Meniscus extrusion and lower leg alignment predict the distribution of subchondral bone density across the knee joint

Stress distribution is the pattern of mechanical load distribution, particularly between the medial and lateral compartments. Lower leg alignment and the meniscus play an important role in this distribution. CT-osteoabsorptiometry estimates stress distribution by analyzing the distribution pattern of subchondral bone density. This study aimed to explore the extent to which lower limb alignment and meniscal extrusion can explain the distribution of subchondral bone density.

This was a retrospective study including 92 patients (73 with osteoarthritis (OA) and 19 without OA). Lower limb alignment, meniscus-extrusion ratio (MER), and subchondral bone density were assessed using CT-osteoabsorptiometry. High-density areas (HDA) on the articular surface were quantitatively analyzed.

Hip-knee-ankle (HKA) angle, medial MER (MMER), lateral MER (LMER), and medial compartment HDA to total HDA ratio (medial ratio) were -4.3°, 46.8 %, 20.4 %, and 70.0 %, respectively. Multiple regression analysis revealed that HKA, MMER, and LMER were significant variables. The adjusted R2 of HKA, MMER, and LMER for the medial ratio was 0.80. The standardized coefficients for HKA, MMER, and LMER were -0.30, 0.40, and -0.41, respectively.

Lower leg alignment and meniscus extrusion explain 80% of the variance in the distribution of subchondral bone density. These findings indicate that both factors can account for approximately 80% of the estimated stress distribution as assessed by CT-osteoabsorptiometry. The distribution of subchondral bone density estimated by HKA and meniscus extrusion was useful for diagnosing and treating knee osteoarthritis.