Have you ever wondered about the impact of the improper use of an injured limb on the rest of the body and how other areas are affected?
The canine knee or “stifle” immediately comes to mind as it is the most problematic joint in the dog.
|Source: The Dog Health Handbook|
Because of this, some veterinarians and therapists embrace the concept of this joint being an “organ”.
Here’s how the structures work: the capsule protects the joint surfaces by being a mechanical barrier, providing blood supply and nutrition to the joint and has a lubricating fluid which gives viscosity for the joint to work. Ligaments provide support to the capsule and “bind” the joint together. The patella or “knee cap” rides in a smooth canal formed a valley in the femur and provides a fulcrum for mechanical advantage to the quadriceps muscles when they contract. The menisci or shock absorbers are triangular wedge-shaped cartilage structures that transfer stress off the joint surfaces.
Now let’s examine what happens and why things can go wrong with the stifle.
The cranial cruciate ligament (CCL), also often referred to as ACL, confronts unique biomechanical forces in canine “down on all fours” gait compared to upright 2-legged human gait. The human ACL tears more acutely, mainly from trauma.
The canine CCL tears from repeated movements, non trauma related and acute tears are less common.
This type of tear is usually a slow gradual degradation followed by complete rupture. It is not only due to different forces on stifle during canine gait but also from the shape and angle of the canine tibial plateau.
In humans the tibial plateau is essentially flat, and sits in a level transverse plane almost parallel to the ground.
In dogs the plateau is more sloping in shape and sits in a plane at an acute angle to the ground.
Therefore gravity affects the canine CCL differently with more shearing forces on it during “walking on all fours” than on the human ACL in upright gait. Now you can see why “TPLO” surgery stands for Tibial Plateau LEVELING Osteotomy!
Once the stability of the CCL becomes compromised, the stifle joint is lax (or loose) and the menisci can tear or degenerate because of repeated stress from the laxity.
Patellar luxation in a medial or inward direction can also develop. With these problems the first outward sign is non-weight bearing (NWB) or partial (PWB) lameness in the affected limb. In turn, this causes increased weight on the other “sound” limbs, both front and back.
“Overuse” syndrome can then occur, leading to inflammation, irritation and crepitus (sounding “crunchy”) during passive range of motion.
That is why dogs with a ruptured CCL have a 20-40 % chance of tearing the other side!
The incidence is also variable by obesity and by certain breeds that have some underlying genetic predisposition, but it is not just the large breeds! There is a correlation to body structure—“straighter leg” dogs of both large and small breeds have more chance of CCL tears than “bowed”.
Breeds with straighter bones have more direct force on the ligament as opposed to breeds with more bowed bones like bulldog, dachshund or corgi.
If the injured CCL goes untreated or has surgery and takes longer to recover, the more likely the other side may “wear and tear” beyond the 40%. If the injured side becomes arthritic there is a 60-70% incidence the other side will tear within 12-16 months (ref: Doverspike et al, JAAHA.)
The key to prevention of “other side” tears is in the TIMING: early diagnosis and surgical correction for complete tears, early post op rehab, healthy diet and ideal body weight.
Otherwise excessive weight shifted onto the sound leg will increase the possibility of that CCL tearing. If the tear is just partial and you see only intermittent lameness, surgery may not be needed but PT with modalities such as laser, functional electrical stimulation and massage can be of great benefit, along with other treatments advised by your veterinarian. Further information on these modalities will be provided in a future post.
For the last 3 years she has been providing PT services to dogs and other animals through her entity Joycare Onsite, LLC in pet’s homes and in vet clinics.
She also provides pro bono services each week to a shelter and sanctuary for neglected and abused animals. Sue is the proud “dog mommy” to Penelope, a miniature Dachshund with “attitude”. For more information see her website www.joycareonsite.com , or follow on Twitter @animalPTsue.
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