Effects of closed versus open kinetic chain knee extensor resistance training on knee laxity and leg function in patients during the 8- to 14-week post-operative period after anterior cruciate ligament reconstruction

Open kinetic chain (OKC) knee extensor resistance training has lost favour in ACLR rehabilitation due to concerns that this exercise is harmful to the graft and will be less effective in improving function. In this randomized, single-blind clinical trial OKC and closed kinetic chain (CKC) knee extensor training were compared for their effects on knee laxity and function in the middle period of ACLR rehabilitation. The study subjects were 49 patients recovering from ACLR surgery (37 M, 12 F; mean age=33 years). Tests were carried out at 8 and 14 weeks after ACLR with knee laxity measured using a ligament arthrometer and function with the Hughston Clinic knee self-assessment questionnaire and single leg, maximal effort jump testing (post-test only). Between tests, subjects trained using either OKC or CKC resistance of their knee and hip extensors as part of formal physical therapy sessions three times per week. No statistically significant (one-way ANOVA, p>0.05) differences were found between the treatment groups in knee laxity or leg function. OKC and CKC knee extensor training in the middle period of rehabilitation after ACLR surgery do not differ in their effects on knee laxity or leg function. Exercise dosages are described in this study and further research is required to assess whether the findings in this study are dosage specific.     

Knee strength outcomes in adolescents by age and sex during late-stage rehabilitation after anterior cruciate ligament reconstruction

ObjectiveTo determine if knee strength differences exist according to age group and sex among adolescents during late-stage anterior cruciate ligament reconstruction (ACLR) rehabilitation.DesignRetrospective cohort study.MethodsConsecutive patients who had undergone ACLR with a hamstring autograft completed isokinetic knee strength assessment. Patients were categorized into early (ages 11–14 years) and middle (ages 15–17 years) adolescence. A two-way MANOVA was used to examine strength differences according to age group and sex.Results144 patients were included in the analysis (56.9% females, age = 15.3 ± 1.5 years; days since surgery = 228.2 ± 41.2). Differences in quadriceps peak torque were identified between age groups on the involved (p = 0.001) and uninvolved limbs (p < 0.001), however, no differences in quadriceps peak torque were found between age groups when normalized to body mass (p = 0.16–0.49). Differences between groups according to sex were identified for each strength outcome (p < 0.01), with decreased normalized quadriceps (12–13%) and hamstring (13–16%) peak torque for females. No interactions between age group and sex were noted, F(8, 133) = 1.48, p = 0.17.ConclusionEarly adolescents produced less quadriceps and hamstring peak torque compared to middle adolescents after ACLR. No differences were found between age groups when normalized to body mass.     

Strain on the anterior cruciate ligament during closed kinetic chain exercises

PURPOSE: The purpose of this investigation was to characterize the ACL strains produced during four commonly prescribed CKC exercises; the step-up, the step-down, the lunge, and the one-legged sit to stand. We hypothesized that the ACL strains produced during the lunge and one-legged sit to stand exercises (the exercises that challenge the leg musculature to a greater extent and utilize greater hip flexion) would be less than those produced during the step-up and step-down exercises. METHODS: The strains in the anteromedial bundle of the ACL were measured while nine subjects, who had normal ligaments, performed the four exercises. Peak ACL strain values and the ACL strain patterns as a function of knee flexion angle were compared between exercises. RESULTS: No significant differences were found between the peak ACL strain values (mean +/- SEM) between exercises (step-up: 2.5 +/- 0.36; step-down: 2.6 +/- 0.34; lunge 1.9 +/- 0.50; one-legged sit to stand: 2.8 +/- 0.27). The mean ACL strain values as a function of knee flexion angle were not significantly different. On average, there was a significant increase in ACL strain as the knee was extended for each exercise. CONCLUSIONS: The ACL strain responses produced during these CKC exercises were equal and similar to those produced during other rehabilitation exercises (i.e., squatting, active extension of the knee) previously tested.     

