Abstract
OBJECTIVES: After anterior cruciate ligament reconstruction (ACLR) athletes commonly report increased fear of re-injury and below normal knee function. Implementing a post-operative training protocol (ACL-SPORTS Training) to improve patient perceived knee function, may improve short term outcomes after surgery. Identifying pre-training measures that predict normal knee function after training may allow us to determine who may respond to the treatment intervention. The purpose of this study was to identify which pre-training patient reported measures of fear of re-injury and knee function predict normal knee function after ACL-SPORTS Training. METHODS: Thirty subjects (13 normal knee function, 17 below normal knee function) with an isolated ACLR, who participated in jumping, cutting and pivoting activities ≥ 50 hrs/yr prior to their injury, were included in this study. Study enrollment required ≥ 80% quadriceps strength, minimal knee joint effusion and ≥ 12 weeks after surgery. Subjects were randomized to two treatment groups. The standard care group received 10 training sessions including quadriceps strengthening exercises, ACL injury prevention exercises and agility drills. The perturbation group received all standard care exercises augmented with perturbation training. Pre-training patient reported measures of fear of re-injury included the Tampa Scale of Kinesiophobia (TSK-11) and the ACL-Return to Sport after Injury (ACL-RSI). Knee function was measured with the Knee injury and Osteoarthritis Outcome Score (KOOS4), as a mean of the pain, symptoms, sports and recreation, and quality of life subscales. Each subscale (KOOS-pain, KOOS-symptoms, KOOS-ADLs, KOOS-sport/rec, KOOS-QoL) was also assessed individually. After the training program was completed, self-reported knee function was measured with the International Knee Documentation Committee subjective knee form (IKDC 2000). Age- and sex-matched normative values were determined based on the top 15th percentile of healthy measures. A binary logistic regression was used to determine which variables significantly predicted normal knee function after training. RESULTS: There was no difference between those who achieved normal knee function and those with below normal knee function for age at the time of surgery (p=0.78), BMI at post-training testing (p=0.71), sex (p=0.13) or time from surgery to post-training testing (p=0.12) and treatment group did not significantly predict normal knee function after training (p=0.96). Higher pre-training ACL-RSI and KOOS4 scores significantly predicted 37.5% and 38.6% of the variance of achieving normal knee function, respectively. Together higher pre-training scores predicted 49.5% of the variance. Of the individual KOOS subscales, higher pre-training KOOS-pain, KOOS-symptoms, KOOS-ADLs, and KOOS-QoL scores significantly predicted 23.8%, 35.9%, 39.5% and 35.6% of the variance of achieving normal knee function, respectively. CONCLUSION: Prior to this ACL-SPORTS training protocol higher ACL-RSI, KOOS4, KOOS-pain, KOOS-symptoms, KOOS-ADLs and KOOS-QoL subscales were able to predict which individuals achieved normal knee function after this treatment protocol. Identifying individuals who do not achieve normal knee function after training may allow us to identify a subgroup of patients that require additional interventions to achieve normal knee function.