Musculus extensor carpi radialis
The extensor carpi radialis originates from the lateral supracondylar crest of the humerus and inserts on the tuberosity of the proximal cannon bone (MC3). It is the main muscle that extends the carpus and is critical for advancing the forelimb during the swing phase. Innervation is via the radial nerve (C7–T1). It is part of the stay apparatus through its connection with the lacertus fibrosus (a strong fibrous band from the biceps brachii). This linkage helps stabilize the shoulder, elbow, and carpus passively when the horse is standing, reducing the muscular effort required.
Origin: Lateral supracondylar crest of the humerus
Insertion: Tuberosity on the dorsal proximal MC3 (cannon bone)
Action: Extends the carpus; part of the stay apparatus linking shoulder to carpus
Innervation: Radial nerve (C7-T1)
The muscle and its tendon can be strained by trauma or overuse. The lacertus fibrosus is palpable and is a useful landmark. Radial-nerve injury affects this muscle along with other extensors.
## Overview Radial nerve paralysis results from damage to the nerve that innervates the extensors of the elbow, carpus, and digit. Common causes are prolonged lateral recumbency during anesthesia or
## Overview Tendinitis of the extensor carpi radialis occurs at or near its insertion on the metacarpal tuberosity. It is an overuse injury seen in sport horses performing intense collected work and
Swelling or heat over the front of the forearm or just above the knee after a fall or hard work should be evaluated. Most muscle strains improve with rest.
## Overview Radial nerve paralysis results from damage to the nerve that innervates the extensors of the elbow, carpus, and digit. Common causes are prolonged lateral recumbency during anesthesia or humeral fracture. The horse has a dropped elbow, cannot extend the limb, knuckles at the fetlock, and drags the toe. ## Causes Compression during anesthesia or trauma (including humeral fracture). ## Diagnosis Characteristic posture and gait. The limb can bear weight if the elbow and carpus are splinted in pure nerve paralysis. ## Treatment Supportive care, splinting, anti-inflammatories, and time for compressive injuries. Humeral fracture cases have a poor outlook. ## Recovery and Prognosis Good for many post-anesthetic compressive injuries if the limb is protected. Poor if associated with fracture. ## Prevention Proper padding and positioning during anesthesia. Signs include: dropped elbow; inability to extend the elbow and carpus; knuckling at the fetlock; dragging the toe
## Overview Tendinitis of the extensor carpi radialis occurs at or near its insertion on the metacarpal tuberosity. It is an overuse injury seen in sport horses performing intense collected work and produces swelling and pain on the dorsal proximal cannon. ## Causes Repetitive strain from collection or sudden overload. ## Diagnosis Palpation of pain and swelling, ultrasound of the tendon insertion, and response to diagnostic analgesia. ## Treatment Rest, anti-inflammatories, controlled rehabilitation, and correction of contributing training factors. ## Recovery and Prognosis Good with adequate rest. Return to full collection is gradual. ## Prevention Progressive conditioning and attention to workload. Signs include: swelling on the dorsal proximal cannon; pain on palpation; subtle lameness worse in collected work
The muscle and its tendon can be strained by trauma or overuse. The lacertus fibrosus is palpable and is a useful landmark. Radial-nerve injury affects this muscle along with other extensors.
Swelling or heat over the front of the forearm or just above the knee after a fall or hard work should be evaluated. Most muscle strains improve with rest.
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