HARP

HARP You will notice in this e-library that knee angle graphs get disproportionate attention [actually close to all the illustration]. The reason is that just about every detail of walking that can be functionally benefited by surgery, brace, or PT. is represented in knee angle graphs. One ring to rule them all my precious? Not obvious. But, it is all in there.

Even so, there is another reason for this choice. The knee angle graph is wrongly seen as what the knee is doing. ?? THE KNEE? DOING? Knee is doing the doing? Brace yourself, here it comes… The knee is NOT DOING nearly ANYTHING that it “is thought to be doing”. At nearly every segment along that graph we see what momentum, inertia, energy from toes, feet, ankles braces, and hips are doing TO

produce that knee graph which is accommodating all of the anatomic parts as they contribute to energy conservation and momentum. It isn’t a graph of a knee DOING but rather a knee reflecting what is being done through it from all directions near and far. It is a window to the COMBINED FUNCTIONAL complex interactions that ALLOW eccentric muscle control to exist. If eccentric accommodation is cut off, then the basic and primitive concentric (brute force) muscle control takes over – at great expense. [Read the Range vs Resist book – a must – mind altering]. In this one graph to rule them all, we see when and from where things go astray in timing and degree. We see hip and ankle FUNCTIONAL contributions better than in their own dedicated graphs having cute ‘normal’

envelopes that mean NOTHING useful.

Maybe this book is for the geeks but it is not opaque. It is intended to redirect our observations from useless secondary details and refocus on actual functional details that we can and should fix. Let’s look at some graphs just to get our minds in sync. Top M shaped = several subjects center pelvis height through one gait cycle with weird

things being worn to see what happens. There’s a lot of these, but look at the obvious, how little it matters. Those two rising humps (against gravity) persist. Thus we see asymmetrical (R&L) peaks over the Right & Left stance phase. You just know (as we have been hinting) these peaks are when we are at midstance (HARP line = vertical) for each leg. Why asymmetrical? Not doing the same test thing to each side. We can GUESS what a ‘FORCE PLATE’ graph would look like! Landing on the plate will drive it down as Isaac Newton pushes the pelvis up as the pelvis rises over the foot. That interplay of landing and actual weight produces a hump that is about 30% greater downward measured pressure than actual body weight. So the force on the floor is almost the same graph with just a different Y label. Pelvis is height above floor. Force plate [aka ground reaction] is pounds or kilos or any pressure type you like. The plate was designed originally to test thoroughbred horse kick thrust out of the starting gate. Gate analysis!! I like that. The ground reaction M shape has its middle V part less than the weight of the person as weight shift from right to left (or L==>R) is partially flight. Interestingly, if the subject slows down more (dampening the pendulum?) then the ground force gets LARGER as feet are now truly supporting the body above which also sways more-so to the supporting side.

Slow walking people (leaving the movies hemmed in) side sway as they sludge forward. Oops ‘excuse me.. oops again, didn’t mean to bump your popcorn… PELVIC ELEVATION So, now we can MENTALLY envision

M Center of pelvis rises over each leg’s stance peak (& HARP – hip ankle relative position) goes vertical. KNEE ANGLE They call this the “knee angle” graph (They lie !!) PRESSURE The floor force plate feels the downward pressure of what is going on above. As pelvic center is

lifted, Isaac Newton would have this be pressed downward. It doesn’t actually budge, (built for horse’s kicks) but the force resisting (called ‘ground reaction’), pressure rises, nearly matching the top pelvic-elevation graph in appearance. These graphs were taken from a mix of volunteer walks testing weird things in their shoes (lifts & cushions) to get a sense of what they do. Most of the asymmetry (R vs L) is because different things are in or not in opposite shoes. Reason: help us to visualize the scope of what donned devices can do. Does unilateral anything matter? Room for simplification. Right?

