Iliopsoas injury in dogs: hip flexor strain and recovery

Overview

The iliopsoas is a muscle and tendon unit that flexes the hip. It consists of the iliacus and psoas major muscles. The unit runs deep beneath the lumbar spine and pelvis towards the femur. Only a small part of this deep muscle can be felt directly by hand.

It brings the hindleg forwards by bending the hip joint. It also helps support the lumbar spine. Injury may affect the muscle itself or its tendon attaching to the femur. The bursa between tendon and bone may also become inflamed.

The bursa normally reduces friction between tendon and bone as the hip moves.

A large agility survey included 4,197 dogs.

Iliopsoas injury was reported in 327 dogs, or 7.8% of the survey population. Diagnoses underlying owners' reports were not checked against veterinary records.

Causes

An acute strain can occur when the muscle lengthens while trying to slow movement. This may happen during a slip, fall or poorly executed jump. A rapid change of direction can load the same muscle and tendon area.

At the end of take-off over an agility jump, the muscle may slow extension of the hip and lumbosacral junction. Muscle fibre damage can involve local bleeding and swelling. Repeated small stresses can instead cause a gradually developing chronic problem.

A chronic tendon problem may be associated with daily games of fetch, for example. Prolonged exertion without enough recovery can also strain the hip flexor when moving through deep snow. Even a quieter pet dog can be injured during an unusually vigorous activity.

An altered gait caused by another musculoskeletal problem can increase iliopsoas loading. The muscle may then be used more than usual to stabilise a joint and compensate for pain.

Risk factors

Iliopsoas injuries are found particularly in active sporting dogs. Ordinary pet dogs can also develop the same injury. In 72 agility dogs assessed with ultrasound, age ranged from 1.5–10 years. Median age in that group was 5 years.

Border Collies accounted for 20/72 dogs, or 27.8%. Their large numbers in injury groups may partly reflect their popularity in active dog sports. A previously injured muscle or tendon is more susceptible to reinjury and chronic strain.

An inadequate warm-up before vigorous activity may increase muscle strain. Muscle fatigue and poor muscular fitness are other possible predisposing factors.

Typical symptoms

At home, symptoms may appear as follows:

• The hindleg stride shortens at a trot, even without obvious severe lameness.

• Your dog is intermittently lame or shifts more weight onto the other hindleg.

• Speed or acceleration decreases compared with previous performance.

• Your dog avoids jumping or abandons a jump because of pain.

• An agility dog starts knocking poles or slows through the weave poles.

• Your dog looks stiff and may struggle to get up.

• Your dog avoids extending the hip and pelvis while moving.

Pain may affect one or both sides. A typical mild iliopsoas strain does not usually cause sudden complete loss of weight-bearing.

Complications and consequences

An untreated acute muscle injury can become chronic. Scar tissue may form in the damaged area, reducing normal muscle function. Severe scarring can cause permanent mechanical lameness and muscle tightness.

The nearby femoral nerve may rarely be damaged or irritated. Tendon bursa inflammation can cause swelling and fluid accumulation. Of 73 agility dogs assessed with ultrasound, 62.8% had acute and chronic changes together.

In a group of 281 agility dogs with reported strains, 69 dogs, or 25%, had experienced 2 strains. At least 3 strains had occurred in 31 dogs, or 11%, in the same group. A single strain episode was reported in 181 dogs, or 64%.

Diagnosis at the vet

The vet assesses gait and pain in the muscle and tendon area. Extending the hip and rotating it inwards may provoke pain during examination. However, muscle tenderness can also occur with another hindquarter condition.

The vet therefore also looks for knee cruciate ligament problems and hip dysplasia. Lower back and lumbosacral pain sources form part of the same overall assessment.

At the initial assessment of 72 agility dogs, other musculoskeletal pain sources were recorded in 53/72, or 73.6%. Iliopsoas injury was initially considered the only musculoskeletal problem in 19/72 dogs, or 26.4%. Cranial cruciate ligament instability was found in 20/72, or 27.8%.

The lumbosacral region was considered the main pain source in 17/72 dogs, or 23.6%. Of these 17, 14 underwent lower back MRI. MRI showed abnormal lumbosacral structure in 5 dogs. Six dogs had normal MRI findings. MRI reports for 3 dogs were unavailable for further assessment.

What does imaging show?

Ultrasound may show disruption of muscle fibre structure. An experienced examiner can distinguish acute and chronic iliopsoas changes with ultrasound. X-rays are not usually the first-choice method for diagnosing soft tissue injury. However, mineral deposits at a chronically affected tendon attachment may be visible on X-rays.

MRI or CT can provide a more detailed assessment of the muscle area. Ultrasound changes on both sides were found in 52/72 dogs, or 72.2%. Changes on the opposite, symptom-free side did not always indicate an equally significant injury.

