USRE44476E1 - Constrained prosthetic knee with rotating bearing - Google Patents

Abstract

A constrained prosthetic knee having a modular hinge post and a rotating bearing. A cannulated hinge post is rotatably connected to the femoral component of the knee prosthesis so that a hinge post extension may be anteriorly positioned through the hinge post and into the tibial component of the knee prosthesis, after positioning of the femoral component in the femur and the tibial component in the tibia. The hinge post is preassembled to the femoral component so that such assembly is not required during the implantation procedure. A meniscal component forming the rotating bearing of the knee prosthesis is packaged together with the hinge post extension so that the appropriate hinge post extension is readily available.

Description

CROSS-REFERENCED TO RELATED APPLICATIONS

This is a continuation of application Ser. No. 09/771,061, filed Jan. 29, 2001, now U.S. Pat. No. 6,485,519.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to prosthetic joints, and, more particularly to a constrained prosthetic knee having a modular hinge post and a rotating bearing.

2. Description of the Related Art

Generally, the knee is formed by the pair of condyles at the distal portion of the femur, the lower surfaces of which bear upon the correspondingly shaped proximal surface plateau of the tibia. The femur and tibia are connected by means of ligaments such as, the posterior cruciate ligament, the lateral collateral ligament, the medial collateral ligament, and the anterior cruciate ligament. These ligaments provide stability to the joint formed by the femur and tibia (i.e., the knee).

In a broad sense, prosthetic knee joints can be considered either constrained or unconstrained. For the purposes of this discussion, constrained prosthetic knees include femoral and tibial prosthetic components which are mechanically linked or constrained to each other by a hinge structure. An unconstrained prosthetic knee includes femoral and tibial components which are not mechanically linked. An unconstrained knee utilizes the patient's existing ligaments to provide joint stability. With this in mind, constrained prosthetic knees have particular applicability to cases in which a patient has experienced ligament loss and/or the existing ligaments do not provide adequate support and stability to the knee.

Tibial components of a prosthetic knee can be formed as a one-piece configuration in which the tibial tray forms the meniscal component of the prosthetic knee. Various other prosthetic knees utilize a modular meniscal component separate from the tibial component. Devices utilizing modular meniscal components include those in which the meniscal component (i.e., tibial bearing surface) is fixed to the tibial tray portion of the tibial component and is incapable of movement relative thereto. Alternative devices utilize a modular meniscal component capable of movement relative to the tibial tray. Devices in which relative rotational movement occurs between the meniscal component and the tibial component are typically referred to as rotating bearing knees. Rotating bearing knees thus allow movement between the bearing (i.e., meniscal component) and the tibial tray, as well as movement between the femoral component and the tibial bearing.

Constrained knees of the prior art include constructions in which a hinge post extension is first positioned within a tibial component (with an end protruding therefrom) and is thereafter connected to the femoral component by positioning the hinge post (rotatably attached to the femoral component) over the top of the protruding end of the hinge post extension and thereafter connecting the hinge post extension to the hinge post, e.g., by threading the hinge post extension into the hinge post. After making this connection, the meniscal component is thereafter slid into position between the femoral component and the tibial component. Meniscal components utilized with these prior art prosthetic knees were fixed to the tibial component.

The present invention is directed to a constrained knee prosthesis with a rotating bearing. The knee prosthesis of the present invention is structured to facilitate implantation thereof. The present invention is further directed to a prosthetic knee implant set having a plurality of matched modular hinge post and meniscal component pairs.

SUMMARY OF THE INVENTION

The present invention provides an improved constrained knee prosthesis having a cannulated hinge post facilitating implantation of the knee prosthesis in a relatively minimally invasive procedure. The prosthetic knee implant set of the current invention includes a separately packaged femoral component, a separately packaged tibial component, and a third package containing a hinge post extension and the meniscal component. Packaging the individual components of a knee prosthesis in this fashion insures that the appropriate hinge post extension is readily available. A bearing box is interposed between the hinge post and the femoral component. The bearing box includes a hyperextension stop which cooperates with the hinge post to prevent hyperextension of the knee prosthesis. Various structures are utilized to prevent the disengagement of the constrained knee prosthesis of the present invention.

