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Wearable Device Generates Electricity From Walking Knee Movements

timothy posted about a year ago | from the walk-to-work dept.

Power 99

Zothecula writes "If you've ever worn a knee brace, then you may have noticed what a large change in angle your knee goes through with every step you take, and how quickly it does so. A team of scientists from the U.K.'s Cranfield University, University of Liverpool and University of Salford certainly noticed, and decided that all that movement should be put to use. The result is a wearable piezoelectric device that converts knee movement into electricity, which could in turn be used to power gadgets such as heart rate monitors, pedometers and accelerometers."

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99 comments

Or.. (5, Funny)

busyqth (2566075) | about a year ago | (#40354509)

It could be used to power a truly awesome joy buzzer.

Re:Or.. (1)

CmdrEdem (2229572) | about a year ago | (#40354647)

...they could power my yet-to-be cybernetic implants. Why do I get the feeling that they the question they should be working on is "How can our bodies handle some metal/semiconductor inside without killing itself?"

Re:Or.. (1)

Dunbal (464142) | about a year ago | (#40354731)

my yet-to-be cybernetic implants

Some of us already have cybernetic implants [bostonscientific.com] you insensitive clod!

Re:Or.. (1)

CmdrEdem (2229572) | about 2 years ago | (#40369009)

I`m sorry for my oversight. I hope you are not offended. I was thinking about optional hardware, that does not need autonomy as pacemakers.

Re:Or.. (2)

Shavano (2541114) | about a year ago | (#40354857)

The really cool stuff is going to have to wait for a device that extracts food (sugars or fats) and oxygen from blood and makes usable electricity so it's directly powered by food. And it would have to give priority to your body, although perhaps you could program it to help you control your weight.

Re:Or.. (2)

p0p0 (1841106) | about a year ago | (#40354877)

Already done. Search slashdot for it. It'll be used to power small implants and uses sugar from the blood.

Re:Or.. (5, Insightful)

Jeremi (14640) | about 2 years ago | (#40356775)

Already done. Search slashdot for it. It'll be used to power small implants and uses sugar from the blood.

That's somewhat useful, but what we Americans really need is a device that runs on the energy stored in body fat. People could connect their home gaming rig to their beer belly's AC socket, and emerge at the end of their 8-hour Skyrim session significantly slimmer than when they started.

Re:Or.. (1)

Anonymous Coward | about 2 years ago | (#40359683)

Won't work. A device which uses the fat before it gets stored would be useful (and help people lose weight and stay thin). But if you solve the problem of getting the body to give up its fat (without side effects), you don't need the device to get thin anymore.

Re:Or.. (-1)

Anonymous Coward | about a year ago | (#40355189)

The really cool stuff is going to have to wait for a device that extracts food (sugars or fats) and oxygen from blood and makes usable electricity so it's directly powered by food. And it would have to give priority to your body, although perhaps you could program it to help you control your weight.

Fatties will do ANYTHING to avoid learning some discipline and self-control. If that offended you, go eat a nice big greasy bucket of comfort food while telling us all how it's not your fault.

Re:Or.. (0)

Anonymous Coward | about 2 years ago | (#40367325)

How about if I just eat the chicken and don't give a fuck what you think?

still waiting on the fart combuster. (1, Funny)

Anonymous Coward | about a year ago | (#40354511)

It'll bring about a bean revolution.

Re:still waiting on the fart combuster. (1)

rishistar (662278) | about 2 years ago | (#40357507)

As with many business decisions it'll depend on what the accountants say. And this one may be tough to get past the bean counters.

More power (1)

Anonymous Coward | about a year ago | (#40354573)

Finally, a way to power our future borg implants.

Re:More power (1)

Anonymous Coward | about a year ago | (#40354701)

I want to be powered by plutonium-238. There's no way I'll be able to power my arm mounted laser cannon with this thing.

Re:More power (5, Informative)

Anonymous Coward | about a year ago | (#40354853)

Finally, a way to power our future borg implants.

Except that we already had this technology in 2008 [slashdot.org]. And /. user Promatrax161 called out the idea in 2005 [slashdot.org]. But then he may have adapted it from a shoe based version in 2001 [slashdot.org].

Re:More power (0)

Anonymous Coward | about 2 years ago | (#40357453)

Eventually they will look to The Matrix for ways to generate electricity from human beings.

