He is rather a quiet representative of his class: the elbow makes compared to other joints of the human body relatively rarely problems and fulfills its task mostly without complaints until old age. Nevertheless, there are diseases of the elbow joint in all age groups, from toddlers to tennis players to senile arthrosis, which can be well understood on the basis of the anatomy of this joint.
What is the elbow?
The elbow joint is a rather complicated joint consisting of three partial joints, each of which articulates with the other. Three tubular bones are involved in the joint structure: the humerus (upper arm bone), the ulna (ulna) that gives it its name, and the radius (radius). The joint between the upper arm and ulna is thereby a pure hinge joint, only in combination with the other two partial joints then still results in a wheel movement, i.e. the rotation of the forearm against the upper arm.
Anatomy and structure
The anatomy is quite palpable at the elbow joint because of the thin soft tissue mantle. At the end of the humeral head, the humeral cartilages, to which the muscles of the forearm are attached, palpate on both sides. Between these cartilages there is a joint roller that communicates with the broad socket of the ulna – this is where the hinge movement between the upper and lower arm takes place. The elbow itself (olecranon) palpates the back of the joint and is familiar to everyone as the “musician’s bone”: the fact that it causes such pain when bumped is due to the superficial course of the ulnar nerve, a nerve that runs here completely unprotected through a bony groove. If the forearm is held with the palm facing upwards, the two bones of the forearm, the ulna and radius, lie parallel to each other: the ulna forms the larger joint surface with the upper arm, and the radius is located to the side of it with the so-called radial head, which is rounded and articulates with both the upper end of the ulna and the head of the upper arm. All three partial joints are surrounded by a common joint capsule. The ligamentous apparatus is quite simple: there are lateral ligaments inside and outside, furthermore an annular ligament from the neck of the ulna loops once around the radial head back to the neck of the ulna, so that the radial head can perform a turning movement in it. Blood vessels and most nerves run along the flexor side of the elbow joint, protected by structures such as the biceps tendon. This is also a more popular site with physicians and less popular with patients for blood sampling from the subcutaneous veins that are clearly visible here.
Function and tasks
Schematic diagram showing the anatomy and structure of the elbow. Click to enlarge. Thus, the elbow joint is held in shape by closely matched bone structures and a relatively simple ligamentous apparatus, allowing for a variety of movements:
The joint between the humerus and ulna is a pure hinge joint and allows only flexion (until soft tissue braking) and extension (until the tip of the elbow abuts the humerus at the back). The joint between the ulna and radius, guided by the annular ligament, allows wheel motion, which is medically termed supination (outward rotation of the forearm) or pronation (inward rotation of the forearm). The joint between the humerus and radius merely makes the two directions of motion of the other joints and allows the combination of both.
Diseases and complaints
Even in infancy, there is an almost typical injury in the elbow joint that always gives parents a good scare, but fortunately is basically harmless and easy to fix: the nanny dislocation. In children, the head of the radius slides relatively freely in the annular ligament and can also be pulled out of it. Typical accident sequence: An adult leads the child by the hand, the child falls, the adult tries to prevent the fall by quickly pulling up the child’s hand. If the head of the radius is dislocated from the ring ligament in this way, it no longer slides back on its own, the child can hardly move the elbow, and there is a lot of crying. However, an experienced doctor can repair the damage with a targeted rotation under traction; after all, nothing is broken. Later, it is mainly tennis elbow that causes complaints. This is an overload and inflammation of the tendons in the attachment area at the outer upper arm cartilage.This is where the muscles of the back of the forearm, i.e. mainly the extensor muscles of the back of the hand, insert. It is thus primarily a backhand overload in tennis. The counterpart at the inner upper arm cartilage is golfer’s elbow. Injuries to the elbow primarily affect the olecranon, i.e. the back of the ulna. Because of the muscular traction here, plaster immobilization is usually not sufficient; these fractures often require surgery.
