Jacob J. Capin

Gait mechanics and second ACL rupture: Implications for delaying return-to-sport

Second anterior cruciate ligament rupture is a common and devastating injury among young women who return to sport after ACL reconstruction, but it is inadequately understood. The purpose of this study was to compare gait biomechanics and return‐to‐sport time frames in a matched cohort of young female athletes who, after primary ACLR, returned to sport without re‐injury or sustained a second ACL injury. Approximately 6 months after primary reconstruction, 14 young women (age 16 ± 2 years) involved in jumping, cutting, and pivoting sports underwent motion analysis testing after physical therapy and impairment resolution. Following objective return‐to‐sport clearance, seven athletes sustained a second ACL rupture within 20 months of surgery (13.4 ± 4.9 months). We matched them by age, sex, and sport‐level to seven athletes who returned to sports without re‐injury. Data were analyzed using a previously validated, EMG‐informed, patient‐specific musculoskeletal model. Compared to athletes without re‐injury, athletes who sustained a second ACL injury received surgery sooner (p = 0.023), had post‐operative impairments resolved earlier (p = 0.022), reached criterion‐based return‐to‐sport benchmarks earlier (p = 0.024), had higher body mass index (p = 0.039), and walked with lower peak knee flexor muscle forces bilaterally (p = 0.021). Athletes who sustained a second injury also tended to walk with larger (p = 0.089) and more symmetrical peak knee flexion angles and less co‐contraction, all indicative of a more normal gait pattern. Statement of Clinical Significance: Delayed return‐to‐sport clearance even in the absence of gait or clinical impairments following primary ACL reconstruction may be necessary to mitigate second ACL injury risk in young women.

Report of the Clinical and Functional Primary Outcomes in Men of the ACL-SPORTS Trial: Similar Outcomes in Men Receiving Secondary Prevention With and Without Perturbation Training 1 and 2 Years After ACL Reconstruction

BackgroundAthletes often are cleared to return to activities 6 months after anterior cruciate ligament (ACL) reconstruction; however, knee function measures continue to improve up to 2 years after surgery. Interventions beyond standard care may facilitate successful return to preinjury activities and improve functional outcomes. Perturbation training has been used in nonoperative ACL injury and preoperative ACL reconstruction rehabilitation, but has not been examined in postoperative ACL reconstruction rehabilitation, specifically return to sport rehabilitation.Questions/PurposesThe purpose of this study was to determine whether there were differences at 1 and 2 years after ACL reconstruction between the male SAP (strengthening, agility, and secondary prevention) and SAP+PERT (SAP protocol with the addition of perturbation training) groups with respect to (1) quadriceps strength and single-legged hop limb symmetry; (2) patient-reported knee outcome scores; (3) the proportion who achieve self-reported normal knee function; and (4) the time from surgery to passing return to sport criteria.MethodsForty men who had completed ACL reconstruction rehabilitation and met enrollment criteria (3–9 months after ACL reconstruction, > 80% quadriceps strength limb symmetry, no pain, full ROM, minimal effusion) were randomized into the SAP or SAP+PERT groups of the Anterior Cruciate Ligament-Specialised Post-Operative Return to Sports trial (ACL-SPORTS), a single-blind randomized clinical study of secondary prevention and return to sport. Quadriceps strength, single-legged hopping, the International Knee Documentation Committee (IKDC) 2000 subjective knee form, Knee Injury and Osteoarthritis Outcome Score (KOOS)-sports and recreation, and KOOS-quality-of-life subscales were collected 1 and 2 years after surgery by investigators blind to group. Athletes were categorized as having normal or abnormal knee function at each time point based on IKDC score, and the time until athletes passed strict return-to-sport criteria was also recorded. T-tests, chi square tests, and analyses of variance were used to identify differences between the treatment groups over time.ResultsThere were no differences between groups for quadriceps symmetry (1 year: SAP = 101% ± 14%, SAP+PERT = 101% ± 14%; 2 years: SAP = 103% ± 11%, SAP+PERT = 98% ± 14%; mean differences between groups at 1 year: 0.4 [−9.0 to 9.8], 2 years = 4.5 [−4.3 to 13.1]; mean difference between 1 and 2 years: SAP = −1.0 [−8.6 to 6.6], SAP+PERT = 3.0 [−4.3 to 10.3], p = 0.45) or single-legged hop test limb symmetry. There were no clinically meaningful differences for any patient-reported outcome measures. There was no difference in the proportion of athletes in each group who achieved normal knee function at 1 year (SAP 14 of 19, SAP+PERT 18 of 20, odds ratio 0.31 [0.5–19.0]; p = 0.18); however, the SAP+PERT group had fewer athletes with normal knee function at 2 years (SAP 17 of 17, SAP+PERT 14 of 19, p = 0.03). There were no differences between groups in the time to pass return to sport criteria (SAP = 325 ± 199 days, SAP+PERT = 233 ± 77 days; mean difference 92 [−9 to 192], p = 0.09).ConclusionsThis randomized trial found few differences between an ACL rehabilitation program consisting of strengthening, agility, and secondary prevention and one consisting of those elements as well as perturbation training. In the absence of clinically meaningful differences between groups in knee function and self-reported outcomes measures, the results indicate that perturbation training may not contribute additional benefit to the strengthening, agility, and secondary prevention base of the ACL-SPORTS training program.Level of EvidenceLevel II, therapeutic study.

