trochleae

Trochleae are anatomical structures named for their pulley-like shape or groove, and the term serves as the plural of trochlea. Derived from Latin, trochlea refers to a wheellike, pulley system that redirects tendinous or muscular force or forms a joint surface to guide movement. In humans and other tetrapods, several distinct trochleae serve different mechanical purposes.

Common examples include: the trochlea of the humerus, a spool-shaped articular surface at the distal end of the humerus that articulates with the trochlear notch of the ulna to form part of the elbow joint; the trochlea tali, the superior articular surface of the talus that interacts with the tibia to compose the ankle joint; and the trochlear groove of the femur, also called the patellar groove or trochlear surface, a groove on the anterior distal femur that guides the patella during knee flexion and extension. Another well-known example is the trochlea of the superior oblique muscle in the orbit, a fibrocartilaginous pulley through which the tendon passes to change its direction as the eye moves.

Functionally, trochleae can act as pulleys that redirect tendon force, or as articular surfaces that convert complex movements into controlled hinge-like actions. They may vary in shape and size across species and individuals, influencing joint mechanics and tendon routing. Clinically, trochlear abnormalities can affect joint stability or tendon function, and pathology of a trochlear pulley, such as trochlear nerve palsy related to the superior oblique tendon, can contribute to ocular diplopia.

In summary, trochleae are diverse pulley-like or grooved structures essential for guiding movement and shaping joint articulation throughout the body.