The palmaris longus muscle is a slender and narrow muscle located in the anterior aspect of the forearm. It is variable in size and can be absent in some individuals.
Originating from the medial epicondyle of the humerus and the antebrachial fascia, the palmaris longus takes its starting point from the bony prominence on the inner side of the elbow joint and the connective tissue covering the forearm.
The muscle inserts into the palmar aponeurosis, a thick fascial structure on the palm of the hand. This insertion site establishes a connection with the connective tissue in the palm.
Functionally, the palmaris longus is considered a weak wrist flexor. It assists in flexing the wrist joint, but its action is not as prominent as some other forearm muscles. Additionally, the muscle is thought to have a role in tensing the palmar aponeurosis, providing support to the hand's fascial structure during gripping and certain hand movements. While its function can vary among individuals due to its absence in some, the palmaris longus contributes to the overall complexity of the forearm musculature and its role in hand function.