Hydraulic prosthetic knee joint with resistance variation mechanism at hyperextension

Abstract

A prosthetic knee joint includes a hydraulic resistance system having an extension hydraulic circuit and a flexion hydraulic circuit. The flexion hydraulic circuit includes a switchable resistance assembly having a mechanical switch. The mechanical switch has an engaged position and a released position. The switchable resistance assembly provides a first hydraulic resistance level when the mechanical switch is in the released position, and provides a second hydraulic resistance level when the mechanical switch is in the engaged position, the second level being less than the first level. When the hydraulic resistance element reaches a predetermined extension position, the mechanical switch moves to the engaged position, and when the fluid flow drops below a predetermined threshold, the mechanical switch moves back to the released position.

Description

[0001] Cross-application of related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 880,233, filed on July 30, 2019, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates generally to prosthetic knee joints and, more particularly, to a hydraulic prosthetic knee joint with variable resistance. Background Art

[0004] The prosthetic knee provides support for the user and also allows for joint movement, allowing the user to walk and swing the leg, as well as sit with the leg bent. Typically, the prosthetic knee includes damping, which is used to control the movement of the lower leg relative to the upper leg. High activity users would benefit from a prosthetic knee with a higher level of control and performance. Summary of the invention

[0005] The present invention provides a prosthetic knee joint in which the flexion resistance is mechanically switched to a lower level when the knee joint reaches a hyperextended position and is mechanically switched back to a higher level when the flexion movement drops below a threshold, thereby providing support once the flexion stops or slows to a certain level.

[0006] A first embodiment of a prosthetic knee joint includes an upper thigh portion and a lower leg portion connected by a joint. The joint allows the leg portion to articulate between an extended position and a flexed position, wherein the extended position is substantially aligned along a leg axis, and wherein the leg portion is tilted posteriorly relative to the thigh portion, wherein movement from the extended position to the flexed position is defined as flexion, and movement from the flexed position to the extended position is defined as extension. A hydraulic resistance system is operable to selectively provide hydraulic resistance to flexion and extension of the knee joint. The hydraulic resistance element has a movable piston, wherein the movable piston defines a first fluid chamber on a first side of the piston and a second fluid chamber on a second side of the piston, wherein the size of the first chamber increases and the size of the second chamber decreases during flexion and wherein the size of the first chamber decreases and the size of the second chamber increases during extension. An extension hydraulic circuit connects the first fluid chamber and the second fluid chamber and has a check valve operable to allow flow from the first fluid chamber to the second fluid chamber and substantially prevent flow from the second fluid chamber to the first fluid chamber. The extension hydraulic circuit also includes a resistance element operable to provide hydraulic resistance to flow from the first fluid chamber to the second fluid chamber. The flex hydraulic circuit connects the first fluid chamber and the second fluid chamber and has a check valve operable to allow flow from the second fluid chamber to the first fluid chamber and substantially prevent flow from the first fluid chamber to the second fluid chamber. The switchable resistance assembly includes a mechanical switch having an engaged position and a released position. The switchable resistance assembly provides a first level of hydraulic resistance to flow from the second fluid chamber to the first fluid chamber when the mechanical switch is in the released position, and provides a second level of hydraulic resistance to flow from the second fluid chamber to the first fluid chamber when the mechanical switch is in the engaged position, the second level being less than the first level. When the hydraulic resistance element reaches a predetermined extension position, the mechanical switch moves to the engaged position, and when flow from the second chamber to the first chamber drops below a predetermined threshold, the mechanical switch moves back to the released position.