The M of the top graph = top center-of-mass in the pelvis [RED] as it goes up & down as walking progresses. The lower M shaped graph is pressure push-back as it reflects the top graph’s travail against gravity. It is for the middle graph to flatten both the top anti-gravity elevation as well as reduce ground reaction push back pressure on the feet. The middle graph is called : “Winning the war of humanity against gravity!” That name hasn’t caught on, so we are stuck with an easy but wrong name - KNEE ANGLE graph, dripping in mud.

The awful academic approach is to get a p value of everything, starting with hair, then eyelids which we suppose have poor p values for associated effects on walking – unless they affect vision? Eventually they get to the p-values of toe nails affecting walking. At a minimum what does that sci-ency method do to help us know a patient’s needs and what choices have the least scope and risk but with a high expectation to satisfy? Not much. Couple that with dated terminology which is, today, really badly misleading. This is why you are here. You might want to read about the footprints in the MUD book first in order to cleanse yourself of the misinformation that current terminology throws at you. If you are comfortable with using that terminology then you really have no idea as to what is really going on. Also some technical documenting of the evolution of our methodology might help fend off some of the mud slung this way. Yes, these books are content redundant. Redundancy & simplicity are at the core of reliability & how we learn languages, in this case a new language of walking.

Muybridge In MUD , we took a broad look at the knee angle graph (minus its erroneous standard deviation envelopes) and eased in a new language of walking. Academics began with footprints in fossilized mud and kind of got stuck in it as well. Strobe flashing light methods eventually followed. Muybridge used a battery of sequentially triggered still photo film cameras. Braune & Fischer

Soon after, Braune & Fischer (using worn strobe lights) whose flashes were collected on large photo-plates seen in two planes (3D).

Actual stick figures (wooden sticks) were built by B&F from their laboriously hand calculated data. They also made advanced maps (including hysteresis curves) and calculations, plus measurements taken from cadavers of centers of mass of each body part.

Later, widely used, others used strobe lighting which made the capture of sequence easier but required other calculation gymnastics to get at measured data.

Well, not exactly rocket science?

But it was! ==>

[Using high speed film] Dr. Sutherland worked with NASA

engineers trying to catch up to Sputnik using the Vanguard (above) film exam device. It sported 2 wheels like an Etch-a-Sketch that mechanically drove, X & Y built-in cross hairs (2 wires). The x & y were pencil logged. Unknowingly the engineers redid what Braun & Fischer had done so long before – math wise - but without the big worn flashing contraption (making clinical use impossible). Dr Sutherland, in California, worked with these measurements from film taken of kids with cerebral palsy (and other stuff ). Now we had ball park measurements of expectation for commonly seen pathology. Now it really begins. Scientific speculation and proposing with numeric tags that can support or refute hypotheses (hypotheses without relevant measurement is called WAG). Sometimes WAG works, but you don’t know for sure. Measurement was possible –

but... again, broad use clinically was not feasible with calculations from tediously etch-a-sketched-like 2 knobs twisting taking weeks to get a data set. It WAS a start. RERC, in Boston,

(MIT/Harvard) rebuilt the Vanguard setting the hand cranked knobs aside, and applying two sound sensors (like long skinny microphones) along the sides of the viewing area.

A mouse-like hand held device let off an ultrasonic squeak and the time lag to each microphone was numerically a screen X & Y which was sent in ‘octal’ form which was easy to feed directly to the computer. In a sense the computer could squeak and know where this mouse looking probe was. It had cross hairs in it. No more pencils. Direct computer data in computational form. Film still needed processing but that could be done quite fast as x ray processors could already easily do it... a sightly modified dedicated film processor had squeaking x, y octal data quick to follow & feeding the computer. An advertising firm that had Channel 5’s 5 image tumble into view helped us to efficiently embed coordinates (each body part having its own spatial existence). The Harvard Math vs the MIT engineering dormitories competed for fresh made apple pies as reward for answers to new obscure computational problems.

