What Is the Iliopsoas Muscle?

The iliopsoas is formed by the fusion of two muscles — the psoas major and the iliacus. According to a 2023 review published in Veterinary Clinics of North America: Small Animal Practice, its primary roles are flexion of the hip, adduction and external rotation of the femur, core stabilization, and lumbar spine flexion. The iliopsoas originates along the lumbar spine (lower back) and extends to the inner thigh/groin region.

Because of its deep location, the iliopsoas is notoriously difficult to examine and easy to overlook. Yet it is also uniquely vulnerable: any pain, instability, or altered movement in the hips, stifles (knees), or spine forces the iliopsoas to compensate, making it a frequent secondary casualty of other diseases.

How Common Are These Injuries?

Iliopsoas injury has been recognized in the peer-reviewed literature since at least 1997, when Breur and Blevins at Purdue University published the first case series in the Journal of the American Veterinary Medical Association. A 2005 study by Nielsen and Pluhar in Veterinary and Comparative Orthopaedics and Traumatology found that the iliopsoas was the single most frequently strained muscle of the pelvic limb among 22 dogs evaluated for hind limb muscle injuries.

A 2017 study in Veterinary Evidence (Cullen, Canapp et al.) evaluated 73 agility dogs with musculoskeletal ultrasound and confirmed that diagnostic imaging is critical to accurately characterize the extent and location of injury — physical examination alone often underestimates severity.

How Do Iliopsoas Strains Happen?

Veterinary research identifies two distinct pathways to iliopsoas injury. Understanding which pathway applies to your dog is essential, because treatment must address the root cause, not just the muscle itself.

1. Primary Injury: Acute Trauma or Overuse

In otherwise healthy dogs, the iliopsoas can be injured directly through:

• Acute stretch-induced trauma: A sudden overstretching — slipping on a hard floor, an awkward landing after a jump, or a rapid direction change at speed — can tear muscle fibers ranging from micro-tears to complete rupture.
• Repetitive microtrauma / overuse: High-intensity repetitive activities (agility, flyball, fetch) cause cumulative micro-tears that lead to chronic inflammation and, over time, fibrosis of the muscle or tendon.

2. Secondary Injury: When Chronic Pain Causes Compensation

This pathway is particularly important for the general pet population and is often underappreciated. As described by Bliss and Evans (DVM, PhD, DACVS, CCRP) in a professional veterinary continuing education article, sustained contraction, fatigue, and spasm of the psoas musculature frequently develop in dogs with a wide range of orthopedic or neurologic disorders as they alter their posture to compensate for painful or dysfunctional limbs.

The mechanism works as follows: when a dog experiences pain — from the hip, stifle (knee), or spine — it instinctively shifts its weight forward to offload the painful limb. This postural adaptation produces a characteristic lumbar roaching (hunching of the lower back into an abnormally kyphotic position). The psoas musculature is one of the primary structures responsible for maintaining this roached posture. When this position becomes chronic, the iliopsoas undergoes sustained, unrelenting contraction rather than its normal cycles of contraction and relaxation, ultimately leading to repetitive strain injury (RSI).

Conditions That Commonly Trigger Secondary Iliopsoas Injury

Peer-reviewed veterinary literature and specialists at Cornell University College of Veterinary Medicine identify several underlying conditions that commonly cause compensatory iliopsoas strain. According to the Veterinary Clinics of North America: Small Animal Practice (2023) overview, concurrent neurologic or orthopedic problems can cause secondary (compensatory) iliopsoas muscle strain, resulting in moderate to severe, short-strided hind limb lameness.

• Hip Dysplasia and Hip Osteoarthritis: Hip dysplasia — a developmental malformation of the coxofemoral (hip) joint — and the osteoarthritis (arthritis) that follows are among the most common triggers. Differentiation between primary hip joint pain, primary iliopsoas injury, and secondary adaptive shortening of the iliopsoas due to other pathology can be a significant diagnostic challenge. When a dog reduces hip extension to guard against pain, the iliopsoas adaptively shortens over time (adaptive shortening), creating a painful feedback loop.
• Cranial Cruciate Ligament (CCL) Disease: CCL disease (degeneration and tearing of the dog “ACL”) is one of the most frequently identified concurrent injuries in dogs with iliopsoas strain. A 2023 study in the Canadian Journal of Veterinary Research found that CCL instability was present in 27.8% of dogs with an iliopsoas strain. The altered, pain-protective gait places massive compensatory demands on the hip flexors.
• Lumbosacral Disease and Spinal Pathology: Lumbosacral disease, intervertebral disc disease (IVDD), and other spinal conditions form an important pathway. Clinical research notes that when hip dysplasia, CCL disease, and patellar luxation are ruled out, lumbosacral intervertebral disc disease (LSIVDD) and iliopsoas strain are the two primary differentials for chronic hind limb lameness — and they frequently coexist.
• Patellar Luxation and Other Stifle Pathology: Dislocation of the kneecap disrupts normal stifle mechanics and produces a characteristic altered gait that shifts extra physical demand directly onto the hip flexors.
• Senior Dogs & Multiple Concurrent Contributors: Older dogs with degenerative joint disease frequently have pain and reduced range of motion in multiple joints simultaneously. Psoas RSI is especially common in geriatric dogs and is a significant, underrecognized cause of pain and decreased mobility in this population.