[0007] A second embodiment of a prosthetic knee joint includes an upper thigh portion and a lower leg portion connected by a joint. The joint allows the leg portion to articulate between an extended position and a flexed position, wherein the thigh portion and the leg portion are generally aligned along a leg axis, and wherein the leg portion is tilted posteriorly relative to the thigh portion, wherein movement from the extended position to the flexed position is defined as flexion, and movement from the flexed position to the extended position is defined as extension. A hydraulic resistance system is operable to selectively provide hydraulic resistance to flexion and extension of the knee joint. The hydraulic resistance element has a movable piston, wherein the movable piston defines a first fluid chamber on a first side of the piston and a second fluid chamber on a second side of the piston, wherein the size of the first chamber increases and the size of the second chamber decreases during flexion and the size of the first chamber decreases and the size of the second chamber increases during extension. An extension hydraulic circuit connects the first fluid chamber and the second fluid chamber and has a check valve, wherein the check valve is operable to allow flow from the first fluid chamber to the second fluid chamber and substantially prevent flow from the second fluid chamber to the first fluid chamber. The extension hydraulic circuit further includes a resistance element operable to provide hydraulic resistance to flow from the first fluid chamber to the second fluid chamber. A first bending hydraulic circuit connects the first fluid chamber and the second fluid chamber and has a check valve operable to allow flow from the second fluid chamber to the first fluid chamber and substantially prevent flow from the first fluid chamber to the second fluid chamber. The bending hydraulic circuit further includes a resistance element operable to provide hydraulic resistance to the flow from the second fluid chamber to the first fluid chamber. A second bending hydraulic circuit connects the first fluid chamber and the second fluid chamber and includes a check valve operable to allow flow from the second fluid chamber to the first fluid chamber and substantially prevent flow from the first fluid chamber to the second fluid chamber. The bending hydraulic circuit further includes a resistance element operable to provide hydraulic resistance to the flow from the second fluid chamber to the first fluid chamber. The resistance element of the first bending hydraulic circuit provides a first hydraulic resistance level, and the resistance element of the second bending hydraulic circuit provides a second hydraulic resistance level, the second level being less than the first level. The mechanical switch has an engaged position, the mechanical switch being operable to allow flow through the second bend hydraulic circuit, thereby allowing flow through the second bend hydraulic circuit during bending, and a released position, the mechanical switch being operable to substantially block the second bend hydraulic circuit, thereby restricting flow to the first bend hydraulic circuit during bending.The mechanical switch moves to the engaged position when the hydraulic resistance element reaches a predetermined extended position, and moves back to the released position when flow from the second chamber to the first chamber drops below a predetermined threshold.

[0008] In some examples, embodiments of the knee joint are entirely mechanical, without electronically controlled valves or switches. In some examples, the hydraulic resistance element is a hydraulic cylinder having a cylinder body, a piston, and a piston rod, the cylinder body having a cylinder bore defined thereon, the piston having a piston head separating the first fluid chamber from the second fluid chamber, and the piston rod being connected to the upper thigh portion and the cylinder body being connected to the lower calf portion.

[0009] In some examples, the flexion and extension resistance levels are adjustable.

[0010] In some examples, the upper thigh portion includes an upper skeletal subassembly.

[0011] In some examples, the hydraulic resistance element includes a piston, and the mechanical switch includes a body and a plunger, the plunger contacting the piston when the hydraulic resistance element reaches the predetermined extended position.

[0012] In some examples, the predetermined extended position is a hyperextended position.

[0013] In some embodiments, the knee joint further comprises an adjustment mechanism for adjusting an amount of force required to engage the mechanical switch.

[0014] In some examples, a single check valve is the check valve of the first bend hydraulic circuit and is the check valve of the second bend hydraulic circuit.

[0015] According to another embodiment, a method of controlling a prosthetic knee joint includes providing a prosthetic knee joint having an upper thigh portion, a lower shank portion, and a joint connecting the two. The joint allows the shank portion to articulate between an extended position and a flexed position, wherein the extended position is where the thigh portion and the shank portion are generally aligned along a leg axis, and wherein the shank portion is tilted rearward relative to the thigh portion, wherein movement from the extended position to the flexed position is defined as flexion, and movement from the flexed position to the extended position is defined as extension. A hydraulic resistance element is operable to selectively provide hydraulic resistance to flexion and extension. The method includes: providing a first level of hydraulic resistance to flexion when the prosthetic knee joint is in a stance mode and the knee joint moves from the front of the user's body to the back of the user's body; when the prosthetic knee joint reaches an extended position at the terminal position of the stance mode, mechanically switching the hydraulic resistance to a second level, the second level of resistance being less than the first level of resistance, the second level of resistance allowing flexion so that the user can swing the knee joint forward in a swing mode in an at least partially flexed position; when the knee joint stops flexion movement, mechanically switching the hydraulic resistance level back to the first level. In some examples, the method can utilize any embodiment or example of the knee joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram showing the gait phases of a person walking;

[0017] Figure 2 is a side view of a prosthetic knee joint according to an embodiment of the present invention;

[0018] Figure 3 is a schematic diagram of an embodiment of a hydraulic resistance system for use with the present invention;

[0019] Figure 4 is a front view of a prosthetic knee joint according to an embodiment of the present invention;

[0020] Figure 5 is a perspective view of an embodiment of a hydraulic cylinder for use with the present invention;

[0021] Figure 6 yes Figure 5 a side view of a hydraulic cylinder shown with portions removed to illustrate the internal structure;

[0022] Figure 7 yes Figure 5 A cross-sectional view of the hydraulic cylinder shown;

[0023] Figure 8 yes Figure 5 Another cross-sectional view of the hydraulic cylinder shown;