Gait mechanics in those with/without medial compartment knee osteoarthritis 5 years after anterior cruciate ligament reconstruction

The objective of the study was to evaluate differences in gait mechanics 5 years after unilateral anterior cruciate ligament reconstruction surgery, for non‐osteoarthritic (n = 24) versus osteoarthritic (n = 9) subjects. For the involved knee, the osteoarthritic group demonstrated significantly lower peak knee flexion angles (non‐osteoarthritic = 24.3 ± 4.6°, osteoarthritic = 19.1 ± 2.9°, p = 0.01) and peak knee flexion moments (non‐osteoarthritic = 5.3 ± 1.2% Body Weight × Height, osteoarthritic = 4.4 ± 1.2% Body Weight × Height, p = 0.05). Differences in peak knee adduction moment approached significance, with a higher magnitude for the osteoarthritic group (non‐osteoarthritic = 2.4 ± 0.8% Body Weight × Height, osteoarthritic = 2.9 ± 0.5% Body Weight × Height, p = 0.09). Peak medial compartment joint load was evaluated using electromyography‐informed neuromusculoskeletal modeling. Peak medial compartment joint load in the involved knee for the two groups was not different (non‐osteoarthritic = 2.4 ± 0.4 Body Weight, osteoarthritic = 2.3 ± 0.6 Body Weight). The results suggest that subjects with dissimilar peak knee moments can have similar peak medial compartment joint load magnitudes. There was no evidence of inter‐limb asymmetry for either group. Given the presence of inter‐group differences (non‐osteoarthritic vs. osteoarthritic) for the involved knee, but an absence of inter‐limb asymmetry in either group, it may be necessary to evaluate how symmetry is achieved, over time, and to differentiate between good versus bad inter‐limb symmetry, when evaluating knee gait parameters.

Functional and Patient-Reported Outcomes Improve Over the Course of Rehabilitation: A Secondary Analysis of the ACL-SPORTS Trial:

