Knee Joint Pad Geometry for Lateral Condyle Rollback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The single-radius design of the condyles lateralis bearing surface in existing knee joint prostheses restricts the femoral prosthesis from rolling back further, negatively affecting high flexion performance.
Innovation Solution
A knee-joint pad with a condyles lateralis bearing surface divided into a first lateralis curved surface portion, a straight portion, and a second lateralis curved surface portion, allowing the femoral condyle to slide smoothly, mimicking the physiological kinematics of 'shifting with the medial condyle as axis', enhancing flexibility and reducing abrasion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-radius arc-shaped condyles lateralis bearing surface is used, then the structure is simple and easy to manufacture, but the femoral prosthesis cannot roll back further during flexion, restricting high flexion performance
Solution Approach 1:
The condyles lateralis bearing surface is divided into three distinct segments: a first curved surface portion (with larger radius of curvature) at the front, a straight portion in the middle, and a second curved surface portion (with smaller radius of curvature) at the rear. This segmentation allows different regions to serve different functions during knee flexion, enabling the femoral condyle to roll back further while maintaining manufacturing feasibility through modular design
Solution Approach 2:
Different portions of the bearing surface are given different geometric properties: the first curved surface portion has a larger radius of curvature to accommodate initial flexion, the straight portion provides a transition zone for rolling back movement, and the second curved surface portion has a smaller radius of curvature to facilitate deep flexion. This local differentiation of geometric properties optimizes flexion performance while maintaining structural integrity
2Device complexity
If a single-radius arc-shaped condyles lateralis bearing surface is used, then the design is simple, but the lateral condyle is restricted by a higher rear side of the lateral pad, preventing further rollback
Solution Approach 1:
The bearing surface is segmented into three portions with progressively changing radii of curvature, where the first curved surface portion has a larger radius, the straight portion provides a transition, and the second curved surface portion has a smaller radius. This segmentation removes the restriction caused by a uniform high rear side, allowing the lateral condyle to roll back further while maintaining reasonable design complexity
Solution Approach 2:
The design transitions from a two-dimensional arc-shaped surface to a three-dimensional composite surface with varying curvature radii across different regions. This dimensional complexity allows the surface to accommodate the complex rollback trajectory of the lateral condyle during flexion, enabling greater flexion range without excessive design complexity
3Device complexity
If the femoral condyle is restricted during flexion, then the prosthesis structure is simpler, but the abrasion between the knee joint pad and lateral condyle surface increases, reducing service life
Solution Approach 1:
Different regions of the bearing surface are optimized for different phases of motion: the first curved surface portion handles initial flexion with larger radius to reduce stress, the straight portion manages the rollback phase with minimal abrasion, and the second curved surface portion accommodates deep flexion with smaller radius. This local optimization reduces overall abrasion and extends service life while maintaining acceptable structural complexity
Solution Approach 2:
The bearing surface is designed to dynamically adapt to the changing contact conditions during flexion, with the transition between curved and straight portions allowing the contact point to move along an optimized trajectory. This dynamic design reduces sliding friction and abrasion compared to a static single-radius design, thereby extending service life
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Provided are a knee joint pad and a knee joint prosthesis having same. The knee joint pad comprises a pad body. A medial condyle supporting surface and a lateral condyle supporting surface which are used for matching a corresponding femoral condyle are formed on the pad body; both the medial condyle supporting surface and the lateral condyle supporting surface are concave curved surfaces; the lateral condyle supporting surface comprises a first external curved surface portion, a linear surface portion and a second external curved surface portion which are sequentially arranged in the front-back direction of the lateral condyle supporting surface; each of the first external curved surface portion and the second external curved surface portion is smoothly connected to the linear surface portion; when the femoral condyle flexes on the pad body, the lateral condyle of the femoral condyle can slide on the linear surface portion; the first external curved surface portion is used for matching the lateral condyle of the femoral condyle and keeping a human body in a standing state.