Higher isokinetic quadriceps peak force is associated with a patient-acceptable symptom-state 1 and 3 years after ACL reconstruction.

PURPOSE: The main purpose was to determine cut-off values for absolute (QNm/kg) and relative (QLSI) isokinetic knee extensor (KE) strength for achieving a patient-acceptable symptom state (PASS) in the Knee injury and Osteoarthritis Outcome Score (KOOS) subscales and for different age groups to determine the association between QNm/kg and QLSI and PASS, at 1 and 3 years after an anterior cruciate ligament reconstruction (ACLR).

METHODS

PASS was defined as reaching cut-off values for all KOOS subscales. Data from follow-ups were extracted from a rehabilitation registry. Male and female patients were divided into two age groups based on their age at primary ACLR: 16-24 years and 25-65 years. Odds Ratios between the QNm/kg and QLSI cut-off values and achieving PASS were calculated. Receiver Operating Characteristic curves were constructed to determine the individual predictive capacity for achieving PASS of QNm/kg and of QLSI using the area under the curve (AUC).

RESULTS

Results from 755 and 145 patients (females = 51% and 52%; preinjury Tegner Activity level ≥6 = 82% and 74%) were used in the 1- and 3-year follow-up analyses. Reaching the cut-off values for the QNm/kg, ranging between ≥2.1 and ≥2.7, entailed between 2.09 and 5.12 times the odds of achieving PASS, across all groups at the 1-year follow-up. At the 3-year follow-up, the cut-off values of ≥3.4 and ≥2.6QNm/kg were associated with patients achieving PASS with acceptable accuracy (AUC = 0.700-0.780) in 16-41 year-old males and females.

CONCLUSION

At 1 year after ACLR, patients of both sexes and age groups reaching cut-off values for absolute KE strength had two to five times the odds, that were clinically relevant, to achieve PASS. Acceptable discriminative capacity was found for the absolute KE strength among male and female patients 16-24 years old, at 3 years after ACLR.

LEVEL OF EVIDENCE: Level III.