Editing Prosthesis (section)

====Knee joint====
{{Main article|Knee replacement}}
In case of a trans-femoral (above knee) amputation, there also is a need for a complex connector providing articulation, allowing flexion during swing-phase but not during stance. As its purpose is to replace the knee, the prosthetic knee joint is the most critical component of the prosthesis for trans-femoral amputees. The function of the good prosthetic knee joint is to mimic the function of the normal knee, such as providing structural support and stability during stance phase but able to flex in a controllable manner during swing phase. Hence it allows users to have a smooth and energy efficient gait and minimize the impact of amputation.<ref>{{Cite journal|last1=Andrysek|first1=Jan|last2=Naumann|first2=Stephen|last3=Cleghorn|first3=William L.|date=December 2004|title=Design characteristics of pediatric prosthetic knees|url=https://pubmed.ncbi.nlm.nih.gov/15614992/|journal=IEEE Transactions on Neural Systems and Rehabilitation Engineering |volume=12|issue=4|pages=369–378|doi=10.1109/TNSRE.2004.838444|issn=1534-4320|pmid=15614992|s2cid=1860735}}</ref> The prosthetic knee is connected to the prosthetic foot by the shank, which is usually made of an aluminum or graphite tube.

One of the most important aspect of a prosthetic knee joint would be its stance-phase control mechanism. The function of stance-phase control is to prevent the leg from buckling when the limb is loaded during weight acceptance. This ensures the stability of the knee in order to support the single limb support task of stance phase and provides a smooth transition to the swing phase. Stance phase control can be achieved in several ways including the mechanical locks,<ref>{{Cite thesis|title=Evaluation and Design of a Globally Applicable Rear-locking Prosthetic Knee Mechanism|url=https://tspace.library.utoronto.ca/handle/1807/33575|date=2012-11-27|degree=Thesis|language=en-ca|first=Dominik|last=Wyss}}</ref> relative alignment of prosthetic components,<ref name=":5">R. Stewart and A. Staros, "Selection and application of knee mechanisms," Bulletin of Prosthetics Research, vol. 18, pp. 90-158, 1972.</ref> weight activated friction control,<ref name=":5" /> and polycentric mechanisms.<ref>M. Greene, "Four bar linkage knee analysis," Prosthetics and Orthotics International, vol. 37, pp. 15-24, 1983.</ref>

=====Microprocessor control=====
To mimic the knee's functionality during gait, microprocessor-controlled knee joints have been developed that control the flexion of the knee. Some examples are [[Otto Bock]]'s C-leg, introduced in 1997, [[Ossur]]'s Rheo Knee, released in 2005, the Power Knee by Ossur, introduced in 2006, the Plié Knee from Freedom Innovations and DAW Industries' Self Learning Knee (SLK).<ref>[http://www.daw-usa.com/Pages/SLK3.html "The SLK, The Self-Learning Knee"] {{Webarchive|url=https://web.archive.org/web/20120425081600/http://www.daw-usa.com/Pages/SLK3.html |date=2012-04-25 }}, DAW Industries. Retrieved 16 March 2008.</ref>

The idea was originally developed by Kelly James, a Canadian engineer, at the [[University of Alberta]].<ref>{{Cite news|url= https://www.nytimes.com/2005/06/20/health/menshealth/20marrbox.html |title = Titanium and Sensors Replace Ahab's Peg Leg |access-date=2008-10-30 |work= The New York Times |date= 2005-06-20 | first=Michel | last=Marriott}}</ref>

A microprocessor is used to interpret and analyze signals from knee-angle sensors and moment sensors. The microprocessor receives signals from its sensors to determine the type of motion being employed by the amputee. Most microprocessor controlled knee-joints are powered by a battery housed inside the prosthesis.

The sensory signals computed by the microprocessor are used to control the resistance generated by [[hydraulic cylinders]] in the knee-joint. Small valves control the amount of [[hydraulic fluid]] that can pass into and out of the cylinder, thus regulating the extension and compression of a piston connected to the upper section of the knee.<ref name=PikeAlvin>Pike, Alvin (May/June 1999). "The New High Tech Prostheses". InMotion Magazine 9 (3)</ref>

The main advantage of a microprocessor-controlled prosthesis is a closer approximation to an amputee's natural gait. Some allow amputees to walk near walking speed or run. Variations in speed are also possible and are taken into account by sensors and communicated to the microprocessor, which adjusts to these changes accordingly. It also enables the amputees to walk downstairs with a step-over-step approach, rather than the one step at a time approach used with mechanical knees.<ref name=MartinCraigW>Martin, Craig W. (November 2003) [http://www.ibrarian.net/navon/paper/Evidence_Based_Practice_Group__EBPG_.pdf?paperid=2575568 "Otto Bock C-leg: A review of its effectiveness"] {{Webarchive|url=https://web.archive.org/web/20161228231356/http://www.ibrarian.net/navon/paper/Evidence_Based_Practice_Group__EBPG_.pdf?paperid=2575568 |date=2016-12-28 }}. WCB Evidence Based Group</ref> There is some research suggesting that people with microprocessor-controlled prostheses report greater satisfaction and improvement in functionality, residual limb health, and safety.<ref name="Kannenberg 2014 1469–1496">{{cite journal |last1=Kannenberg |first1=Andreas |last2=Zacharias |first2=Britta |last3=Pröbsting |first3=Eva |title=Benefits of microprocessor-controlled prosthetic knees to limited community ambulators: Systematic review |journal=Journal of Rehabilitation Research and Development |date=2014 |volume=51 |issue=10 |pages=1469–1496 |doi=10.1682/JRRD.2014.05.0118 |pmid=25856664 |s2cid=5942534 }}</ref> People may be able to perform everyday activities at greater speeds, even while multitasking, and reduce their risk of falls.<ref name="Kannenberg 2014 1469–1496"/>

However, some have some significant drawbacks that impair its use. They can be susceptible to water damage and thus great care must be taken to ensure that the prosthesis remains dry.<ref>{{cite journal |last1=Highsmith |first1=M. Jason |last2=Kahle |first2=Jason T. |last3=Bongiorni |first3=Dennis R. |last4=Sutton |first4=Bryce S. |last5=Groer |first5=Shirley |last6=Kaufman |first6=Kenton R. |title=Safety, Energy Efficiency, and Cost Efficacy of the C-Leg for Transfemoral Amputees: A Review of the Literature |journal=Prosthetics and Orthotics International |date=December 2010 |volume=34 |issue=4 |pages=362–377 |doi=10.3109/03093646.2010.520054 |pmid=20969495 |s2cid=23608311 }}</ref>