Re:More power (1)

mcgrew (92797) | about 2 years ago | (#40358975)

My eye implant is powered by the eye's muscles. Most cybernetic implants are non-electronic and likewise are powered by the cyborg's human musclature. There are probably a lot more artificial joints than there are pacemakers and cochlear implants.

Re:More power (3, Interesting)

AngryDeuce (2205124) | about a year ago | (#40354945)

I was thinking more along the lines of the stillsuit [wikia.com], which if I recall correctly was powered in via movement.

Re:More power (3, Informative)

thesuperbigfrog (715362) | about 2 years ago | (#40356977)

You are correct.

"It's basically a micro-sandwich -- a high-efficiency filter and heat-exchange system. The skin-contact layer's porous. Perspiration passes through it, having cooled the body ... near-normal evaporation process. The next two layers . . . include heat exchange filaments and salt precipitators. Salt's reclaimed. Motions of the body, especially breathing and some osmotic action provide the pumping force. Reclaimed water circulates to catchpockets from which you draw it through this tube in the clip at your neck... Urine and feces are processed in the thigh pads. In the open desert, you wear this filter across your face, this tube in the nostrils with these plugs to ensure a tight fit. Breathe in through the mouth filter, out through the nose tube. With a Fremen suit in good working order, you won't lose more than a thimbleful of moisture a day..."

Re:More power (1)

ongelovigehond (2522526) | about 2 years ago | (#40357205)

Sweat only cools when it evaporates, so the suit won't work.

Re:More power (1)

mwvdlee (775178) | about 2 years ago | (#40357421)

Sweat cools when it leaves the body, what happens afterwards doesn't matter.

Re:More power (4, Informative)

ongelovigehond (2522526) | about 2 years ago | (#40357459)

Sweat cools because the phase transition from liquid to vapor absorbs a lot of energy to break the bonds. This energy is provided by the skin, so as a result, the skin gets cooler. Likewise, if you condense the vapor back into a liquid, the exact same amount of energy is released again. If that condensation happens inside the suit, the suit will get warm, defeating the purpose of sweating in the first place. It would be like running in the desert in a raincoat.

Re:More power (0)

Anonymous Coward | about 2 years ago | (#40358077)

" include heat exchange filaments"

I want... (0)

Anonymous Coward | about a year ago | (#40354631)

... the display-suit from "Continuum", if possible including the hot brunette....

Next up ... (0)

Anonymous Coward | about a year ago | (#40354735)

Sex Power!

Re:Next up ... (5, Funny)

PNutts (199112) | about a year ago | (#40355013)

Sex Power!

Well, since this is /. you're talking about something that mounts to one wrist.

What about your feet? (0)

Zakabog (603757) | about a year ago | (#40354759)

Didn't read the article but don't your feet move a further distance at a higher rate of speed than your knees? Or is it the bending movement of the knees that helps generate electricity?

Bending, not lateral movement (2)

QuasiSteve (2042606) | about a year ago | (#40354779)

You could actually read the article.. only takes a few seconds.

Known as the pizzicato knee-joint energy harvester, the device fits onto the outside of the knee. It is circular, and consists of a central hub equipped with four protruding arms, surrounded by an outer ring bearing 72 plectra (a plectrum is a plucking tool, such as a guitar pick). The ring rotates about a quarter of a turn with every bend of the knee, causing the plectra to pluck the arms. This causes the arms to vibrate (not unlike a guitar string), and itâ(TM)s those vibrations that are used to generate electrical energy.

Re:What about your feet? (0)

Anonymous Coward | about a year ago | (#40354791)

it's all about angular velocity, and the rig's size needs to remain minimal

Re:What about your feet? (1)

Shavano (2541114) | about a year ago | (#40354835)

The hip would be much better. It moves through a larger arc while walking and is powered by stronger muscles. But I suspect the energy-harvesting device would be even less comfortable than the knee brace.

So what you're saying is... (0)

Anonymous Coward | about a year ago | (#40354793)

...it's useless for elderly people who are unable to bend their knees.

a sucker born every day. (1)

starworks5 (139327) | about a year ago | (#40354821)

Great instead of using a small battery, so now i can walk around with 2 knee braces, while conveniently trickle charging my ipod.