[0024] Fig. 9A is a schematic diagram showing three gait phases;

[0025] Fig. 9B It is shown Fig. 9A Schematic diagram of fluid flow at various stages shown;

[0026] Fig. 9C is a partial cross-sectional view of a hydraulic cylinder showing the flow of fluid;

[0027] Fig. 10A is a schematic diagram showing three gait phases;

[0028] Fig. 10B is a schematic diagram showing a plunger of a mechanical switch being depressed;

[0029] Fig. 10C is a cross-sectional view of a portion of a hydraulic cylinder showing a plunger being depressed;

[0030] Fig.11A is a schematic diagram showing two gait phases;

[0031] Fig. 11B It is shown Fig.11A Schematic diagram of fluid flow at various stages shown;

[0032] Fig. 11C is a cross-sectional view of a hydraulic cylinder showing fluid flow;

[0033] Fig.11D is a partial cross-sectional view of a hydraulic cylinder showing the flow of fluid;

[0034] Fig. 12A is a schematic diagram showing two gait phases;

[0035] Fig. 12B It is shown Fig. 12A Schematic diagram of fluid flow at various stages shown;

[0036] Fig. 12C is a cross-sectional view of a hydraulic cylinder;

[0037] Fig.12D is a partial cross-sectional view of a hydraulic cylinder showing the flow of fluid;

[0038] Figures 13A-13F is a diagram showing three mode switch positions and associated fluid flows;

[0039] Fig.14A is a cross-sectional side view of a knee joint showing an example of an adjustment mechanism;

[0040] Fig. 14B yes Fig.14A a cross-sectional front view of the knee joint shown; and

[0041] Fig.15 yes Fig.14A and Fig. 14B A detailed view of the institution. DETAILED DESCRIPTION

[0042] As is known to those skilled in the art, a prosthetic knee joint must provide different levels of support to a user depending on the user's gait phase. A prosthetic knee joint typically has an upper thigh portion connected to a lower calf portion by a joint. The joint allows the calf portion to articulate between an extended position and a flexed position, in which the thigh portion and calf portion are generally aligned along the leg axis, and in a flexed position, the calf portion is tilted rearwardly relative to the thigh portion. Movement from the extended position to the flexed position is defined as flexion, and movement from the flexed position to the extended position is defined as extension. A hydraulic resistance system is operable to selectively provide hydraulic resistance to flexion and extension of the knee joint.

[0043] Figure 1 The gait phases of a person walking are shown. These phases will be described for the user's right leg, which is the foreground leg in the figure. In the figure, the right leg is the leg that includes the prosthetic knee joint. Figure 1 Starting on the left side of the figure, the user begins to stride at 10, with the leg fully extended and in the most forward position relative to the user's body. The heel of the leg touches the walking surface at this position, which can be considered the heel-on position. As the user moves forward, a load is placed on the leg at the position shown at 12, and the leg then reaches a position directly under the user's body, as shown at 14, which is called the mid-stance position.

[0044] Continuing forward, the leg reaches the rearmost position, shown at 16, referred to as the terminal stance phase. How far forward the leg is at position 10 and how far rearward the leg is at position 16 depends on the stride length of the user, but for a given stride, these positions are considered to be the forward and rearmost positions, respectively.

[0045] The user then moves their thigh forward, as shown at 18. Preferably, the knee joint is allowed to flex so that the forward movement of the thigh causes the calf of the leg to bend upward to a partially bent position. As the user continues to swing their thigh forward, as shown at 20, the knee joint continues to bend and the toes are lifted, known as toe-off. As the thigh continues to move forward of the body, the movement of the thigh is slowed by momentum, causing the calf to swing forward. This is shown at 22 and is known as the mid-swing position. At 24, the thigh has reached its forwardmost position and the calf swings forward to a fully extended position, with the calf and thigh generally aligned along the axis of the leg. This is known as the terminal swing position and occurs just before the heel strikes, as shown in position 10.

[0046] When the user reaches the heel strike position, the leg should provide a high amount of support corresponding to the high level of resistance to knee flexion, and the leg should maintain a high amount of support when the leg is loaded and the user moves through position 12 to the intermediate stance position 14 and then to the terminal stance position 16. However, the leg begins just after the terminal stance position 16 and no longer needs to support the user. Instead, it is desired that the knee joint has a very low level of flexion resistance so that when the user moves to the pre-swing position 18 and toe-off position 20, the knee joint allows the calf to swing upward easily. In the intermediate swing position 22, the knee joint allows extension so that the calf can swing forward. Typically, the leg does not need to provide support in this position because the leg does not contact the ground. When the leg reaches the terminal swing phase 24, the leg needs to be ready to provide support again.

