Lower limb prosthesis

1. A lower limb prosthesis, comprising:

a knee chassis;

a shin carrier pivotally connected to the knee chassis; and

a piston and cylinder assembly pivotally connected to the knee chassis and the shin carrier, the piston and cylinder assembly comprising:

a piston assembly comprising a piston mounted on a piston rod; and

a cylinder body having a cavity defining a cylinder within which the piston is arranged to reciprocate;

wherein:

the knee chassis is pivotally connected to the shin carrier to pivot around an anterior knee pivot axis (A);

the knee chassis is pivotally connected to the piston and cylinder assembly to pivot around a posterior knee pivot axis (C); and

the shin carrier is pivotally connected to the piston and cylinder assembly to pivot around a distal pivot axis (B),

wherein the piston and cylinder assembly further comprises, distal to the distal pivot axis (B), a foot component having a distal surface, and a distance from the anterior knee pivot axis (A) to the distal pivot axis (B) is more than 20% of a distance from the anterior knee pivot axis (A) to the distal surface of the foot component, or

the piston and cylinder assembly further comprises, distal to the distal pivot axis (B), a connector for attaching a foot component to the piston and cylinder assembly, said foot component having a distal surface, and, in use, when said foot component is attached to the connector a distance from the anterior knee pivot axis (A) to the distal pivot axis (B) is more than 20% of a distance from the anterior knee pivot axis (A) to the distal surface of said foot component,

wherein the piston and cylinder assembly, the knee chassis and the shin carrier define a polycentric linkage.

2. The lower limb prosthesis as claimed in claim 1 , wherein the distance between the anterior knee pivot axis (A) and the distal pivot axis (B) is more than 20%, 25%, 30%, 35%, 40% or 45% of the distance from the anterior knee pivot axis (A) to the distal surface of the foot component.

3. The lower limb prosthesis as claimed in claim 1 and further comprising a controller configured to control relative movement between the cylinder body and the piston assembly.

4. The lower limb prosthesis as claimed in claim 3 , wherein the controller is configured to control relative movement between the cylinder body and the piston assembly in dependence on the position of the prosthesis in a gait cycle.

5. The lower limb prosthesis as claimed in claim 3 , wherein the controller is a hydraulic or pneumatic controller, comprising at least one electronically-controlled valve.

6. The lower limb prosthesis as claimed in claim 3 , wherein the controller comprises a micro-processor, the micro-processor being comprised in or on the lower limb prosthesis.

7. The lower limb prosthesis as claimed in claim 1 , wherein the cylinder body comprises a cylinder sleeve, the cylinder sleeve being configured to receive the piston such that translational movement of the piston within the cylinder sleeve is permitted, and the connector is fixedly attached to or forms part of the cylinder sleeve.

8. The lower limb prosthesis as claimed in claim 1 , wherein the foot component is a shin, ankle or foot prosthesis.

9. The lower limb prosthesis as claimed in claim 1 , wherein the connector is a pyramid connector.

10. The lower limb prosthesis as claimed in claim 1 , wherein the piston rod defines an internal cavity.

11. The lower limb prosthesis as claimed in claim 1 , wherein the piston rod is a single unitary piece of titanium alloy.

12. The lower limb prosthesis as claimed in claim 1 , further comprising an adaptive control system having a flexion control device arranged to resist flexion at a knee joint hydraulically, and an electronic processing circuit electrically coupled to a sensor, and a control device for automatically adjusting the hydraulic resistance to knee flexion according to actions of the user.

13. The lower limb prosthesis as claimed in claim 1 , further comprising a micro-processor for controlling knee flexion.

14. The lower limb prosthesis as claimed in claim 1 , further comprising at least one valve for flexion and/or extension control.

15. The lower limb prosthesis as claimed in claim 1 , further comprising a flexion flow control valve and an extension flow control valve.

