Biomechanics of lameness
Biomechanics Of Lameness
Jean Luc Cornille
Jean Luc and Chazot
"The Biomechanics of Lameness"
James Rooney pioneered the idea that the kinematics abnormality was there first and that it was the repetition of the kinematics abnormality that caused the lesion. . "The gait abnormality created by a specific lesion is the gait abnormality that causes the lesion." Rooney's findings paved the way for the ability to correct the gait abnormality before it becomes a lesion. Instead, the veterinary medicine elected to wait for the lesion focusing on greater diagnostic tools. During a recent conference a statement was made, "If the therapy does not work, it is because the diagnosis is not precise enough." The financial purpose of the statement is easy to understand as the author is involved in creating better diagnosis tool. There is no doubt that greater diagnostic tools could eventually prevent the lesion. For instance, before becoming apparent in the cartilage, arthritis commences with micro fracture or other lesion in the subchondral bone. However we are far from routine MRI as a preventing tool for early detection of arthritis. Genetics is field of research that promise prevention but meanwhile, horses move crooked and gait abnormalities create lesions. The kinematics abnormality causing the lesion can be corrected. "The horse's athletic ability is the result of good genetics and training interaction." (Eric Barrey, 2002) Whatever progresses are made in diagnosis or in genetics, the quality of the training remains the difference between lameness and soundness. Rooney's legacy is that instead of being the cause of lameness as it is usually the case, the training can become the source of soundness.
Every training techniques promise educating the horse's physique but in reality, they submit the horse's physique to stereotypes. Formulas are repeated from one generation to the next without sound understanding of the underlying biomechanics factors. The engagement of the hind legs for instance is the base of all riding and training technique. The general belief is that the hind leg engages under the belly and propels the horse body upward as soon as ground contact. This is not the reality. The alighting hind leg produces first a decelerating action resisting gravity and inertia forces. The propulsive activity commences after the peak vertical when the hind leg is vertical under the croup. This biomechanical reality fundamentally changes all the principles of riding and training.
Rooney talks about "The abnormal illumining the normal." By studying the kinematics abnormality causing suspensory damages, bow tendons, arthritis and other issues, the abnormal is effectively redefining the normal. Many training techniques and judging standards, which are regarded as the norm, are indeed, pathomechanics; they are kinematics abnormalities leading to pathological changes and therefore injuries. For instance, any trot without suspension such as the way working trot is defined, is a gait abnormality. The forelegs are designed to propel the body upward. "In horses, and most other mammalian quadrupeds, 57% of the vertical impulse is applied through the thoracic limbs, and only 43% through the hind limbs." (H. W. Merkens, H. C. Schamhardt,G. J. van Osch, A. J. van den Bogert, 1993). Vaulting the body weight form one front limb over the other as it is rewarded in dressage, hunter jumper and western pleasure rings, is a kinematics abnormality leading to lameness.
The forelegs' upward propulsive activity results for a great part from an elastic strain energy stored in long tendons and aponeurosis. The distal limb of the horse has been shown to function like a pogo stick, storing and returning energy in long, spring-like tendons throughout the gait cycle (Biewener, 1998 ; Wilson et al., 2001 ).
The horse is a large animal capable of running faster and longer than most of his predators. Nature allowed this survival capacity creating long tendons and aponeurosis as it cost less energy to produce locomotion through elastic recoil of long tendons and aponeurosis than shortening and lengthening of muscles fibers "The elastic energy stored in and recovered from tendons during cyclical locomotion can reduce the metabolic cost of locomotion." (Cavagna et al., 1977 ; Alexander, 1988 ; Roberts et al., 1997 ).
Tendons store energy as they elongate and restitute the energy as they return to their normal length. Greater efficiency is achieved when they function at their designed frequency. "The ability of the muscle-tendon units to recover elastic strain energy is apparently energetically so advantageous that the most economical stride frequency in running may be set by this key component alone." (Paul C. LaStayo, PT, PhD. John M. Woolf, PT, MS, ATC. Michael D. Lewek, PT. Lynn Snyde-Mackler, PT, ScD. Trugo Relch, BS. Stan L. Lindstedt, PhD. Eccentric Muscle Contractions: Their contribution to injury, prevention, rehabilitation, and sport. Journal of Orthopaedic & sports physical therapy. 557-571. Volume 33, NUMBER 10, October 2003)
Hind and front limbs work differently at the walk, the trot, or the canter. "In inverted pendulum gaits like walk, the limbs act as rigid struts over which the body vaults. In the bouncing gaits like trot, the limbs act as a spring and the body center of mass moves like a bouncing ball. Equine gallop might have both bouncing and pendulum aspect." (Mechanical Analysis of Locomotion, Liduin S. Meershoek and Anton J. van den Bogert). Training misconception such as driving the horse onto the bit, long and low, etc., which increase the load on the forelegs alter proper mechanism of the front limbs. Instead of propelling the horse's body upward and forward as they are designed to do, the front limbs act at the trot as they do at the walk, they function like struts over which the body vaults over the other foreleg. The trot is then a flat gait executed without suspension.