Re:a sucker born every day. (1)

dogbert_2001 (1309553) | about 2 years ago | (#40358727)

Great instead of using a small battery, so now i can walk around with 2 knee braces, while conveniently trickle charging my ipod.

Soon, they'll create a device that uses urine, so you can tinkle charge your iPod.

Travel! (5, Funny)

rbowen (112459) | about a year ago | (#40354833)

You could even use the power generated by your knees to travel from one place to another!

Re:Travel! (1, Insightful)

Trepidity (597) | about a year ago | (#40354841)

At 2 mW currently, with hopes of raising that to 30 mW, you won't be traveling very fast...

Re:Travel! (4, Funny)

rbowen (112459) | about a year ago | (#40354863)

I was talking about "walking." It was funny. Now it's not any more. Thanks a lot.

Re:Travel! (1)

GoodNewsJimDotCom (2244874) | about a year ago | (#40355165)

Walking isn't funny, unless someone is wearing a knee brace thinking they're harvesting free energy.

Silly walks are also funny. And it is well known that funny things can help us heal, relieve stress and have a longer lifespan.

If I was a leader of a country, I'd have a ministry of silly walks in order to improve health care.

Re:Travel! (0)

Anonymous Coward | about 2 years ago | (#40356351)

I was talking about "walking." It was funny. Now it's not any more. Thanks a lot.

I got it and laughed. So it is still funny. :)

Re:Travel! (3, Interesting)

lobiusmoop (305328) | about a year ago | (#40354917)

Quick comparison with a regular AA battery... they are usually around 2000mAh, 1.5V, or about 3Wh energy. So about 1500 hours of constant knee movement at 2mW. Assuming a generous 4 hours/day of walking, this generates the equivalent of a single AA cell every year. Meh.

Re:Travel! (2)

Anonymous Coward | about 2 years ago | (#40355381)

It's not quite as bad as your math. For one things, AA batteries do not stay at 1.5v, they slowly drop eventually reaching close to 1v when they are dead. A better estimate would be 1.2/1.3v. Also, this is the initial stage, they want to eventually improve it to "provide at least 30 milliwatts" which is quite better then the 2mW figure you are using as it's not like this will be out on the market right away.

But yes, I really don't see the point. Those small lithium cell batteries would provide years of life for this scale of power while being simpler and less annoying then a wearable device that may eventually break. This device provides no extra benefits, is more complex, and in the end, feels pretty gimmicky. I also have trouble seeing it being cheaper though admittedly, those small lithium batteries can be pricey sometimes.

Re:Travel! (1)

reboot246 (623534) | about 2 years ago | (#40356465)

Yeah, you'd be better off with solar cells on your cap, or maybe a wind-powered generator on your head?

Failure (4, Insightful)

hort_wort (1401963) | about a year ago | (#40354889)

I'm willing to go out on a knee here (sorry) and declare this experiment a failure. They have generated 2 milliwatts. Milliwatts -- my spellchecker doesn't even recognize that. For $15, I could get a 1,000 milliwatt solarpanel, tape it to my dang knee, and just sit there. Peizoelectric tech has amazing applications, but this one appears to be a dud.

Re:Failure (2)

Yosho-sama (800703) | about 2 years ago | (#40355323)

"So far, the device has been able to harvest about two milliwatts of power. The researchers, however, believe that it should be a relatively easy to improve its performance to the point that it is able to provide at least 30 milliwatts – this ought to be enough to power a GPS tracking system, and to allow for advanced signal processing electronics, plus more frequent and longer wireless transmissions."

Put that into perspective for whoever is giving this guy mod points. This device is in prototype stage. It has functional applications at a level which the inventors think would be an easily accomplished goal. Solar or batteries can be unavailable/cumbersome. I think the idea of this project is functionality at any time necessary.

Re:Failure (0)

Anonymous Coward | about 2 years ago | (#40355751)

I saw a study where two scientists were able to generate more electricity by attaching electrodes to a tree.

Re:Failure (1)

ongelovigehond (2522526) | about 2 years ago | (#40357373)

The energy doesn't come out of the tree. It comes out of the electrodes. The tree is only there to provide the electrolytes. It's much easier to put those electrolytes in a small container, and put the electrodes in there. That way you can carry it around, instead of having it rooted in the ground.

