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Orthopaedic, Trauma & Prosthetics
Wonderful 3FH-7ARH

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Wonderful Orthopaedic, Trauma & Prosthetics

Wonderful 3FH-7ARH

Product Code: OTAP-PLAC-2916

The pivot point moves as the knee bends, with hydraulic damping throughout.

A single-hinge knee turns about one fixed point. A multi-bar linkage does not: its effective centre of rotation shifts as the joint moves, and that shifting geometry is what governs stability under load and clearance during swing. This joint is listed on Medigear.uk for UK business buyers.

Sections

Prosthetic Feet & Knees

Categories

Orthopaedic, Trauma & Prosthetics

Condition

New

Origin

China

Seller Type

Certified Professional Seller

CE & ISO Certified

Global Shipping

Supplier: Medigear

The knee has to do two things that a simple hinge does badly at the same time. Under load it must resist collapse, and during swing it must shorten enough for the foot to clear the ground.

A polycentric linkage addresses both through geometry. Rather than a single pin, the joint is built from linked bars whose relative motion places the effective centre of rotation somewhere other than at any physical pivot. In extension that centre sits behind and above the anatomical knee position, so body weight passing down the limb tends to hold the joint extended rather than fold it, and stability is a property of the linkage itself. As the knee flexes, the centre moves forward and down, and the geometry shortens the shank relative to a single-axis joint at the same flexion angle, which is what produces toe clearance through mid-swing.

This joint uses a seven-axis linkage as described by the manufacturer, with a hydraulic damping cylinder working alongside it. Where the linkage sets the geometry, the hydraulic element governs speed: fluid forced through a restriction resists motion in proportion to how fast the joint is moving, so a fast flexion meets more damping than a slow one, and the knee's behaviour follows walking speed instead of being fixed at one cadence.

Flexion reaches 165 degrees, which covers kneeling and deep sitting alongside the range required for walking, and the linkage folds compactly at full flexion.

Construction is titanium alloy with magnesium-aluminium alloy. The housing is stated by the manufacturer as resistant to seawater, fresh water and chlorinated water, which bears on whether a user needs a separate limb for wet environments, though suitability for any given activity is a clinical judgement taken alongside the manufacturer's stated conditions of use.

Polycentric knees carry practical fitting considerations that a prosthetist will already be weighing: build height and the linkage envelope both matter, and they are particularly relevant in knee disarticulation and long residual limb fittings where space below the socket is limited. Those figures are established for this component before it is specified into a build.

This is a component rather than a finished prosthesis. It is fitted, aligned and adjusted by a qualified prosthetist as part of a limb assembled around the individual, and selection, alignment, damping settings and suitability for a given patient are clinical decisions taken by that professional. The manufacturer, year, load rating, mobility grade, indicated amputation levels, build heights and connection types are provided by the seller at quotation, with UKCA or CE marking documentation, the declaration of conformity, instructions for use and warranty terms issued by the manufacturer or held by the seller.

Transfemoral prosthetic fitting is the primary application, with the joint supplied as a component for a prosthetist to align and adjust within a complete limb.

Knee disarticulation and long residual limb fittings are where polycentric geometry is most often specified, since the linkage folds compactly and build height below the socket is limited.

Users needing toe clearance through swing are served by linkage geometry that shortens the shank as the knee flexes.

Stance stability is supported by an effective centre of rotation that sits behind and above the anatomical knee position in extension.

Users walking at varying speeds are served by hydraulic damping proportional to angular velocity, so the joint responds differently to a fast step and a slow one.

Kneeling and deep sitting are accommodated by flexion to 165 degrees.

Water-based activity is supported by a housing the manufacturer states as resistant to seawater, fresh water and chlorinated water, subject to the stated conditions of use.

Stability Built Into the Geometry

With the effective centre of rotation behind and above the anatomical knee position in extension, load passing down the limb tends to hold the joint extended.

Clearance Produced by the Linkage

As the knee flexes, the geometry shortens the shank, which is what gives the foot room through mid-swing.

A Centre of Rotation That Moves

The effective pivot shifts through flexion, so stability in extension and clearance in swing are served by the same mechanism.

Damping That Follows Walking Speed

The hydraulic cylinder resists motion in proportion to angular velocity, so behaviour tracks pace instead of being fixed at one cadence.

Flexion to 165 Degrees

Covering kneeling and deep sitting positions alongside the range walking requires, with the linkage folding compactly.