Background: The Anterior Cruciate Ligament–Specialized Post-Operative Return to Sports (ACL-SPORTS) randomized controlled trial was designed to address deficits in functional and patient-reported outcomes. The trial examined the effects of a secondary ACL prevention program that included progressive strengthening, agility training, plyometrics (SAP), and other components of current primary prevention protocols, with perturbation training (SAP + PERT group) and without PERT (SAP group). A secondary purpose of this study was to examine whether study outcomes differed between men and women. Hypotheses: (1) Athletes in both the SAP and SAP + PERT groups will have improved knee function and patient-reported outcome measures from pre- to posttraining, (2) the SAP + PERT group would have higher outcome scores than the SAP group, and (3) outcomes will differ by sex. Study Design: Randomized controlled trial (NCT01773317). Level of Evidence: Level 2. Methods: A total of 79 athletes (39 women) were randomized into the SAP and SAP + PERT groups. All athletes had undergone primary ACL reconstruction and achieved 80% quadriceps strength limb symmetry (QI), full range of motion, had minimal effusion, and had no pain. Additionally, all had begun running again. Prior to and after the training program, athletes’ QI, hopping, and patient-reported outcomes were assessed. Repeated-measures analyses of variance were used to determine whether there were differences between groups. Subsequently, the SAP and SAP + PERT groups were collapsed to analyze differences between sexes. Results: There were significant increases for all variables, with the exception of QI. There were no differences between the SAP and SAP + PERT groups. Both men and women made significant improvements in all knee function and patient-reported outcome measures except QI. Men made significant improvements in QI, whereas women did not. Conclusion: The common elements of the training program that all athletes received (10 sessions of progressive strengthening, agility training, plyometrics, and secondary prevention) may be a beneficial addition to the return-to-sport phase of ACL reconstruction rehabilitation. The results suggest that women may require further quadriceps strengthening to maintain and improve QI, an important focus given the relationship between QI and risk for reinjury. Clinical Relevance: During the return-to-sport phase of ACL reconstruction rehabilitation, clinicians tend to shift their focus away from strengthening toward more advanced sports-related tasks. These results indicate that women in particular need continued focus on quadriceps strengthening.

Return-to-Play Criteria: The Delaware Experience

Most rehabilitation protocols and return-to-play (RTP) decisions are time-based rather than criterion-based. For over two decades, clinician-scientists at the University of Delaware have been implementing and advocating for the use of objective criteria to guide rehabilitation progression and RTP decision-making after anterior cruciate ligament (ACL) rupture and other knee injuries. Recent, high-quality research both from our cohorts and elsewhere supports and validates our approach. We have used the same objective clinical, functional, patient-reported, and time-based criteria to determine appropriate rehabilitation progression and RTP clearance for more than 20 years. Key clinical measures include achieving and maintaining full and symmetrical range of motion, minimal to no effusion, and no joint soreness. Functional testing consists of quadriceps strength and single-leg hop testing (single, crossover, triple, and 6 m timed hop tests); we compare the involved to uninvolved limb values to calculate limb symmetry indexes (LSI) with scores of 90% or greater representing symmetrical performance. Patient-reported outcomes, including the Knee Outcome Survey-Activities of Daily Living Subscale (KOS-ADLS) and Global Rating Scale of Perceived Function (GRS), assess patients’ self-evaluation of their knee function. Finally, we advocate for more delayed RTP time frames given the substantially increased risk of reinjury among athletes who return to high-level sports, such as football, prior to 9 months after primary ACL reconstruction. Our validated, objective RTP criteria include clinical impairment resolution and maintenance, ≥90% LSI for quadriceps strength and all four single-leg hop tests, ≥90% scores on the KOS-ADLS and GRS, and appropriate healing time (i.e., ≥9 months after primary ACL reconstruction). Athletes may then initiate a gradual RTP progression: individual drills, unopposed team drills, opposed individual and team drills, full practice, and finally competition. Using the Delaware RTP criteria may improve outcomes and lower reinjury risk.

Gait mechanics and tibiofemoral loading in men of the ACL-SPORTS randomized control trial: ACL-SPORTS TRAINING AND GAIT MECHANICS

The risk for post‐traumatic osteoarthritis is elevated after anterior cruciate ligament reconstruction (ACLR), and may be especially high among individuals with aberrant walking mechanics, such as medial tibiofemoral joint underloading 6 months postoperatively. Rehabilitation training programs have been proposed as one strategy to address aberrant gait mechanics. We developed the anterior cruciate ligament specialized post‐operative return‐to‐sports (ACL‐SPORTS) randomized control trial to test the effect of 10 post‐operative training sessions consisting of strength, agility, plyometric, and secondary prevention exercises (SAPP) or SAPP plus perturbation (SAPP + PERT) training on gait mechanics after ACLR. A total of 40 male athletes (age 23 ± 7 years) after primary ACLR were randomized to SAPP or SAPP + PERT training and tested at three distinct, post‐operative time points: 1) after impairment resolution (Pre‐training); 2) following 10 training sessions (Post‐training); and 3) 2 years after ACLR. Knee kinematic and kinetic variables as well as muscle and joint contact forces were calculated via inverse dynamics and a validated electromyography‐informed musculoskeletal model. There were no significant improvements from Pre‐training to Post‐training in either intervention group. Smaller peak knee flexion angles, extension moments, extensor muscle forces, medial compartment contact forces, and tibiofemoral contact forces were present across group and time, however the magnitude of interlimb differences were generally smaller and likely not meaningful 2 years postoperatively. Neither SAPP nor SAPP + PERT training appears effective at altering gait mechanics in men in the short‐term; however, meaningful gait asymmetries mostly resolved between post‐training and 2 years after ACLR regardless of intervention group.