In a mild grade I strain, muscle structure and function are preserved. Swelling or bleeding affects less than 5% of the muscle. A moderate grade II injury involves partial fibre disruption and reduced strength. More than 5% of the muscle is involved in a moderate injury. In a severe grade III injury, tearing of fibres and fascia is extensive.

Treatment

Treatment is planned according to the injury and concurrent diseases. Treating another underlying problem may also help the muscle area heal. Most injuries are managed conservatively, without surgery. Complete detachment from the attachment site may require surgery.

Rest and pain management

An isolated iliopsoas tendon injury needs at least 4 weeks of initial rest. An acute injury may initially require complete rest. Running, jumping and sudden movements are excluded during the early phase. Keep your dog on a lead outdoors to control movement.

The vet may prescribe a non-steroidal anti-inflammatory drug for pain from an isolated tendon injury. The muscle relaxant methocarbamol may form part of individual pain management. Gabapentin, which acts on nerve pain, may also be used at the vet's discretion. Better-looking movement while taking painkillers does not remove activity restrictions.

Gradually progressing rehabilitation

Rehabilitation for most dogs is planned over about 4–12 weeks. A more severe or prolonged injury may need longer. Activity increases gradually under the vet's or veterinary physiotherapist's guidance. Strengthening trunk and pelvic muscles is a key goal.

Home exercises may later include controlled sideways steps, for example. Walking backwards may be another part of an individual programme. Water walking and strengthening exercises may be added later in rehabilitation. Heat treatment or therapeutic ultrasound may also be used for chronic problems.

The rehabilitation professional may teach suitable massage techniques and passive movement exercises. Changing exercises yourself can worsen the problem. Short, controlled lead walks are lengthened gradually as the programme progresses.

Returning to training and competition

In the agility survey, return-to-competition information was available for 301 dogs. Within 3 months, 169 dogs, or 56% of this group, returned. Another 71, or 24%, returned within 3–6 months. Forty-three dogs, or 14%, took more than 6 months. Eighteen, or 6%, retired from competition.

A return to agility may begin with low, straight jumps. Jump height and turns are increased slowly. Weave poles are reintroduced last. An older dog with other musculoskeletal problems may need a gentler activity.

Surgery for a persistent problem

Persistently recurring pain that does not respond to other treatment may sometimes be treated by tendon release surgery. This cuts the tendon near its femoral attachment. Most dogs do not return to their previous sporting level after this operation.

Prevention

Use a consistent warm-up before strenuous activity. It may include walking and trotting before the main activity. A calm cool-down period is also needed afterwards.

A healthy dog's warm-up may also include a few low jumps and gentle stretches. Slippery turns and icy winter surfaces can worsen an existing muscle problem.

A previously injured dog may benefit from a long-term injury prevention programme. Concurrent orthopaedic problems must be considered when assessing overall activity. Stopping rehabilitation too early may predispose to reinjury.

Important for dog owners

Record when the stride shortens and when lameness becomes visible. Note slips, unusual exertion and pain during jumps. Bring details of previous knee, hip and back problems to the appointment.

Quiet scent work and food puzzles can provide activity while exercise is restricted. Perform home exercises according to the rehabilitation professional's instructions.

Ask which findings confirm the injury's location and whether your dog has other pain sources. Agree on the next review and when walking, jumping and sport-specific training can increase. Keep a training diary of activity and movement the following day.

Frequently asked questions

Can an iliopsoas injury affect both hindlegs?

Pain can affect one or both sides. In the ultrasound group of 72 agility dogs, bilateral changes were found in 52/72, or 72.2%. However, findings on the opposite, symptom-free side were often considered milder and related to compensation.

Does a hip flexor strain show on X-rays?

An ordinary soft tissue injury is not usually visible on X-rays. However, chronic mineralisation at the tendon attachment may be seen. Ultrasound helps assess fibre structure. MRI or CT can also provide a more detailed assessment. X-rays may additionally reveal concurrent hip changes.

How long does an iliopsoas injury take to heal?

A rehabilitation programme lasts about 4–12 weeks for most dogs. More severe injury may require longer rehabilitation. Returning to competition can take more than 6 months. Return is gradual as the dog improves with clinical and home rehabilitation.

Can my dog return to agility while taking painkillers?

Medication can mask pain, so better-looking movement does not remove rehabilitation restrictions. Exercise increases gradually under professional guidance. Agility weave poles are reintroduced only at the end of the return programme. An older dog or one with several health problems may need a gentler activity.

Why does the vet also examine the knee and back?

Iliopsoas tenderness may be associated with other hindquarter conditions. Cruciate ligament injury and hip dysplasia are possible concurrent pain sources. Lower back and lumbosacral problems are also assessed. Treating the underlying problem may help the muscle heal. In the clinical assessment of 72 agility dogs, cruciate instability occurred in 20, or 27.8%.