Re:Failure (1)

bemymonkey (1244086) | about 2 years ago | (#40356627)

Not only that, but their "We could some day generate up to XX milliwats!" figure is 30! 30 mW is the dream number! I can generate more than that scooting my ass on the carpet, and the battery weight required to provide 2-30mW over a period of days is pretty much neglible (a 10 Wh lithium ion battery doesn't weigh a lot and will last 5000 hours (@2mW) or 333.33 hours (30mW). And as a reminder, most smartphone batteries are around 7Wh now and they're tiny and weigh practically nothing, so using that 30mA dream firgure, we could save maybe 30-40g of battery weight by strapping a power generating contraption to our knees... and that probably weighs more than the battery weight saved.

Re:Failure (1)

Tastecicles (1153671) | about 2 years ago | (#40357203)

this got me wondering if this is a poor attempt at distraction, since modern dry batteries use lithium. There is an obscene amount of lithium in Afghanistan. Enough to ensure the financial stability of a medium sized country. Or offset the military expenditure of a large one.

Re:Failure (1)

Anonymous Coward | about 2 years ago | (#40357491)

Keep in mind a parallel of Moore's law -- Koomey's law, which states that the amount of energy taken to perform calculations decreases over time. There are already completely integrated sensors with RF transmit capability that can operate on as little as nanowatts. Of course, this is all a matter of duty cycle but milliwatts of continuous power is plenty of power for a lot of sensing applications.

Here's an example: http://www.eecs.umich.edu/eecs/about/articles/2011/millimeterscalecomputing.html

Re:Failure (1)

necro81 (917438) | about 2 years ago | (#40359009)

Indeed. You could probably harvest as much energy from the temperature difference between the skin and air, or from the quivering of the leg muscles themselves, or even from the static charge you pick up while walking on carpet!

Failed product (0)

Anonymous Coward | about a year ago | (#40355037)

What about millions of fat Americans that don't move very much? This product is literally going nowhere.

The only (obvious) problem: We're not walking. (0)

Anonymous Coward | about a year ago | (#40355115)

It won't do much, because all we do, is hang in front of the computer. ;)

walk or die. (0)

Anonymous Coward | about a year ago | (#40355207)

Didn't Stephen King (as Richard Bachman) already write about this in "The Long Walk"?

I used to charge my phone in the wall socket once, (1)

Anonymous Coward | about a year ago | (#40355233)

just like you. But then i got a wearable piezoelectic device to the knee...

The human dynamo (4, Interesting)

namgge (777284) | about 2 years ago | (#40355435)

Walking is a very low-energy form of movement that relies on some highly evolved bio-mechnics. Attempting to harvest a useful amount of energy introduces dissipation in parts of the 'mechanism' that have not evolved to handle it. The result can be anything from mild discomfort to quite serious injuries. So, such techniques are limited to a few mW, and are in most respects inferior to using a battery.

It's been years since I saw a bicycle with a dynamo on it for similar reasons.

Re:The human dynamo (1)

MarcoAtWork (28889) | about 2 years ago | (#40355467)

that is because people running dynamos (usually randonneurs and/or long-distance cyclists in general) run hub dynamos, which are more efficient and don't chew your tires... as much as I agree that likely anything impinging on the walking mechanics could cause injuries, it really depends by the kind of dynamic resistance this type of device has and in which part of the walking cycle it would provide it.

Re:The human dynamo (0)

Anonymous Coward | about 2 years ago | (#40355761)

You haven't seen a bicycle dynamo because you think people haven't evolved to use the muscles required? Is that what you are saying? Why do I even read the comments anymore, the fuck did you people find a computer and then figure out how to turn it on AND find slashdot?

Re:The human dynamo (1)

ongelovigehond (2522526) | about 2 years ago | (#40357253)

My bike has a dynamo, mounted in the hub. The extra force required to power it is quite small compared to the power already required to propel the bike, and it doesn't change anything the biomechanics of pushing the pedals around.

Re:The human dynamo (1)

namgge (777284) | about 2 years ago | (#40357485)

I was referring to this type of dynamo:
    http://en.wikipedia.org/wiki/Bottle_dynamo [wikipedia.org]
which generates about 5W with an efficiency of about 50% and damages tires in the process.

I couldn't think of a car analogy.

