This study primarily investigates the correlation between KOA MME and the lower limb alignment parameters. Patients included in the study all suffer from KOA with MME, thereby limiting the applicability of the findings to cases suspected of KOA with MME presence only. This does not reflect the characteristics of all KOA patients. However, research by Özdemir et al[24] found that 64% of KOA patients exhibit MME. Consequently, our results can reflect the alignment characteristics of the vast majority of KOA patients.
MME was categorized into mild and severe groups for comparison of differences between groups; Pearson correlation analysis was initially used to explore the correlation between lower limb alignment parameters and KOA MME, followed by a multivariate stepwise regression analysis to re-examine the independence among various parameters. Ultimately, a binary logistic regression model was employed to determine the parameters influencing KOA MME. Higher JLCA, AMA, and mLDFA were identified as significant alignment factors increasing the degree of MME, all positively correlated with MME, indicating that with increasing angles of JLCA, AMA, and mLDFA, the distance of MME also increases. Severe meniscal compression occurs at JLCA = 3.55°, AMA = 6.33°, and mLDFA = 86.34°, serving as the threshold for severe MME. Abnormal lower limb alignments directly affect the degree of meniscal compression by altering the shearing stress on the knee meniscus[25]. Additionally, changes in shearing stress can lead to inappropriate joint mechanical loads, manifesting OA characteristics in the cartilage, degradation of extracellular matrix macromolecules, and reduced cartilage cell protein expression[26], thus promoting the development of KOA. Therefore, investigating the correlation between lower limb alignment parameters and MME can fundamentally prevent the progression of KOA.
High Tibial Osteotomy (HTO), a classical surgery in "knee preservation" treatments[27], has been proven effective in correcting lower limb alignment and relieving joint pain. Research on abnormal alignment parameters can provide reference standards for HTO. A study by Young Gon Na et al[28] on 80 HTO patients revealed a mean postoperative reduction of 0.9° in JLCA, emphasizing that surgeons should consider changes in JLCA during preoperative planning and intraoperative procedures for HTO. Our results indicate that when a KOA patient's JLCA exceeds 3.55°, MME significantly increases; thus, incorporating JLCA > 3.55° into surgical standards for HTO could reduce the progression of KOA. Similarly, AMA > 6.33° and mLDFA > 86.34° should also be considered for guiding HTO indications and postoperative lower limb alignment metrics. Not only should HTO consider changes in alignment parameters, but novel non-invasive methods under exploration, such as custom orthotics and knee braces, should also take alignment into consideration. Studies have shown that using 3D-printed insoles for patients with normal arches can reduce both the medial force on the ankle and knee joints, thereby increasing foot comfort[29]. This is likely due to changes in ankle inversion angle affecting lower limb alignment and knee joint shearing stress. However, most studies have focused on normal arches, with limited evidence for flat feet. Incorporating considerations of knee joint alignment parameters when customizing orthotics for flat feet could open new research areas. Moreover, when designing 3D-printed insoles for normal arches, keeping within the angles of JLCA, AMA, and mLDFA can maximally reduce ankle inversion, potentially reducing ankle damage and limiting KOA progression.
This study, being retrospective, faces biases and limitations in data collection and analysis. Moreover, since the participant population is from the East China region, the scope is somewhat limited, potentially affecting the diversity in patient demographics, disease severity, and treatment methods. Addressing these limitations in future research could deepen our understanding of biomechanical factors affecting KOA and MME, ultimately improving clinical management and patient outcomes.
In summary, lower limb alignment, especially factors such as AMA, JLCA, and mLDFA, significantly impacts the biomechanical balance of the knee joint. Changes in these parameters can significantly affect the internal stress distribution within the knee joint[28, 30, 31], thereby influencing MME. Adjustments in lower limb alignment play a crucial role in preventing MME and KOA. With a deeper understanding of knee joint biomechanics and continuous advancements in treatment techniques, effective prevention and management of MME and KOA, along with related diseases, can be achieved through appropriate alignment adjustment strategies.