In an effort to convey a rather lengthy (and perhaps counter-intuitive) perspective, I generated three seperate posts on re-defining the joint. Although they essentially morph quite well into each other, they are spread across a number of months and therefore the message sometimes gets diffused or gets read in another order than the one intended. Therefore, I have decided to "amalgamate" all three into a single post...indeed, much longer but hopefully it results in a better flow of information and provides enhanced clarity.
Each on its own should provide some "food for thought", but as a whole I am hoping that the result is greater than the sum of all parts. Cheers!
Redefining the Joint: Part 1
Why in the world would I suggest that the word "joint" be re-defined?
It's a simple thing, right? Let's look at the definition as quoted in
the Merriam-Webster Dictionary:
the point of contact between elements of an animal skeleton with the parts that surround and support it .
This definition conjures up the image that likely popped up in your
mind...2 bones, some soft tissue around it, and maybe a meniscus in
between.
The above image is nothing new to anyone. You have the pivot joint, the
ball-and-socket joint, and the infamous hinge joint. This image
follows the quoted definition quite nicely. The unfortunate thing is
that the mechanics of human movement cannot be compacted into a simple
definition and certainly not be explained by simple mathematical models.
"Well, what is the right definition then?"...I would be naive to
suggest that this definition is "wrong" per se, rather I merely suggest
that it is very simplistic. Complex systems, by definition, demand
complex explanation and understanding...therefore a more global
perspective is required. As per "Gavin's New Trans-anatomical
Dictionary", a joint is defined as:
Linear and/or angular displacement between separate biological elements .
To many of you, this may seem like a fancier way of saying the same
thing...however, you couldn't be further from the truth. The reality is
that the skeleton (bones) has a "monopoly" on everything joint-related.
Why is this so?...by convention! It's in the dictionary, Gavin. But
if you look at my definition, the skeleton is only a PART of it. Linear
and/or angular displacement indeed occurs at all of the "typical" spots
you would think of (knees, elbows, shoulders, etc)...however, if
linear and/or angular displacement is a key element in this definition, you need to consider EVERY area that experiences this displacement as a true joint!!
It is not sufficient to suggest that movement only occurs at the
"joints" and the soft tissue is simply a "biological sleeve" that fit
over it. It clearly involves sliding of specific fascial layers one on
top of the other. For example, the tendons of the wrist actively slide
against each other when activated...which, by definition constitutes a
joint. As you flex your arms, the fascial layers (from the skin to the
triceps) on the back of the arm slide against each other and along the
humerus...this constitutes a joint. The fundamental question is:
who decides that if there is no bone, there is no joint?".
If you consider the scenario where these movements are restrictied or
blocked (fascial layers are "glued" together), you would have NO
PRODUCTIVE MOVEMENT AT ALL. Therefore, when you consider this fact, the
whole idea of "assessing range of motion" becomes something quite
daunting...and perhaps even seemingly impossible. We therefore come to a
crossroad of sorts. You can either go one way down "Newtonian
Anatomical Model Boulevard" and be quite happy and comfortable with the
status quo (which is a completely acceptable decision)...or you can go
the other way and travel on "Trans-Anatomical Model Road" and walk a
path of some unknowns and new discoveries.
I will go into more detail on the transanatomical definition of movement
in part 2. For now, i will let you pause at the "crossroad"...digest
the concept...and for all of you who choose Transanatomical Road, see
you around the corner!
Re-defining The Joint: Part 2
This post is intended to supplement my earlier post "Re-defining The
Joint: Part" and to continue the journey down the trans-anatomical road
of discovery (or re-discovery, to be precise). If you haven't read part
1, I would recommend that you refer to that post before moving on with
this one. It will certainly help in the understanding as well as give
valuable insight as to what the main message is.
http://thescienceofphysicalrehabilitation.blogspot.com/2011/09/redefining-joint-part-1.html
To briefly summarize, I have proposed a revised definition of a "joint" as:
Linear and/or angular displacement between separate biological elements .
This definition is more precise and accurate...but it also opens up an
entirely new perspective on what actually constitutes a joint. As
previously mentioned in my blog, connective tissue has 2 appearances
which are seemingly paradoxical: it connects AND disconnects! The
connection element is the obvious one (tendons, ligaments, joint
capsules, etc) whereas the "disconnection" function is somewhat more
counter-intuitive. If you haven't seen Gil Hedley's Integral Anatomy
Series videos, then I highly recommend you make a point to watch them.
Using standard dissection methods, he intelligently demonstrates the
fundamental role of fascia (connective tissue) in SEPARATING body
compartments, muscular groups, and systemic organs so that they do not
mechanically influence each other. In essense, it allows the elements
to "slide" against each other. For example, the liver "articulating"
with the diaphragm, deep muscles of the hand (flexor digitorum
profundus, for example) sliding underneath the more superficial muscles
in the forearm when the fingers are flexed. It doesn't matter whether
we actually agree on the definition of a joint...the reality is that
without this fundamental characteristic, we would not be able to
move...period. We would be as mobile and functional as a Ken (or
Barbie) doll..."watered down" to simple hinge joints mixed with a couple
of ball and socket joints for good measure.
Therefore, we must add to the understanding and definition of what a
joint truly is. This will require some additional qualifying of the
term "joint" when making statements or comments. We can consider our
typical understanding of joints as SKELETAL ARTICULATIONS...because
that's what they are. Therefore, I bring in a new term:
FASCIAL ARTICULATIONS.
