The Elbow Kinematics Flashcards
List the components of the ‘elbow and forearm complex’ – specify joints.
Specify elbow proper joints
Radialhumeral joint (elbow proper) Ulnar-humeral (elbow proper) Proximal radio-ulnar joint Distal radio-ulnar joint.
What is unique about the joint capsule of the elbow region?
One joint capsule contains 3 joints.
If one joint is injured, the whole joint is affected.
List the osteokinematic motions, degrees of freedom and plane in which motion takes place in the elbow joint proper.
Modified hinge joint.
1 plane of motion.
Sagittal flexion/extension.
Identify location and describe orientation as well as direction of the joint axis of motion for the elbow proper.
Medial-lateral axis of rotation in the medial epicondyle to lateral epicondyle of the humerus. Axis swings obliquely, slightly superior laterally ( or lightly inferior medially) due to trochlear adjustments.
Define cubitus valgus more commenly known as carrying angle and define cubitus varus.
Due to the prolongation of the humerus, the ulna deviates laterally relative to the humerus.
Cubitus Varus, the ulna abnormally deviates medially. (Turned inward) (Gunstock deformity) Usually from fracture of the distal humeral head. Elbow sticks out.
Describe the shape of the trochlea.
The trochlea resembles a spool of thread or bow tie. The medial lip is most prominent and extends further distally than the lateral lip. The trochlear groove sits in the middle of the trochlea and spirals toward the medial direction, when viewed posterior to anterior.
What is the significance of the shape of the trochlea on ‘cubitus valgus’?
The shape of the trochlea determines the degree of deviation (cubitus valgus) the ulna will exhibit. The distal ulna is pushed laterally as it extends distally by the shape of the trochlea.
Identify the specific arthrokinematic motion for each joint using convex-concave rule on each joint motion.
Radiohumeral and Ulnar-humeral are concave on convex–roll up, slide up (both move in the same direction).
If close-chained, convex on concave. Arthrokinematics are opposite…so roll down, slide up.
What percent of compression force passes through the radiocarpal joint and by what mechanism does the interosseous membrane transmit some of this force to the ulna?
80% of force goes through the radiohumeral joint. The radius will try to slide passed the ulna, vertically. The interosseus fibers are oriented so that the fibers instantly tense as the radius moves superiorly in order to transmit tension to the ulna . More common to break the head rather than the mid-radius.
What assists in keeping the forearm stable during pulling activites of the forearm/upper extremity?
The brachioradialis is a translator to hold radius against capitulum. Grasping muscles, finger flexers, etc. hold the radius in check. Also, the Oblique cord and the annular ligament.
List the osteokinematic motions, degrees of freedom and plane in which motion takes place in the forearm joints.
Supination/Pronation
1 plane of motion.
Transverse or horizontal plane.
Identify location and direction of the joint axis for the forearm as related to the proximal and distal radioulnar joints.
Superior–radius–convex proximately
Inferior–Ulna–convex distally.
The total axis runs through the center of the head of the radius through the head of the ulna.
Describe arthrokinematics at proximal and distal radio-ulnar joint articulation for pronation/supination and apply the convex-concave rule to them.
What happens in closed-chain?
Pronation/Supination, the radius spins within the annular ligament and radial notch. The distal radio-ulnar joint, the radius rolls and spins on the ulna in the same direction (concave on convex). Distal, the radius glides and rolls laterally, then moves posterior. Proximal, the radius spins/glides anteriorly.
Closed chain–the ulna moves around the radius and causes the humerus to rotate which creates spin at the radiohumeral joints.
Describe the unique “spin” of the radiohumeral joint
Spin (fancy glide) takes place at the capitulum. Radius is convex, ulna is concave. Annular ligament binds tightly around the head of the radius. Does not allow the bone to translate forward or backward. There is articulating cartilage (joint cartilage) between the ligament and radius. The radius glides against the ulna because the annular ligament does not allow roll.
What are normal ranges of motion and functional ranges of motion for the elbow and forearm? Why is functional ROM less than normal ROM?
Normal range of motion is 0-80 degrees approximately of pronation and supination. Functional supination adn rotation are 50 degrees on each side of neutral. Functional ROM is less than normal ROM because the reduced range of motion encapsulates most routine activities of daily living.
Normal ROM for elbow flexion is -5 to 145 degrees. Functional is 30 to 130 degrees. (100 degree rule).
