To assess the changes in patient strength and function from 4- to 6-month assessments following ACLR, determine relationships between changes in strength to changes in subjective function, and identify factors that predict patients that fail to increase in strength. Prospective, Cohort Study. Controlled Laboratory. Forty-seven patients(27 female, 24.3 ± 11.1 years) completed a battery of performance assessments at approximately 4- and 6-months following primary ACLR (4.03 ±0 .49 and 6.46 ±0 .68 months). Subjective scores and isokinetic knee flexor and extensor strength were compared across visits. Patients were categorized per their ability to increase in strength beyond a previously defined threshold(0.22 Nm/kg). Binary logistic regression models were used to determine predictors of patients that failed to meet strength changes. Patients demonstrated improvements in patient-reported outcomes and strength measures between visits(P’s < 0.05). Higher age (B = −0.073, P = .039), lower pre-injury activity levels (B = 0.61, P = .022), and higher limb symmetry indexes (B = −0.044, P = .05) at 4-months were predictors of patients that did not achieve improvements in quadriceps strength between assessments. From 4- to 6-months post-ACLR, increases in subjective function, strength and symmetry were observed. High quadriceps symmetry at interim assessments without consideration of the magnitude of strength values could overestimate recovery of quadriceps function. •Higher age, lower activity, and higher LSI were predictors of low strength gains.•Interim assessments can provide clinical timelines to achieve goals post-ACLR.•High quadriceps LSI without considering strength could overestimate patient recovery.