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Anatomy of the Elbow
Anatomy of the Elbow
The elbow is a joint that, although we all learn about it in anatomy, most massage therapists do not do much with. To release tension in the elbow we work the forearm muscles or the upper arm muscles, both of which will give some relieve to the elbow. At times, however, the ligaments in the elbow itself need to be released and mobilized.
The first thing we need to do is understand the full anatomy of the elbow. The elbow joint is actually three individual, distinct joints: 1) the humeroradial joint, 2) the humeroulnar joint, and 3) the proximal radioulnar joint. These three joints are encapsulated in the joint capsule of the elbow. The elbow itself is classified as a hinge joint, which is a diarthrodial joint with synovial fluid and a joint capsule that only moves in a sagittal plane, meaning it only does flexion and extension.
The first joint, the humeroulnar joint is an articulation between the trochlea of the humerus and the trochlear notch of the ulna. This is the primary joint within the elbow, and it is on the medial side of the humerus and forearm. The humeroulnar joint is a true hinge joint, only moving into flexion and extension. When the elbow is extended, the olecranon process of the ulna fits into the olecranon fossa of the posterior humerus. This is a mechanism to effectively stop the extension from going too far. The same is true when the elbow is in flexion, but the mechanism is that the coronoid process of the ulna fits into the coronoid fossa on the anterior humerus. This stops the elbow from flexing beyond its capacity. As the bones hook together, movement beyond flexion and extension is limited or impossible.
The second joint, the humeroradial joint is an articulation between the capitulum of the humerus and the head of the radius, and it is located on the lateral side of the humerus and forearm. The humeroradial joint is classified in different ways, at times it is classified as a hinge joint or a modified hinge joint, and at other times as a modified ball and socket joint. Because of its construction, the way the articulation happens between the capitulum and the radial head, if this joint stood alone, it could move in all planes. However, it is forever attached to the ulna by the anular ligament of the radius. This ligament connects the head of the radius to the radial notch of the ulna, keeping the radius tethered to the ulna, and therefore restricting its movements. This means that flexion and extension are the main movements of the humeroradial joint, but it is able to do minor rotation, which it has to do during pronation and supination.
The third joint, the proximal radioulnar joint is an articulation between the proximal radius and the proximal ulna. This joint is located just distal to the humeroradial and humeroulnar joints at the top of the forearm. It is classified as a pivot joint, which means this joint does rotation only. This movement happens in a transverse plane. The rotation at this joint happens during pronation and supination. When your forearm twists the head of the radius rotates around the ulna to help produce this motion.
So, we could say the ulna is fixed, bound to its position by how it interlocks into the humerus. This means the ulna is subject to misalignment and immobilization from the humeral position. If the humerus is not aligned (and it is not completely aligned in most people), the ulna will need to follow it. The radius is attached to the ulna through the anular ligament and the proximal radioulnar joint. If the ulna is influenced by the humeral position, it will in turn influence the position of the radius.That is one example of how the elbow can become misaligned or immobilized. Another would be if the wrist were misaligned (this again is common). This would influence the alignment of the radius, which would influence the alignment of the ulna, which would influence the alignment of the humerus.
Now that we understand the joints, our next few articles will continue our look at the elbow by examining the ligaments and the muscles. The alignment and mobilization of the bones affects the tension of the ligaments and muscles, and vice versa.
Tags: anatomy, articulation, elbow
