The lesser trochanter is a distinct, prominent feature of the femur, the long bone of the upper leg. A trochanter is defined as a large, often blunt, projection found only on the femur. The lesser trochanter (LT) serves a highly specific function as an anchor point for some of the body’s most powerful muscles, making it a mechanically important structure within the hip and thigh complex.
Precise Location on the Femur
The lesser trochanter is a small, conical bony prominence situated on the proximal end of the femur. It projects from the back and inside (posteromedial) aspect of the bone, near where the femoral neck meets the main shaft. This positioning is below the smooth, spherical head of the femur that fits into the hip socket and slightly inferior to the femoral neck.
Its shape is conical, resembling a small pyramid, and it is significantly smaller and less prominent than the greater trochanter, which is located on the outer side of the hip. The surface of the lesser trochanter is rough, which provides a strong point of attachment for the anchoring tendon. The LT is connected to the greater trochanter by the intertrochanteric crest, a prominent ridge that runs across the back surface of the proximal femur.
The Iliopsoas Connection
The functional significance of the lesser trochanter is directly linked to the muscle group that attaches to it, collectively known as the iliopsoas. The iliopsoas is a compound muscle formed by the psoas major and the iliacus muscles, which originate deep within the abdomen and pelvis. These two muscles join to form a single, strong tendon that inserts almost exclusively onto the lesser trochanter.
This attachment makes the iliopsoas the strongest and primary muscle responsible for hip flexion. The lesser trochanter acts as a fixed point on the femur, allowing the iliopsoas to exert its force to pull the thigh forward during activities like walking, running, and climbing stairs. Without this specific anchor, the powerful mechanics of hip flexion would be compromised.
Common Injuries Involving the Lesser Trochanter
Because of the extreme force exerted by the iliopsoas muscle, the most common injury to the lesser trochanter is an avulsion fracture. An avulsion fracture occurs when the tendon pulls strongly enough to rip a piece of the bone away from the main structure. In adolescents and young athletes, this injury typically occurs during sudden, forceful movements like sprinting, jumping, or martial arts.
In this younger population, the bone is still developing, and the growth plate (apophysis) at the LT is weaker than the tendon itself, making it prone to being pulled off. The mechanism of injury in adults, however, is markedly different and raises a serious concern. An isolated lesser trochanter avulsion fracture in an adult with minimal or no trauma is frequently considered a pathological fracture until proven otherwise. Since the adult bone is usually stronger than the tendon, a fracture suggests the bone has been weakened by an underlying condition, most often a tumor or metastatic cancer. Most isolated LT fractures in adults are pathological, making it a unique diagnostic sign that prompts a thorough investigation for malignancy using imaging like X-rays and MRI.