A prosthetic knee constructed in accordance with the present invention includes a femoral component having a pair of condyler surfaces and a hinge post rotatably connected to the femoral component between the condyler surfaces. The hinge post is cannulated and accommodates insertion of a hinge post extension shaft therein. The hinge post and hinge post extension include cooperating locking tapers for locking the hinge post extension to the hinge post. Additionally, the hinge post includes internal threads so that a set screw may be threaded therein to further hold the hinge post extension in place. The tibial component includes a hinge post extension aperture into which the hinge post is seated. The meniscal component similarly includes an aperture to accommodate the hinge post and hinge post extension. The meniscal component of the current invention is free to rotate about the hinge post during flexion and extension of the knee joint.

Having a cannulated hinge post through which a hinge post extension may be anteriorly positioned and secured advantageously allows for a relatively minimally invasive knee replacement procedure.

The present invention advantageously provides a constrained prosthetic knee having a rotating bearing flush with the condyler surfaces of the femoral component.

Another advantage of the present invention is the packaging of the prosthesis components and specifically the packaging of the appropriate hinge post extension together with a meniscal component.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention, and the manner of attaining of them, will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a perspective view of an assembled knee prosthesis in accordance with the present invention;

FIG. 2 is an exploded view thereof;

FIG. 3 is a cutaway, exploded view illustrating assembly of the knee prosthesis of the current invention including the anterior positioning of the hinge post extension into the hinge post;

FIG. 4 is a cutaway view illustrating securement of the hinge plug (i.e., set screw) in the hinge post to facilitate locking of the hinge post extension therein;

FIG. 5 is a cutaway, exploded view illustrating removal of the hinge post extension;

FIG. 6 is a bottom elevational view of the meniscal component of the present invention;

FIG. 7 is a front elevational view thereof;

FIG. 8 is a top elevational view of a tibial component in accordance with the present invention;

FIG. 9 is a sectional view of a hinge plug in accordance with the present invention;

FIG. 10 is a side elevational view of a bearing box in accordance with the present invention;

FIG. 11 is a front elevational view thereof;

FIG. 12 is a top elevational view thereof;

FIG. 13 is a cutaway, exploded view of an alternative embodiment of the knee prosthesis of the present invention;

FIG. 14 is a cutaway view of an assembled knee prosthesis in accordance with the embodiment illustrated inFIG. 13;

FIG. 15 is a fragmentary, cutaway view of an alternative embodiment of the hinge post extension and tibial bushing of the present invention;

FIG. 16 is a fragmentary, cutaway view of the embodiment ofFIG. 15 illustrating insertion of the hinge post extension into the tibial bushing;

FIG. 17 is a fragmentary, cutaway view of the embodiment ofFIG. 15 illustrating the hinge post extension fully inserted into the tibial bushing;

FIG. 18 is an exploded view of an alternative embodiment of the knee prosthesis of the current invention;

FIG. 19 is a sectional view of a meniscal component in accordance with an alternative embodiment of the present invention; and

FIG. 20 is an elevational view of a hinge post in accordance with an alternative embodiment of the present invention.

Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of the invention, the drawings are not necessarily to scale and certain features may be exaggerated to better illustrate and explain the invention. The exemplifications set out herein illustrate embodiments of the invention, in alternative forms, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION

Referring now to the drawings and particularly toFIG. 2,knee prosthesis20 in accordance with the present invention is illustrated.Knee prosthesis20 generally includesfemoral component22,tibial component24, andmeniscal component26. Hinge post40 is rotatably connected tofemoral component22 and includes elongate hinge post extension aperture112 (FIGS. 3-6,13, and14).Elongate aperture112 accommodates placement ofhinge post extension42 therein.Hinge post extension42 thereafter traverses hingepost aperture114 inmeniscal component26 and hinge post extension aperture110 (FIGS. 3-6,13 and14) intibial component24. Elongate hingepost extension aperture112 of hinge post40 advantageously allows for anterior placement ofhinge post extension42 during surgical implantation ofknee prosthesis20 of the present invention.