[0047] If the user stumbles or suddenly shortens their stride, causing the user to attempt to place weight on the leg in any of positions 18-22, a typical prosthetic knee joint may collapse because the low flexion resistance allows the calf to bend easily toward the thigh.

[0048] According to an embodiment of the present invention, the prosthetic knee joint switches from a high flexion resistance at the terminal stance position when the knee joint is slightly hyperextended to a low flexion resistance to allow the knee joint to bend during the swing phase of gait. Then, when the knee joint stops bending or the bending rate drops below a threshold, the prosthetic knee joint switches back to a high flexion resistance, allowing the leg to bear the weight of the user. This typically occurs at position 24 when the knee joint stops bending and begins to extend. The knee joint is then ready to bear weight. However, the embodiment also provides support for the user in other situations. For example, if the user stumbles and stops moving his thigh forward at position 20 or position 22, the bending will slow down or temporarily stop when the calf stops bending upward, and the knee joint will switch to a high flexion resistance level. Then, if the user places a load on the leg, the leg will provide a high level of support.

[0049] Figure 2 A prosthetic knee joint 50 is shown in accordance with an embodiment of the present invention. The knee joint 50 has an upper portion 52 and a lower portion 54 connected to each other by a joint 56. In this embodiment, the joint is a pivot joint between the upper portion 52 and the lower portion 54. When connected to a user's thigh or thigh prosthesis (typically through a thigh joint socket), the upper portion 52 may be referred to as the thigh portion. The lower portion 54 may be referred to as the calf portion. The rearward movement of the lower calf portion 54 causes it to pivot at the joint 56 and move toward the user's thigh. This condition is referred to as flexion. Movement in the opposite direction is referred to as extension.

[0050] The knee joint also has a hydraulic resistance system 60 that provides resistance to flexion and extension. The level or resistance depends on many factors and can be further adjusted. In the illustrated embodiment, the hydraulic resistance system takes the form of a hydraulic cylinder having a cylinder body 62, a cylinder bore, a piston and a piston rod 64, wherein the cylinder bore is defined in the cylinder body (not shown), and the piston has a piston head, which is located in the cylinder bore. In this embodiment, the cylinder body 62 is connected to the lower part 54, and the piston rod 64 is connected to the upper part 52, so that the bending movement moves the piston rod 64 into the cylinder body 62, and the extension movement causes the piston rod 64 to extend from the cylinder body 62. The system can be inverted, wherein the cylinder body 62 is connected to the upper part 52 and the piston rod 64 is connected to the lower part 54, or so that the movement caused by bending and extension is inverted. As will be clear to those skilled in the art, other types of hydraulic resistance systems can be used, such as hydraulic cylinders for bending and hydraulic dampers for rotation. In each case, the damper or resistance system has two parts that move relative to each other, so that the hydraulic fluid flows between the chambers. This resistance or obstruction to flow arrests or stops the movement.

[0051] Figure 3 is a schematic diagram of an embodiment of a hydraulic resistance system 70 for use with the present invention. The system 70 includes a hydraulic resistance element 72, the interior area of ​​which is divided by the head of a piston 78 into a first fluid chamber 74 and a second fluid chamber 76. In the illustrated embodiment, the first chamber 74 is located on the upper side of the piston 78 and the second chamber 76 is located on the lower side of the piston 78. A hydraulic circuit system extends between the two chambers so that fluid can flow between the chambers when the piston moves. If the resistance element 72 is as shown Figure 2 76 and 77. The hydraulic cylinder shown in FIG. 1 shows a hydraulic cylinder 200, wherein the flexion movement of the knee joint causes the piston 78 to move downward, thereby reducing the size of the second chamber 76 and increasing the size of the first chamber 74. The extension of the knee joint causes the opposite operation; the piston 78 moves upward, thereby reducing the size of the first chamber 74 and increasing the size of the second chamber 76. Ports are typically provided in the fluid chamber for fluid communication with the hydraulic circuit. The hydraulic circuits may share ports and components of the flow path, or they may be completely independent, for example, having different ports.

[0052] The extension hydraulic circuit 80 connects the first chamber and the second chamber and has a check valve 82 that is operable to prevent flow from the second chamber 76 to the first chamber 74 and to allow flow from the first chamber 74 to the second chamber 76. This means that fluid flows through the extension hydraulic circuit 80 when the knee joint is extended. The extension hydraulic circuit 80 has a resistance element 84 that can prevent fluid flow. The resistance element 84 can take the form of a valve and can be adjustable, such as by the user or technician to set the amount of resistance to knee extension. For this element, the resistance is typically low. During stride, the resistance is typically not adjusted or non-adjustable; the resistance is not actively adjusted. Instead, the resistance is set at the beginning of use or before, and then the resistance setting remains unchanged for a longer period of time.

