Which muscle flexes the elbow in any position?

The brachialis muscle is the primary flexor of the elbow, functioning effectively regardless of the position of the forearm. This muscle lies underneath the biceps brachii and attaches to the humerus and the ulnar tuberosity, enabling it to pull the forearm towards the upper arm during elbow flexion. Its anatomy allows it to work independently of the position of the forearm, meaning it can flex the elbow whether the palm is facing up, down, or sideways.

While both the biceps brachii and brachioradialis also contribute to elbow flexion, they are position-dependent to varying degrees. The biceps brachii, for example, is most effective during supination of the forearm, and the brachioradialis is particularly effective when the forearm is in a neutral position. The triceps brachii serves as the antagonist muscle to elbow flexion, being responsible for extending the elbow instead. Therefore, the brachialis is distinctly recognized for its ability to flex the elbow through a full range of positions.