As illustrated inFIG. 2, hingepost extension42 includes lockingtaper46 andcylindrical extension48. Hingepost extension aperture112 includes a mating locking taper to cooperate with lockingtaper46 and lock hingepost extension42 to hingepost40. After positioning ofhinge post extension42 throughapertures112,114, and110, hinge plug38 may be threaded intohinge plug threads54 inelongate aperture112 of hinge post40 (FIG. 4).Hinge plug38 abuts the end ofhinge post extension42 and thereby facilitates locking ofmorse taper46 inelongate aperture112. In one exemplary embodiment, lockingtaper46 comprises a two degree locking taper. Whenprosthetic knee20 is assembled as illustrated inFIG. 1, condyler bearing surfaces28,30 abut bearing surfaces86,88 (see, e.g.,FIG. 2) inmeniscal component26.

Hinge post extension42 is typically formed as a one-piece construction of an inert metal such as, e.g., a cobalt-chromium alloy.Hinge post extension42 may, however, be constructed of other bio-compatible metals or alloys, such as titanium. Throughout this document reference will be made to various components formed of a cobalt-chromium alloy. Any such component may also be constructed of other bio-compatible metals or alloys such as titanium, as is well-known. As illustrated inFIG. 4, hingeplug wrench102 is utilized to thread hinge plug38 intohinge plug threads54 ofhinge post40. As illustrated inFIG. 9, hingeplug38 includes lockingmaterial100 to provide a locking connection betweenhinge plug38 and hingeplug threads54 inhinge post40.Hinge plug38 is, in one exemplary embodiment formed of a cobalt-chromium alloy. Lockingmaterial100 comprises any suitable biocompatible polymer such as, e.g., ultra-high molecular weight polyethylene (UHMWPE).

As illustrated, e.g., inFIG. 2,femoral component22 includes condyler bearing surfaces28,30 with bearingbox wall76 positioned therebetween.Femoral component22 further includesexternal side walls82, only one of which can be seen inFIG. 2. Condyler bearing surfaces28,30 are smooth and highly polished, generally spheroidally shaped and extend outwardly fromexternal side walls82, as is well known in the industry.Femoral component22 further includes modularfemoral stem32 for insertion into femur116 (FIGS. 3-5,13, and14), as is known in the art.Femoral component22 further includes internal side walls80, only one of which is illustrated inFIG. 2. Internal side walls80 are substantially perpendicular to bearingbox wall76 and extend outwardly therefrom.Femoral component22 is typically formed as a one-piece construction of an inert metal such as, e.g., a cobalt-chromium alloy.

Bearing box70 is designed for placement between condyler bearing surfaces28,30 offemoral component22 as illustrated, e.g., inFIG. 1.Bearing box70 is further illustrated inFIGS. 10-12 and includes affixingprotrusions72,hinge pin aperture62, hyperextension stop66, andanti-rotation surface78. As illustrated inFIG. 2,femoral component22 includes affixingprotrusion apertures74 sized to receive affixingprotrusions72.FIG. 1 illustrates bearingbox70 operably positioned onfemoral component22, withanti-rotation surface78 flush with bearingbox wall76 offemoral component22, and affixingprotrusions72 received in affixingprotrusion apertures74. The abutting relationship ofanti-rotation surface78 with bearingbox wall76 discourages rotation of bearingbox70 about the longitudinal axis of affixingprotrusions72. When bearingbox70 is positioned onfemoral component22,hinge pin apertures62 of bearingbox70 align with threadedhinge pin aperture56 andhinge pin aperture58 offemoral component22.Bearing box70 can be formed of any suitable plastic, such as, e.g., UHMWPE.

Hinge post40 is rotatably connected tofemoral component22 viahinge pin34. Hinge post40 is placed between opposing walls of bearingbox70 and is positioned so thathinge pin aperture52 is aligned withapertures56,58, and62. The opposing walls of bearingbox70 thus act as a bearing surface betweenhinge post40 and internal side walls80 offemoral component22. Prior to placement of hinge post40 between opposing walls of bearingbox70,hinge pin sleeve36 is operably positioned withinhinge pin aperture52 ofhinge post40. Hinge post40 is formed from a cobalt-chromium alloy, whilehinge pin sleeve36 is formed from a suitable plastic, such as, e.g., UHMWPE.Hinge pin sleeve36 acts as a bearing betweenhinge pin aperture52 ofhinge post40 andhinge pin34. Accordingly,hinge pin sleeve36 includeshinge pin aperture50 sized to accommodatehinge pin34. After positioning of hinge post40 between the opposing walls of bearingbox70,hinge pin34 is positioned throughapertures56,62,50, and58.Hinge pin threads60 are thereafter threadedly engaged in the threads of threadedhinge pin aperture56 until the head ofhinge pin34 is flush withexternal side wall82.