[0053] In this embodiment, the bending hydraulic circuit takes the form of two circuits. The first bending hydraulic circuit 90 connects the first chamber and the second chamber and has a check valve 92, which is operable to prevent flow from the first chamber 74 to the second chamber 76 and allow flow from the second chamber 76 to the first chamber 74. This means that fluid flows through the first bending hydraulic circuit 90 when the knee joint is bent. The first bending hydraulic circuit 90 has a resistance element 94 that can prevent fluid flow. The resistance element 94 can take the form of a valve and can be adjustable, but not actively adjusted, such as during stride.

[0054] The second bending hydraulic circuit 100 also connects the first chamber and the second chamber, and in this embodiment, shares the check valve 92 with the first bending hydraulic circuit. Alternatively, a separate check valve may be used. The second bending hydraulic circuit has a resistance element 104 that resists flow. Unlike the first bending hydraulic circuit 90, the second bending hydraulic circuit 100 includes a mechanical switch 106 that selectively allows or prevents fluid flow. In the illustrated embodiment, the mechanical switch has a body 108 and a plunger 110, wherein the plunger extends from the body. When the plunger 110 is pressed into the body 108, the mechanical switch is in an engaged position, which allows flow through the second bending hydraulic circuit. When the plunger 110 is extended, the switch is in a released position and substantially prevents flow through the second bending hydraulic circuit 100. When the flow is prevented, fluid flow during bending is limited to the first bending hydraulic circuit 90. The flow resistance in the first bending hydraulic circuit 90 is higher than the flow resistance in the second bending hydraulic circuit 100. Thus, when the mechanical switch 106 is engaged, thereby allowing flow through the second bend hydraulic circuit 100, the bend resistance is much lower than when the mechanical switch is released and bend flow is restricted to the higher resistance first bend hydraulic circuit 90. Figure 3 As can be clearly seen in FIG. 1 , when the mechanical switch is engaged and allows flow through the second bend hydraulic circuit 100, fluid can also pass through the first bend hydraulic circuit 90. However, the majority of the fluid will pass through the lower resistance second bend hydraulic circuit 100.

[0055] In this embodiment, when the piston 78 reaches the upper position and contacts the plunger 110, the plunger 110 is depressed. The system is designed so that the piston 78 contacts the plunger 110 when the leg and knee are in a fully extended position, and hyperextension of the knee joint will cause the piston 78 to depress the plunger 110. This hyperextension may occur at the terminal stance position 16, depending on how the user loads the leg. The mechanical switch 106 is designed so that once the mechanical switch is depressed, it remains depressed as long as there is flexural fluid flow through the switch and the fluid flow is above a threshold. Once the flow drops below the threshold, the plunger 10 extends as long as the piston is not in contact. Return to Reference Figure 1 , when the lower leg begins to extend forward, the flexion flow through the switch will decrease or stop, and the knee joint will extend in position 22 or position 24. This reduction in flow will cause the switch to return to the release position blocking flow in the second flexion hydraulic circuit 100, and the flexion resistance returns to a level that allows the knee joint to fully support the user's weight.

[0056] It should be noted that certain embodiments of the present invention provide a fully mechanical knee joint having a fully mechanical flexion and extension resistance system. In these particular embodiments, a mechanical system is used to adjust the level of flexion resistance, and no electronic control or adjustment is provided. It should also be noted that the resistance element of any circuit can be formed by a hole or a channel that provides some flow resistance. Adjustable resistance elements can be used in whole or in part. In some forms, check valves and resistance elements can be combined. Mechanical switch 106 can provide resistance to element 104, for example by setting the size of the hole in the switch.

[0057] Reference now Figure 4-8 , the hydraulic resistance system will be described in more detail. Figure 4 Shows Figure 2 of a prosthetic knee joint, but from the front, to better illustrate the hydraulic cylinders which define the resistance system 60. Figure 5 A hydraulic cylinder 60 is shown having a cylinder body 62 and a piston rod 64. In this embodiment, the front portion of the body 62 includes an adjustment fitting that can be engaged with a tool and used to adjust the resistance provided by the resistance element. The adjustment fitting 120 is used to adjust Figure 3 The resistance element 84 in the extension hydraulic circuit 80. The adjustment fitting 122 is used to adjust Figure 3 The first bending hydraulic circuit 90 of the embodiment of the present invention is used to adjust the resistance element 94 in the first bending hydraulic circuit 90. The adjustment fitting 124 is used to adjust the resistance element 104 in the second bending hydraulic circuit 100. Some embodiments of the hydraulic cylinder 60 can also include a mode selection switch or knob 126. In the embodiment shown, the mode selection switch surrounds the piston rod 64 at the upper end of the cylinder body 62 and rotates about the axis of the piston rod to select a mode. These modes will be discussed below.

