Study on the Relationship between Cartilage Injury of Knee Tibiofemoral Joint and Joint Axis Angle

Objective: To investigate the relationship between cartilage injury of knee tibiofemoral and femoral angle, tibial angle, femorotibial angle and joint space angle of knee joint. Methods: A retrospective analysis was made of 587 patients who underwent knee joint MRI examination in the Southern Hospital of Chengde Medical College from January 2017 to June 2017. 100 patients in the case group and 100 patients in the control group were randomly selected through inclusion and exclusion criteria. The femoral angle, tibial angle, femorotibial angle and joint space angle were measured in two groups, and the correlation angle data were statistically analyzed by SPSS19.0. The statistical methods included rank sum test, Spearman correlation test and ROC curve. Results: The femur angle, tibial angle, femorotibial angle and joint space angle of the case group were 83.22 (81.85 to 84.40) degrees, 95.60 (94.10 to 96.87) degrees, 179 (177.50 to 180.25) degrees and 1.92 (1.43 to 2.43) degrees, respectively. The femoral angle, tibial angle, femur tibial angle and joint clearance angle of the control group were 82.50 (81.70 to 83.60) degrees, 94.25 (93.20 to 95.52) degrees, 177.20 (175.90 to 178.17) degrees and 175.90 (0.50 to 0.95) degrees. There were significant differences in tibial angle, femorotibial angle and joint space angle between the two groups (P<0.05), but there was no significant difference in femoral angle (P>0.05), cartilage injury was positively correlated with the joint space angle (r_s=0.852, P<0.001), but not with tibial angle and femorotibial angle. The optimal threshold value, sensitivity and specificity of tibial angle were 95.15 degrees, 56% and 72%, respectively. The optimum critical value, sensitivity and specificity of femorotibial angle were 179.05 degrees, 49% and 92% respectively, and the optimum critical value, sensitivity and specificity of joint space angle were 1.255 degrees, 84% and 96%, respectively. Conclusion: The increase of tibial angle, femorotibial angle and joint space angle will affect the tibiofemoral joint cartilage and lead to the injury of tibiofemoral joint cartilage. And with the increase of joint space angle, the injury degree of the tibiofemoral joint cartilage is aggravated.