This is the anterior view of the forearm. We can observe from proximal to distal the Humero-Ulnar joint (elbow), Humero-Radial joint, proximal Radio-Ulnar and distal Radio-Ulnar.
This is the so called "arm bone". It has a glenoid in its proximal part and a trochlea in its distal part. The trochlea allows the movements of flexion and extension. The humerus intervenes in 3 joints from proximal to distal: glenohumeral (shoulder), Humero-Ulnar (true elbow) and Radio-Humeral. We will be focusing in the last two.
This is the most distal joint in the forearm before getting to the wrist. This joint is only involved in the pronation and supination of the arm.
This is the anterior view of the forearm. We can observe from proximal to distal the Humero-Ulnar joint (elbow), Humero-Radial joint, proximal Radio-Ulnar and distal Radio-Ulnar.
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We are a group of students from Spain in first year of Physical Therapy in the university of San Jorge Zaragoza. This blog is dedicated to our project, to disseminate and share our knowledge and mobilization techniques on the radiohumeral and radioulnar joints. Don't hesitate to give us your ideas or comments to improve our site. Thank you and we hope you enjoy it! The more you learn.
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Forearm Anatomy & Biomechanics
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Key Words:
Resting Position: position where the ligaments of the articulation are the most relaxed. There we will also find the most distance between articulations. We will find this position to do the tractions.
Blocking Position: this is the opposite to the resting position. Here we will find the least movement and the two structures that form the joint are the closest.
Capsular Pattern: this tells us which movements are limited.
Convex Rule: this rule states that in an articulation formed by a Concave and a Convex, if the structure to mobilize is the convex one, the movement of the structure will be opposite to its gliding.
Concave Rule: this rule is the opposite to the Convex Rule. In this case, BOTH movements go in the same direction.
Treatment Plane: imaginary line located at the base of the concave structure. This will be our guide to know which direction apply force. The force must go PERPENDICULAR to the treatment plane.
Biomechanics
Flexion: this movement consists of realizing a linear movement of the forearm on a forward direction, realizing this movement around an axis located in the elbow. Its normal range of motion (ROM) in active flexion is around 140º-145º. In a pasive way it reaches 160º.
Limits on Flexion:
- Impact with the muscular mass of the biceps.
Extension: this is the opposite to flexion: in consists on a linear movemtn in a backwards direction. Arm and forearm should make a straight line when in an anatomical position.
Limits on Extension:
- Impact of the olecranon with the olecranon fossa.
- Tension of the anterior part of the capsule.
- Resistance of the flexor muscles (biceps braquii, braquialis anterior, radiobraquialis).
Pronation & Supination: pronation the movement od the rotation of the forearm. it rotates around its longitudinal axis. This allows the elbow a 3rd grade of movement. In order to be able to perform this movement we will need our PROXIMAL RADIO-ULNAR JOINT and DISTAL RADIO-ULNAR JOINT.
- Anatomical position/zero position: elbow in a 90º flexion. Thumb pointing uppwards palmar side of the hand facing inwards.
- Supinated Position: thumb facing outwards and palmar side of the hand facing upprwards.
- Pronated Position: thumb facing inwards and palmar side facind downwards.