As illustrated inFIG. 1,hinge pin plug120 is positioned within the hexagonal indentation ofhinge pin34 after installation ofhinge pin34 as described above. When positioned within the hexagonal indentation ofhinge pin34,hinge pin plug120 is flush with the head ofhinge pin34. In use,hinge pin plug120 substantially prohibits the entry of foreign materials into the hexagonal indentation ofhinge pin34. For example,hinge pin plug120 substantially prohibits bone growth into the hexagonal indentation ofhinge pin34, as well as prohibiting positioning of bone cement therein. The above-described connection of hinge post40 tofemoral component22 is performed prior to implantation offemoral component22.Femoral component22 is packaged and sold with bearingbox70, hingepost40,hinge pin sleeve36,hinge pin34, and hingepin plug120 preassembled as described above, with the assembly preferably occurring in the manufacturing environment.

Pre-assembly of hinge post40 tofemoral component22 eliminates a number of meticulous assembly steps (many of which were performed during implantation) which were required with constrained knees of the prior art. Furthermore, the assembly ofhinge post40 andfemoral component22 as described above facilitates replacement of various portions ofknee prosthesis20. Specifically, the threaded connection ofhinge pin34 tofemoral component22 allows for removal and replacement of various components of knee prosthesis including, e.g., bearingbox70,hinge pin sleeve36, and hingepost40.

In use, femoral bone stock may abutexternal side walls82 offemoral component22 and extend to the underside of condyler bearing surfaces28,30. To removehinge pin34, a hole saw is utilized to remove a relatively small portion of femoral bone stock to provide access to hingepin34. Advantageously,femoral component22 does not require extensive removal of femoral bone stock for implantation thereof (since bone stock can extend to the underside of condylar bearing surfaces28,30), and, furthermore, does not require removal offemoral component22 to effect replacement of, e.g., hingepost40, bearingbox70, or hingepin sleeve36. Upon accessing hinge pin34 (e.g., utilizing a hole saw as described above),hinge pin plug120 is removed, e.g., with a scalpel and forceps to provide access to the hexagonal indentation ofhinge pin34 so that a hexagonal wrench may be inserted therein to unthreadhinge pin34 fromfemoral component22.

Knee prosthesis20 includes a pair of hyperextension stop mechanisms. The first hyperextension stop comprises a portion of condylar bearing surfaces28,30 of increased radius of curvature as compared to the remaining condylar bearing surface. At three degrees of hyperextension this portion of increased radius of curvature will contactmeniscal component26 and act to retard further hyperextension. If hyperextension continues, the area of increased radius of curvature will causefemoral component22 to lift away frommeniscal component26. The second hyperextension stop mechanism functions at four degrees of hyperextension to prohibit further hyperextension ofknee prosthesis20. The second hyperextension stop mechanism compriseshyperextension stop surface66 ofhinge post40 and hyperextension stop68 of bearingbox70.Hyperextension stop surface66 comprises the concave back wall of cannulatedhinge post40 as illustrated, e.g., inFIGS. 2 and 3. Hyperextension stop68 of bearingbox70 comprises a protrusion extending from the back wall of bearingbox70opposite anti-rotation surface78. Hyperextension stop68 includes a convex outer surface as illustrated, e.g., inFIG. 12.Hyperextension stop surface66 ofhinge post40 cooperates with hyperextension stop68 of bearingbox70 to provide a hyperextension stop forknee prosthesis20. Concave hyperextension stopsurface66 becomes flush with the convex outer surface of hyperextension stop68 of bearingbox70 at four degrees of hyperextension to prevent further hyperextension ofknee prosthesis20.

