Varus alignment of the hip and knee 2 years after anterior cruciate ligament injury is associated with medial tibiofemoral osteoarthritis 3 years later

Purpose

To investigate if hip and knee alignment assessed 2 years after anterior cruciate ligament (ACL) injury is associated with compartment-specific radiographic knee osteoarthritis (OA) 3 years later.

Methods

An exploratory analysis was conducted in the knee ACL, nonsurgical versus surgical treatment (KANON) trial (ISRCTN84752559); 115 subjects with acute ACL injury were assessed at the 2-year follow-up; full-limb images of the injured leg were acquired, and the neck-shaft angle (NSA) and hip-knee-ankle angle (HKA) were measured. At the 5-year follow-up, weight-bearing tibiofemoral and patellofemoral radiographs were obtained. Radiographs were graded according to the OA Research Society International Atlas and Radiographic OA was defined as approximating Kellgren & Lawrence grade 2 or worse. Analysis of covariance adjusting for sex, age, body mass index, randomization and partial meniscectomy recorded at the 2-year follow-up was performed.

Results

In patients who had developed medial tibiofemoral OA at the 5-year follow-up, the NSA and the HKA at the 2-year follow-up were smaller (NSA, mean difference = −4.6° [95% confidence interval {CI} −7.9° to −1.1°]; HKA, mean difference = −2.3° [95% CI −4.2° to −0.4°]). No association was observed between the NSA or HKA at the 2-year follow-up and lateral tibiofemoral OA, nor patellofemoral OA at the 5-year follow-up.

Conclusion

A smaller NSA and HKA angle of the ACL injured leg (i.e., more varus hip and varus knee alignment) 2 years after the injury was associated with medial tibiofemoral radiographic OA 3 years later.

Level of Evidence

Level II exploratory post hoc analysis of an RCT.