Musculus brachialis
The brachialis is a purely fleshy muscle that arises from the caudal and lateral surfaces of the proximal humerus within the musculospiral groove. It winds laterally then cranially across the flexor surface of the elbow to insert on the medial aspect of the proximal radius and ulna. It is a dedicated elbow flexor whose long fibers allow substantial shortening. It is covered proximally by the triceps and becomes more superficial distally. Clinically, isolated brachialis injury is uncommon. Because it shares innervation with the biceps, musculocutaneous nerve lesions affect both primary elbow flexors, though gait effects are often mild on flat ground because other muscles can compensate.
Origin: Caudolateral surface of the proximal humeral shaft (musculospiral groove)
Insertion: Medial surface of the proximal radius and ulna
Action: Flexes the elbow joint
Innervation: Musculocutaneous nerve (C6-C7)
Rarely the primary focus of lameness. Ultrasound can identify the muscle in the spiral groove. Radial nerve contribution is variable.
## Overview Brachialis strain is an uncommon injury to the brachialis muscle, which lies deep to the biceps brachii and is a primary flexor of the elbow. Because the muscle is rarely discussed in the
Elbow-region swelling or reluctance to flex the leg after trauma should be examined. Most isolated muscle strains improve with rest.
## Overview Brachialis strain is an uncommon injury to the brachialis muscle, which lies deep to the biceps brachii and is a primary flexor of the elbow. Because the muscle is rarely discussed in the equine literature, most knowledge is extrapolated from analogous human injuries and general principles of equine muscle strain. Overload during resisted elbow flexion or eccentric lengthening can tear fibers and produce localized pain and mild forelimb lameness. ## Causes Sudden increases in work that require strong elbow flexion, slipping with the limb extended, or compensatory overload from other forelimb problems are plausible causes. The evidence specific to horses is limited. ## Diagnosis Pain on deep palpation of the cranial distal humerus, discomfort during elbow flexion against resistance, and mild lameness suggest the diagnosis. Ultrasound can identify fiber disruption or hematoma when the lesion is accessible. ## Treatment Rest, cold therapy, anti-inflammatory medication, and gradual return to controlled exercise follow standard muscle-strain protocols. Most mild strains resolve with conservative care. ## Recovery and Prognosis Prognosis for mild to moderate strains is good. Severe tears are rare but would require longer rehabilitation. Specific equine outcome data are limited. ## Prevention Progressive conditioning and avoidance of sudden workload spikes reduce risk of any muscle strain, including the brachialis. Signs include: mild forelimb lameness; pain on deep palpation cranial to the elbow; discomfort when the elbow is flexed against resistance
Rarely the primary focus of lameness. Ultrasound can identify the muscle in the spiral groove. Radial nerve contribution is variable.
Elbow-region swelling or reluctance to flex the leg after trauma should be examined. Most isolated muscle strains improve with rest.
See the Brachialis on our interactive 3D horse model. Open 3D Model