Key messages
- More severe grades of knee osteoarthritis (KOA) show more than fourfold increase in knee joint force, indicating greater joint stress and KOA progress.
- Knee movement stimulation systems can help early OA diagnosis and personalized treatment plans.
- Enhanced joint function visualization through simulation helps understand the impact of different activities on cartilage health.
Study information
Details of the study
“Knee measurement system with osteoarthritis levels using artificial cartilage and skeletons”(1)
Methods
The knee measurement system was based on the four-bar-link model. It can mimic knee movements with four points and two links. In it, two bones (femur and tibia) and two ligaments (anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL)) are linked to form the four-bar mechanism. Both ligaments act as links between the bones, and the four points are the spots where the ligaments are attached to the bone.
Different models were created to represent 1-4 Kellgren-Lawrence (KL) scale osteoarthritic knees. Femur, tibia and knee cartilages were manufactured using 3D printers, adjusting their characteristics to the KL 1-4 severity grades. A force measurement sensor was attached in a load cell under the full-crafted tibia to evaluate the amount of force change in x, y and z axis during knee movement. The sensor can measure forces in the axial and anterior dimensions.
Two motors mimicked joint real-life movements. The artificial femur was connected to the motors by threads, resulting in pulling and adjusting the bone as in diƯerent movement scenarios. Force measures are presented in relation to the direction of force during usual knee movements. Experiment was conducted on a normal knee model and 1-4 grades KL scale models.
Main results
A positive correlation between the load applied on the knee, cartilage thickness, and skeletal geometry was revealed in this study. Bone and cartilage presented variations depending on the OA severity mimicked. Quantification of the resulting force from the induced motion in this 3D knee model showed a positive correlation between OA grade on the KL scale and the peak force observed. The greatest force measured at grade 1 with this model was 0.5 N (Newton), whereas at grade 4 was 2.2 N. This revealed a fourfold increase in force measures between the lower and the higher KL grades studied.
Everyday activities and environmental factors (overweight, movement repetition, heavy load lifting…) may increase mechanical stress on knee cartilage. The diƯerent KL grade knee models were intended to imitate these additional stress situations. In those models, the load was directed upward and forward during the movement simulation, which reflected real life stress on the joint.
Also, captured joint movement and simulated trajectories were measured. Bar 1 (ACL) theoretical and experimental trajectory was confirmed to be similar in the normal model and the KOA grade 4 model. Bar 2 (PCL) showed diƯerences between both trajectory values in the patient model.
Conclusion
3D-printed KOA and knee joint models significantly advance the way we understand this condition. These models show a clear link between increased knee load and OA severity, helping in early diagnosis and customized treatment. This approach also enables the development of patient-specific prosthetic joints, improving patient outcomes and OA management strategies.
Bibliography
1. Kang M, Seo S, Lee H, Han MW. Knee Measurement System with Osteoarthritis Levels Using Artificial Cartilage and Skeletons. Biomim Basel Switz. 2024 Mar 8;9(3):166.
Link to the full study
This article is a summary based on the following study. For further information and details, please consult the full study. Please do not hesitate to contact us if you have any comments. https://pubmed.ncbi.nlm.nih.gov/38534851/