Which Dogs Are Most at Risk?

• Athletic dogs: Agility, flyball, disc dogs, and active companions (primary injury from overuse).
• Dogs with hip dysplasia or hip arthritis: Compensatory shortening and RSI secondary to pain-protective gait.
• Dogs with CCL disease: One of the most common concurrent injuries found in diagnostic studies.
• Dogs with lumbosacral or spinal disease: Psoas recruited into sustained, painful postural contraction.
• Dogs with patellar luxation: Altered stifle mechanics that constantly shift strain onto the hip flexors.
• Overweight dogs: Constant extra load on the hip flexors and load-bearing joints.
• Senior dogs: Reduced muscle elasticity and multiple concurrent degenerative changes.
• Post-surgical dogs: Postural adjustments during recovery after TPLO, FHO, or other orthopedic procedures.

Sources: Sack et al., Can J Vet Res 2023; Bliss & Evans, VetBloom 2016; Fry et al., Front Vet Sci 2022; Pechette Markley, Vet Clin North Am 2023; Cornell University CVM; VCA Animal Hospitals

Recognizing the Signs

Iliopsoas strains produce a variable and subtle clinical picture. Signs range from intermittent mild hind limb lameness to severe, non-weight-bearing lameness. Many dogs only show a shorter stride in the rear when trotting, and in chronic low-grade cases, owners may not notice an obvious gait abnormality until a secondary event — such as slipping on a floor — exacerbates the problem.

Watch for these indicators:

• Hind limb limping, often worse after exercise or after getting up from rest
• Reluctance to jump on or off furniture, or climb into the car
• Stiffness when rising from a lying position
• External rotation of the affected hind limb during walking (knee/leg rotated outward)
• Shortened stride or reduced stance phase on the rear leg (reluctance to bear weight for long)
• Hunched lower back or persistent lumbar roaching
• Pain, tension, or flinching when the hip is extended during examination
• In athletic dogs: Slowing through weave poles, knocking bars, or refusing jumps
• In dogs with known hip/stifle/spine disease: Worsening lameness not fully explained by the primary diagnosis

Diagnosis: Why X-Rays Alone Are Not Enough

Radiographs (X-rays) may reveal concurrent hip dysplasia, stifle pathology, or mineralization at the iliopsoas insertion on the femur. However, normal radiographs do not rule out an iliopsoas strain. Definitive diagnosis of soft tissue structures requires advanced assessment tools:

Clinical Note: Because the iliopsoas lies close to other sensitive structures — including the lumbar spine, hip joint, and sacroiliac region — a thorough exam is crucial to isolate the exact source of pain.

Treatment: Address the Root Cause First

Veterinary consensus is clear: if an iliopsoas injury is secondary to another problem, that primary problem must be addressed. Simply managing the iliopsoas while leaving hip dysplasia, CCL instability, or spinal disease untreated will not produce durable improvement.

Phase 1 — Acute Management (Weeks 1–2)

• Strict Activity Restriction: Strict rest is the cornerstone of initial care. No running, jumping, stairs, or off-leash activity. Short, leashed bathroom walks only.
• Address Primary Pathology: Concurrent hip dysplasia, CCL disease, or spinal conditions must be managed via orthopedic consultation, medical management, or surgical repair.
• Pain & Inflammation Control: Targeted NSAIDs, muscle relaxants (such as methocarbamol), and nerve-pain medications (such as gabapentin) are utilized. Medications mask discomfort — strict restriction remains critical even if your dog seems comfortable.
• Cold Therapy: Ice application to the groin/inner thigh region in the first 48–72 hours helps reduce acute swelling and pain.

