Relationships between Morphological Changes of Lower Limbs and Gender During Medial Compartment Knee Osteoarthritis

To evaluate the dynamic changes of key morphology indicators of the lower extremities in the coronal plane with progressing medial compartment knee osteoarthritis (KOA) with an emphasis on gender-dependent regional differences.

The radiographs of patients with non-traumatic knee pain and varying degrees of genu varus were reviewed. Radiographs were studied in 1538 lower limbs of 883 consecutive patients who visited our hospital from January to July 2017; all patients had long-standing anteroposterior image-splicing radiographs taken of their lower limbs. Morphological indicators of bones and joints that can change the alignment of lower limbs or reflect cartilage wear and soft-tissue relaxation were selected and measured with the help of picture archiving and communication systems. After comparing the data of different genders, the data of males and females was separated into three age groups, <40 years, 40-60 years, >60 years respectively, and then compared among age groups using the Kruskal-Wallis and Mann-Whitney U tests. Scatterplots of age and all the measurements were drawn to determine the strength of the relations. The Pearson correlation test was performed to reveal correlations of measurements and age.

Femoral bowing angle (FBA) and joint line convergence angle (JLCA) have obvious differences between different genders (P = 0.001, 0.000, respectively). This suggests that females have greater femoral curvature and joint space angle than males. Significant differences were found in hip-knee-ankle angle (HKA), FBA, distal femoral valgus resection angle (DFVRA), medial proximal tibial angle (MPTA), JLCA, and minimum joint space width (min-JSW) by age groups in females (P = 0.000, 0.000, 0.000, 0.000, 0.003, 0.002, respectively). The difference of mechanical medial distal femoral angle (mMDFA) was significant with P values less than 0.05 deemed significant (P = 0.030). Significant correlations were found between age and all measurements (r = -0.166, 0.253, 0.270, -0.147, 0.089, -0.105, -0.076, respectively, P < 0.01). Whereas, the difference in min-JSW by age group was the only significant one in males (P = 0.001), and no significant correlation was found between age and measurements (r = -0.107, 0.041, 0.134, -0.067, 0.079, -0.134, -0.098, respectively, P > 0.01).

As KOA progressed, both dynamic deformation of lower extremities and degeneration of articular cartilage could be found in females, while no obvious dynamic deformations were found in males. Dynamic deformation of lower extremities was the important feature and the major causative factor of KOA in females.