Failure to Achieve the Patient Acceptable Symptom State 2 Years After Anterior Cruciate Ligament Reconstruction Reflects Poor Knee Loading Patterns

Abstract

Background:

Clinical outcomes vary after anterior cruciate ligament reconstruction (ACLR), and osteoarthritis (OA) risk remains high. Consequently, early identification is needed of patients who show potentially modifiable loading patterns suggestive of higher risk for worse outcomes and pre-OA.

Hypothesis:

This study tested the hypothesis that (1) Patient Acceptable Symptom State (PASS) status derived from the Knee injury and Osteoarthritis Outcome Score (KOOS) is associated with knee loading patterns 2 years after ACLR and (2) failure to achieve the PASS reflects worse knee loading mechanics.

Study Design:

Cross-sectional study; Level of evidence, 4.

Methods:

Fifty-nine participants with unilateral ACLR (mean ± SD, 33 ± 10 years; 33 [56%] females) assessed by gait analysis and KOOS at 2-year follow-up were categorized according to published KOOS PASS thresholds. Independent t tests compared knee flexion moment (KFM), knee adduction moment (KAM), and their relative percentage contributions to total joint moment between PASS statuses. Associations between loading metrics and PASS were examined using mixed effects logistic regression.

Results:

Although PASS rates for KOOS subscales ranged from 42% to 100%, only 36% of participants achieved the PASS on all 5 KOOS subscales. Patients achieving the PASS on a given KOOS subscale exhibited different loading patterns when compared with those who did not (PASS-no). Specifically, PASS-no for pain and knee-related quality of life showed lower KFM (P ≤ .024), and PASS-no for activities of daily living showed higher KAM (P = .009). Lower KFM and higher KAM were associated with lower likelihood of achieving the PASS on the KOOS subscales (P ≤ .035). A shift from KFM dominance to KAM dominance in PASS-no, as suggested by lower percentage KFM (P ≤ .026) and higher percentage KAM (P ≤ .047) to total joint moment, was consistent across the KOOS subscales for pain, knee related quality of life, and function in activities of daily living. Additionally, failure to achieve the PASS on some KOOS subscales was associated with more varus alignments (P ≤ .043), earlier ACLR (P = .006), and lower Tegner activity levels (P = .043).

Conclusion:

Nearly two-thirds of ACLR recipients failed to achieve the PASS on all KOOS subscales 2 years after ACLR. Failure to achieve the PASS was associated with knee loading patterns linked to worse longer-term outcomes and greater OA risk.

Clinical Relevance:

The KOOS PASS criterion is an accessible screening tool for identifying patients in need of further assessment and treatment to improve knee health and reduce OA risk after ACLR.