Several clinical and demographic factors were collectively associated with early physical activity after ACLR, but they explained only a small portion of the variance, suggesting additional factors likely influence early recovery.
Key Findings
Results
The combination of sex, kinesiophobia, subjective knee function, graft type, meniscus repair status, and quadriceps strength was significantly associated with daily step counts at 6 months after ACLR.
Multiple linear regression analysis was used to determine associations between these variables and PA outcomes.
The model for daily steps at 6 months yielded R² = 0.260, adjusted R² = 0.147, P = .042.
The model explained approximately 14.7% of the variance in daily steps when adjusted for the number of predictors.
No individual factor within the model was a significant predictor of daily steps (all Ps > .05).
Results
The combination of clinical and demographic variables was significantly associated with moderate-to-vigorous physical activity (MVPA) at both 4 and 6 months after ACLR.
At 4 months, the model for MVPA yielded R² = 0.249, adjusted R² = 0.142, P = .040.
At 6 months, the model for MVPA yielded R² = 0.272, adjusted R² = 0.162, P = .031.
No individual factor was a significant predictor of MVPA at either time point (all Ps > .05).
The adjusted R² values indicate the models explained approximately 14–16% of the variance in MVPA.
Results
No single clinical or demographic factor individually predicted physical activity at either 4 or 6 months after ACLR.
Predictors examined individually included sex, Tampa Scale of Kinesiophobia (TSK-11) scores, IKDC Subjective Knee Form scores, graft type, meniscus repair status, and quadriceps strength.
All individual predictor p-values were > .05 for both daily steps and MVPA at both time points.
This finding suggests that the collective combination of factors, rather than any single variable, drives the association with early PA.
Methods
The study population consisted of 63 participants aged 13 to 35 years who underwent ACLR and were assessed at 4 and 6 months postoperatively.
Mean age was 19.6 ± 5.0 years; 55.6% of participants were female.
Participants were recruited from an academic health science center and a private sports medicine clinic.
Physical activity was assessed using a 3-axis accelerometer worn during waking hours for 7 consecutive days at each time point.
Outcomes included daily step counts and MVPA minutes.
Background
The study identified a gap in knowledge about physical activity levels during the first 6 months after ACLR, a period when PA is understudied compared to the 6-month to 5-year window.
Prior literature has documented reduced PA between 6 months and 5 years post-ACLR, but PA during the first 6 months had received little attention.
The study design was a prospective cohort study with assessments specifically targeting the early postoperative period at 4 and 6 months.
The authors note that the collective variables explained only a small portion of variance, suggesting 'additional factors likely influence early recovery.'
Conclusions
The authors concluded that further research is needed to identify additional factors influencing early PA and to understand the long-term impact of early PA after ACLR.
The adjusted R² values across models ranged from approximately 0.142 to 0.162, indicating that the majority of variance in early PA remains unexplained.
The authors suggest 'additional factors likely influence early recovery' beyond those measured in this study.
The study called for future research into both unmeasured predictors and the downstream effects of early postoperative PA levels.
What This Means
This research suggests that recovering from ACL surgery involves complex influences on how physically active patients are during the first six months after the procedure. The study followed 63 patients aged 13–35 who had ACL reconstruction surgery and tracked their daily steps and moderate-to-vigorous physical activity using wearable accelerometers at 4 and 6 months post-surgery. Researchers also measured fear of movement (kinesiophobia), self-reported knee function, quadriceps muscle strength, type of graft used, and whether a meniscus repair was also performed.
When all these factors were combined in a statistical model, they were significantly linked to how active patients were — both in terms of daily steps and more intense physical activity. However, none of the individual factors on their own was a strong enough predictor to stand out, and the full set of variables together only explained about 14–16% of the differences in activity levels between patients. This means that the vast majority of what drives early physical activity after ACL surgery remains unknown.
This research suggests that simply measuring common clinical markers like muscle strength or fear of movement is not enough to predict who will be more or less active during early recovery. Additional, yet-to-be-identified factors — possibly psychological, social, or environmental — likely play important roles. Understanding these factors could help clinicians better support patients during this early and potentially critical phase of recovery, and future studies should investigate what else shapes activity levels and how early activity patterns affect long-term outcomes.
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Romero-Padron M, Weaver B, Sacco G, Werner D, Post A, Tao M, et al.. (2026). Predictors of Physical Activity Early After Anterior Cruciate Ligament Reconstruction.. Journal of athletic training. https://doi.org/10.4085/1062-6050-0467.25