Phase 2 — Rehabilitation & Healing (Weeks 2–8+)

Evidence-based rehabilitation modalities used to promote structured tissue healing include:

• Therapeutic Laser (Photobiomodulation): Accelerates cellular repair and reduces deep tissue inflammation.
• Acupuncture: Highly effective adjunct therapy for pain modulation and easing chronic psoas muscle spasms.
• Heat Therapy: Applied prior to rehab exercises to relax tight muscle fibers and increase tissue extensibility.
• Hydrotherapy / Underwater Treadmill: Allows low-impact, controlled weight-bearing exercise that builds strength without overloading joints.
• Targeted Therapeutic Exercise: Controlled Cavaletti poles, balance boards, and core exercises progressed under professional guidance.
• Manual Therapy: Specialized massage, myofascial release, and strain-counterstrain techniques relieve chronic trigger points.

Phase 3 — Long-Term Management & Recurrence Prevention

A 2022 survey in Frontiers in Veterinary Science found that 25% of dogs with iliopsoas strains sustained a second strain, and 11% sustained three or more. Preventing re-injury requires a gradual return to activity and lifelong management of any underlying joint disease.

Prevention: Protecting Your Dog’s Hip Flexors

• Pre-Activity Warm-Ups: Incorporate 5–10 minutes of walking, light jogging, and low-effort movements before high-intensity play or athletic competition.
• Manage Joint Disease Proactively: Consistent medical management of underlying hip dysplasia, arthritis, and knee conditions prevents compensatory gait changes.
• Maintain an Ideal Weight: Keeping your dog lean dramatically reduces chronic strain on the hip flexors and surrounding joints.
• Strengthen the Core: Core stabilization exercises improve spinal and pelvic support, reducing strain vulnerability.
• Provide Non-Slip Flooring: Use runners or mats on hardwood or tile floors — slipping is one of the most common causes of acute iliopsoas tears.
• Schedule Regular Check-Ups: Dogs with chronic joint conditions should have their iliopsoas specifically evaluated during routine veterinary visits.

Is Your Dog Showing Signs of Lameness?

Whether your dog is an athlete, a senior, or is currently being managed for hip, stifle, or spine disease, iliopsoas involvement may be contributing to unresolved pain. Our veterinary team at TLC Animal Hospital in El Paso is here to provide comprehensive orthopedic evaluations and tailored rehabilitation plans.

Veterinary References

1. Breur GJ, Blevins WE. Traumatic injury of the iliopsoas muscle in three dogs. J Am Vet Med Assoc. 1997;210(11):1631–1634.
2. Nielsen C, Pluhar GE. Diagnosis and treatment of hind limb muscle strain injuries in 22 dogs. Vet Comp Orthopaed. 2005;18:247–253.
3. Cullen R, Canapp D, Dycus D, Carr B, Ibrahim V, Canapp S. Clinical evaluation of iliopsoas strain with findings from diagnostic musculoskeletal ultrasound in agility performance canines — 73 cases. Veterinary Evidence. 2017;2.
4. Sack D, Canapp D, Canapp S, et al. Iliopsoas strain demographics, concurrent injuries, and grade determined by musculoskeletal ultrasound in 72 agility dogs. Can J Vet Res. 2023;87(3):196–201. PMC10291697.
5. Fry LM, Kieves NR, Shoben AB, Rychel JK, Pechette Markley A. Internet survey evaluation of iliopsoas injury in dogs participating in agility competitions. Front Vet Sci. 2022;9:930450.
6. Markley AP, Shoben AB, Kieves NR. Internet-based survey of the frequency and types of orthopedic conditions and injuries experienced by dogs competing in agility. J Am Vet Med Assoc. 2021;259:1001–1008.
7. Pechette Markley A. Iliopsoas [book chapter overview]. Vet Clin North Am Small Anim Pract. 2023.
8. Bliss S, Evans C. Repetitive strain injury of the psoas muscle in dogs. VetBloom Continuing Veterinary Education. Port City Veterinary Referral Hospital, Portsmouth, NH; 2016.
9. Johnston SA, Tobias KM. Veterinary Surgery: Small Animal Expert Consult. St. Louis: Saunders; 2017.
10. Cornell University College of Veterinary Medicine, Riney Canine Health Center. Iliopsoas Injury. DogWatch Newsletter, Belvoir Media Group. Accessed 2025.
11. VCA Animal Hospitals. Iliopsoas Injury and Rehabilitation. Clinical client handout reviewed by veterinary specialists. Accessed 2025.
12. VetTimes. Diagnosis of hip dysplasia [clinical overview including LSIVDD and iliopsoas differential diagnosis]. Accessed 2025.
13. Online Pet Health. What do we know about iliopsoas strain? [veterinary clinical summary]. Accessed 2025.

This document is provided for educational purposes and does not replace an individualized veterinary examination. Please contact TLC Animal Hospital for guidance specific to your pet.