[0058] Figure 6 A side view of a hydraulic cylinder 60 is provided in which some features of the internal structure are visible. The piston includes a piston head 65 that is movable in a cylinder bore 63, with a first fluid chamber located above the piston head and a second fluid chamber located below the piston head. The first fluid chamber is labeled 74 to correspond to Figure 3 , and the second fluid chamber is labeled 76 to correspond to Figure 3 A spring or other biasing member may be provided in one or both chambers to bias the piston. Figure 3 As described above, the extension hydraulic circuit includes a check valve 82. Figure 6 In the embodiment of the present invention, the check valve 82 is located near the cylinder bore 63 at the lower end of the cylinder body and is in fluid communication with the second fluid chamber 76. The fluid passage 83 extends upward to a resistance element 84, which is connected to the first fluid chamber 74 through another passage 85. For bending resistance, another check valve 92 is provided at the lower end of the cylinder body and is in fluid communication with the second fluid chamber 76. Figure 3 As shown, fluid passage 93 connects check valve 92 to resistance element 94, and another passage 95 is in fluid communication with first fluid chamber 74. The same passage 93 is also connected to resistance element 104, and another passage 105 extends from the resistance element to the mechanical switch ( Figure 6 not shown).

[0059] Figure 7 and Figure 8 1 is a cross-sectional view of the hydraulic cylinder 60 and the mechanical switch 106. The switch 106 has a body 108 and a plunger 110 extending downward from the body 108, and the lower end of the plunger is disposed at the upper end of the cylinder bore 63. Figure 7 In the embodiment, the piston head 65 is spaced a short distance from the upper end of the cylinder bore 63, and the plunger is extended so that the switch 106 is in the released position and flow through the passage 105 is blocked. Figure 8 In the embodiment of the present invention, the piston head 65 is located at or near the upper end of the cylinder bore 63 and contacts the plunger 110 so that the plunger is depressed, thereby placing the switch in the engaged position. Then, a flow opening 112 is defined below the plunger. Other arrangements that allow similar functions can be provided.

[0060] Fig. 9A -C shows the operation of an embodiment of the resistance system when the knee joint is in stance mode with high flexion resistance. Fig. 9A Locations 10, 12 and 14 are shown where high bending resistance is required. Fig. 9B A schematic diagram of a corresponding hydraulic resistance system is shown, highlighting the first curved hydraulic circuit 90. The direction of fluid flow and piston head movement is also shown. Fig. 9C Similar to Figure 6, where the arrows indicate the path of fluid flow in standing mode.

[0061] Fig. 10A The terminal stance position 16 is shown, Fig. 10B The mechanical switch 106 is shown with the plunger depressed in the direction of the arrow. The reason for this is that the piston head 65 reaches a position corresponding to hyperextension of the knee joint. Fig. 10C is similar to Figure 8 , showing the plunger 110 depressed by the piston head 65 to expose the passage 112. It is noted that the term "hyperextension" as used herein, when referring to a knee joint or leg, refers to a position beyond the "fully extended" position of the knee joint or leg. The "fully extended" position is where the leg normally supports the user in a standing position, and generally corresponds to the thigh and calf being in a straight line with each other. However, the full extended position can be slightly different from the thigh and calf being in a straight line with each other. Thus, "hyperextension" is a position that is at least slightly beyond the "fully extended" position, and is not necessarily a position that is beyond the position where the upper and lower portions are in a straight line. The hyperextension position may also be referred to as a predetermined extension position. When the leg is in the fully extended position, the piston reaches a position where it may or may not contact the switch, and when the leg or knee joint is in the hyperextension position, the piston depresses the plunger.

[0062] Fig.11A -D shows the result of the mechanical switch 106 being engaged when the user moves to the flexion mode and the knee joint is flexed. Fig.11A The user is shown in position 18 and position 20, wherein low resistance knee flexion occurs. Fig. 11B A schematic diagram is shown with the mechanical switch 106 engaged, with the arrows indicating the piston moving downward and low resistance fluid flowing through the second curved hydraulic circuit 100 . Fig. 11C and Fig.11D Arrows are provided to illustrate the flow of fluid in this mode.