Tibial component24 is depicted inFIGS. 1-5,8,13, and14. As illustrated, e.g., inFIG. 2,tibial component24 includestibial tray98 connected totibial stem92. Stabilizingribs94 stabilizetibial tray98 relative totibial stem92 and impede rotation oftibial component24 in tibia118 (see, e.g.,FIG. 3). In one exemplary embodiment,tibial component24 is formed from a cobalt-chromium alloy.Tibial component24 further includestibial bushing64 positioned within hingepost extension aperture110.Tibial bushing64 is formed of plastic, such as, e.g., UHMWPE and provides a bearing surface betweenhinge post extension42 and hingepost extension aperture110 oftibial component24. As described above,meniscal component26 comprises a rotating bearing, and, thus, hingepost extension42 will rotate relative totibial component24.Tibial bushing64 facilitates this rotation ofhinge post extension42.

Tibial component24 further includesrotation protrusion96. As illustrated, e.g., inFIG. 3,rotation protrusion96 protrudes upwardly fromtibial tray98 oftibial component24 and further extends in a plane substantially parallel totibial tray98.Rotation protrusion96 cooperates withcutout90 ofmeniscal component26 to guide rotation ofmeniscal component26 abouthinge post extension42, as further described hereinbelow.

One embodiment ofmeniscal component26 is illustrated inFIGS. 1-7,13, and14.Meniscal component26 is formed from a suitable plastic such as, e.g., UHMWPE and provides a rotating bearing surface betweenfemoral component22 andtibial component24.Meniscal component26 includes bearing surfaces86,88 which contact condylar bearing surfaces28,30 offemoral component22 during movement ofknee prosthesis20. As described above,meniscal component26 further includeshinge post aperture114 accommodating passage ofhinge post40 and, consequently, hingepost extension42 therethrough.Meniscal component26 is operable to rotate about the longitudinal axis ofhinge post extension42 to form a rotating bearing.

Meniscal components of varying heights may be constructed in accordance with the present invention. In one advantageous aspect of the present invention,meniscal component26 is packaged for sale and use together withhinge post extension42 to facilitate component choice and, in one embodiment, to ensure proper extension ofhinge post extension42 intotibial component24. The extension ofhinge post extension42 intotibial component24 functions to prevent separation ofknee prosthesis20 after implantation thereof. As is known in the art, the femoral component of a knee prosthesis may, in some situations, move relative to and away from the tibial component in a direction parallel to the longitudinal axis of the hinge post extension. With this in mind, hingepost extension42 is made to be of sufficient length to be retained withintibial component24 even in situations in whichfemoral component22 moves as described immediately supra. In one exemplary embodiment, hingepost extension42 extends four centimeters into hingepost extension aperture110 intibial component24.

Meniscal component26 includescutout90 which cooperates withrotation protrusion96 oftibial component24 to guide rotation ofmeniscal component26 and to resist lifting ofmeniscal component26 fromtibial tray98 oftibial component24. As illustrated, e.g., inFIG. 3,cutout90 accommodates the portion (i.e., lip) ofrotation protrusion96 extending in a plane substantially parallel to the plane containingtibial tray98, with a portion (i.e., lip) ofmeniscal component26 being positioned betweenrotation protrusion96 andtibial tray98 in a direction substantially perpendicular to the plane containingtibial tray98. This configuration functions to discourage displacement ofmeniscal component26 away fromtibial tray98 in a direction parallel to the longitudinal axis ofhinge post extension42. Furthermore,rotation protrusion96 acts against the back ofcutout90 to limit rotation ofmeniscal component26 about the longitudinal axis ofhinge post extension42.

As illustrated inFIG. 5,meniscal component26 may be slid out from betweentibial component24 andfemoral component22 when thehinge post extension42 has been removed fromknee prosthesis20. As illustrated, hingepost aperture114 is sized to allow rotation of hinge post40 so thatmeniscal component26 may be slid out from its position betweenfemoral component22 andtibial component24. This configuration allows for replacement of an implantedmeniscal component26 without requiring removal ofhinge post40.FIG. 5 illustrates removal ofhinge post extension42 to accommodate replacement ofmeniscal component26. As illustrated, hingeplug wrench102 engageshinge plug38 for removal thereof. After removal ofhinge plug38,slap hammer104 is threadedly engaged with threadedaperture44 inhinge post extension42.Slap hammer104 may then be utilized to unlock the engagement of lockingtaper46 in elongate hingepost extension aperture112 so thathinge post extension42 may be removed.