16. The lower limb prosthesis as claimed in claim 15 , wherein the flexion flow control valve and the extension flow control valve are both controlled by a single actuator, the actuator being controlled by micro-processor control.

17. A lower limb prosthesis, comprising:

a knee chassis;

a shin carrier pivotally connected to the knee chassis; and

a piston and cylinder assembly pivotally connected to the knee chassis and the shin carrier and having a piston and cylinder assembly axis, the piston and cylinder assembly comprising:

a piston assembly comprising a piston mounted on a piston rod;

a cylinder body having a cavity defining a cylinder within which the piston is arranged to reciprocate along the piston and cylinder assembly axis; and

a foot component or a connector for attaching a foot component to the piston and cylinder assembly;

wherein:

the knee chassis is pivotally connected to the shin carrier to pivot around a first knee pivot axis (A);

the knee chassis is pivotally connected to the piston and cylinder assembly to pivot around a second knee pivot axis (C); and

the shin carrier is pivotally connected to the piston and cylinder assembly to pivot around a distal pivot axis (B),

the lower limb prosthesis having a centrode about which the prosthesis rotates, the instantaneous center of rotation being a point where a line passing through the first knee pivot axis (A) and the distal pivot axis (B) intersects a line passing through the second knee pivot axis (C) and which is perpendicular to the piston and cylinder assembly axis,

wherein the piston and cylinder assembly, the knee chassis and the shin carrier define a polycentric linkage such that when the piston reciprocates within the cylinder the instantaneous center of rotation of the lower limb prosthesis follows a centrode twice intersecting a line passing through the first knee pivot axis (A) and the second knee pivot axis (C).

18. The lower limb prosthesis as claimed in claim 17 , wherein when the piston reciprocates within the cylinder the centrode substantially defines a semi-circle circumference or two thirds of a circle circumference.

19. A lower limb prosthesis, comprising:

a knee chassis;

a shin carrier pivotally connected to the knee chassis; and

a piston and cylinder assembly pivotally connected to the knee chassis and the shin carrier and having a piston and cylinder assembly axis, the piston and cylinder assembly comprising:

a piston assembly comprising a piston mounted on a piston rod;

a cylinder body having a cavity defining a cylinder within which the piston is arranged to reciprocate along the piston and cylinder assembly axis; and

a foot component or a connector for attaching a foot component to the piston and cylinder assembly;

wherein:

the knee chassis is pivotally connected to the shin carrier to pivot around an anterior knee pivot axis (A);

the knee chassis is pivotally connected to the piston and cylinder assembly to pivot around a posterior knee pivot axis (C); and

the shin carrier is pivotally connected to the piston and cylinder assembly to pivot around a distal pivot axis (B),

wherein the piston and cylinder assembly, the knee chassis and the shin carrier define a polycentric linkage; and

wherein the piston and cylinder assembly axis and a line passing through the anterior knee pivot axis (A) and the distal pivot axis (B) are substantially parallel as the knee flexes.

20. A lower limb prosthesis, comprising:

a knee chassis;

a shin carrier pivotally connected to the knee chassis; and

a piston and cylinder assembly pivotally connected to the knee chassis and the shin carrier and having a piston and cylinder assembly axis, the piston and cylinder assembly comprising:

a piston assembly comprising a piston mounted on a piston rod;

a cylinder body having a cavity defining a cylinder within which the piston is arranged to reciprocate along the piston and cylinder assembly axis; and

a foot component or a connector for attaching a foot component to the piston and cylinder assembly;

wherein:

the knee chassis is pivotally connected to the shin carrier to pivot around an anterior knee pivot axis (A);

the knee chassis is pivotally connected to the piston and cylinder assembly to pivot around a posterior knee pivot axis (C);

wherein the piston and cylinder assembly, the knee chassis and the shin carrier define a polycentric linkage; and

the shin carrier is pivotally connected to the piston and cylinder assembly to pivot around a distal pivot axis (B) which lies substantially on the piston and cylinder assembly axis.