Lesser Trochanter

The lesser trochanter is a conical, posteromedially positioned bony prominence located at the junction of the femoral neck and shaft on the proximal femur. Though smaller than the greater trochanter, it serves as a crucial anatomical landmark and a site of major muscular attachment. Functionally, it acts as a lever for hip flexion and contributes to stability of the femur during gait and movement. Despite its deep location, the lesser trochanter has important clinical relevance, especially in hip fractures and muscular avulsion injuries.

Structure

The lesser trochanter is a pyramidal projection composed of dense cortical bone, located inferior and medial to the femoral neck. It is typically more prominent in males than females and varies in size with muscle development and activity level. The apex of the trochanter is often slightly rounded and angled posteromedially toward the body’s midline.

Dimensions and Orientation

• Average height: ~1.5 to 2.0 cm in adults
• Located posteromedially at the junction between the neck and shaft
• Projects more medially than posteriorly in anatomical position

Composition

• Outer layer: Dense cortical bone that withstands pulling forces from attached muscles
• Internal architecture: Contains trabecular bone oriented to transmit muscular force into the femoral shaft

Location

The lesser trochanter lies just inferior to the femoral neck and medial to the shaft. It is situated opposite the greater trochanter on the posterior side of the femur. Anatomically, it is located at the junction where the femoral shaft transitions into the neck, within the proximal metaphyseal region. It is deeply embedded within the musculature of the thigh and pelvis and is not palpable externally.

• Medial: Femoral shaft
• Lateral: Femoral neck and intertrochanteric crest
• Anterior: Femoral vein and artery at higher levels; iliopsoas muscle belly
• Posterior: Quadratus femoris and adjacent structures

Function

The primary role of the lesser trochanter is to serve as the insertion site for the iliopsoas muscle, which is the strongest hip flexor. Through this insertion, it contributes to several critical functions:

• Hip flexion: Transmits contraction force from the iliopsoas to the femur, enabling powerful flexion at the hip joint.
• Stabilization: Provides medial rotational stability and contributes to the maintenance of posture, especially during activities involving flexion against resistance.
• Gait mechanics: Plays a role in the swing phase of walking and climbing stairs by initiating hip flexion.

Muscular Attachments

The only muscle that inserts directly into the lesser trochanter is the iliopsoas muscle, which is composed of the psoas major and the iliacus muscles.

Muscle	Origin	Insertion	Action
Iliopsoas	Psoas major: T12–L5 vertebral bodies Iliacus: Iliac fossa	Lesser trochanter of femur	Hip flexion and slight lateral rotation

Relations

Due to its deep location, the lesser trochanter is not directly visible or palpable, but it is intimately related to surrounding neurovascular and muscular structures:

• Anterior: Iliopsoas muscle, femoral artery and vein at proximal levels
• Medial: Femoral shaft and medial circumflex femoral vessels
• Lateral: Intertrochanteric line and capsule of the hip joint
• Posterior: Quadratus femoris and obturator externus muscles

Blood Supply

The lesser trochanter receives vascular branches from surrounding arteries that also supply the proximal femur:

• Medial circumflex femoral artery: Principal blood supply to the posterior region of the femoral neck and lesser trochanter
• Lateral circumflex femoral artery: Contributes via anastomoses, especially to periosteal surfaces
• Obturator artery: Via small perforating branches in some individuals

Nerve Supply

The lesser trochanter itself is not directly innervated, but the iliopsoas muscle that inserts here receives innervation from the femoral nerve (L2–L4). The overlying capsule and periosteum receive sensory innervation via articular branches from the femoral and obturator nerves, which can refer pain from nearby injuries.

Ossification

The lesser trochanter develops from a separate secondary ossification center. This center appears around ages 11–13 and typically fuses with the shaft of the femur by age 16–17. It forms under the influence of traction forces exerted by the iliopsoas muscle.

• Type: Traction apophysis
• Fusion age: Approximately 16 years
• Developmental anomalies: Enlargement may occur in athletes due to repetitive stress

Clinical Significance

• Avulsion fracture: Seen in adolescents and young athletes during forceful hip flexion. Results from sudden contraction of the iliopsoas pulling the ossification center off the bone.
• Pathologic fracture: In adults, isolated fractures of the lesser trochanter are rare but often signify metastatic bone disease (e.g., from prostate, breast, or lung cancer).
• Iliopsoas bursitis: Inflammation near the lesser trochanter can mimic hip joint pain due to proximity to the insertion site.
• Impingement syndrome: Prominent lesser trochanter can contribute to ischiofemoral impingement, causing posterior hip pain.

Radiographic Appearance

The lesser trochanter is visible on standard pelvic and hip radiographs as a radiopaque protuberance on the medial aspect of the proximal femur. It is best visualized in the frog-leg lateral view.

• Normal variant: It is typically smaller in females and may not be clearly seen unless traction is applied during imaging.
• Enlarged or displaced: Suggests avulsion, tumor infiltration, or reactive bone formation.

Surgical Relevance

• Landmark in intramedullary nailing: The lesser trochanter serves as a radiographic reference point when inserting femoral nails or assessing rotation.
• Muscle-sparing approaches: Some anterior hip replacement approaches aim to preserve the iliopsoas insertion to maintain flexion strength and reduce postoperative complications.