What do we Really Know About Iliopsoas Strain?

In recent years, the iliopsoas muscle complex has come under scrutiny as the veterinary community has begun to move away from the all-too-common ‘soft tissue injury’ diagnosis and focus on the specific identification and treatment of the anatomical origins of lameness. This has led to a greater awareness of certain muscle structures, such as the iliopsoas, which are so frequently identified as a factor in lameness.

This blog takes a snapshot overview of what we currently know about iliopsoas strain in dogs.

How much of a problem is this condition really?

Working and competitive dogs are commonly assessed for muscular strains, with a survey showing that 32% of agility dogs suffered from some kind of orthopaedic lameness during the course of their training. Of these dogs, 53% of the lameness’s were caused by muscle or tendon injuries (Cullen, et al 2013). Further research has revealed that 32% of hind limb lameness involves the iliopsoas muscle group (Carmichael, et al 2015).

A quick search of our Small Animal Vetrehabbers Facebook Community reveals over 50 posts (I stopped counting…) where Vetrehabbers have specifically asked for advice about iliopsoas-related injuries. That’s a significant amount of cases that have cropped up where Vetrehabbers felt they needed advice and feedback from the community to have the best possible outcome for their patient. If you would like to benefit from that advice, please join the community and search for Iliopsoas. Everything is discussed from diagnostics, rehabilitation protocols, timelines, modalities, when UWT should be introduced, rest, and more.

The anatomy of the iliopsoas complex

The psoas minor arises from the ventral surfaces of the last thoracic and first four lumbar vertebrae, and inserts on the ilium adjacent to the iliopubic eminence. The psoas major muscle arises laterally to the psoas minor the last two thoracic vertebrae and ribs and most of the lumbar vertebrae. It inserts in common with the iliacus muscle as the iliopsoas on the lesser trochanter of the femur. The iliacus muscle arises from the ilium and fuses with the psoas major muscle to insert on the lesser trochanter of the femur. There is a bursa under the tendon of insertion on the lesser trochanter of the femur (Levine, et al 2014).

The femoral nerve innervates this muscle group, originating from L4-6.

The main function of the iliopsoas muscle is the flexion of the hip joint and adduction and external rotation of the femur. It also plays an important core stabilization role as it aids in flexion and stabilization of the lumbar spine when the hindlimb is weight-bearing, and caudal traction on the trunk when the hindlimb is in extension (Levine, et al 2014).

The causes of injury

Iliopsoas muscle injury is usually due to excessive stretch or stretch while the muscle is activated during an eccentric contraction. The damage is commonly localized close to the muscle-tendon unit or origin of the muscle, and less common within the muscle belly.  Chronic repetitive microtrauma is a large factor in canines. In acute cases, the trauma usually occurs during an explosive movement such as turning or twisting during a jump, fall or slip, where the lumbar spine extends and the hindlimb extends and abducts. Weak core musculature can be a predisposing factor in working and sporting dogs, as can inflexibility, inadequate warm-up and muscle fatigue. Concurrent orthopaedic conditions such as hip dysplasia, cranial cruciate ligament insufficiency, lower lumbar malalignment, lower lumbar disk disease and sacroiliac malalignment can all predispose to a strain of the iliopsoas.

The presentation of injury

The lameness or gait abnormality may vary in severity and may be acute or chronic, as well as unilateral or bilateral. Gait analysis will show an off-loading during the stance phase, a shortened stride, and overloaded forelimbs. Direct palpation should be performed from the origin to the insertion of the muscle. The condition can be recurring in a persistent, chronic lameness if the muscle is not allowed to heal and rehabilitate. Direct palpation of the iliopsoas muscle and its insertion at the greater trochanter will elicit a pain response. Extension of the hip with abduction of the limb will be painful (Cullen et al, 2017). The psoas bounce test will reveal pain and spasm – in a standing position, place both hands just in front of the hindlimbs and lift the weight off the limbs in a small bounce. There may also be a reduced thigh circumference in the affected limb.

The femoral nerve may on occasion be affected by iliopsoas strain where the myofascia is involved, fibrosis occurs or hematoma is severe. Symptoms may then include a reduced patellar reflex and conscious proprioception, hindlimb weakness and quadriceps muscle atrophy.

The diagnosis of an iliopsoas injury

It is imperative to make a correct and complete diagnosis if we hope to be successful in rehabilitating lameness and returning to sport or work. Findings on physical examination will give a good indication and starting point; however, the diagnosis should be confirmed through imaging in order to determine the severity of the condition and the presence of any concurrent conditions that may have caused the iliopsoas strain or worsened the condition.