Also Dr. Dudley of the Smithsonian Astrophysical Observatory, over the phone, recited the math to track an object that can't be seen if you know other objects that circle it. Hip center is orbited by a knee and pelvic points. And yes, whoever contributed a solution to a lingering problem got a fresh baked apple pie (or two or three…)! Apple computing… ?? The computer, itself had a fatal flaw… in scope of gobbling and computing all that possible data.. 7 bits was not enough. So students with a Berkeley wizard leading converted it to an 8 bit machine with out and in control capability. Speed limitation… film.

Years came and so did video engineers to New Jersey. We built a control stick driven cross-hair seen in the video, live or in freeze frames.

Things are moving fast now ….. Then ooooooo… replace real time mainframe super computer with a … .. a ..

DESKTOP COMPUTER ?? ... and shortly after we got ''home' [desktop] computers designed to work with video ... live video or playback… late 1980s..

which grew & grew making it fast and easy[er] and now part of the routine clinical office exam. This office tool allowed VISUAL testing in routine office visits. With measurement, now or later. Small town local office ==>

In the early 1990’s, with some crazy chips that we built, feeding others that we pulled from desktop computers, we could put 8 channels of real time EMG into video recordings & playback.

It took a lot of engineering to make video EMG so very easy. Tah dahhh?? Everything now so clear? No. What we saw was that when a person’s function was overloaded, their EMG simply went

bonkers. Looked illogical. All channels topped out making no functional sense. The extended exam was born. In our other smaller office, a much simpler mechanism was even more simple. Guitar wireless transmitters (& they come in stereo)

Replace the ¼ guitar stereo plug with two EMG sensors. Plug the receiver left and right audio out plugs into the video recorder’s left and right audio inputs (white & red RCA jacks). That’s it. EMG is now seen as the sound channel in any video editor. With (more toys) the audio of each frame (power) as bars layer onto the video [using the closed captioning circuits that are always there but often go unused].

With this, it was easy to do hands on exams with isolated movements at whatever speeds or scope seemed to tell the most about how this individual was wired. Having many channels of EMG was not as useful as 1 or 2 which allowed live viewing (the handsome fellow with saddle shoes is looking at a video monitor as he fast & slow tests hamstring and rectus femoris reactions as well as seeing if something (maybe other leg etc.) afar also reacts. “Cross reaction” awareness is born and becomes quickly a major player in how the patient is being thwarted by seemingly unrelated things.

Meanwhile we are finding that the knee angle graph is NOT a knee driven graph. It is a composite of everything in the entire walking mechanism. All of it… including the ground! Geek talk: 5 regular Fourier harmonics and a sixth built on the fly from the other 5 can exactly map every single normal or pathological gait recorded (thousands of them, & many diagnoses). This is detailed in the other eBooks on our shelf. BUT

Notice the ellipses that fight to exist even in very odd pathology where some function remains and fights to keep the patient mobile. Ellipses? Circles with two relative centers. OK. Two joints working as one in concert.

RECAP: THOSE MUDDY FOOTPRINTS! All this didn't shed the mud! Approved terminology has remained an anchor. What part of the brain or what harmonic is altered in GMFS III? II? I?? How much dystonic vs spastic or tissue contracture accounts for the joint constraints and asymmetry in the allowed reports? MUD. New mud. But still mud. Basics: A huge question was “What is midstance?” mid by time? By progression, distance? But what was STANCE and what was SWING (again muddy footprints). How do we relate the x,y,z graphs to the actual thing seen?

[ maybe stop here & read the MUD book first]

Y axis is whatever thing is being plotted vs X = time. Mark the time axis with “events” [things seen]. Right heel strike (RHS) etc.. Things seen in the MUD? Mostly. But a grimace could be an event.

Yes. MUDDY FOOTPRINTS to make sense of the graph. Here distance of center of mass vs time... The blue line is a computed least distance pathway vs the actual patient data showing an excess of movement. A similar graph of both using side plane 2D is plenty good. In it we see steps as forward travel is in packets of go & stop. These graphs are called STEPPING as is the gait. Stepping is NOT walking. Stepping is almost certainly concentric. It uses the primitive reptilian ‘ this muscle does that’ type of control. NICE. But it took hours of work to get that detail which was obvious simply looking at the video. There are no numbers to publish by just looking at video. Without taking a good 'p' you can't wear a red ribbon at meetings. Mmmmmm.