The abnormal illumining the normal, it is the biomechanics of lameness that leads to the biomechanics of soundness. The condition of course is not limiting the research to the kinematics abnormalities causing injuries. For instance, knowing how inward rotations of the hock joints can create aberrant stresses on the junction between Mt3 and T3 or T3 and TC, is a first step but only a first step toward a more interesting application of knowledge, which is how to correct the kinematics abnormality altering proper coordination between flexion and extension of the hock and inward rotation of its four joints. Rooney made a first step in this direction explaining that a gait abnormality creating functional straight hocks will induce the same stresses between Mt3 and T3 than a morphological straight hock. As well, functional sickle hocks will induce the same aberrant stresses between T3 and TC than morphological sickle hocks. The next step is how to prevent or correct functional straight or sickle hocks.
This is where advanced understanding of how the vertebral column mechanism influences hind and front limbs kinematics converts an equitation causing injuries into an equitation preventing or rehabilitating the horse from injuries. Albert Einstein wrote, "The significant problems we face today cannot be solved at the same level of thinking we were at when we created them." Quite evidently, the differences between riding and training techniques failing to prepare efficiently the horse's physique for the athletic demand of the performance and the science of motion which orchestrates optimally the horse's physique for the effort, are significant. Elementary equitation talked about gestures, shifts of the rider's weight, rider's aids, neck posture, etc. A more elaborated equitation talks about nuances in muscle tone and muscular coordination creating forces. The science of motion works with the energy that is created through muscular work of the rider's body. This level of subtlety is the horse true comfort zone. Intelligent, finesse and sophistication are in line with the horse's nature. Instead, obedience, leadership and behavior are in line with human ego. A horse does not resist a movement as long as his physique is properly developed and efficiently coordinated for the effort. A horse will at the contrary resist or fear a movement if the move induces pain on all or different parts of his physique. This is why all the training and riding techniques situating the rider's leadership at the level of reward and punishment or social order are ineffective and archaic.
A visually identical hind limb extension in late stance may be accomplished by only hip extensor muscles, only knee extensor muscles or any combination of these." (Liduin S. Meershoek and Anton J. van den Bogert. Mechanical Analysis of Locomotion.) For exactly the same appearance, there are many movements that the horse can execute using different muscles combinations. There is not any neck posture, exercise or gimmick that can stimulate optimal coordination of the horse's body. Only the horse's brain can process the most efficient orchestration of the horse's physique. Indeed, guiding the horse's brain toward highly functional body coordination cannot be achieved at the level of thinking our ancestors were at when they promoted submission, reward and punishment and other forms of domination. Only the horse brain can select the muscular combination optimally adapted to the move and the mental processing will include wrong choices, bad memories and errors. Errors are great insights as they provide to the rider instant and precise information of the horse's body state. Punishing the error is a psychology of the past placing the rider in the past. Punishments might satisfy one's need for domination but depraves the rider from a valuable source of information. The error is already done and punishing it is a waste of time creating fear and restriction in the horse mind. If afraid of error, the horse will never explore beyond the limits of natural reflexes. At the contrary, when the rider reformulates the question based on the information provided by the horse's error, the dialogue can lead the horse brain toward sophisticated body control.
In many instances, horses come at the science of motion' center with a long history of refusing flying change, or piaff or passage, or placing an extra stride in the middle of an in and out, or refusing to jump the water, etc. Members of our online course saw that the horse that would not jump the water was in fact a horse which did not have any issue with the water but torsion of the spine that induced sharp pain at the landing of long and low jumps such as the river. Others come for kissing spine, sacroiliac problem, navicular syndrome or other issues. Every single time, the source of the problem is a dysfunctional thoracolumbar spine. Either the dysfunction hampers the horse's ability to perform or induces limb kinematics abnormality causing injury. Whether the aim is performance or soundness, the therapy is about recreating a functional thoracolumbar spine. This is why talking about biomechanics is just empty talks as long as riding and training principles are not resolutely updated to actual knowledge. No injury can be truly cured as long as the kinematics abnormality causing the lesion is not corrected. Whatever the value of the treatment regimen or therapy applied, the recovery will not be completed as long as the source of the abnormal stress is not identified and corrected. This is how we resolve "impossible" problems. The truth is that they were not impossible, they were simply reactivated every stride as long as the source of the abnormal locomotor pattern was not identified and corrected.
Jean Luc Cornille 2014