High muscle co-contraction does not result in high joint forces during gait in anterior cruciate ligament deficient knees: MUSCLE CO-CONTRACTION AND JOINT FORCES

The mechanism of knee osteoarthritis development after anterior cruciate ligament injuries is poorly understood. The objective of this study was to evaluate knee gait variables, muscle co‐contraction indices and knee joint loading in young subjects with anterior cruciate ligament deficiency (ACLD, n = 36), versus control subjects (n = 12). A validated, electromyography‐informed model was used to estimate joint loading. For the involved limb of ACLD subjects versus control, muscle co‐contraction indices were higher for the medial (p = 0.018, effect size = 0.93) and lateral (p = 0.028, effect size = 0.83) agonist–antagonist muscle pairs. Despite higher muscle co‐contraction, medial compartment contact force was lower for the involved limb, compared to both the uninvolved limb (mean difference = 0.39 body weight, p = 0.009, effect size = 0.70) as well as the control limb (mean difference = 0.57 body weight, p = 0.007, effect size = 1.14). Similar observations were made for total contact force. For involved versus uninvolved limb, the ACLD group demonstrated lower vertical ground reaction force (mean difference = 0.08 body weight, p = 0.010, effect size = 0.70) and knee flexion moment (mean difference = 1.32% body weight * height, p = 0.003, effect size = 0.76), during weight acceptance. These results indicate that high muscle co‐contraction does not always result in high knee joint loading, which is thought to be associated with knee osteoarthritis. Long‐term follow‐up is required to evaluate how gait alterations progress in non‐osteoarthritic versus osteoarthritic subjects.

Psychological Readiness to Return to Sport Is Associated With Knee Kinematic Asymmetry During Gait Following ACL Reconstruction

• BACKGROUND: Gait asymmetry is frequently observed following anterior cruciate ligament reconstruction (ACLR). Psychological readiness to return to sport is associated with functional and activity‐related outcomes after ACLR. However, the association between gait asymmetry and psychological readiness to return to sport is unknown. • OBJECTIVES: To determine the relationship between kinematic and kinetic measures of knee symmetry during gait and psychological readiness to return to sport following ACLR. • METHODS: In this controlled laboratory, cross‐sectional study, 79 athletes (39 women) underwent gait analysis following impairment resolution after ACLR (ie, full range of motion, minimal or no effusion, quadriceps strength index of 80% or greater). Interlimb differences during gait were calculated for sagittal plane knee angles at initial contact, peak knee flexion, and peak knee extension, as well as for peak knee flexion moment and peak knee adduction moment. Athletes completed the Anterior Cruciate Ligament‐Return to Sport after Injury scale (ACL‐RSI) to assess psychological readiness to return to sport. Pearson correlations were used to examine the association between ACL‐RSI score and each gait symmetry variable. • RESULTS: Significant negative correlations were observed between the ACL‐RSI and 2 kinematic variables: knee flexion angle at initial contact (r = ‐0.281, P = .012) and peak knee flexion (r = ‐0.248, P = .027). In general, lower scores on the ACL‐RSI were associated with greater interlimb asymmetry. • CONCLUSION: There was a weak association between psychological readiness to return to sport and knee kinematic asymmetry during gait.