Looking at our anatomic wheels in the lab, the spokes (long bones) are whatever they are. That leaves pendulum and velocity properties. We can shorten the overall leg length by hyper-flexing the knee and pointing the foot, as speed runners do, for faster thigh forward flexion. Our main variable is speed. It costs energy equally to go faster or to go slower than pendulum properties. Speed in a chosen direction gives us velocity – a vector with magnitude and a relationship to the ground as well as to the person. Slow has more time to oxygenate so has less fatigue despite equal inefficiency. If we consider the whole leg, then, the big contribution is knee motion (flexion/extension) as pivoted on the hip center. Leg = H-K-A which typically is tracked as an angle.

However, the distance from hip center to ankle (harp) 1. also measures what the knee angle is, flexion/extension 2. measures hip flexion/extension 3. measures the effective spatial orientation to the floor 4. scales everything, scope of action to patient stature 5. measures (in cms, inches, or statures) forward progression 6. measures (in cms, inches, or statures) clearance contributions All this from the same data as knee angle. So we have the hip to ankle line relative to the room... Hip Ankle Relative Positioning . HARP Line vs knee angle (measure same thing?)

We will call the longest string of this HARP the Harp Line .

We can imagine smaller harps with one long string or just smaller strings as representing smaller (younger?) statures. The string is always = 1 stature, but stature has a sub value (cms etc.). In many ways this is akin to radian measure except that the harp line is straight and not curved to the wheel's perimeter. _____ Geek talk: This is at its heart, in part, an orthopedic version of radians. The difference in length between the arc of circumference during knee angle change to the sin(theta) of the hip to ankle line in the ranges we see clinically isn’t worth the purist overhead of radians. Also radians are NOT vectors. HARP is a vector that can be played as a tensor. _____

The HARP line tracks the environmental effects of knee motion as opposed to merely giving two knee angles (or the values between them).

You quickly find yourself looking at an event and asking just what did THAT take to get there? Or, what did that accomplish? Center the video on the key event frame then

the harp function looks forward and backward in time . You can adjust how far and what intervals.

Adding 10 degrees of knee flexion may or may not clear the foot over an obstacle. It depends on the orientation of the entire leg to the ground. In one orientation most of the angular change is in the vertical direction. However, in a different orientation the same knee angular change may contribute close to nothing in the vertical direction. So a seething dog bites your butt or not, depending on the height of that fence, your speed, and whether the knee angle attained was in a best spatial orientation to clear the fence.

Also, we have pointed out that sequential knee angle is not merely about the knee. It is – potentially – a measure of EVERYTHING intended and attained.

Example: Here's a left midstance. What did the knee do on coming into midstance and then on going out? Did it help or hurt?

Or... here is a left midswing. What did the knee do to help (or hurt)? Pick midswing frame and before & after frames to bracket the span concerned.

All the angles are there, but the harp lines tell us what that did.

Hip, knee and ankle trajectories are likewise tracked and we get to

know what knee flexion did to contribute... or... where it failed. Pick two other start stop frames (green & orange)...We get to see what that portion contributed to win or woe.

Select a vector (orange here) and check it vs the environment. Horizontal progression of both ends and vertical orientation and clearance (below) and vertical rise above...

HARP can be followed from neck pubis heel in frontal view to dissect if sway is pathological (against energy) or functional (source of clearance of stiff swing leg.

Harp shoulder, bat grip & bat end? Hand to mouth? Reach to object? It is time for your imagination to take over here.....

OK, Enough rest, back to those graphs. We can trim away one of the M graphs. If you have seen one you have seen both.