Readiness for return to sport in non-surgically treated patients with anterior cruciate ligament injury following a public municipal rehabilitation program

ObjectivesTo investigate the proportion of patients that pass a return to sport (RTS) test battery and assess changes in patient-reported outcomes and lower extremity muscle strength following three months of exericse-based rehabilitation in non-surgically treated patients with anterior cruciate ligament (ACL) injury.DesignProspective cohort study.SettingClinical environment (public municipal).ParticipantsThirty-nine ACL injured patients (54% female, median age (IQR) 28 years (24–35).Main outcome measuresThe Knee Injury and Osteoarthritis Outcome Score, Knee Outcome Survey Activities of Daily Living Scale, single hop for distance, crossover hop for distance, side hop test, the Agility T-test, and quadriceps and hamstrings isometric maximal voluntary contraction (MVC).ResultsFollowing 3 months of rehabilitation, patients had statistically significant improvements in all patients-reported outcomes and in quadriceps and hamstring MVC. Of 28 patients who completed all RTS tests, 11% passed six RTS criteria, 14% five criteria, 11% four criteria, 4% three criteria, 18% two criteria, 21% one criterion, and 21% none of the criteria.ConclusionsThe results suggest that three months of public municipal rehabilitation improves patient-reported outcomes and lower extremity muscle strength in non-surgically treated patients with ACL injury. However, only one in every 10 patients passed all RTS criteria.     

Compensatory mechanisms in anterior cruciate ligament deficiency

The literature cites numerous studies involving the analysis of movement patterns in anterior cruciate ligament deficient (ACLD) patients. Although several in vivo biomechanical studies have shown that ACLD patients develop protective mechanisms against degenerative diseases, it seems that these adaptations fail to protect the knee from future pathology. Some authors state that ACLD patients adapt to the injury by avoiding quadriceps contraction during gait when the knee is near full extension. However, others have found increased hamstrings and decreased gastrocnemius activity, which normally contribute to the stability of the knee. It seems that further in vivo biomechanical investigation is required to understand the mechanisms of pathological knee joint motions and develop rehabilitation programs, which would delay the progress of developing long-term degenerative diseases.     

Ability of a new hop test to determine functional deficits after anterior cruciate ligament reconstruction

The aim of this study was to investigate the ability of a new hop test to determine functional deficits after anterior cruciate ligament (ACL) reconstruction. The test consists of a pre-exhaustion exercise protocol combined with a single-leg hop. Nineteen male patients with ACL reconstruction (mean time after operation 11 months) who exhibited normal single-leg hop symmetry values (90% compared with the non-involved extremity) were tested for one-repetition maximum (1 RM) strength of a knee-extension exercise. The patients then performed single-leg hops following a standardised pre-exhaustion exercise protocol, which consisted of unilateral weight machine knee-extensions until failure at 50% of 1 RM. Although no patients displayed abnormal hop symmetry when non-fatigued, 68% of the patients showed abnormal hop symmetry for the fatigued test condition. Sixty-three per cent exhibited 1 RM strength scores of below 90% of the non-involved leg. Eighty-four percent of the patients exhibited abnormal symmetry in at least one of the tests. Our findings indicate that patients are not fully rehabilitated 11 months after ACL reconstruction. It is concluded that the pre-exhaustion exercise protocol, combined with the single-leg hop test, improved testing sensitivity when evaluating lower-extremity function after ACL reconstruction. For a more comprehensive evaluation of lower-extremity function after ACL reconstruction, it is therefore suggested that functional testing should be performed both under non-fatigued and fatigued test conditions.     

A deficient anterior cruciate ligament does not lead to quadriceps avoidance gait

Without an intact anterior cruciate ligament (ACL) to resist anterior tibial translation, it is commonly believed that ACL-deficient patients employ alterations in walking. Although there is no consensus in the literature about the specific kinematic and kinetic adaptations in these patients with ACL tears, the gait adaptation of quadriceps avoidance is perhaps the one most popularized. The purpose of our study was to determine whether quadriceps avoidance is common in patients with ACL-deficiency. We used a video-based motion analysis system and surface electromyography (EMG) to study 18 patients with ACL-deficiency. All patients demonstrated an internal knee extension moment during early mid-stance (similar to normal subjects). Quadriceps EMG activity was noted throughout most of stance. No patients demonstrated an internal knee flexion moment, a decreased internal knee extension moment or a decreased duration of quadriceps EMG activity during stance. The findings of this study would suggest that quadriceps avoidance as a gait adaptation in ACL-deficient patients may be less common than previously reported.     

Knee isokinetic performance following anterior cruciate ligament reconstruction: patellar tendon versus hamstrings graft

Objective: To compare knee isokinetic performance six months after reconstruction of the anterior cruciate ligament using grafts from either the patellar tendon or the hamstrings among patients who underwent the same rehabilitation protocol.

Methods: Thirty-four patients were evaluated (17 with grafts from the patellar tendon and 17 with grafts from the hamstrings). Operated and non-operated knees were compared with regards to the variables of peak torque, work and the hamstring/quadriceps relationship at velocities of 60º/s and 180º/s and power of 180º/s after six months of surgery.

Results: The patients with ACL reconstruction using the patellar tendon (BPTB) showed quadriceps deficits for all variables, but the flexor musculature was balanced. In the hamstring group, both the extensors and the flexors showed deficits for the variables analyzed, except for hamstring power at 180º/s.

