CONDITION
Iliopsoas Strain
An iliopsoas strain refers to an injury affecting one of the deep hip flexor muscles that runs from the lower spine and pelvis to the inner thigh. This muscle group is involved in lifting the hind leg forward during walking and running, and strain can occur from sudden exertion, repetitive activity, or awkward movement. The injury may involve stretched fibres, partial tears, or inflammation within the muscle or its tendon. Owners often notice a change in how their dog moves—perhaps a subtle shortening of stride on one hind leg, reluctance to jump into the car, or stiffness after rest that seems to ease with gentle movement. The signs can be intermittent and may not always look like obvious limping. Some dogs show discomfort when stretching that leg backward or when rising from lying down. This page explores the patterns that may suggest iliopsoas involvement, what happens within the muscle and surrounding structures during strain, how the condition is investigated through examination and imaging, and the range of approaches used to support recovery and manage discomfort.
Why this matters now
Iliopsoas strain tends to appear in middle-aged to older dogs, particularly those engaged in active pursuits such as agility, working roles, or regular off-lead running. Certain athletic breeds—including Border Collies, Labrador Retrievers, and working Spaniels—may be represented more often, though the injury can occur in any dog that experiences sudden exertion or repetitive hip flexion. Younger dogs may strain the muscle during play or training, while older animals sometimes develop the pattern alongside other degenerative changes in the hips or lower spine.
The course can vary considerably between individuals. Some dogs show intermittent discomfort over weeks or months, with signs waxing and waning in relation to activity level. In other cases, an acute episode follows a single event—a misstep, a jump, or a sudden sprint—and the signs may improve gradually over days to weeks with reduced activity. Chronic or recurrent strain may develop if the underlying cause—such as altered gait from hip dysplasia or compensatory loading—is not addressed, leading to persistent low-grade discomfort rather than dramatic worsening.
Signals & patterns
Early signals
Shortened stride on one side
The affected hind leg may not reach as far forward during walking, creating a subtle asymmetry that can be easier to notice from behind or when the dog is moving slowly on a loose lead. This reflects guarding of the hip flexor during the forward swing phase of the stride.
Reluctance to jump or climb
A dog may hesitate before jumping into the car, onto furniture, or up stairs, or may begin using a different launching strategy. The iliopsoas is recruited forcefully during these movements, and discomfort can lead to avoidance or altered mechanics.
Stiffness after rest
The dog may appear stiff or slow to move when first rising from sleep or prolonged lying down, with improvement after a few steps. This pattern often reflects inflammation or mild spasm within the muscle that eases as circulation increases and tissues warm.
Discomfort when stretching backward
Some dogs show subtle resistance or a flinch when the affected hind leg is extended behind the body, such as during play bows or when stepping over obstacles. This movement lengthens the iliopsoas and can provoke discomfort if the muscle or tendon is inflamed.
Later signals
Persistent lameness at walk or trot
What may have begun as intermittent stiffness can progress to a more consistent limp, particularly noticeable when the dog is moving at a steady pace. The lameness may be subtle but present across multiple surfaces and speeds.
Muscle atrophy along the thigh
Prolonged underuse of the affected limb can lead to visible thinning of the muscles along the inner or front aspect of the thigh, reflecting reduced weight-bearing and muscle recruitment over weeks to months. This change is often more apparent when comparing both hind legs from the front or side.
Altered sitting or lying posture
Dogs with ongoing discomfort may sit with the affected leg extended to the side rather than tucked beneath the body, or may favour lying on one hip to avoid pressure on the strained muscle. These postural shifts can become habitual as the dog seeks comfort.
Click to read about the biological mechanisms
How this is usually investigated
Options & trade-offs
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