When Fear Doesn’t Follow Function: What ACL Athletes Feel at Return to Sport
After months of grueling rehab following an ACL reconstruction, athletes face a defining moment: clearance to return to sport. Their strength numbers check out. Their hop tests pass. Their balance holds. And yet, for many, the fear of getting hurt again lingers — seemingly untouched by the physical progress they’ve made. A recent cross-sectional study published in the International Journal of Sports Physical Therapy took a closer look at exactly this disconnect.
What the Study Set Out to Do
Researchers at a single academic institution recruited 27 participants — 14 males and 13 females — who had undergone ACL reconstruction and were assessed within two months of receiving clearance for unrestricted return to sport (RTS). All participants completed a comprehensive 90-minute battery of tests measuring lower extremity range of motion, isometric and isokinetic strength, dynamic postural stability, hop test performance, and biomechanics during a single-leg stop-jump task. Fear of reinjury was quantified using the Tampa Scale of Kinesiophobia-11 (TSK-11), a well-validated 11–44 point scale where higher scores indicate greater fear of movement due to pain or reinjury. Participants were divided into a low fear group (TSK-11 < 17, n = 8) and a high fear group (TSK-11 ≥ 17, n = 19) based on a cutoff established by prior literature.
Key Findings
1. High fear was common — but scores were still relatively low overall.
The average TSK-11 score across the entire cohort was 19.22 ± 4.78, with 70% of participants falling into the “high fear” category. However, the authors note this cohort’s scores are consistent with those reported in other studies of athletes who successfully returned to sport, and would still fall below cutoffs used in chronic pain or injury populations that consider scores of 25 or higher as clinically elevated.
2. Physical function was nearly identical between the two groups.
With one exception, no statistically significant differences were found between the high and low TSK-11 groups across range of motion, hip and knee strength, dynamic postural stability, limb symmetry index, or hop test performance. Effect sizes for most of these variables were small, suggesting the groups were functionally very similar despite their different fear levels.
3. Gastrocnemius flexibility was the lone standout.
The only non-biomechanical variable that separated the groups was gastrocnemius extensibility measured by the weight-bearing ankle dorsiflexion lunge test, which showed a statistically significant difference with a large effect size favoring the low-fear group. The authors do not offer a definitive explanation for this finding.
4. Biomechanics told a similar story — mostly.
In the subset of 16 participants with usable biomechanical data from the stop-jump task, maximum knee valgus angle was the only variable to reach statistical significance, and it showed a large effect size. Maximum tibial shear force also demonstrated a large effect size, though it did not reach statistical significance — a finding the authors attribute in part to the reduced sample size for that analysis.
5. Fear may reflect something beyond physical readiness.
The study’s central takeaway is that elevated kinesiophobia at RTS appears to be influenced by factors outside the neuromuscular, musculoskeletal, and biomechanical domains. The authors reference a prospective study by Paterno et al. in which patients with high kinesiophobia were found to be thirteen times more likely to sustain a second ACL injury after RTS — underscoring why psychological readiness warrants its own attention, separate from physical benchmarks.
Limitations the Authors Acknowledged
The authors are candid about the study’s constraints. The sample size was small (27 participants overall, with only 16 contributing usable biomechanical data), and no a priori power analysis was conducted — meaning the study was likely underpowered to detect smaller between-group effects, increasing the risk of missing real differences. The authors explicitly describe the biomechanical findings as exploratory and intended to inform future, more adequately powered investigations.
Additionally, the cutoff score used to classify “high” versus “low” kinesiophobia is not universally accepted, and the cohort — consisting entirely of athletes who had already been cleared for RTS — may represent a self-selected group with naturally lower fear levels. Athletes with more significant kinesiophobia may have never reached RTS clearance, which could limit how broadly these findings generalize.
Why This Matters
For clinicians working in orthopedics, sports rehab, or performance settings, this study raises a practical question: if two athletes pass the same physical benchmarks but report very different levels of fear, what is driving that fear — and what should be done about it? This study doesn’t answer that question, but it adds weight to the argument that passing a hop test is not the same as being psychologically ready to play.
Disclosure: This post is based exclusively on Lennon AR, Faherty MS, Killelea C, Le DT, and Sell TC, “An Examination of the Relationship Between Fear of Reinjury and Neuromuscular, Musculoskeletal, and Biomechanical Characteristics at the Time of Return to Sport,” published in the International Journal of Sports Physical Therapy (2026). All findings, statistics, and conclusions presented here reflect that study alone and should not be interpreted as a consensus of the broader scientific literature.
Glenn Wellmann DPT 
Leave a comment