View source for Trochlea of humerus

{{short description|Articular surface of the elbow joint which articulates with the trochlear notch of the ulna}}
{{Infobox bone
| Name        = Trochlea of humerus
| Latin       = trochlea humeri
| Image       = Gray207-trochlea-capitulum.png
| Caption     = Anterior view of distal part of left humerus
| Image2      = Gray208-trochlea.png
| Caption2    = Posterior view of distal part of left humerus
| Width       = 125
}}
In the human arm, the [[Humerus|humeral]] '''trochlea''' is the medial portion of the articular surface of the [[elbow]] joint which articulates with the [[trochlear notch]] on the [[ulna]] in the forearm.

==Structure==
In humans and other [[ape]]s, it is trochleariform (or trochleiform), as opposed to cylindrical in most [[monkey]]s and conical in some [[prosimian]]s.<ref>Bernard F. Morrey, Joaquin Sanchez-Sotelo (2009) ''The Elbow and Its Disorders'' [https://books.google.com/books?id=G9SdBoI6KjsC&pg=PA4 p.4]</ref> It presents a deep depression between two well-marked borders; it is convex from before backward, concave from side to side, and occupies the anterior, lower, and posterior parts of the extremity.
[[File:Trochlea.jpg|alt=Trochlea of Humerus|none|thumb|400x400px|Trochlea of humerus]]

The trochlea has the [[capitulum of the humerus|capitulum]] located on its lateral side and the [[Medial epicondyle of the humerus|medial epicondyle]] on its medial.  It is directly inferior to the [[coronoid fossa]] anteriorly and to the [[olecranon fossa]] posteriorly.  In humans, these two fossae, the most prominent in the humerus, are occasionally transformed into a hole, the [[supratrochlear foramen]],<ref>{{cite book
| last      = Platzer | first = Werner
| title     = Color Atlas of Human Anatomy, Vol. 1: Locomotor System
| publisher = Thieme | isbn = 3-13-533305-1<!---US: 1-58890-159-9--->
| year      = 2004 | edition = 5th | page = 114
}}</ref> which is regularly present in, for example, dogs.

===Carrying angle===
When viewed from in front or behind, the trochlea looks roughly cylindrical, but when viewed from below its true oblique shape and the spiralling nature of its groove become apparent.  The spiralling nature of the trochlear groove results in the varying transverse axes of the elbow joint.<ref name="Kapandji-1984-84">{{cite book
| last      = Kapandji | first = Ibrahim Adalbert
| title     = The Physiology of the Joints: Volume One Upper Limb
| publisher = Churchill Livingstone | location = New York
| year      = 1982 | edition = 5th | page = 84
}}</ref>

Most frequently, the groove is vertical on the anterior side but runs down laterally on the posterior side.  During elbow flexion, the vertical anterior part of the trochlea keeps the upper arm and forearm aligned (when viewed in front). During elbow extension, however, the oblique posterior part makes contact with the trochlear notch on the ulna so that this obliquity forces the main axis of the forearm to form a small angle with that of the upper arm. This angle is known as the ''carrying angle'' and is more prominent in women than in men.<ref name="Kapandji-1984-84" />

Less frequently, the anterior part is oblique too, but in the opposite direction of the posterior side. Consequently, during full elbow flexion, the hand tends to rest outside the shoulder. Very rarely, the anterior part is oblique in the opposite direction, resulting in the hand's resting on the chest during flexion.<ref name="Kapandji-1984-84" />

==Function==
[[File:MedialHumerusRadiusUlnaArticulated.jpg|thumb|left|The trochlea articulated with the trochlear notch and coronoid]]
The elbow is a [[hinge joint]] with a rotatory component where the trochlea forms the convex, proximal surface which articulates with the concave, distal surface on the ulna, the trochlear notch.  While the trochlea together with its associated fossae almost covers a 360° angle, the trochlear notch on the ulna forms a 190° arc and the gap in between allows flexion and extension at the elbow.  Maximum elbow flexion and extension is made possible because the two fossae accommodates to [[Coronoid process of the ulna|coronoid]] and [[Olecranon|olecranon processes]].
<ref name="Wells-Ablove-2008">{{Cite journal
| last1   = Wells | first1 = Jason
| last2   = Ablove | first2 = Robert H.
| title   = Coronoid Fractures of the Elbow | location = Anatomy of the Elbow
| journal = Clin Med Res |date=May 2008 | volume = 6 | issue = 1 | pages = 40–44
| doi     = 10.3121/cmr.2008.753 | pmc = 2442031 | pmid=18591378
}}</ref>

==Ossification==
While the ossification of the capitulum has started a year after birth, the ossification of the trochlea begins at 8–9 years of age; that of the [[head of radius]] and the medial epicondyle at 4–5 years and that of the lateral condyle at 10 years.
<ref>{{Cite journal
| last1   = Brubacher | first1 = Jacob W.
| last2   = Dodd | first2 = Seth D.
| title   = Pediatric supracondylar fractures of the distal humerus
| journal = Curr Rev Musculoskelet Med. |date=December 2008 | volume = 1 | issue = 3–4 | pages = 190–196
| doi     = 10.1007/s12178-008-9027-2 | pmc = 2682409 | pmid=19468905
}}</ref>

{{Clear}}

==Additional images==
<gallery>
File:Elbow joint - deep dissection (anterior view, human cadaver).jpg|Elbow joint. Deep dissection. Anterior view.
File:Slide2xzxzxz.JPG|Elbow joint. Deep dissection. Anterior view.
</gallery>

==References==
{{Reflist|30em}}

==External links==
* {{SUNYAnatomyFigs|07|02|04}}

{{Bones of upper extremity}}
{{Authority control}}

[[Category:Bones of the upper limb]]
[[Category:Humerus]]