Certified Hand Therapist (CHT) Practice Exam

Which ligament serves as the primary stabilizer of the thumb CMC joint anteriorly?

1. Transverse retinacular ligament

2. Oblique retinacular ligament

3. Oblique beak ligament

4. Triangular ligament

The correct answer is: Oblique beak ligament

The oblique beak ligament is recognized as the primary stabilizer of the thumb carpometacarpal (CMC) joint anteriorly. This ligament functions to provide stability to this joint, which is crucial for the thumb's unique range of motion and its ability to grip and pinch. The oblique beak ligament arises from the tubercle of the trapezium bone and extends to the base of the first metacarpal, forming a critical structure that reinforces the joint capsule. By anchoring the thumb metacarpal to the carpal bones, it helps maintain the integrity of the joint during various thumb movements, particularly during opposition, which is essential for functional activities. In contrast, the other ligaments listed do not play a primary role in stabilizing the anterior aspect of the thumb CMC joint. The transverse retinacular ligament provides support to the distal phalanx and does not directly stabilize the CMC joint. The oblique retinacular ligament primarily functions around the proximal interphalangeal joint, and the triangular ligament refers to a structure in the wrist that does not relate to the stability of the thumb CMC joint. Thus, the oblique beak ligament's specific anatomical position and function clarify its role as