[0063] As described above, once the deflection drops below the threshold, the switch 106 returns to the released position. Fig. 12A The user is shown in position 22 and position 24, where flexion has ceased, the switch has been released, and knee extension has occurred. Fig. 12B A schematic diagram of the flow of stretching fluid through the stretching circuit 80 is shown. Fig. 12C The switch 106 is shown to be released, while Fig.12D The flow of stretch fluid through circuit 80 is shown. Note that since the switch is released, the knee joint will provide a high level of resistance if the user places a load on the knee joint. The cycle is then repeated from FIG. 9

[0064] FIG. 13 illustrates various modes of operation that may be provided with some embodiments of the present invention. Fig.13A and Fig. 13B The hydraulic resistance system is shown in the locked position, where the mode selector switch has been turned clockwise. In this mode, the fluid passage is blocked, thereby locking the knee joint in place. Fig. 13C and Fig.13D "Normal" operation is shown, in which the knee joint operates as described above. The mode selector switch is in the middle position. Fig.13E and Fig.13F The mode selector switch is shown turned counterclockwise, which places the knee joint in free swing mode. In this position, an additional fluid passage is opened, allowing fluid to flow freely between the first hydraulic chamber and the second hydraulic chamber without being directed through any resistance element. This may be referred to as the bypass position.

[0065] For some embodiments of the present invention, an adjustment mechanism may be provided for adjusting the amount of force required to engage the mechanical switch. An example of such an adjustment mechanism is Fig.14A , 14B and 15 are shown. Fig.14A A side view of the knee joint assembly 50 is provided, wherein 205 represents an upper bone subassembly and 210 represents a physical stop, such as a stop pin, which limits the rotational movement of the upper bone subassembly 205 by engaging the adjustable stop mechanism 200 . Fig. 14B A front view of a knee joint assembly 50 is shown having an adjustable stop mechanism 200 and a stop pin 210 .

[0066] Fig.15 An upper bone subassembly 205 is shown that is comprised of an adjustable stop assembly 200. Within the adjustable stop assembly is a wedge 220 that engages a bumper 230. The bumper then engages a stop pin 210 that limits rotational movement of the knee joint. As will be apparent to one skilled in the art, by utilizing a wedge system, if the wedge 220 moves laterally, the bumper 230 will move along a vertical plane that will engage or disengage the stop pin 210. The use of this mechanism allows the user to adjust the force required to trigger hyperextension. As shown in FIG. 10 , triggering hyperextension is to allow the knee joint to flex at toe-off.

[0067] Other aspects of the prosthetic knee joint may also be adjustable. For example, the amount of force required to depress a plunger of a mechanical switch may be adjustable, as may the amount of travel required to switch to a second resistance level.

[0068] As will be apparent to those skilled in the art, the embodiments of the invention described herein may be modified in various ways without departing from the scope of the invention. Any feature described for use with any embodiment may also be used with other embodiments, as will be apparent to those skilled in the art. The following claims include all equivalents that define the scope of the invention.

Claims

1. A prosthetic knee joint, comprising: upper thigh; lower calf; a joint connecting the upper thigh portion and the lower leg portion, the joint allowing the lower leg portion to articulate between an extended position in which the upper thigh portion and the lower leg portion are generally aligned along a leg axis and a flexed position in which the lower leg portion is tilted rearwardly relative to the upper thigh portion, movement from the extended position to the flexed position being defined as flexion, and movement from the flexed position to the extended position being defined as extension; as well as A hydraulic resistance system, the hydraulic resistance system selectively providing hydraulic resistance to the flexion and extension of the knee joint, the hydraulic resistance system comprising: a hydraulic resistance element having a movable piston defining a first fluid chamber on a first side of the piston and a second fluid chamber on a second side of the piston, the first fluid chamber increasing in size and the second fluid chamber decreasing in size during flexion and the first fluid chamber decreasing in size and the second fluid chamber increasing in size during extension; an extension hydraulic circuit connecting the first fluid chamber and the second fluid chamber, the extension hydraulic circuit having a check valve for allowing flow from the first fluid chamber to the second fluid chamber and substantially preventing flow from the second fluid chamber to the first fluid chamber, and the extension hydraulic circuit also having a resistance element for providing hydraulic resistance to the flow from the first fluid chamber to the second fluid chamber; a curved hydraulic circuit connecting the first fluid chamber and the second fluid chamber, the curved hydraulic circuit having; a check valve configured to allow flow from the second fluid chamber to the first fluid chamber and substantially prevent flow from the first fluid chamber to the second fluid chamber; and a switchable resistance assembly including a mechanical switch having an engaged position and a released position, the switchable resistance assembly providing a first level of hydraulic resistance to flow from the second fluid chamber to the first fluid chamber when the mechanical switch is in the released position and providing a second level of hydraulic resistance to flow from the second fluid chamber to the first fluid chamber when the mechanical switch is in the engaged position, the second level of hydraulic resistance being less than the first level of hydraulic resistance; The mechanical switch moves to the engaged position when the hydraulic resistance element reaches a predetermined extended position, and moves back to the released position when flow from the second fluid chamber to the first fluid chamber drops below a predetermined threshold.

