Certified Hand Therapist (CHT) Practice Exam

What is considered functional extension for the thumb IP joint?

1. 10 degrees

2. 18 degrees

3. 21 degrees

4. 25 degrees

The correct answer is: 18 degrees

Functional extension for the thumb interphalangeal (IP) joint is understood to be the positioning of the joint in a way that allows for effective hand function, particularly in grasp and pinching tasks. The ideal range for functional extension at the thumb IP joint is around 10 to 20 degrees. The choice of 18 degrees is significant as it falls within that functional range. In occupational therapy and hand rehabilitation, determining functional ranges is essential for assessing a patient’s ability to perform daily activities. A thumb IP joint extension of about 18 degrees allows the thumb to oppose effectively and contributes to grasping objects securely, making it a critical value for clinicians when evaluating a patient's hand function. Values outside of this optimal range would indicate either limited or excessive extension, which could compromise the thumb's ability to fulfill its role in fine motor tasks. Therefore, understanding the concept of functional extension is vital in hand therapy as it directly relates to the patient's rehabilitation process and overall functionality.