Radiography is usually the first tool we turn to, but it is not particularly useful in identifying iliopsoas strain. It may help us to identify concurrent conditions such as hip dysplasia, and reveal any remodelling of the insertion, which would indicate an insertionopathy. It may also reveal any calcification or an avulsion at the lesser trochanter (Da Silva, et al 2009). Computed tomography can reveal intramuscular oedema and inflammation (Rossmeisl, et al 2004). Magnetic resonance imaging can accurately detect musculotendinous lesions (Bui, et al 2008). However, CT and MRI scans are expensive and often not available. At this point our best tool is musculoskeletal ultrasound, which is affordable, can be performed on an awake dog during a dynamic and static evaluation and can be carried out during the rehabilitation and healing phases to ensure correct healing is occurring (Cullen et al, 2017).

The Treatment Plan

Traditionally iliopsoas strain is non-responsive to rest and NSAID treatment, and rehabilitation therapy has proven to be invaluable in the full recovery of this condition. Rehabilitation therapy will include all the usual tools utilized in pain control, including the use of Photobiomodulation. Muscle relaxants can be employed when needed. Progressions in therapy will be made according to the healing timeline of muscle, as well as the rate of healing and progression of the individual. You will want to progress from rest and pain control, to stretching and strengthening the muscle, to active resistance and finally a return to activity (Levine, et al 2014).

If rehabilitation fails or the lesion is diagnosed as severe, regenerative medicine may be employed followed again by rehabilitation. Always consider the restrictions in your therapy when regenerative medicine is used (Canapp, et al 2016).

Resources

1. Cullen, RE. et al. (2017) Evaluation of Iliopsoas Strain with Findings from Diagnostic Musculoskeletal Ultrasound in Agility Performance Canines – 73 Cases.
2. Canapp, S.O. (2007) Non-responsive hind-limb lameness in agility dogs: Iliopsoas strains. Clean Run; 2-5.
3. Cullen, K. et al. (2013) Internet-based survey of the nature and perceived causes of injury to dogs participating in agility training and competition events. Journal of the American Veterinary Medical Association, 243 (7), pp. 1010-1018. http://dx.doi.org/10.2460/javma.243.7.1010
4. Carmichael, S. Marshall, W. (2012) Muscle and tendon disorders. In: Tobias KM, Johnston SA, eds. Veterinary Surgery: Small Animal. St. Louis, MO: Elsevier. 1127-1134.
5. Da Silva, C.G. et el. (2009) Fibrotic myopathy of the iliopsoas muscle in a dog. Veterinary and Comparative Orthopaedics and Traumatology, (22), pp. 238-242.
6. Stepnik, M.W. et al. (2006) Femoral neuropathy in a dog with iliopsoas muscle injury. Veterinary Surgery, 35 (2), pp. 186-190. http://dx.doi.org/10.1111/j.1532-950X.2006.00130.x
7. Laksito, M.A. et al. (2011) Fibrotic myopathy of the iliopsoas muscle in a dog. Australian Veterinary Journal, 89 (4), pp. 117-121. http://dx.doi.org/10.1111/j.1751-0813.2011.00694.x
8. Cannon, M.S. Puchalski, S.M. (2008) Ultrasonographic evaluation of normal canine iliopsoas muscle. Veterinary Radiology & Ultrasound, 49 (4), pp. 378-382. http://dx.doi.org/10.1111/j.1740-8261.2008.00385.x
9. Bui, K.L. et al. (2008) Iliopsoas injury: an MRI study of patterns and prevalence correlated with clinical findings 37 (3), 245-249. http://dx.doi.org/10.1007/s00256-007-0414-3
10. Rossmeisl, J.H. et al. (2004) Computed tomographic features of suspected traumatic injury to the iliopsoas and pelvic limb musculature of a dog. Veterinary Radiology & Ultrasound (45), 388-392. http://dx.doi.org/10.1111/j.1740-8261.2004.04070.x
11. Baltzer, W. (2012) Sporting dog injuries. Veterinary Medicine dvm360.com; 166-177.
12. Nielson, C. Pluhar, G.E. (2005) Diagnosis and treatment of hind limb muscle strain injuries in 22 dogs. Veterinary and Comparative Orthopaedics and Traumatology, (18), 247-253.