Conclusion: Patients in the patellar tendon group had a greater quadriceps deficit compared with those in the hamstrings group. Patients in the hamstrings group had a greater muscular deficit in the flexor mechanism compared with the contralateral knee. An unbalanced H/Q ratio was observed regardless of graft type, but this was more evident in the BPTB group.     

Effects of open versus closed kinetic chain training on knee laxity in the early period after anterior cruciate ligament reconstruction

Knee extensor resistance training using open kinetic chain (OKC) exercise for patients recovering from anterior cruciate ligament reconstruction (ACLR) surgery has lost favour mainly because of research indicating that OKC exercise causes greater ACL strain than closed kinetic chain (CKC) exercise. In this prospective, randomized clinical trial the effects of these two regimes on knee laxity were compared in the early period after ACLR surgery. Thirty-six patients recovering from ACLR surgery (29 males, 7 females; age mean = 30) were tested at 2 and 6 weeks after ACLR with knee laxity measured using the Knee Signature System arthrometer. Between tests subjects trained using either OKC or CKC resistance of their knee and hip extensors in formal physical therapy sessions three times per week. Following adjustment for site of treatment, pretraining injured knee laxity, and untreated knee laxity at post-training, the use of OKC exercise, when compared to CKC exercise, was found to lead to a 9% increase in looseness with a 95% confidence interval of -8% to +29%. These results indicate that the great concern about the safety of OKC knee extensor training in the early period after ACLR surgery may not be well founded.     

Knee function after anterior cruciate ligament injury in elite collegiate athletes

BACKGROUND: Anterior cruciate ligament injuries are common in athletes, but there are few studies of long-term outcomes. HYPOTHESIS: Long-term knee function of anterior cruciate ligament-injured athletes is inferior to that of their uninjured teammates. STUDY DESIGN: Retrospective cohort study. METHODS: Thirty-three Division I-A athletes who had sustained an anterior cruciate ligament injury during their college career completed a series of questionnaires that assessed knee function and quality of life 2 to 14 years after injury. Their responses were compared with those of a matched cohort of their uninjured teammates. RESULTS: There were no differences in the mean Tegner scores, modified Lysholm scores, or in the scores of the SF-36 between groups. Sixteen anterior cruciate ligament-injured athletes scored A or B in the subjective portion of the International Knee Documentation Committee score and 17 scored C or D, whereas 24 control subjects scored A or B and 9 scored C or D, a statistically significant difference between groups. Five injured and 14 control athletes had participated at a professional or national team level after college. CONCLUSIONS: Quality of life of elite collegiate athletes who sustained an anterior cruciate ligament injury was not significantly different from that of their uninjured teammates, but knee function differed between groups.     

Corticomotor excitability associated with unilateral knee dysfunction secondary to anterior cruciate ligament injury

In the present report, we investigated changes in corticomotor excitability associated with unilateral knee dysfunction secondary to anterior cruciate ligament (ACL) injury. Ten participants, each with a previous history of unilateral ACL injury (median time post-injury 22 months) and eight healthy controls underwent transcranial magnetic stimulation (TMS) to assess excitability of the lower limb motor representation. Resting motor thresholds (RMTs) and stimulus response curves were measured at rest, while amplitude of motor evoked potentials and silent period duration were measured during active contraction. Correlations between these indices of excitability and three clinical measures of knee function were identified. Paired comparisons of indices by hemisphere revealed an asymmetry only in RMTs, which were significantly reduced on the side of injury in the ACL group. Correlations with clinical measures showed that the extent of quadriceps motor representation, as reflected by the steepness of SR curves, was strongly associated with quadriceps strength (r ²=0.71) on the injured side. The RMT asymmetry reported here in the context of ACL injury is consistent with other recent reports describing enhanced excitability of corticomotor projections targeting muscles adjacent to an immobilized or a painful joint. In such conditions, alterations in the quantity and quality of sensory feedback from the affected limb may underlie the rise in cortical excitability.     

