Essay on Differences in Elbow and Radioulnar Joint Muscle Activity

All vertebrate move when the muscles pull on the joints. The muscle joints are classified into three; freely movable, immovable and slightly movable. For instance, elbow and radioulnar joints are freely movable. Their articulation surfaces are separated by a layer known as hyaline cartilage. It is located between the upper and lower parts of the arm. In contrast, the radioulnar joint is near the elbow, where the ulna and radius articulate in the forearm. However, these joints articulate in different ways.

The elbow joint has two movements; flexion and extension movements. These movements are supination and pronation movements that occur near the radioulnar joints. When an arm is flexed at 90° to the elbow, it causes external rotation(Suzuki et al., 2001). For instance, when grabbing the doorknob and turning it clockwise, the elbow joint extends. This extension movement is afforded at the proximal radioulnar joint that accords to the elbow joint. When the elbow joint is fully extended, the bones forming it produces a hinge joint called the synovial joint.

In contrast, radius and ulna are connected to the distal, proximal and middle radioulnar joints. The radioulnar joint is a synovial joint formed between the ulna radial notch and annular ligament(Gofton et al., 2004). At this joint, Supination movement is required to turn the doorknob using the right hand and push it open. The radioulnar joint requires the triceps and biceps brachii to extend the elbow when turning a doorknob.

Moreover, when the elbow undergoes flexion, the forearm moves towards the body and bends the elbow. Elbow flexion happens when we turn the doorknob counterclockwise and pulling it to open. However, to enable elbow flexion, three bones are involved; they include the ulna, radius and the humerus of the upper arm(Suzuki et. al, 2001). The elbow flexion follows after elbow extension to relax the joint. When pulling the door open, the upper arm rotated to the centre of the elbow joint. As opposed, the radioulnar cycle occurs when the forearm undergoes pronation movement. When pulling the door open, the radioulnar rotates, moving through the ulna head. The radioulnar rotates and relaxes from the supination movement caused by elbow extension.

The arm muscles cause the external and internal movements of the elbow and radioulnar joints. For instance, the triceps muscles relax the arm during elbow extension, which occurs when turning the doorknob clockwise. Biceps muscles contract causing elbow flexion when pulling the door open in a counterclockwise direction. Supination and pronation of the elbow are by the extensor carpi radials brevis and extensor digitorum forearm muscles(Suzuki et. al, 2001). Carpiradials muscles help the hand move forward while the digitorum muscles help the figures move. Apart from the muscles, the tendons and ligaments also support the elbow joint. They include the medial ligaments and radial ligaments. These are groups of tissues that fix the elbow bones together. The blood vessels and elbow nerves also aid in external and internal movements of the elbow. The biceps and supinator muscles control elbow extension, where the muscles contract to straighten the forearm. In radioulnar joints, during pronation, pronator teres and pronator quadratus muscles relax to bend the forearm. In addition, the radioulnar joint is stabilized by annular ligaments and covered by an interosseous membrane(Gofton et. al, 2004). Briefly, the forearm movement depends on how the elbow and radioulnar joints activities.

References

Suzuki, M., Shiller, D. M., Gribble, P. L., & Ostry, D. J. (2001). Relationship between contraction, movement kinematics and phasic muscle activity in single-joint arm movement. Experimental brain research, 140(2), 171-181.

Gofton, W. T., Gordon, K. D., Dunning, C. E., Johnson, J. A., & King, G. J. (2004). Soft-tissue stabilizers of the distal radioulnar joint: an in vitro kinematic study. The Journal of hand surgery, 29(3), 423-431.