Background: Different posterior tibial slopes (PTS) after posterior-stabilized total knee arthroplasty (PS-TKA) may lead to different biomechanical characteristics of knee joint. This cadaveric study was designed to investigate the tibiofemoral kinematics and contact pressures after PS-TKA with different PTS.Methods: Nine human cadaveric knee specimens were used for PS-TKA with the PTS of 3°, 6°, and 9°. The tibiofemoral kinematics and contact pressures were measured during knee flexion angle changing from 0 to 120° (with an increment of 10°) with an axial load of 1000 N at each angle.Results: The root mean square (RMS) of the tibiofemoral contact area and the mean and peak contact pressures during knee flexion were 586.2 mm², 1.85 MPa, and 5.39 MPa before TKA and changed to 130.2 mm², 7.56 MPa, and 17.98 MPa after TKA, respectively. Larger contact area and smaller mean and peak contact pressures were found in the joints with the larger PTS after TKA. The RMS differences of femoral rotation before and after TKA were more than 9.9°. The posterior translation of the lateral condyle with larger PTS was more than that with smaller PTS, while overall, the RMS differences before and after TKA were more than 11.4 mm.Conclusion: After TKA, the tibiofemoral contact area is reduced, and the contact pressure is increased greatly. Approximately 80% of the femoral rotation is lost, and only about 60% of the femoral translation of lateral condyle is recovered. TKA with larger PTS results in more posterior femoral translation, larger contact area, and smaller contact pressure, indicating that with caution, it may be beneficial to properly increase PTS for PS-TKA.

Background: Studies have given some pieces of evidence for the effect of total knee arthroplasty (TKA) on knee proprioception of patients with knee osteoarthritis (KOA), but their results were conflicting. This review was performed to provide an updated evidence-based meta-analysis investigating the influence of TKA on knee proprioception. Methods: The electronic databases including PubMed, Google Scholar, and the Cochrane Library were accessed from their inception to March 2020. Two reviewers identified the studies that met the selection criteria for this review. Information on study type, participants, follow-up time, and outcome measures was extracted. Methodological quality was independently assessed by two reviewers using the Cochrane Handbook 5.1.0. Eleven studies with 475 participants were included in the meta-analysis. Results: The I² index assessed the heterogeneity between studies. The results showed that the pooled standard mean difference of mean angle of error was − 0.58° (95% CI − 1 to – 0.16; P = 0.007; I² = 69%), and the joint position sense of KOA patients was better after TKA surgery than that before surgery. Pooled standard mean difference of displacement of center of pressure (COP) was − 0.39 (95% CI − 0.72 to − 0.06; P = 0.02; I² = 51%), and KOA patients had better static balance after TKA surgery than before surgery. Conclusions: To conclude, no standardized comprehensive evaluation protocol presently exists though different assessment tools are available to measure proprioception. Contrasting results were found in the literature since some studies found that TKA improves proprioception in KOA patients, while others found no difference in proprioception. These differences are seen whether the proprioception was assessed by joint position sense (JPS), or it was indirectly assessed by static balance. However, the lack of sufficient data on the threshold to detect passive movement (TTDPM) and dynamic balance made it difficult to draw a conclusion about whether or not the sense of motion improved after surgery. The method for measuring and evaluating knee joint force sense is worth paying attention, which will make progress with knee proprioception on TKA patients.

Knee valgus and varus morbidity is at the second top place in children lower limb deformity diseases. It may cause abnormal stress distribution. The magnitude and location of contact forces on tibia plateau during gait cycle have been indicated as markers for risk of osteoarthritis. So far, few studies reported the contact stress and force distribution on tibial plateau of valgus knee of children. To estimate the contact stresses and forces on tibial plateau of an 8-year old obese boy with valgus knee and a 7-year old healthy boy, three-dimensional (3D) finite element (FE) models of their left knee joints were developed. The valgus knee model has 36,897 nodes and 1,65,106 elements, and the normal knee model has 78,278 nodes and 1,18,756 elements. Paired t test was used for the comparison between the results from the 3D FE analysis method and the results from traditional kinematic measurement methods. The p value of paired t test is 0.12. Maximum stresses shifted to lateral plateau in knee valgus children while maximum stresses were on medial plateau in normal knee child at the first peak of vertical GRF of stance phase. The locations of contact centers on medial plateau changed 3.38 mm more than that on lateral plateau, while the locations of contact centers on medial plateau changed 1.22 mm less than that on lateral plateau for healthy child from the first peak to second peak of vertical GRF of stance phase. The paired t test result shows that there is no significant difference between the two methods. The results of FE analysis method suggest that knee valgus malalignment could be the reason for abnormal knee load that may cause knee problems in obese children with valgus knee in the long-term. This study may help to understand biomechanical mechanism of valgus knees of obese children.