FIGS. 13 and 14 illustrate an alternative embodiment of the knee prosthesis of the current invention. This alternative embodiment utilizes hingepost extension42a having lockingtaper46a,cylindrical extension48a, andflange106. In this embodiment, a locking instrument may be utilized to apply force atophinge post extension42a so that lockingtaper46a is seated in elongate hingepost extension aperture112 and locked therein.Flange106 may be utilized to facilitate removal ofhinge post extension42a. As illustrated inFIG. 13, setscrew108 may be utilized as a secondary lock forhinge post extension42a. In all other respects, the knee prosthesis illustrated inFIGS. 13 and 14 is constructed as described above with respect to the first embodiment of the knee prosthesis in accordance with the present invention.

FIGS. 15,16 and17 illustrate an alternative embodiment of the hinge post extension and tibial bushing of the present invention. In this embodiment,tibial component24a includes annular tibialbushing expansion groove122 formed in hingepost extension aperture110.Tibial bushing64a includes retainingflange130 positioned within annular tibialbushing expansion groove122.FIG. 15 illustrates insertion ofcylindrical extension48b of the hinge post extension intotibial bushing64a positioned withintibial component24a. Ascylindrical extension48b proceeds intotibial bushing64a, bevel126 contacts annular lockingprotrusion128 oftibial bushing64a and causes outward movement of retainingflange130 to allowcylindrical extension48b to proceed to its seated position as illustrated inFIG. 17. Annular tibialbushing expansion groove122 is sized to allow radial expansion of retainingflange130 to accommodate placement ofcylindrical extension48b withintibial bushing64a. In the fully seated position (FIG. 17)cylindrical extension48b is locked in place by the engagement ofannular locking protrusion128 inannular locking groove124. Furthermore, retainingflange130 cooperates with annular tibialbushing expansion groove122 to prohibit axial displacement oftibial bushing64a and, consequently,cylindrical extension48b. In this embodiment, the femoral component is retained in abutting relationship to the meniscal component and lift off of the femoral component is substantially prohibited.Tibial bushing64a is, in one exemplary embodiment, formed of UHMWPE

FIGS. 18 and 19 illustrate another alternative embodiment of the knee prosthesis of the current invention. In this embodiment, lockingclip134 is utilized to retain the position ofhinge post40b withinhinge post aperture114 ofmeniscal component26a.Hinge post40b is rotatably attached tofemoral component22 utilizinghinge pin34 as described above. In this embodiment, hingepost40b includes lockingclip grooves132, andmeniscal component26a includes lockingclip apertures136. Upon positioning ofhinge post40b withinhinge post aperture114, lockingclip134 is positioned as illustrated inFIG. 19 with each prong of lockingclip134 being inserted into lockingclip apertures136 ofmeniscal component26a. As illustrated inFIG. 19, lockingclip134 engages lockingclip grooves132 to retainhinge post40b withinhinge post aperture114 ofmeniscal component26a. In this embodiment, lift off offemoral component22 is prohibited by the engagement ofhinge post40b withmeniscal component26a. This embodiment of the knee prosthesis of the current invention may further utilize a meniscal component cutout together with a rotation protrusion on the tibial component to resist lifting of the meniscal component from the tibial tray as described above.

FIG. 20 illustrates a further alternative embodiment of the hinge post of the present invention.Hinge post40c illustrated inFIG. 20 includes reinforcingmaterial138 to strengthenhinge post40c.

While this invention has been described as having exemplary designs, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.

Claims (22)

What is claimed is:

1. A prosthetic femoral component, comprising:

a femoral component body;

a hinge post having a longitudinal axis, said hinge post rotatably connected to said femoral component body, said hinge post rotatable relative to said femoral component body bout an axis of rotation, said hinge post including an elongate aperture, along said longitudinal axis aid elongate aperture transverse to said axis of rotation.

