OBJECTIVE Knee cartilage damage is often linked to mechanical overloading. However, cartilage requires mechanical load to remain healthy, suggesting that underloading may be detrimental. This study was undertaken to examine knee overloading and underloading by defining cumulative load as the joint effects of body mass index (BMI) and daily walking, and examine the relationship between cumulative load and worsening cartilage damage over 2 years. METHODS We used data from the Multicenter Osteoarthritis Study. Steps/day, measured by accelerometry, and BMI were calculated at the 60-month visit. Cartilage damage on magnetic resonance imaging was semiquantitatively scored using the Whole-Organ Magnetic Resonance Imaging Score (WORMS) at the 60-month and 84-month visits; worsening damage was defined as increased WORMS between visits. Risk ratios (RRs) and 95% confidence intervals (95% CIs) were calculated using binomial regression, with adjustment for potential confounders. RESULTS Our study included 964 participants, 62% of whom were female, with a mean ± SD age of 66.9 ± 7.5 years. Participants had a mean ± SD BMI of 29.7 ± 4.8 kg/m2 and walked a mean ± SD of 7,153 ± 2,591 steps/day. Participants who walked a moderate number of steps/day (6,000-7,900) or a high number of steps/day (>7,900) and had a high BMI (>31 kg/m2 ) had a greater risk of worsening medial tibiofemoral (TF) damage (RR 2.83 [95% CI 1.46-5.48] and RR 2.61 [95% CI 1.50-4.54], respectively) compared with those who walked similar steps/day and had a low BMI (18-27 kg/m2 ). Participants with a low number of steps/day (<6,000) and a low BMI had a greater risk of worsening medial TF and lateral patellofemoral (PF) damage (RR 2.03 [95% CI 1.06-3.92] and RR 2.28 [95% CI 1.06-4.85], respectively) compared with those who walked a high number of steps/day and had a low BMI. Effect estimates for other compartments of the knee did not reach statistical significance. CONCLUSION This study provides preliminary evidence that both overloading and underloading may be detrimental to medial TF cartilage, and underloading may be detrimental to lateral PF cartilage.

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使用累积负荷来解释体重指数和每日步行如何与两年内恶化的膝关节软骨损伤相关：MOST 研究。

目的 膝关节软骨损伤通常与机械过载有关。然而，软骨需要机械负荷才能保持健康，这表明负荷不足可能是有害的。本研究通过将累积负荷定义为体重指数 (BMI) 和每日步行的联合效应来检查膝关节超负荷和欠负荷，并检查 2 年内累积负荷与软骨损伤恶化之间的关系。方法 我们使用来自多中心骨关节炎研究的数据。在 60 个月就诊时计算通过加速度计测量的步数/天和 BMI。在 60 个月和 84 个月就诊时，使用全器官磁共振成像评分 (WORMS) 对磁共振成像的软骨损伤进行半定量评分；恶化的损害被定义为访问之间的蠕虫增加。使用二项式回归计算风险比 (RR) 和 95% 置信区间 (95% CI)，并对潜在的混杂因素进行了调整。结果 我们的研究包括 964 名参与者，其中 62% 为女性，平均 ± SD 年龄为 66.9 ± 7.5 岁。参与者的平均 ± SD BMI 为 29.7 ± 4.8 kg/m2，步行平均 ± SD 为 7,153 ± 2,591 步/天。每天步行中等步数 (6,000-7,900) 或每天步行较多 (>7,900) 且 BMI 较高 (>31 kg/m2) 的参与者发生内侧胫股骨 (TF) 恶化的风险更大与每天步行相似步数且 BMI 较低 (18-27 kg/m2) 的人相比，损伤（分别为 RR 2.83 [95% CI 1.46-5.48] 和 RR 2.61 [95% CI 1.50-4.54]）。每天步数较少的参与者（<6，000）和低 BMI 与那些每天走很多步，BMI 很低。膝关节其他部分的效果估计没有达到统计学意义。结论 本研究提供了初步证据，即超载和欠载都可能对内侧 TF 软骨有害，而欠载可能对外侧 PF 软骨有害。