Re:The human dynamo (2)

olau (314197) | about 2 years ago | (#40357757)

Reelights [reelight.com] and Free Lights [freelights.co.uk] are examples of non-friction (in the mechanical sense) dynamos that are becoming quite popular. They don't generate an awful lot of power, but enough for LED safety lights, which is all you need if you live in a city with street lamps.

Re:The human dynamo (1)

dunkelfalke (91624) | about 2 years ago | (#40358069)

You don't see a bicycle with a dynamo for two reasons
1) A large part of bikes sold are MTB-wannabes, they don't have a dynamo in first place since they are meant for sports.
2) Most bikes sold with a dynamo come with a hub dynamo nowadays. The better ones have got an efficiency of 60%-70%, depending on the speed (higher speed means lower efficiency due to eddy current, higher bearing friction and so on). Still, you get a guaranteed 3W at 6V. You can even charge your phone with it, in addition to the lights. Still, a loss of 2-3W while biking is mostly negligible. You get way more loss if you use knobby tyres on a paved road.

Re:The human dynamo (0)

Anonymous Coward | about 2 years ago | (#40359313)

You actually use your hamstrings to "break" at the end of an extension of your legs (to stop your leg from over extending). I remember an article in the science and technology section of the economist about using the brace as a break, to effectively reduce the energy used for walking. I think the application was to recharge military infantry gadgets.

Re:The human dynamo (1)

cellocgw (617879) | about 2 years ago | (#40360447)

Just what I was going to write. The basic rule is TINSSTAFL.

The only time you get energy "for free" is when the energy would otherwise have been dissipated as heat. Oblig car example: heating cabin air w/ engine heat that would otherwise have dumped into the radiator.
I had a bicycle dynamo as a kid. I got a bright light and an exruciatingly tiring ride. It was like riding up a steep hill all the way. Hanging stuff off a knee brace will be no different.

Reminds me of an afrotech mod.. (0)

Anonymous Coward | about 2 years ago | (#40355567)

http://afrotechmods.com/cheap/tape_measure_generator/tape_measure_generator.htm

Perspective (2, Interesting)

subreality (157447) | about 2 years ago | (#40355579)

At 2 mW, you'd have to walk for over 1000 hours to generate the energy held in 1 AA battery. Rather than strapping a wonky device to my knee, I'd rather just carry a spare battery.

Related, my bug out bag doesn't contain a hand-crank radio or flashlight. It has a couple packs of AAs, which are much lighter than the food to replace the energy I'd expend cranking. They'll last me at least a few weeks. If civilization can't reestablish itself in that time, I'm probably fucked, regardless of electricity.

Re:Perspective (1)

bemymonkey (1244086) | about 2 years ago | (#40356635)

"Related, my bug out bag doesn't contain a hand-crank radio or flashlight. It has a couple packs of AAs, which are much lighter than the food to replace the energy I'd expend cranking. They'll last me at least a few weeks. If civilization can't reestablish itself in that time, I'm probably fucked, regardless of electricity."

Have you considered a foldable/rollable solar panel? I've seen 10W (with bright sunlight) panels from $150, which is pretty awesome IMO :)

I want one for my Thinkpad :D

Re:Perspective (1)

subreality (157447) | about 2 years ago | (#40356799)

I have a 5W panel so I can run the radios at home, but I'd never bother carrying it. It's a lot bigger and heavier than the batteries, and spare batteries are relatively trouble free. :)

Re:Perspective (1)

bemymonkey (1244086) | about 2 years ago | (#40356855)

How heavy is it exactly?

Re:Perspective (1)

subreality (157447) | about 2 years ago | (#40356945)

Perhaps a pound. It's a 1 square foot glass panel, not a roll-up. http://amzn.com/B0006JO0TC [amzn.com] Not that heavy, but neither are batteries.

Re:Perspective (2)

bemymonkey (1244086) | about 2 years ago | (#40356975)

Ah ok, I wouldn't like to carry that around either... I'm considering a fold-up 10W panel right now, which should weigh in at a similar weight, but I'm assuming I'll get 5W out of it at best... I suppose you use yours solely for charging a battery, which then powers the radios?

I'm hoping to somehow transform up to 19V and then charge my Thinkpads (which idle just under 5W) with the 10W panel... might actually be enough to charge on particularly bright days, and enough to maintain charge level on not so sunny days.

