The Dangers of Winter Injuries Resulting in Hip Flexor Strains
By Sherman O. Canapp Jr.,
DVM., MS., Diplomate ACVS &
Debra A. Canapp DVM., CCRT
With the winter upon us it is important to be aware of certain
environmental factors that can lead to injury in your dog. In
particular,
the ice, snow and sleet that frequent the Baltimore-Washington
metropolitan area during the winter can be treacherous for our
canine companions. It is not uncommon for dogs to slip on icy,
slick surfaces causing one or both rear legs to splay, resulting in
an acute strain injury. One such strain injury, which commonly
occurs from a slip or splayed-leg event, is an iliopsoas strain.
An Uncommon Diagnosis
Acute, stretch-induced muscle injuries are estimated to
account for more than 30 percent of injuries seen in a typical
human sports medicine practice, and have been reported
to be the most common injury seen in human general
practices. But until recently, acute muscle injuries were
rarely reported in the small animal veterinary literature,
and most discussion of chronic muscle disorders in dogs
continues to be limited to a handful of classic syndromes
or inflammatory conditions. Given the similarities
between the human and canine musculoskeletal system,
it's not hard to see why common injuries in humans would
also be common in canines. More likely, the low reported
prevalence of muscle injury in dogs is actually due to a
failure to correctly diagnose the condition.
Causes
Hip flexor strains, also known as Iliopsoas strains, occur
when excessive force acts on the Iliopsoas muscle. This
injury is commonly associated with dogs participating
in highly athletic activities requiring much agility, but
common factors can also lead to these strains in more
sedate companion animals. These injuries often occur
where the muscle and tendons meet, which is the weakest
part of the muscle-tendon unit. Jumping out of a vehicle,
aggressive agility training, or rough housing with other
dogs may lead to slipping into a splayed-leg position
and triggering a serious lameness. It is not uncommon
to find dogs with iliopsoas strains that also have other
orthopedic problems, or that have recently undergone
surgical treatment for another orthopedic condition, such
as cranial cruciate ligament rupture (knee injury).
The iliopsoas muscle, located along the back and groin
area, connects on the inside portion of the thigh bone. The
action of this muscle is to move the hind limb forward.
Diagnosis
Commonly, dogs with iliopsoas strains have a history
of limping on one of their back legs that gets worse with
increased activity. These dogs are often reluctant to jump
onto furniture or into the car. When examined, the dog
appears to be in pain, and there is spasm in the affected
muscle. Pain and spasm may also be detected when
stretching the muscle; by placing the hip in extension,
by moving the limb out to the side, or by simultaneous
extension of the hip with internal rotation of the
hind limb.
While x-rays are of little value in the early phase of
the strain, they can sometimes reveal mineralization in
chronic cases. The use of advanced imaging techniques t
identify lesions of the affected muscle and/or tendon can
increase confidence in the diagnosis. Ultrasonography is
a relatively inexpensive, non-invasive imaging modality
for canine orthopedic evaluation with the additional
advantage of not requiring general anesthesia. But this
imaging modality is particularly dependent on the
expertise of the operator, which may limit the ability to
get a definitive diagnosis.
Advanced diagnostics such as CT (computerized
tomography) and MRI (magnetic resonance imaging
may be used to identify iliopsoas strains. Both are widely
used in diagnosing acute, stretch-induced muscle injury
in human patients. Although the CT is valuable for
identifying soft tissue lesions, the use of the MRI has
greatly increased the ability to detect very small lesions.
Treatment Options
Acute iliopsoas strains should be treated conservatively.
Muscle relaxants may be prescribed in severe cases to
reduce pain and muscle spasms. Medical management
may also include non-steroidal anti-inflammatory drugs
(NSAIDs), ice therapy and restricted or controlled activity.
Fortunately, rehabilitation therapy can be very effective.
Treatments may include cold laser therapy to increase
circulation, remove waste products, and promote healing.
Pain-free, passive range of motion and home exercises
also are recommended. Acute strain injuries should not
be stretched, since small tears may occur. Passive range
of motion exercises, transelectrical neurostimulation,
stabilization exercises, and gradual increases in weightbearing
activities are usually prescribed. Active range
of motion and strengthening exercises are added later
in the healing process. Strengthening exercises might
include three-legged standing, para-standing (lifting
both the front and hind limbs simultaneously while
the dog balances on the other two limbs), paws on the
counter, and the use of a wobble board. Like in humans,
acupuncture may also be helpful to assist with pain
control and to promote healing.
The risk of re-injuring a strained muscle is well
established in human patients. In fact, a minor injury to
the area frequently occurs before a major strain. The risk
of a more significant strain increases when a strain injury
has not completely healed. This also appears to be the
case in canine patients; pain from iliopsoas strain injuries
may recur. Surgical treatment is warranted for those that do
not respond to conservative medical management and
rehabilitation therapy. In cases where there is irreversible
change to the tendon, such as fibrosis where the muscle
and tendon meet, surgically releasing or reattaching the
tendon may be needed. Surgical intervention should
be considered when the strain injury recurs at regular
intervals or does not respond to medical treatment or
rehabilitation therapy, although the lesion should be first
confirmed with ultrasonography, CT, or MRI. Surgical
results are generally good to excellent, but excessive,
intense exercise may still be restricted.
Avoiding Injury
Of course, it's best to avoid injury. There are several
precautions dog owners can take to help prevent iliopsoas
injuries. When slick surfaces develop, clear your walking
area and provide a stable surface for you and your dog
to walk on. This also applies to the backyard. If a layer
of ice develops over the snow, take a moment to break
away a path and walk your dog on a leash to help prevent
slip-outs. Fitting your dog with extra traction boots can
also make playing in the snow safer. Keep a towel or an
area rug near the entrance, to dry your dog's paws when
they come in from outside. Wet feet are extremely prone
to slipping on hardwood or tile floors. Provide stable
footing - a piece of mat works fine -that
will allow your dog to safely jump into or out of your vehicle. Creating
an ounce of prevention is worth avoiding the time and cost
of the cure!
Additional Reading:
Nielsen C, Pluhar E. Diagnosis and treatment of hind limb
muscle strain injuries in 22 dogs. 18:247-53, 2005.
Breur GJ, Blevins WE. Traumatic injury of the iliopsoas muscle
in three dogs. J Am Vet Med Assoc 210: 163-164, 1997.
Janssens LA. Trigger points in 48 dogs with myofascial pain
syndromes. Vet Surg 20:274-8, 1991.
By Sherman O. Canapp Jr.,
Advanced diagnostics such as CT (computerized
tomography) and MRI (magnetic resonance imaging
may be used to identify iliopsoas strains. Both are widely
used in diagnosing acute, stretch-induced muscle injury
in human patients. Although the CT is valuable for
identifying soft tissue lesions, the use of the MRI has
greatly increased the ability to detect very small lesions.