Altered quadriceps control in people with anterior cruciate ligament deficiency

PURPOSE: The purpose of this study was to determine whether similar patterns of quadriceps dysfunction are observed when people with anterior cruciate ligament (ACL) deficiency perform static and dynamic tasks. METHODS: EMG data were collected from 15 subjects with an ACL deficient knee and 15 uninjured subjects as they performed static and dynamic tasks that were isolated to the knee and presented no threat to joint stability. The dynamic task was cyclic flexion and extension in the terminal 30 degrees of knee extension; the static task was an established isometric target-matching protocol. The muscle activity patterns observed during the tasks were evaluated and compared. RESULTS: The subjects with ACL deficiency exhibited quadriceps muscle control strategies that were significantly different from those of the uninjured subjects. This was true in both the dynamic and the static tasks. The findings were most noteworthy in the vastus lateralis muscle. Good agreement (r = -0.73 to -0.75) was observed in subjects' static and dynamic VL results; more moderate agreement was observed in results of the other quadriceps muscles. CONCLUSION: Diminished quadriceps control was observed when people with ACL deficiency performed static and dynamic tasks. The most striking feature of this impaired control was failure to turn the quadriceps "off" when performing flexion tasks in which the knee extensors are usually "silent." Our findings suggest that quadriceps dyskinesia after ACL injury is relatively global. Changes in neural function and muscle physiology after ACL injury are put forth as the most likely source of the observed dyskinesia.     

Feasibility,correlates, and validity of the one-leg sit-to-stand test in individuals following anterior cruciate ligament reconstruction

ObjectiveRegular quadriceps strength assessment is important following anterior cruciate ligament reconstruction (ACLR). The one-leg sit-to-stand (OLSTS) test potentially overcomes the barrier of accessibility to specialised testing equipment. However, feasibility and validity testing of OLSTS is lacking in the ACLR population. This study aims to examine the feasibility, correlates, and predictive validity of OLSTS with self-reported running and jumping difficulty in individuals post-ACLR.DesignRetrospective longitudinal study.Methods20 patients with primary unilateral ACLR were tested at 6-months and 1-year post-ACLR. Feasibility was assessed by the number of patients who had safely performed OLSTS at both timepoints. Cross-sectional gender-adjusted Spearman correlations of OLSTS with quadriceps strength, physical impairments, and psychological variables were measured at 6-months. Predictive validity was assessed via ordinal regression, quantifying the associations of OLSTS with self-reported running and jumping difficulty across time-points.ResultsAll patients understood the instructions to and were able to self-administer the OLSTS test safely. OLSTS is a valid measure of quadriceps strength (gender-adjusted Spearman's ρ = 0.53, P = 0.02). Knee pain (ρ = 0.44, P = 0.046) and readiness to return-to-sport (ρ = 0.55, P = 0.02) were additional correlates. Greater OLSTS performance was associated with greater odds of better self-reported running and jumping function (interquartile-range ORs, 12.0 [95% CI: 3.6–45] and 18.5 [95% CI: 5–67], respectively).ConclusionOLSTS is a feasible and valid test of quadriceps strength, demonstrating predictive validity with self-reported running and jumping post-ACLR. OLSTS potentially allows independent tracking of ACLR rehabilitation progress at home – an increasingly urgent necessity in the face of a global pandemic.     

Mechanisms of compensating for anterior cruciate ligament deficiency during gait

INTRODUCTION: The quadriceps avoidance gait pattern may not be as common in ACL deficient (ACLd) gait as previously described. PURPOSE: The purpose of this study was to investigate the existence of the quadriceps avoidance pattern in ACL deficient patients and to further identify gait compensations that may exist in this subject pool. METHODS: In the present study, hip, knee, and ankle gait kinematics, and kinetics and thigh EMG profiles were recorded and compared for 16 ACLd and 8 control subjects. RESULTS: The quadriceps avoidance gait pattern was not observed for any of the subjects. Hip, knee, and ankle kinematics and kinetics were not different between groups. However, nine ACLd subjects (group A) demonstrated a normal biphasic knee moment pattern, whereas seven (group B) demonstrated an all knee extensor pattern. This indicates different adaptive mechanisms may be present in ACLd gait. Group A exhibited a hip strategy that increased hip extensor output, decreased knee extensor output, and allowed normal knee kinematics. Group B demonstrated a knee strategy that increased the stiffness of the joint and utilized a flexed knee gait. CONCLUSION: The prevalence of multiple adaptive strategies to compensate for ACL deficiency has several important ramifications. First, an ACLd subject pool with mixed compensating strategies may deter the identification of specific coping mechanisms and account for the confounding results in the literature. Second, the importance of the hip extensors should not be overlooked when studying this population.     