2. The prosthetic femoral component ofclaim 1, further comprising: A prosthetic knee assembly, comprising:

a femoral component body that includes a first internal side wall opposing a second internal side wall;

a hinge pin having a longitudinal hinge pin axis;

a hinge post positioned between the first internal side wall and the second internal side wall of the femoral component body and having a longitudinal hinge post axis, said hinge pin fixed to said femoral component body and passing through a hinge pin aperture in said hinge post for rotatably, hingedly connecting said hinge post to said femoral component body so that rotation of said hinge post relative to said femoral component body is defined about the longitudinal hinge pin axis, said hinge post including an elongate hinge post extension aperture along said longitudinal hinge post axis, said elongate hinge post extension aperture transverse to said longitudinal hinge pin axis; and

a hinge post extension removeably locked to said hinge post, said elongate hinge post extension aperture of said hinge post sized for placement of said hinge post extension therein, whereby said hinge post extension traverses a first end of said elongate hinge post extension aperture of said hinge post and protrudes from a second end of said elongate hinge post extension aperture of said hinge post.

3. The prosthetic femoral component knee assembly ofclaim 2, further comprising:

securing means for securing said hinge post extension to said hinge post further comprising a tibial component into which the hinge post extension can be received, wherein, when the femoral component is attached to a femur and the tibial component is attached to a tibia opposite the femur, said hinge post extension can be separated from said hinge post to allow rotation of said hinge post about said longitudinal hinge pin axis without having to rotate the femur or tibia about said longitudinal hinge pin axis.

4. The prosthetic femoral component knee assembly of claim3, wherein said securing means comprises:

a male taper positioned on said hinge post extension; and

a female taper positioned in said elongate aperture, said male taper engageable in said female taper to secure said hinge post extension to said hinge post 2 including cooperating locking tapers removeably locking the hinge post extension to the hinge post.

5. The prosthetic femoral component knee assembly of claim1 2, further comprising:

a bearing box connected to said femoral component body, said bearing box interposed between said hinge post and said femoral component body, said bearing box including a hyperextension stop, said hinge post including a hyperextension stop surface, said hyperextension stop contacting said hyperextension stop surface to prevent further hyperextension of the prosthetic femoral component body beyond a predetermined point of hyperextension.

6. The prosthetic femoral component knee assembly ofclaim 5, wherein said predetermined point of hyperextension comprises four degrees of hyperextension of the prosthetic knee femoral component body.

7. The prosthetic femoral component knee assembly ofclaim 5, wherein said hyperextension stop comprises a convex protrusion.

8. The prosthetic femoral component knee assembly ofclaim 5, wherein said hinge post includes an internal wall, said hyperextension stop surface comprising said internal wall of said hinge post.

9. A prosthetic femoral component, comprising:

a femoral component body;

a hinge post rotatably connected to said femoral component body; and

a bearing box connected to said femoral component body, said bearing box interposed between said hinge post and said femoral component body, said bearing box including a hyperextension stop, said hinge post including a hyperextension stop surface, said hyperextension stop contacting said hyperextension stop surface to prevent further hyperextension of the prosthetic femoral component body beyond a predetermined point of hyperextension.

10. The prosthetic femoral component ofclaim 9, further comprising: A prosthetic knee assembly, comprising:

a femoral component body;

a hinge post rotatably connected to said femoral component body about a rotational axis;

a bearing box connected to said femoral component body, said bearing box interposed between said hinge post and said femoral component body, said bearing box including a hyperextension stop, said hinge post including a hyperextension stop surface, said hyperextension stop contacting said hyperextension stop surface to prevent further hyperextension of the prosthetic femoral component body beyond a predetermined point of hyperextension; and

a hinge post extension having a longitudinal axis and being removeably locked to said hinge post, an elongate aperture of said hinge post sized for placement of said hinge post extension therein, whereby said hinge post extension traverses a first end of said elongate aperture of said post and protrudes from a second end of said elongate aperture of said hinge post, wherein the longitudinal axis of said hinge post extension is non-intersecting with said rotational axis.

11. The prosthetic femoral component knee assembly ofclaim 10, further comprising:

securing means for securing said hinge post extension to said hinge post.

