Concepts for Cartilage Behavior

Why does cartilage wear out?  Understanding cartilage behavior.

Man versus Nature
The objective of Nature and the objective of knee-user are somewhat at odds. Biological systems deteriorate with time.  Joints are extraordinarily ordered systems and Nature will try to undo that order.  The rate of deterioration is governed by the material properties of the tissue and the forces placed upon them. Quantity, direction and frequency of joint forces can be modulated through one’s kinematic behavior.  The objective is KINEMATIC DISCIPLINE.

Laws of Cartilage Behavior 

Law 1. Cartilage wear is a function of the concentration of forces, or stress, on its surface.  Stress concentration is bad for cartilage.  In essence, this is the wrong amount of force in a given area within the joint.

Law 2. Joints will tend to take the path of least resistance (and least energy expenditure) creating sub-optimal joint mechanics, which imparts high stress concentrations to the joint surface.  The result, over time, is increased stress concentration, which according to Law 1, may lead to joint surface damage.

How about repairing and rebuilding cartilage?  Cartilage is notorious for its poor healing capacity.  It is under-nourished (avascular) and over-worked. However, the inherent beauty of biological tissues is that they contain the machinery to regenerate given the correct environment.  The key, as in most disease processes, is early intervention. Joints generally abide by a principle whereby they strengthen themselves according to the demands placed upon them, a principle that has come to be known as Wolff’s Law.

Law 3. Cartilage is self-rejuvenating when the cells receive the proper signals.  This is Wolff’s Law of form and function.  The appropriate tissue stress creates the ideal tissue structure.

Law 4. Optimal joint mechanics lead to optimal stress concentrations.

Understanding these 4 laws and how they inter-relate is intention of this book.  A joint that takes the path of least resistance will often lead to increased stress concentration (compression/tension/SHEAR) within the joint.  Pressure will not be optimally distributed, but localized to smaller areas, something known as peak loading.  Stress concentration leads to increased wear on the cartilage surface. This is the path of joint destruction.  However, the reverse of this pathway also holds true, that is;

Optimal joint mechanics Þ Minimize stress concentration Þ Send optimal signals for cartilage regeneration

The key to knee health is to optimize the force vectors that travel through your body; up, down and within. This begins with the position of your head and down through the shoulders, moves through your torso, the core and on through the pelvis, hips, knees, ankle, foot and even toes.  All of the intervening joints are connected in a complicated and elegant way.  It is the ability to link these interconnections in an ideal manner that will protect the cartilage of these joints.

MASTER LAW 4 through kinematic discipline.
Our objective is to master Law 4; create optimal joint mechanics, ie, control the forces that go through your joints.  The goal will be to minimize stress concentration with the joint and maximize the effects of Wolffs law.  To accomplish this, we must teach the body a new positional language; the knee joint must have disciplined movement as not to drift into the path of least resistance.  Optimal joint mechanics, in general requires;

  • The forces going in to the joint must be minimized.
  • The pressure within the joint must be optimally distributed
  • The action of the affected joint must be to maximally absorb and attenuate those forces. 

The Theory of 5 Principles

The “code” of cartilage longevity is unlocked by system of 5 principles, a control system of the knee. I will consider this system a theory because research is ongoing, and it is very likely that new information will shift these principles in the future.  The 5 principles are the building blocks of cartilage health by way of proper joint mechanics (Law 4).

The 5 principles are

  • Vectors: directional control
  • Vectors: force regulation
  • Energy
  • Elasticity
  • Power

Much of energy modulation comes from muscles.  Muscles produce power and attenuate shock.  Production of power is their first order of business (particularly in youth) while attenuation of shock is secondary.  The code strives to reverse that.  

Muscles and the motion they control, will default to that direction that requires the least exertion and energy expenditure.  The code strives to undo that.  It requires re-programming the circuit that governs joint behavior, or kinematic discipline.  This generally requires more energy, not less.  Incorporating the theory of 5 principles into your daily movement patterns will accomplish this.

What we do at VCC
The vector control program at VCC teaches on how to understand the forces across the knee joint and answer the questions;

  • What are the optimal lines of force across the joint? 
  • How does one control these lines of force? 
  • How can one change the way their body works to improve joint forces over a lifetime? 
  • Will all this, in the end, increase cartilage longevity?  I think so¾though at the very least, it’s the best you can