Athletes with a Positive Psychological Response to Return to Sport Training Have Better Outcomes One and Two Years after ACL Reconstruction

Objectives: Fear of re-injury and psychological readiness to return to sport have emerged as important factors affecting outcomes following anterior cruciate ligament reconstruction (ACLR). The time when athletes transition from rehabilitation to return to sport can be especially fearful. Psychological factors are potentially modifiable at this time, and improving them may lead to better outcomes. The purpose of this study was to evaluate whether athletes who showed a positive psychological response to a return to sport training program have better self-reported function and activity outcomes compared to athletes who do not have a clinically meaningful change in their psychological response. Methods: Following ACLR and completion of formal rehabilitation, 67 level I/II athletes (27 female) completed the following self-report measures at enrollment: Anterior Cruciate Ligament Return to Sport after Injury scale (ACL-RSI), International Knee Documentation Committee Subjective Knee Form (IKDC), and global rating scale (GRS). Subjects then underwent ten additional sessions, including injury prevention exercises, progressive strength training, agility training, and plyometric training, to transition the athlete to sport-specific activities. All self-report measures were repeated after training (post). Subjects subsequently completed the IKDC, a GRS, and indicated whether they had returned to the same level of sport one and two years after ACLR. Subjects were dichotomized into 2 groups based on their ACL-RSI scores. Subjects who displayed an increase in ACL-RSI score from enrollment to post that exceeded the MCID (≥1.9) were defined as having a positive psychological response (responder) to training while those who did not were defined as non-responders. Independent t-tests and chi-square tests were used to measure group differences with all outcome measures at all time points (alpha = 0.05). Results: Fourteen of sixty-seven athletes (21%) demonstrated a positive psychological response to treatment. Significant group differences were found with the IKDC one year, and two years after ACLR(Table 1). Ninety-two percent of the responder group returned to their preinjury level of sport at one year while only sixty-nine percent of the non-responder group returned (Figure 1) (Pearson chi-square=2.93, p=.087). Ninety-two percent of the responder group and eighty-eight percent of the non-responder group had returned at 2 years (Pearson chi-square=.074, p=.785). There were no group differences in time from surgery to enrollment (mean ± SD, responder: 22.6 ± 8.0 weeks, non-responder: 23.0 ±8.1 weeks, p=.882) or age (responder: 20.9 ± 6.1 years, non-responder: 22.1 ± 8.5 years, p=.624). Conclusion: Athletes who experienced a positive psychological response to return to sport training demonstrated better self-reported knee function following treatment and one and two years after ACLR. At one year, while non-responders were similar to published mean return to sport level rates (sixty-five percent in a recent meta-analysis), responders demonstrated return rates far exceeding these mean rates. The findings of this study suggest that in some athletes, return to sport training improved psychological readiness. These changes may be related to better functional and return to sport outcomes. Additional strategies may need to be added to this training program so that more athletes see improvements in their psychological response.

On-Ice Return-to-Hockey Progression After Anterior Cruciate Ligament Reconstruction

Synopsis The literature pertaining to the rehabilitation of ice hockey players seeking to return to sport after anterior cruciate ligament reconstruction (ACLR) is currently limited. The purpose of this clinical commentary was to present a criterion-based progression for return to ice hockey for athletes after ACLR. First, we review pertinent literature and provide previously published guidelines on general rehabilitation after ACLR. Then, we present a 4-phase, on-ice skating progression with objective criteria to initiate each phase. During the early on-ice phase, the athlete is reintroduced to specific demands, including graded exposure to forward, backward, and crossover skating. In the intermediate on-ice phase, the emphasis shifts to developing power and introducing anticipated changes of direction within a controlled environment. During the late on-ice phase, the focus progresses to developing anaerobic endurance and introducing unanticipated changes of direction, but still without other players or contact. Finally, once objective return-to-sport criteria are met, noncontact team drills, outnumbered and even-numbered drills, practices, scrimmages, and games are progressively reintroduced during the return-to-sport phase. Recommendations for off-ice strength and conditioning exercises complement the on-ice progression. Additionally, we apply the return-to-hockey progression framework to a case report of a female collegiate defensive ice hockey player who returned to sport successfully after ACLR. This criterion-based return-to-hockey progression may guide rehabilitation specialists managing athletes returning to ice hockey after ACLR. J Orthop Sports Phys Ther 2017;47(5):324-333. Epub 29 Mar 2017. doi:10.2519/jospt.2017.7245.