The elbow joint consists of three anatomically joined joints and surrounded by a joint capsule. The high complexity of the elbow joint, as well as the fact that it is often (over) used intensively, means that it is often injured.

The elbow joint is often described as a hinge joint, but this is a simplification because it is actually a series of joints working together. Thehumeral-elbowandbrachial-radialjoints allow you to performflexion and extension of the forearm , while the joint radial-ulnar distaltogether withradial-ulnar distal(which lies on the other end of the forearm and is not part of the elbow joint) allowrotations forearms inwards( converting ) andoutwards( turning ).

Elbow joint - structure

The elbow joint consists of two joints -hinged( humeral-elbow ) andspherical(brachial-radial ) - which work together to performflexionandextensionof the elbow. Apart from them, the elbow joint also includes the elbow joint functionally independent of the other tworotary( radial-ulnar closer ).

The head of the humeral-elbow joint ishumerus blockand the acetabulumulna block indentationlimited by the ulnar and pitted processes. It covers the head of the humerus like pincers.

The head of the radial brachial joint is formed by thehumeral head , which is almost spherical in shape, but only its anterior and lower surfaces, as articular surfaces, are covered with cartilage. The acetabulum isdimple in the head of the radial bone .

The proximal radioulnar jointispivot joint , for whichthe articular head is the articular circumference of the radial head , andthe acetabulum is a radial indentation of the ulna and the annular ligament . The annular ligament complements the bone acetabulum. It attaches to the anterior and posterior edge of the radial notch of the ulna and covers the articular circumference of the radial head. This head is firmly seated in it, which makes it difficult to dislocate the joint. Onlyin children whose ligament is not yet so strong, it is easier to dislocate the joint by pulling it by the hand. Both bones of the forearm are also connected byquadrilateral ligament .

The articular bagof the elbow joint on the sides is taut and reinforced with ligaments, while at the front and back it is spacious and thin. Thanks to this, when bending, its front wall relaxes, and the shoulder strap above it pulls back and tightens the bag so that it does not become entangled in the joint. When the elbow is straightened, the bag protrudes at the back on both sides of the ulnar process, and the medial head of the triceps muscle prevents the bag from collapsing.

The surfaces of the bones that are inside the articular capsule of the elbow but not covered by articular cartilage are lined with a smooth and shiny synovium.

The side walls of the elbow joint capsule are reinforced with strong ligaments that protect the joint against dislocation. The front and back walls are usually the weaker sides of the bag. The following are responsible for the lateral and medial strengthening of the joint:

  • ulnar collateral ligament , which runs from the medial epicondyle to the edge of the ulnar block indentation, and whose thick bundle also attaches at the base of the pointed process. The ulnar collateral ligament prevents the ulna from shifting radially;
  • radial collateral ligament , which is located on the radial side of the capsule. Its course begins at the lateral epicondyle, then divides into two divergent arms: one is directed forward, the other towards the back of the radial head. They are attached to the ulna partly forwards and partly backwards from the radial notch. Between the arms of this ligament there are fibers that run from the epicondyle to further connect with the fibers of the annular ligament. Thus, the radial collateral ligament does not attach to the radius bone and therefore does not restrict its rotational movements. However, it prevents the radial bone from moving towards the ulna and strengthens the annular ligament.

Elbow joint - features

The most visible movement in the elbow is theflexionandstraighteninginvolving both bones in the forearm. This is because the annular ligament attaches the radius to the ulna, so it moves with the ulna.The elbow joint(shoulder-elbow joint) is considered to behinge joint , although there are slight deviations from the mean axis during movementpond.

In an upright position, the upper arm and forearm form an angle of 175-180 degrees. Higher values ​​are the so-called elbow hyperextension, which is more common in women than in men, and most often in children who have less developed pitted and elbow processes. Exceeding the norm by more than 10 degrees is considered pathological. In the position of maximum flexion, the arm and forearm form an angle of approximately 40 degrees. Inhibition of the flexion movement occurs when the elbow rests against the bottom of the elbow fossa, and also as a result of the tension of the posterior wall of the articular capsule and the muscles straightening the forearm. The elbow extension movement inhibits the contact of the pointed process with the bottom of this process. The flexion-extension range of motion in a he althy person in the elbow joint is 140-150 degrees.

In addition to bending and straightening, there are alsorotational movements of the radial head on the humeral headcombined with rotational movementsin the proximal radioulnar joint, i.e.converting( pronation ) andinversion( supination )forearm . The ranges of forearm rotational movement are approximately 90 degrees for supination and approximately 80-90 degrees for pronation.

Forbending the elbow jointcorrespond to the muscles:

  • two-headed arm
  • shoulder
  • brachial-radial (assistive)
  • reversible rounded (to a lesser extent)
  • long wrist extensor (to a lesser extent)

The mainextensors of the elbow jointare the muscles:

  • three-headed arm
  • ulnar (auxiliary action)

Conversion( internal rotation )forearmmuscles cause:

  • recurrent rounded (especially with a bent elbow)
  • reversible quadrilateral
  • radial wrist flexor
  • long wrist radial extensor

Inverting( external rotation )forearmis done by the following muscles:

  • two-headed arm
  • forearm reverser
  • long thumb abductor
  • long thumb extensor
  • short extensor of the thumb
  • pointer rectifier

Elbow joint - pain and injuries

The elbow joint is exposed to numerous injuries both due to its complex structure and due to frequent overloading of its structures during everyday activities and sports. Among the most common diseases and injuries are:

  • fractures of the point and ulnar process;
  • tennis elbow;
  • golfer's elbow;
  • periarticular or intra-articular ossification;
  • muscle contractures;
  • degenerative changes;
  • ulnar nerve groove syndrome (ulnar canal syndrome);
  • bursitis;
  • bruises.

Many of them are associated with severe pain that may prevent normal functioning even for a long time. Due to the fact that many of these injuries result from overloading the structures of the elbow joint, it is worth paying special attention to work ergonomics and appropriate training methods.

Bibliography

Bochenek A., Reicher M., Human Anatomy, Volume I, PZWL Medical Publishing, Warsaw 2012.

Category:

Anatomy