Background/Purpose: Tibiofemoral radiographic osteoarthritis (TFROA) can occur in medial, lateral, or both compartments. While several risk factors have been found to be associated with the risk of TFROA, no study has formally examined if the risk factor profile (or magnitude of association) differs among the subtype of TFROA (i.e., medial and lateral TFROA). Elucidation of the relationship between the putative risk factors and the occurrence of each subtype of TFROA can improve our understanding of its causality, thereby guiding the development of precision medicine and strategies.

Methods: Among participants in the Osteoarthritis Initiative, we identified subjects without compartment-specific ROA in either knee at baseline (i.e., joint space narrowing =0 in both medial and lateral tibiofemoral compartments). Subjects were followed for up to 72 months with annual bilateral knee X-rays. Medial or lateral TFROA was defined by Kellgren and Lawrence grade ≥2 and joint space narrowing ≥1 in the respective compartments. We examined traditional risk factors (i.e., sex, age, body mass index [BMI], race, knee injury) on the risk of TFROA subtypes (i.e., medial vs. lateral TFROA) and tested the heterogeneity of TFROA subtypes using the duplication method for nominal polytomous logistic regression.

Results: Of 2874 subjects (5748 knees) without TFROA in either compartment at baseline (mean age=59.9, 58.9% women, mean BMI=27.8 kg/m², 29.0% with a history of knee injury), 306 knees (5.3%) developed medial, 84 (1.5%) developed lateral, and 5 (0.1%) developed bilateral compartment TFROA. Women had a 3.7 times higher risk of developing lateral compartment TFROA than men (RR=3.70, 95% CI: 2.08-6.57), whereas no such association existed on the risk of medial compartment TFROA, suggesting a different impact of sex on the risk of TFROA between the two subtypes (P for heterogeneity < 0.001) (Table). A higher BMI tended to have a larger association with the risk of medial compartment TFROA than with lateral compartment TFROA (P for heterogeneity=0.06). Furthermore, non-Whites appeared to be at a higher risk for lateral compartment TFROA than Whites, but not for medical compartment TFROA (P for heterogeneity=0.09). Associations with age and a history of knee injury did not differ between medial and lateral compartment involvement (Table).

Conclusion: The risk factor profile for medial compartment TFROA may differ from that for lateral disease. Wide hips among women might explain high risk of lateral compartment TFROA whereas weight gravity falling more on the medial side might explain high risk of medial compartment TFROA. These findings suggest that personalized preventive and treatment strategies may be feasible for individuals with differential susceptibility to a specific subtype of TFROA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/difference-in-risk-factor-profile-between-medial-and-lateral-compartment-involvement-in-tibiofemoral-knee-osteoarthritis/