Alloy Construction

Titanium alloy with magnesium-aluminium alloy through the linkage and housing.

Rated for Immersion

The manufacturer states resistance to seawater, fresh water and chlorinated water.

Suited to Limited Build Height

Polycentric geometry is commonly specified in knee disarticulation and long residual limb fittings where space below the socket is short.

Damping Set to the Individual

Hydraulic characteristics are adjusted by the prosthetist to the user's weight, activity and gait.

Figures Confirmed Before Fitting

Load rating, build heights and connection types are established in writing rather than taken from a listing.

Supply and Documentation Arranged

Medigear.uk can arrange supply, documentation and the provision of spares and consumables.

Polycentric Multi-Bar Knee Joint

A linked-bar mechanism placing the effective centre of rotation away from any physical pivot.

Seven-Axis Linkage

The mechanism as described by the manufacturer for this reference.

Hydraulic Damping Cylinder

Resistance proportional to angular velocity through the gait cycle.

Adjustable Damping

Set by the prosthetist to the individual user.

Maximum Knee Flexion: 165 Degrees

Covering kneeling and deep sitting positions.

Load Rating: 125 kg

As published for this reference, and to be confirmed against the instructions for use.

Materials

Titanium alloy with magnesium-aluminium alloy.

Water Resistance

Stated by the manufacturer as resistant to seawater, fresh water and chlorinated water.

Weight and Build Heights

Not published for this reference in the available material, and confirmed at quotation.

Proximal and Distal Connections

Connection types confirmed at quotation for compatibility with the intended build.

Mobility Grade and Indications

Confirmed at quotation against the manufacturer's instructions for use.

Item Reference

3FH-7ARH, to be confirmed against the manufacturer's marking.

Manufacturer and Year

Confirmed at quotation.

UKCA or CE Marking and Declaration of Conformity

Issued by the manufacturer and requested from the seller at quotation.

Instructions for Use

Provided by the seller at quotation, and required before fitting.

Warranty Terms

Set by the seller at quotation.

The 3FH-7ARH is a polycentric hydraulic prosthetic knee joint, and the case for it rests on what a linkage can do that a single hinge cannot. A knee must resist collapse under load and shorten enough during swing for the foot to clear the ground, and a multi-bar mechanism serves both through geometry: in extension the effective centre of rotation sits behind and above the anatomical knee position, so weight passing down the limb tends to hold the joint extended, while through flexion that centre moves forward and down and the shank shortens, producing clearance in mid-swing. A hydraulic damping cylinder works alongside the linkage, resisting motion in proportion to angular velocity so the joint's behaviour follows walking speed rather than sitting at one cadence. Flexion reaches 165 degrees, construction is titanium alloy with magnesium-aluminium alloy, and the manufacturer states resistance to seawater, fresh water and chlorinated water. Selection, alignment, damping settings and suitability remain clinical decisions for the prescribing prosthetist. The manufacturer, load rating, build heights, mobility grade, indicated amputation levels and connection types are provided by the seller at quotation, alongside UKCA or CE documentation and instructions for use. Medigear.uk lists the joint for UK business buyers and can arrange supply, documentation and the provision of spares and consumables. Enquire for a written quotation.

FAQ

Frequently Asked Questions

Everything buyers need to know about sourcing medical equipment through MediGear.

It is a polycentric prosthetic knee joint with a multi-bar linkage and a hydraulic damping cylinder, supplied as a component for a prosthetist to fit within an above-knee prosthesis.

The joint turns about an effective centre of rotation that moves as the knee flexes, rather than about one fixed pin.

In extension the effective centre sits behind and above the anatomical knee position, so load passing down the limb tends to hold the joint extended.

As the knee flexes, the linkage geometry shortens the shank relative to a single-axis joint at the same angle, which gives clearance through mid-swing.

Resistance proportional to speed, so a fast flexion meets more damping than a slow one and the joint's behaviour follows walking pace.

165 degrees, covering kneeling and deep sitting as well as the range walking requires.

125 kg as published for this reference, to be confirmed against the manufacturer's instructions for use before fitting.

Titanium alloy with magnesium-aluminium alloy.

The manufacturer states resistance to seawater, fresh water and chlorinated water, subject to the conditions of use in the instructions.

Weight and build heights are not published for this reference in the available material and are confirmed at quotation, which matters most in knee disarticulation and long residual limb fittings.

A qualified prosthetist, who sets alignment and damping to the individual as part of a complete prosthesis.