**Question:** Lateral movement is produced by anterior translation of one condyle producing rotation about the

A. condyloid fossa
B. sigmoid notch
C. trochlear groove
D. trochlear fossa

**Correct Answer:** C. trochlear groove

**Core Concept:** Lateral movement in the glenohumeral joint is a result of specific joint motion involving the rotation of the humeral head about the trochlear groove and the translation of the glenoid fossa.

**Why the Correct Answer is Right:** The correct answer, trochlear groove, refers to the concave surface on the underside of the humerus that houses the head of the radius during pronation and supination. When the glenoid fossa (a saddle-shaped depression on the scapula) translates anteriorly (forward), it induces circumduction (a continuous circular motion) of the humeral head, which results in lateral movement. This motion involves the rotation of the humeral head about the trochlear groove.

**Why Each Wrong Option is Incorrect:**

A. Condyloid fossa (also known as the capitulum fossa) is a shallow, concave surface on the head of the radius, not related to glenohumeral joint movement.

B. Sigmoid notch is a notch on the ulna that houses the head of the radius during pronation and supination, not related to glenohumeral joint movement.

D. Trochlear fossa is incorrect, as it refers to the concave surface on the humerus that houses the head of the radius during supination and pronation, not related to lateral glenohumeral joint movement.

**Clinical Pearl:** Understanding the specific joint motions and the roles of various anatomical structures in joint movement is essential for accurate clinical examination and diagnosis. Familiarize yourself with the complex anatomy and biomechanics of the glenohumeral joint to effectively evaluate and treat shoulder disorders.