12. The prosthetic femoral component knee assembly ofclaim 11, wherein said securing means comprises:

a male taper positioned on said hinge post extension; and

a female taper positioned in said elongate aperture, said male taper engageable in said female taper to secure said hinge post extension to said hinge post.

13. The prosthetic femoral component knee assembly of claim9 10, wherein said predetermined point of hyperextension comprises four degrees of hyperextension of the prosthetic femoral component body.

14. The prosthetic femoral component knee assembly of claim9 10, wherein said hyperextension stop comprises a convex protrusion.

15. The prosthetic femoral component knee assembly of claim9 10, wherein said hinge post includes an internal wall, said hyperextension stop surface comprising said internal wall of said hinge post.

16. A prosthetic knee, comprising:

a femoral component;

a tibial component;

a meniscal component positioned between said femoral component and said tibial component, said femoral component including a condylar bearing surface, said meniscal component including a cooperative bearing surface facing said condylar bearing surface of said femoral component for contacting said condylar bearing surface, said femoral component rotatably connected to said tibial component;

a hinge pin having a longitudinal hinge pin axis;

a hinge post rotatably connected to said femoral component which includes said hinge pin passing through a hinge pin aperture in said hinge post for rotatably, hingedly connecting said hinge post to said femoral component so that rotation of said hinge post relative to said femoral component is defined about the longitudinal hinge pin axis, said meniscal component including an a hinge post aperture with a longitudinal hinge post aperture axis that is non-intersecting with said longitudinal hinge pin axis, said hinge post positioned within said hinge post aperture; and

a locking clip, said meniscal component including a locking clip aperture, said hinge post including a locking clip groove, said locking clip traversing said locking clip aperture and engaging said locking clip groove to retain said hinge post within said hinge post aperture.

17. A prosthetic knee, comprising:

a femoral component;

a tibial component;

a meniscal component positioned between said femoral component and said tibial component, said femoral component including a condylar bearing surface, said meniscal component including a cooperative bearing surface facing said condylar bearing surface of said femoral component, said femoral component rotatably connected to said tibial component;

a hinge post extension, said hinge post extension rotatably connected to said femoral component, said hinge post extension including an annular groove; and

a tibial bushing including an annular locking protrusion and a retaining flange, said tibial component having a tibial bushing expansion groove, said retaining flange positioned in said tibial bushing expansion groove, said annular locking protrusion engaged in said annular groove.

18. A prosthetic knee, comprising:

a femoral component having a hinge post rotatably connected thereto about a rotational axis;

a tibial component;

a meniscal component positioned between said femoral component and said tibial component, said femoral component including a condylar bearing surface, said meniscal component including a cooperative bearing surface facing said condylar bearing surface of said femoral component for contacting said condylar bearing surface, said meniscal component including an a hinge post aperture having a longitudinal axis that is non-intersecting with said rotational axis, whereby said hinge post is positioned within said hinge post aperture when the prosthetic knee is operably assembled; and

a locking clip, said meniscal component including a locking clip aperture, said hinge post including a locking clip groove, said locking clip traversing said locking clip aperture and engaging said locking clip groove to retain said hinge post within said hinge post aperture.

19. The prosthetic femoral component of claim 2, wherein said first end of said elongate aperture of said hinge post is positioned closer to said hinge pin than said second end of said elongate aperture so that said hinge post extension protrudes from said second end of said elongate aperture of said hinge post in a direction away from said hinge pin.

20. The prosthetic femoral component of claim 10, wherein said first end of said elongate aperture of said hinge post is positioned closer to said femoral component body than said second end of said elongate aperture of said hinge post so that said hinge post extension protrudes from said second end of said elongate aperture of said hinge post in a direction away from said femoral component body.

21. The prosthetic femoral component of claim 2, wherein said hinge pin includes a hexagonal indentation on a first end thereof, said first end being flush with said femoral component, said prosthetic femoral component further comprising a hinge pin plug positioned within said hexagonal indentation and being flush with said first end of said hinge pin.

22. The prosthetic femoral component of claim 2, wherein said longitudinal hinge post axis is non-intersecting with said longitudinal hinge pin axis.

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