Normative values of radiographic parameters in coronal plane lower limb alignment in a general Japanese population: A cross-sectional study in the Iwaki cohort

The purpose of this study was to estimate normative values of radiographic parameters in lower limb alignment and investigate age-related changes in lower limb alignment in a general Japanese population.

A total of 1474 knees in 737 volunteers (307 men and 430 women) who participated in the Iwaki cohort study were enroled. Standing anterior-posterior radiographs were assessed using the Kellgren-Lawrence (KL) grading scale, with KL ≥Grade 2 defined as osteoarthritis (OA). Radiographic parameters measured included the hip-knee-ankle angle (HKAA), femorotibial angle (FTA), mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), joint line convergence angle (JLCA) and weight-bearing line ratio (WBLR). Normative values were estimated as the mean ± 2 standard deviations for all participants without knee OA (KOA) aged 18-39 years, and associations with age were analyzed.

Normative values in overall young healthy participants were: HKAA, 1.8 ± 5.1°; FTA, 175.7 ± 6.5°; mLDFA, 86.4 ± 3.4°; MPTA, 85.8 ± 4.1°; JLCA, 1.2 ± 2.7° and WBLR, 39.7 ± 23.7%. The HKAA, FTA, MPTA and WBLR values differed significantly between sexes. In men without KOA, HKAA, FTA, MPTA and WBLR values correlated very weakly with age (r = -0.189 to 0.220). In contrast, only HKAA correlated very weakly with age in women without KOA (r = 0.096).

Estimated normative values of radiographic parameters in coronal plane lower limb alignment differed significantly between sexes. These data might be useful when considering the aetiology and therapeutic strategy for KOA.

Level II.