Musculus iliacus
The iliacus lines the ventral (inner) surface of the wing of the ilium. It originates from the iliac fossa (and related pelvic surfaces) and inserts with the psoas major on the lesser trochanter of the femur. Together they form the iliopsoas, the primary flexor of the hip joint and the main muscle responsible for protracting the hind limb. Innervation is via the femoral nerve and ventral branches of the lumbar nerves. Because it lies deep under the pelvis, it is not externally visible or palpable. It is essential for the forward swing of the hind limb. Reduced protraction or a shortened cranial phase of the stride can involve the iliopsoas region, often secondarily to pelvic or lumbar issues.
Origin: Ventral surface of the wing of the ilium (iliac fossa)
Insertion: Lesser trochanter of the femur (with psoas major)
Action: Flexes the hip joint; advances the hindlimb
Innervation: Femoral nerve and ventral branches of lumbar nerves (L3-L5)
Isolated strain is uncommon. Pain or dysfunction in the iliopsoas area is occasionally recognized in performance horses with concurrent sacroiliac or lumbar problems. Advanced imaging can evaluate the muscle when indicated.
## Overview Iliopsoas strain is injury to the iliopsoas muscle group, which flexes the hip and stabilizes the lumbar spine. It causes a shortened hind-limb stride, reluctance to engage the hindquarte
A horse that shortens the forward reach of one hind limb or shows reduced engagement after work may have deep hip flexor involvement. Have a veterinarian localize the problem rather than assuming it is lower in the limb.
## Overview Iliopsoas strain is injury to the iliopsoas muscle group, which flexes the hip and stabilizes the lumbar spine. It causes a shortened hind-limb stride, reluctance to engage the hindquarters, and difficulty with canter departures or collection. Pain can be elicited on rectal palpation or seen on ultrasound. ## Causes Overload from steep hill work, sudden hip extension, collection, or slips. ## Diagnosis Clinical gait changes, pain on deep palpation or rectal examination, and ultrasound of the muscle. ## Treatment Rest, anti-inflammatories, and gradual rehabilitation with core-strengthening exercises. Avoid collection and steep hills until healed. ## Recovery and Prognosis Good with adequate rest. Return to full athletic work takes weeks to months. ## Prevention Progressive conditioning and avoidance of sudden maximal efforts. Signs include: shortened hind-limb stride; reluctance to engage hindquarters; pain on rectal palpation; difficulty with canter departures
Isolated strain is uncommon. Pain or dysfunction in the iliopsoas area is occasionally recognized in performance horses with concurrent sacroiliac or lumbar problems. Advanced imaging can evaluate the muscle when indicated.
A horse that shortens the forward reach of one hind limb or shows reduced engagement after work may have deep hip flexor involvement. Have a veterinarian localize the problem rather than assuming it is lower in the limb.
See the Iliacus on our interactive 3D horse model. Open 3D Model