The lesser trochanter is a conical posteromedial bony projection of the femoral shaft. it serves as the principal insertion site of the

iliopsoas muscle The iliopsoas muscle (; from lat, ile, lit=groin and grc, ψόᾱ, psóā, muscles of the loins) refers to the joined psoas major and the iliacus muscles. The two muscles are separate in the abdomen, but usually merge in the thigh. They are us ...

Structure

The lesser trochanter is a conical posteromedial projection of the shaft of the

femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates wit ...

, projecting from the posteroinferior aspect of its junction with the

femoral neck The femoral neck (femur neck or neck of the femur) is a flattened pyramidal process of bone, connecting the femoral head with the femoral shaft, and forming with the latter a wide angle opening medialward. Structure The neck is flattened from ...

. The summit and anterior surface of the lesser trochanter are rough, whereas its posterior surface is smooth. From its apex three well-marked borders extend: * two of these are above ** a medial continuous with the lower border of the femur neck ** a lateral with the

intertrochanteric crest The intertrochanteric crest is a prominent bony ridge upon the posterior surface of the femur at the junction of the neck and the shaft of the femur. It extends between the greater trochanter superiorly, and the lesser trochanter inferiorly. Ana ...

* the inferior border is continuous with the middle division of the

linea aspera The linea aspera ( la, rough line) is a ridge of roughened surface on the posterior surface of the shaft of the femur. It is the site of attachments of muscles and the intermuscular septum. Its margins diverge above and below. The linea aspera ...

Attachments

The summit of the lesser trochanter gives insertion to the tendon of the

psoas major muscle The psoas major ( or ; from grc, ψόᾱ, psóā, muscles of the loins) is a long fusiform muscle located in the lateral lumbar region between the vertebral column and the brim of the lesser pelvis. It joins the iliacus muscle to form the il ...

and the

iliacus muscle The iliacus is a flat, triangular muscle which fills the iliac fossa. It forms the lateral portion of iliopsoas, providing flexion of the thigh and lower limb at the acetabulofemoral joint. Structure The iliacus arises from the iliac foss ...

; the lesser trochanter represents the principal attachment of the

iliopsoas The iliopsoas muscle (; from lat, ile, lit=groin and grc, ψόᾱ, psóā, muscles of the loins) refers to the joined psoas major and the iliacus muscles. The two muscles are separate in the abdomen, but usually merge in the thigh. They are usua ...

Anatomical relations

The

(which demarcates the junction of the femoral shaft and neck posteriorly) extends between the lesser trochanter and the

greater trochanter The greater trochanter of the femur is a large, irregular, quadrilateral eminence and a part of the skeletal system. It is directed lateral and medially and slightly posterior. In the adult it is about 2–4 cm lower than the femoral head.Stan ...

on the posterior surface of the femur.

Clinical significance

The lesser trochanter can be involved in an

avulsion fracture An avulsion fracture is a bone fracture which occurs when a fragment of bone tears away from the main mass of bone as a result of physical trauma. This can occur at the ligament by the application of forces external to the body (such as a fal ...

Other animals

Paleontology

The position of the lesser trochanter close to the head of the

is one of the defining characteristics of the

Prozostrodontia Prozostrodontia is a clade of cynodonts including mammaliaforms and their closest relatives such as Tritheledontidae and Tritylodontidae. It was erected as a node-based taxon by Liu and Olsen (2010) and defined as the least inclusive clade cont ...

, which is the clade of

cynodont The cynodonts () ( clade Cynodontia) are a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 mya), and extensively diversified after the Permian–Triassic extinction event. Cynodonts had a wide variet ...

s including mammals and their closest non- mammaliform relatives. It was erected as a

node-based taxon Phylogenetic nomenclature is a method of nomenclature for taxa in biology that uses phylogenetic definitions for taxon names as explained below. This contrasts with the traditional approach, in which taxon names are defined by a ''type'', which c ...

as the least inclusive clade containing ''

Prozostrodon brasiliensis ''Prozostrodon'' is an extinct genus of advanced cynodonts that was closely related to the ancestors of mammals. The remains were found in Brazil and are dated middle to late Triassic. It was originally described as a species of '' Thrinaxodon' ...

'', '' Tritylodon langaevus'', '' Pachygenelus monus'', and ''

Mus musculus Mus or MUS may refer to: Abbreviations * MUS, the NATO country code for Mauritius * MUS, the IATA airport code for Minami Torishima Airport * MUS, abbreviation for the Centre for Modern Urban Studies on Campus The Hague, Leiden University, Ne ...

'' (the house mouse). All living mammals have a lesser trochanter, whose size, shape, and position is distinctive to their species.

Additional images

File:Gray245.png, Right femur. Posterior surface. File:Gray339.png, Right hip-joint from the front. File:Gray343.png, Capsule of hip-joint (distended). Posterior aspect. File:Slide2DAD.JPG, Hip joint. Lateral view. Lesser trochanter File:Slide1BIBI.JPG, Muscles of Thigh. Anterior views.

References

External links

* * (, ) {{Authority control Bones of the lower limb Femur