palmaris longus
☆Elbow extensors;
Triceps Brachii and Anconeus
☆Major work on the radioulnar joint;
Supinator and Pronator Teres.