Re:Perspective (2)

subreality (157447) | about 2 years ago | (#40357131)

Yes, I just charge a small 12v gel cell and then use DC-DC converters to get whatever voltage I need.

I'm not sure if the Thinkpads will charge from a 10W panel. The power port doesn't connect directly to the battery. There's a charging circuit which regulates current to the lesser of what the battery or power supply can handle. So if you connect a 65W power supply, the charging circuit pulls until it sees the voltage start dropping (which happens sooner than a 90W power supply), then just holds that charge rate. The trouble is the charging circuit may decide something is wrong when the voltage starts dropping when it's only pulling 10W.

Fortunately, it's easy to try out! What you need is a "dc-dc boost converter", aka a "step up converter". Like this: boost converter [suntekstore.com]. Warning, Chinese seller; it'll take a couple weeks to arrive, but I've bought buck converters (convert DC down instead of up) from them a couple times and never had a problem. Take one of those and try converting up from a 12V wall wart and see if it works before you get the panels.

One potential problem: the voltage out of the solar panels will vary with load. Mine goes up to about 20V with no load. The boost converter will not convert down. There are two ways to address it: either add a small gel cell battery to hold the voltage near 12V, or use a buck-boost converter [suntekstore.com]. That's just what it sounds like: boost the voltage up to say 35V, then convert back down to 19V. Of course you take a double hit on conversion efficiency doing this. It's likely not a real problem though; the laptop probably won't care, and as soon as it starts pulling power it'll go right back into the range the boost converter can handle.

Re:Perspective (1)

bemymonkey (1244086) | about 2 years ago | (#40357193)

Those are some very interesting points, thanks. I was actually thinking more along the lines of the Thinkpad car charger, which takes a 12V input that should be more in line with most solar panels. I'm also hoping it'll be more tolerant of voltage drops and overvoltage :)

That buck boost converter looks interesting though - I'll keep it in mind :)

Re:Perspective (1)

subreality (157447) | about 2 years ago | (#40367213)

Car chargers are usually just boost converters. With the higher rating it'll push more current when connected to a battery, but it will probably perform about the same given a 10W source.

What about alternative uses? (0)

Anonymous Coward | about 2 years ago | (#40355591)

So, would this still work while having sex? If so, can it generate enough power to spin a small off-balanced electric motor? ;-)

I used to generate electricity like you ... (4, Funny)

dbIII (701233) | about 2 years ago | (#40355831)

I used to generate electricity like you, but then I took an arrow to the knee.

Re:I used to generate electricity like you ... (0)

Anonymous Coward | about 2 years ago | (#40356723)

shocking!

A similar method to harness body heat? (1)

Ka D'Argo (857749) | about 2 years ago | (#40356387)

I've done some real basic searching online never turned up much (I didn't dig too deep) but is there a method to say hook some kind of heat absorbing sensors to the human body, store that heat and charge a battery up? I ask cause, time to time when I get hot and sweaty which is fairly easy for an overweight dude, the cheeks on my face stays incredibly warm for a long time. I also can get the "alcohol flush" from the tiniest amounts of alcohol as well where the face stays very warm and kind of reddish since the blood is closer to the surface. I'm not saying I could power anything of huge significance but I'm curious whenever I get these hot streaks for whatever reason just what body thermal energy I could get from my face in terms of battery supply.

Re:A similar method to harness body heat? (1)

Tastecicles (1153671) | about 2 years ago | (#40357225)

a thermocouple would work, I don't know how many you'd need to say, power an mp3 player though...

Re:A similar method to harness body heat? (1)

ongelovigehond (2522526) | about 2 years ago | (#40357291)

It would theoretically be possible, but it would make you even less comfortable. Also, it's only possible to extract energy out of a temperature difference, so it would only work when your skin is hot, and the surrounding air is cool. In hot weather, the device would be ineffective.

Re:A similar method to harness body heat? (2, Informative)

Anonymous Coward | about 2 years ago | (#40357391)

There's wristwatches that do that -- look up seiko thermic.

Knee surgery anyone? (0)

Anonymous Coward | about 2 years ago | (#40357993)

After you prematurely wear out your knees with this thing, you can rest sured that they can be temporarily restored by a knee surgeon.

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