There are several muscles associated with the flexor retinaculum. Situated deep to the flexor retinaculum are the four tendons of the flexor digitorum superficialis. The flexor digitorum superficialis, which is in the anterior compartment of the forearm, originates at the medial epicondyle of the humerus as well as parts of the radius and ulna. The flexor digitorum superficialis inserts on the base of the second to fifth middle phalanges.[6] The innervation of the flexor digitorum superficialis is the median nerve. The main action of the flexor digitorum superficialis is flexion of the phalanges, primarily at the proximal interphalangeal joints. Deep to the flexor digitorum superficialis is the flexor digitorum profundus. The origin and insertion are the proximal anteromedial surface of the ulna and the distal interphalangeal joints of the phalanges, respectively.[6] The flexor digitorum profundus is innervated medially by the ulnar nerve and laterally by the median nerve. The main action is the flexion of the distal interphalangeal joints, then secondarily flexes proximal interphalangeal joints, metacarpal phalangeal joints, and wrist. Below the flexor retinaculum and lateral to the flexor digitorum superficialis lies the flexor pollicis longus. The origin of the flexor pollicis longus is the middle half of the volar radius, and the insertion is the base of the distal phalanx of the thumb.[6] The innervation of the flexor pollicis longus is a branch of the median nerve, the anterior interosseous nerve. 

The main anatomical variations concerning the flexor retinaculum have to do with the median nerve. As previously stated, the median nerve enters the carpal tunnel deep to the flexor retinaculum. A bifid median nerve occurs in some humans, which occurs when the median nerve splits proximally to the flexor retinaculum instead of distally like normal anatomy.[2] Several studies have demonstrated a wide range of variations in the motor branch of the median nerve.[2] These different courses may explain why patients present differently in cases of severe compression of the median nerve. 

If conservative management for carpal tunnel does not work, surgical options are available.[1] If the flexor retinaculum is the cause of a patient's carpal tunnel symptoms, surgical release is often necessary. This procedure releases the pressure on the median nerve and can often relieve or eliminate the patient's symptoms. Like any surgery, there are risks involved; knowing the anatomy is key to avoiding damaging any surrounding structures. Because so many vital structures surround the flexor retinaculum, one must be aware of where each tendon, artery, and nerve are relative to the flexor retinaculum. 

If the patient suffers from systemic diseases, the recurrence rate after surgery is very high.

The flexor retinaculum can entrap and compress the median nerve causing the condition of carpal tunnel.[7] Carpal tunnel is the most common compression neuropathy in the upper extremity. Several causes for compression of the median nerve ranging from repetitive motions, space-occupying lesions, or certain health conditions like diabetes mellitus or hypothyroidism. Clinically patients may present with numbness and tingling in the radial three fingers.[7] Often symptoms are worse at night. Patients may have difficulty holding objects and regularly report dropping items. Clinically patients frequently will have thenar atrophy and weakness. Evaluating sensations in the fingers may show decreased sensation in radial three fingers.[7] Compression of the flexor retinaculum and, therefore, the median nerve may reproduce the patient's symptoms. A classic physical exam maneuver used to diagnose carpal tunnel is the Tinel test. The Tinel test is performed by repeatedly tapping on the flexor retinaculum and seeing if it reproduces the patient's symptoms. Treatments to consider include wrist splinting, work-related ergonomic modification, NSAIDs, steroid injections, and surgical management. 

When the retinaculum compresses the underlying nerve, it undergoes a thickening, reducing its elastic capacity. According to a recent study, there is a difference in size between males and females. In women, the retinaculum is smaller; in the female sex, the carpal tunnel syndrome has a higher prevalence.

In carpal tunnel syndrome, in the early stages of the disorder, the proliferation of myofibroblasts seems to play an important role, which not only increases inflammatory responses but reduces tissue elasticity.