This case series reveals considerable individual variability in self-reported knee-related QOL in young athletes over the 12 months following ACLR. More interestingly, our findings demonstrate that knee-related QOL of young athletes who undergo a sport-related ACLR does not always reach an acceptable symptoms state or normative values by 12 months. From an exploratory perspective, we provide preliminary evidence that 6-month knee symptoms may be related to 12-month knee-related QOL. These observations highlight the importance of assessing knee-related QOL to understand recovery from the perspective of the patient.
Given the paucity of knowledge in this area, a case series design allowed us to explore and subsequently reveal the unique knee-related QOL trajectory that individual patients experience in response to ACL injury and ACLR. As demonstrated in Fig. 2, the trajectory of knee-related QOL of the participants was highly variable with many experiencing fluctuations over the 12 months following ACLR. This dynamic trajectory emphasizes the complex and multidimensional nature of knee-related QOL. At any given time during rehabilitation, there are many physical (e.g., symptoms, activity, pain), psychological (e.g., fear of movement or re-injury, knee confidence), or social (e.g., isolation from sporting community, frustration and anxiety with RTS) factors that may result in improvements or deteriorations in the health- and knee-related QOL of young athletes.
Many of the participants in this case series did not consider their knee-related QOL as acceptable at 12 months following ACLR suggesting that young athletes can have deficits in knee-related QOL at what is typically considered the end of the rehabilitation period. This is congruent with the findings of other studies of similar cohorts following ACLR, including young American military students (mean KOOS QOL score 68.00 ± 20.51)[49] and young Swedish patients (mean KOOS QOL score 60.0 ± 23.7).[50] Furthermore, there is evidence to suggest that young female athletes exhibit deficits in health-related QOL after suffering a knee injury.[14, 51] Combined with previous evidence, our findings suggest that clinicians should regularly monitor health- and knee-related QOL throughout rehabilitation and adjust their treatment approach if they detect any deteriorations in QOL.
Previous reports have lead us to believe that individuals who successfully RTS after ACLR would report favourable health- and knee-related QOL whereas those who fail to RTS would report poor QOL.[29] However, this case series provides preliminary evidence of a discrepancy between successful RTS and reporting acceptable knee-related QOL which challenges this assumption. This discrepancy suggests that some participants remained unsatisfied with their knee-related QOL, regardless of returning to their main sport. It is possible that these individuals continue to experience issues with their knee function or have not yet achieved return to performance[52] despite resuming training or competitive play. Lifestyle adjustments and activity modification has been theorized to contribute to improved knee-related QOL in ACLR patients 5–16 years following surgery[12] and could be an option to discuss with individuals who report QOL deficits but wish to participate in sports. This apparent mismatch between successful RTS and acceptable knee-related QOL displayed by some young athletes following ACLR emphasizes the importance of addressing QOL on an individual basis while facilitating safe RTS during rehabilitation.
There is limited research examining factors that are associated with health- or knee-related QOL in young athletes with a sport-related ACL injury beyond RTS. Our exploratory analyses provide preliminary evidence that fewer knee symptoms (e.g., swelling, stiffness, and clicking) at 6 months may be associated with higher knee-related QOL at 12 months. One possible explanation for this finding is that participants who have fewer symptoms at the 6-month mark progress through rehabilitation with fewer setbacks than those with persistent symptoms.
Although previous research has reported a relationship between exercise and health-related QOL,[1, 17, 19–21] our exploratory analyses did not find evidence of an association between 6-month MVPA or kinesiophobia and 12-month knee-related QOL. This is likely due to a lack of statistical power. Despite the lack of association, exercise modification based on recovery stage and patient preference remains important for young athletes to ensure that they meet recommended physical activity levels throughout ACLR rehabilitation. Additionally, there is growing evidence that fear of movement and re-injury hinders physical function and restricts sport participation.[24, 25, 53] Kinesiophobia could be regarded as a negative factor influencing knee-related QOL if individuals with heightened fear of movement progress slowly through rehabilitation and experience delays in RTS. Future investigations should continue to assess the association between self-reported knee symptoms, physical activity, and self-reported kinesiophobia with health- and knee-related QOL to inform treatment strategies aimed at optimizing QOL following ACLR in young athletes.
Strengths and Limitations
Unlike previous studies which use RTS as the primary outcome of successful recovery after ACLR,[6, 10, 11] this case series provides an intriguing argument for an equally important target: acceptable knee-related QOL. By employing frequent three-month testing, this novel case series demonstrates the unique and dynamic trajectory of knee-related QOL that young athletes may experience over the first year following ACLR. To the best of our knowledge, this case series is one of the first studies to explore physical and psychological factors that may be associated with knee-related QOL in young athletes who have undergone ACLR. It is important to understand the changes in knee-related QOL in order to generate strategies to combat any associated physical, psychological, environmental, and social deficits.
As with any case series, the limited convenience sample is associated with a high possibility of selection bias and type 1 error. Given that all our participants came from one university-based sports medicine clinic in an urban Canadian city, it is unlikely that our findings are generalizable to all young athletes who undergo ACLR. The exploratory analyses of the association between knee symptoms, kinesiophobia, and MPVA at 6-months and knee-related QOL at 12 months was not adequately powered and should be interpreted with caution. Specifically, it is possible that the association identified between 6-months KOOS symptoms and 12 months KOOS QOL subscale scores may be due to a type I error (false positive), another variable (e.g., amount and quality of rehabilitation), or the previous observation that the KOOS symptoms and KOOS QOL subscales are moderately correlated.[15, 16] Lastly, it is important to highlight that the four items contained in the KOOS QOL subscale likely do not capture the breadth and complexity of knee-related QOL. Future investigations should consider including additional instruments to further assess knee-related QOL (e.g., Anterior Cruciate Ligament-Quality of Life questionnaire) and health-related QOL (e.g., Youth Quality of Life instrument) to provide a more complete understanding of QOL in youth populations.[54–56]
Future Directions
There is a paucity of research examining health- and knee-related QOL and its determinants in young athletes in the first 12 months following ACLR. Research should continue to evaluate both health- and knee-related QOL in this population with a more rigorous study design, appropriate sample size and comprehensive measures of health- and knee-related QOL. Additional factors should be examined in attempt to identify determinants of youth QOL (e.g., sex, pre-operative rehabilitation, concomitant injuries, knee confidence, social support). A richer understanding of QOL and what factors might influence it can contribute to tailored interventions that optimize both short- and long-term QOL in young athletes.