Each separate colour represents an individual fascial "compartment" and
therefore can be considered as a separate biological element. This
concept is easily extrapolated into the extremities as well...each
individual muscle, muscle group, etc. is compartmentalized as well. It
is important to remember that, when we are active (moving), these
elements are articulating between each other! Consider a typical tennis
swing...with its significant rotational components within the spine.
There is a considerable angular displacement between the endothoracic
fascia (fascia of the thorax) and the extended fascia of the abdomen
(peritoneum). In addition, the follow-through of the arm at the
completion of the swing is achievable through, not only the skeletal
articulation, but the fascial articulations in the neck (deep, middle,
superficial cervical fascia), the shoulder blade (endothoracic fascia),
as well as the inter-muscular articulations.
Although it may be difficult to integrate "fascial articulations" into
your mental hard drive, it should be easy to understand the obvious role
of fascia in human movement...in both connection and disconnection.
This provides a "bridge" to a more complete understanding of
biomechanics...which is essentially the Trans-anatomical understanding
of movement. Fascia is both friend and foe...when it is healthy and
strong, you are feeling good. When it is damaged or otherwise
unhealthy, it can be your worst enemy. From the most highly conditioned
athlete to the the most severely affected child with Cerebral Palsy
(who are near and dear to my heart), fascia is THE key fundamental
structure in their health, maintenance, and development...period.
I hope the journey to date has been productive...and to those who are
still "on the bus", part 3 will go into specifics about trans-anatomical
movement and fascial articulations by using an age-old standard test
(straight-leg lift) as an example. Hopefully it will engage and
enlighten!
Cheers!
It has been quite awhile since the posting of part 1 and part 2, however
there has been a recent ¨spike¨ in reads for both parts (currently rank
#2 and #9 in the top 10 reads) therefore I think it is an appropriate
time to complete the trilogy. As per part 1 and 2, a radical alteration
of conceptual understanding of joints must take place in order to fully
grasp (and appreciate) the complexity of human movement.
I read a book called The Structure of Scientific Revolutions that
effectively demonstrates a ¨fatal¨ flaw in the evolution of
science...most (if not all) of the new ¨scientific discoveries¨ are
derived from already established paradigms. To be specific, research
into human movement and (bio)mechanics assumes that the traditional
mathematical model (single pivotal movement) is the ¨law¨...therefore
every hypothesis, design, conclusion is derived from this ¨fact¨.
Common sense dictates that, if the overriding paradigm is flawed (or
otherwise over-simplified), then the results / conclusions will also be
so. Although over-simplification has some merit in making treatment
protocols easier to ¨digest¨and conform to current health care delivery
methods, it does not mean than more precise and effective understanding
should be ignored. In fact, deeper understanding does not disregard the
current formula...rather it ABSORBS IT.
In order to fully appreciate part 3, I suggest a read (or re-read) of parts 1 and 2. However, to summarize the main message:
The true definition of a joint must be expanded into a broader understanding that it is the
linear or angular displacement between separate biological elements.
Therefore, simple pivotal movement is only a fraction of the equation.
There are 2 fundamental realities that also exist alongside of the
classical mathematical model:
1) Fascial Articulations: This term defines the very real movement
potential between the individual fascial layers that exist from the
surface of the skin to the periosteum of the bone (and indeed even
deeper into the very cell itself).
The above image illustrates an example of the fascial relationship
between muscle/tendon and adjacent structures. Effective movement
requires, not only proper ¨connective¨ elements, but selective
¨DISCONNECTIVE¨ properties. In other words, the ¨sliding¨ (hence
articulation) of fascial layers between each other is essential. By
definition, this constitutes a joint...without these characteristics,
movement potential is significantly altered leading to movement
dysfunction, irregualr load bearing and stress distribution, and
ultimately deterioration.
2) Movement is more precisely ¨Gear-like¨: This is perhaps confusing
and counter-intuitive, however it is none-the-less a reality. The
pivotal model suggests that movement is a summation of single pivots
moving at the same time. Once again, this is a serious
over-simplification.
True function is achieved through a complex of gear-like movements that
are NOT the sum of individual movements rather a single unified systemic
response.
The image to the left clearly illustrates that single pivotal movement
(hip joint) is effectively a small contributor to the performance of a
straight leg raise (hip flexion). This movement is defined by gear-like
movement between the individual vertebrae of the lumbar spine, the
pelvis, and the hip. In addition, this requires proper fascial
articulation (sliding) of the fascial layers of the posterior leg.
It is precisely these realities that highlight some of the current flaws
in assessment and evaluation protocols. The fundamental question
remmains: how can an effective treatment protocol be formulated when
only one third of the mechanism is observed and identified??! At best,
these types of approaches will be successful only 33% of the time and/or
resolve only 33% of the initial problem. The concept of re-defining
the definition of a joint only serves to enhance understanding and by
default result in more effective interventions.
The switch from pivotal understanding to the ¨gear ratio¨ perspective
will provide some valuable insight and clarity into the amazing movement
potential of the human body. I am reminded of an ¨Old School¨ kids
game called Spirograph. My brother and I played with this quite alot,
but it has its merits from a conceptual perspective.
It involved placing variuos small gear-like tools into the center of a
larger circle with gear teeth. You would then insert pencils of
different colour into the smaller gear and spin it around the outer
circle. The result was a myriad of amazing shapes and images.
Although it is a simplistic analogy, it reveals the sophistication and
complexity that exists in this model...whch is reflected in the everyday
marvel of human movement.
I hope this trilogy has been both informative and insightful. If
nothing else, it serves as an example of the need to reach beyond
current accepted paradigms in an effort to evolve your understanding.
Cheers.
