By Dr. Luke Peterson, DVM
Muscle injuries are more common in athletic dogs than we once thought. Advancements in medical imaging such as magnetic resonance imaging (MRI), computed tomography (CT scans) and ultrasound, along with a willingness on the part of those with the financial means to pursue such testing have allowed us to identify and further understand common muscle injuries in canine athletes. This information has helped veterinarians to correlate specific, consistent abnormal physical exam findings to specific muscle injuries. In turn, we are better able to make a clinical diagnosis in these conditions with a higher degree of certainty while not having to rely as heavily on advanced imaging (which is nice, since most veterinarians don’t have an MRI and most of our clients would rather not have to pay for one either). Although there are many common injuries, the most frequently seen in athletic dogs are those of the iliopsoas muscle.
In people, the iliopsoas muscle is more commonly referred to as the groin. Next time you are dressing game, you can study this muscle as I’m sure most of you have seen it regularly and may refer to it as the tenderloin or “hanging tenders”. The iliopsoas muscle is actually a combination of two muscles. The psoas major muscle arises from the lumbar vertebrae of the lower spinal column and the iliacus arises from the lower surface of the one of the hip bones. The two muscles combine and attach to the upper part of the femur. The action of this muscle is to move the rear limb forward toward the trunk of the body, resulting in flexing the hip joint. This muscle is typically injured when muscle fibers are stretched too far as the legs are extended away from the body (see Image 1).
The most common ways this muscle is injured are:
- Repetitive use without variation in motion
- Rapid stretching of the muscle without being warmed up – for example – slipping on ice and having a splay leg, jumping out of a truck
- Compensating for another underlying orthopedic injury
- Dogs that are infrequently active and overextend themselves can experience this injury as well or dogs just starting to get reconditioned after being penned up for a while
Symptoms range in severity from signs of decreased performance, difficulty rising, and a shortened stiff gait in the hind limbs, non-weight bearing lameness and in the most severe cases, femoral nerve paralysis. I suspect most beagles with this injury override their pain while running but you may notice a decrease in performance or soreness after running. The diagnosis is typically made by identifying pain when the muscle is palpated and painful responses when the muscle is stretched (see Images 2 and 3). For those wishing to determine the extent and severity of the injury, ultrasound, CT scan, or MRI scan can be done to see the extent of damage.
There are a myriad of therapeutic options for treatment of muscle injuries depending on severity of the injury and your budget. The most important aspect of therapy to remember is muscle injuries take a long time to fully heal. Returning to full use prior to full healing typically results in re-injury and increases the likelihood for more muscle damage to develop. At best, recovery time is 4-6 weeks with more severe injuries likely to take as long as 12 weeks. Therapy options include icing, non-steroidal anti-inflammatory drugs, passive range of motion exercises, and cold laser therapy. The most severe cases in which the muscle tendon has torn from its attachment to the femur may require surgery. Once healing is initiated, a physical therapy regimen can begin to slowly rehabilitate the muscle to full strength.
Prevention of injury is focused on warming up before strenuous running. A brief leash walk prior to a trial run or hunt can help the muscles get warmed up before they start to burn one up. Stretching the muscle prior to the workout probably won’t help and may actually hurt as research has shown stretching cold muscles often causes more undue muscle fiber tearing than it helps prevent (this is true for us too).