Remember as quoted in the constraint vs resistance eBook that even in thin subjects with casts applied from groin to ankle directly on skin we measured 10 to 15 degrees of flexion in stance phase? No. We DID and that got reported in C.O.R.R . It was seen as a warning to knee brace wearers as to the extreme forces in play in stance phase. Think of the heel strike as landing on a trampoline. Tension expects the hit and gives somewhat and then recovers. On landing the knee yields to the downward force

Harp goes vertical here as knee yields some assuaging flexion (governed by the eccentric quadriceps)

Where the stance is ending, the psoas gives a strong but brief swing oomph to the THIGH. The FOOT is still fully planted. If the foot is too

planted, then the heel cannot rise as the thigh is urged to flex. Make no mistake here. The Iliopsoas muscle, which is NOT in the leg but rather in the abdomen, is powering the swing as does a mother pushing a child in a swing. She is not in the swing. Does the thigh then flex and thus bend the knee? Well the foot mechanics decides that. The wobble zone is where ground based forces (ground reaction) is revealed to us. HERE is where more than ½ of all interventions are addressed, of all kinds, shoe types to surgery. Transitions- from stepper to walker - live in this zone as well.

If ground based resistance to heel rise is too high, then swing phase initiation (which is NOT toe off) FAILS. It is an energy hemorrhage.

An unyielding ankle with even 90 degrees is an impediment to heel rise. A rocker shoe sole will back thrust and kill hip flexion. Hinged AFOs that do not ASSERT a small degree of dorsiflexion will not get the needed range from the ankle by magic. Hinges are passive. They do not assure heel rise. Toe walking is far better than planted plantar-flexion. Too soft a heel will collapse backward – not good. The center image is measuring the oxygen consumption and energy use of a volunteer in AFOs which have precise angular adjustment. Hills matter. Toe plates – if stiff – kill hip flexion. Foot roll-over (heel rise) is on the ball of the foot, NOT the toes. Toe plates kill walking. Those with enough intact proprioception quickly learn to rotate their legs inward or outward to bypass toe plate rollover resistance. If you are a strong advocate of AFO toe plates then you are part of the problem. Hinges are not magic. They only allow dorsiflexion if reactive reflexes are asleep. Flexible SOLID AFOs had better dorsiflexion range than did hinged AFOs as the solid AFO blunted the abnormal overflow heel strike reflexes that trigger plantar-flexion. Hinges & toe places can kill hip flexion and defeat the transition into swing.

The psoas initiation of thigh swing (in red) increases knee flexion angle as seen with the supple (if not reflexively dampened). The heel is rising with the ball of the foot as the increasingly bearing pivot line. The ball of the foot leaves the ground (“toe off”) as the green line leaves the blue box. Clearly, nothing much happened new in that blue box. Pendulum inertia does the rest of the green line flexion (pendulum shin under a pendulum thigh). Hamstrings not only extend hips in weight lifting. In walking they dampen the swing of both femur (thigh) and lower leg (knee).

The full pendulum swing is terminated (eccentrically) as hamstrings resist further swing and slow elongation. That energy has to go somewhere. If too much hamstring has been sacrificed to get range of motion (the golden calf) then there is no conduit to have that energy (via hamstring) pull the pelvis over the other leg stance hill. The green dotted line is hamstring deceleration of swing that recaptures the energy that the psoas had earlier put into the swing. Dampening also makes the dual pendulum non-chaotic whereas insufficient dampening allows chaos. Let’s look further at this dampening. If it happens too soon, then dampening swing early has a down pointing energy transfer path of the pelvis toward the floor. That’s not nice. The supine fast /slow knee extension test is looking at this part of the energy transfer mechanism. Fine tuning only by cutting tissue has fine adjustment difficulties. Ethanol selective focal nerve dysmyelination allows this to be fine tuned as contracture is not a thing. It is a mix of things which includes over reaction of reflexes superimposed on intentional movement. Considering each chunk of a continuous process in a nut shell? Is there a nut shell?

There is.

Ask the right questions

if you want useful answers.