2. A prosthetic knee joint, comprising: upper thigh; lower calf; a joint connecting the upper thigh portion and the lower leg portion, the joint allowing the lower leg portion to articulate between an extended position in which the upper thigh portion and the lower leg portion are generally aligned along a leg axis and a flexed position in which the lower leg portion is tilted rearwardly relative to the upper thigh portion, movement from the extended position to the flexed position being defined as flexion, and movement from the flexed position to the extended position being defined as extension; as well as A hydraulic resistance system, the hydraulic resistance system selectively providing hydraulic resistance to the flexion and extension of the knee joint, the hydraulic resistance system comprising: a hydraulic resistance element having a movable piston defining a first fluid chamber on a first side of the piston and a second fluid chamber on a second side of the piston, the first fluid chamber increasing in size and the second fluid chamber decreasing in size during flexion and the first fluid chamber decreasing in size and the second fluid chamber increasing in size during extension; an extension hydraulic circuit connecting the first fluid chamber and the second fluid chamber, the extension hydraulic circuit having a check valve for allowing flow from the first fluid chamber to the second fluid chamber and substantially preventing flow from the second fluid chamber to the first fluid chamber, and the extension hydraulic circuit also having a resistance element for providing hydraulic resistance to the flow from the first fluid chamber to the second fluid chamber; a first bending hydraulic circuit connecting the first fluid chamber and the second fluid chamber, the first bending hydraulic circuit having a check valve for allowing flow from the second fluid chamber to the first fluid chamber and substantially preventing flow from the first fluid chamber to the second fluid chamber, and the first bending hydraulic circuit further having a resistance element for providing hydraulic resistance to the flow from the second fluid chamber to the first fluid chamber; a second bending hydraulic circuit connecting the first fluid chamber and the second fluid chamber, the second bending hydraulic circuit having a check valve for allowing flow from the second fluid chamber to the first fluid chamber and substantially preventing flow from the first fluid chamber to the second fluid chamber, and the second bending hydraulic circuit further having a resistance element for providing hydraulic resistance to the flow from the second fluid chamber to the first fluid chamber; The resistance element of the first bending hydraulic circuit provides a first hydraulic resistance level, and the resistance element of the second bending hydraulic circuit provides a second hydraulic resistance level, the second hydraulic resistance level being less than the first hydraulic resistance level; and a mechanical switch having an engaged position to allow flow through the second bending hydraulic circuit, thereby allowing flow through the second bending hydraulic circuit during bending, and a released position to substantially block the second bending hydraulic circuit, thereby restricting flow into the first bending hydraulic circuit during bending, the mechanical switch moving to the engaged position when the hydraulic resistance element reaches a predetermined extended position, and moving back to the released position when flow from the second fluid chamber to the first fluid chamber drops below a predetermined threshold.

3. The prosthetic knee joint according to claim 1 or 2, wherein: The knee joint is completely mechanical, with no electronically controlled valves or switches.

4. The prosthetic knee joint according to claim 1 or 2, wherein: The hydraulic resistance element includes a hydraulic cylinder having a cylinder body, a piston and a piston rod, the cylinder body having a cylinder bore defined thereon, the piston having a piston head separating the first fluid chamber from the second fluid chamber, and the piston rod being connected to the upper thigh portion and the cylinder body being connected to the lower calf portion.

5. The prosthetic knee joint according to claim 1 or 2, wherein: The flexion and extension resistance levels are adjustable.

6. The prosthetic knee joint according to claim 1 or 2, wherein: The upper thigh portion includes an upper skeletal subassembly.

7. The prosthetic knee joint according to claim 1 or 2, wherein: The hydraulic resistance element includes a piston, and the mechanical switch includes a body and a plunger, the plunger contacting the piston when the hydraulic resistance element reaches the predetermined extended position.

8. The prosthetic knee joint according to claim 1 or 2, wherein: The predetermined extended position is a hyperextended position.

9. The prosthetic knee joint of claim 1 or 2, further comprising an adjustment mechanism for adjusting the amount of force required to engage the mechanical switch.

10. The prosthetic knee joint according to claim 2, wherein: A single check valve is the check valve of the first bending hydraulic circuit and is the check valve of the second bending hydraulic circuit.

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