Quadriceps strength changes across the continuum of care in adolescent male and female athletes with anterior cruciate ligament injury and reconstruction

ObjectivesTo examine the quadriceps strength (QUADS) on the surgical (SURG) and non-surgical (Non-SURG) limbs in adolescent male and female athletes at pre-operative (PRE), 12 weeks post-operative (12WK), and return to sport (RTS) time points following ACL injury and reconstruction.DesignProspective cohort study design.SettingClinical Research Laboratory.Participants66 adolescent athletes.Main outcome measuresIsokinetic QUADS of the SURG and Non-SURG limbs at the PRE, 12WK, and RTS time points were assessed and compared between each time point.ResultsBoth male and female participants had significantly lower 12 WK QUADS in the SURG limb than the PRE QUADS, but the RTS QUADS was significantly greater than the 12WK QUAD (p < 0.05). However, only female participants had greater RTS QUADS as compared to the PRE QUADS (p < 0.001). For the Non-SURG limb, only male participants had a significant improvement over time (PRE vs RTS; p < 0.001).ConclusionAdolescent males and females differ in their QUADS recovery across the continuum of care following ACLR. Clinicians should consider this pattern of recovery when treating adolescent males and females.     

The relationship between quadriceps strength asymmetry and knee biomechanics asymmetry during walking in individuals with anterior cruciate ligament reconstruction

BackgroundLower extremity movement asymmetries may lead to re-injury and knee osteoarthritis after anterior cruciate ligament (ACL) reconstruction surgery. However, there is no consensus regarding the effect of quadriceps strength asymmetry on lower extremity movement asymmetry after ACL reconstruction.Research questionWhat is the relationship between quadriceps strength asymmetry and asymmetries in lower extremity kinematics and kinetics during walking in individuals who underwent ACL reconstruction surgery?.MethodsIsometric quadriceps strength, kinematic, and kinetic data during walking were collected from 24 men with unilateral ACL reconstruction. Knee joint angles and moments were reduced. Pearson correlation coefficients between asymmetry in selected knee biomechanics and isometric quadriceps strength asymmetry were determined.ResultsThe isometric quadriceps strength of the injured leg was significantly lower than that of the uninjured leg (P < 0.001). Knee flexion angles and knee extension moments were smaller in the injured leg than that in the uninjured leg during both loading response (P = 0.007, P = 0.047) and mid-stance phases (P = 0.005, P = 0.028). Isometric quadriceps strength asymmetry was significantly correlated with asymmetry in the peak knee flexion angle during loading response and mid-stance phases (r = −0.48, P = 0.017, r = −0.48, P = 0.017). Isometric quadriceps strength asymmetry was also significantly correlated with asymmetry in the peak knee extension moment during the mid-stance phase (r = −0.44, P = 0.033).SignificanceIndividuals with ACL reconstruction demonstrate knee movement asymmetry in the sagittal plane. Isometric quadriceps strength asymmetry is significantly correlated with asymmetry in knee flexion angles during the early stance phase and knee extension moments during the mid-stance phase. Rehabilitation programs should emphasise eccentric exercise to beneficially modify quadriceps neuromuscular control.     

Type of measurement used influences central and peripheral contributions to quadriceps weakness after anterior cruciate ligament (ACL) reconstruction

ObjectiveThe relative contribution of muscle size and voluntary activation (VA) on quadriceps strength after anterior cruciate ligament (ACL) reconstruction remains inconclusive. Here, we aimed to determine the contributions of muscle size and VA on quadriceps strength in ACL-reconstructed patients and determine if contributions were similar if unilateral outcomes (i.e. ACL-reconstructed limb) or the LSI was used. Design: A cross-sectional study.SettingA university research laboratory.ParticipantsSixteen individuals 6–12 months after ACL reconstruction (Age: 22.3 ± 6.0yr, Height: 1.7 ± 0.1 m, Mass: 68.7 ± 11.5 kg) were recruited.Main outcome measuresQuadriceps isometric strength and VA, via the interpolated triplet technique, were assessed bilaterally. Ultrasound images were acquired of the vastus lateralis to calculate cross-sectional area (CSA) in both legs. LSI’s were computed for all variables by expressing values of the reconstructed leg as a percent of the non-reconstructed leg. Separate stepwise linear regressions were performed to examine the contribution of VA and CSA on quadriceps strength. Model 1 used LSI for all outcomes and model 2 used outcomes from the reconstructed leg.ResultsWe observed between limb deficits of 27.78% in quadriceps strength, 13.61% in vastus lateralis CSA, and 13.18% in VA (P < 0.05). Strength LSI was significantly predicted by VA LSI (R² = 0.45, P < 0.01), but not by CSA LSI (R² = 0.01, P =0.87). Reconstructed leg strength was significantly predicted by VL CSA (R² = 0.50, P < 0.01) but not quadriceps VA (R² = 0.08, P =0.11).ConclusionsThe contributions of VA and CSA on quadriceps PT differed greatly if LSI or reconstructed leg outcomes were used. Evaluation of VA and CSA in unison may be provide a more holistic understanding of the sources of muscle weakness after ACL reconstruction.