Table 3

Causation criteria and scores for the identified knee joint loading exposures

Knee joint load exposureStrength* Summary or OR (95% CI)Consistency† N (%)Temporality‡ N (%)Biological gradient§ N (%)Causation score (number of criteria met)
Peak KAM1.90 (0.85 to 4.25)2/4 (50%)1/4 (25%)0/4 (0%)0
KAM impulse0.42 (0.12 to 1.48)¶−**0/1 (0%)1/1 (100%)−††
Peak overall compressionNo group difference−**1/1 (100%)0/1 (0%)−††
  • *Strong association is defined as a pooled OR ≥5 with lower 95% CI excluding 2.0. Moderate association is any statistically significant association.

  • †Consistency is defined as ≥75% of associations showing strong or moderate associations.

  • ‡In cohort studies it is difficult if not impossible to ensure temporal correctness because participants in the studies are expected to walk daily and are, therefore, exposed to knee joint loading throughout the observation period. In the current analysis, the temporality criterion is satisfied in studies that relate baseline knee joint loading exposures to disease progression over time from that baseline and demonstrate a statistically significant association with structural disease progression.

  • §Biological gradient is defined as demonstrated when the rate of progression increases (or decreases) incrementally as dose of exposure increases.

  • ¶Estimate based on one cohort study29 assessing baseline KAM impulse to progression of cartilage defects assessed by semiquantitative grading of MRI.

  • **Consistency not possible to assess with only one cohort.

  • ††Causality score not calculated because only one study available.

  • KAM, knee adduction moment.