Reflex inhibition of the quadriceps femoris muscle after injury or reconstruction of the anterior cruciate ligament

Functional performance 6 months after ACL reconstruction can predict return to participation in the same preinjury activity level 12 and 24 months after surgery

BACKGROUND

Assessing athletes' readiness is a key component for successful outcomes after ACL reconstruction (ACLR).

OBJECTIVES

To investigate whether return-to-activity criteria, individually or in combination, at 6 months after ACLR can predict return to participation in the same preinjury activity level at 12 and 24 months after ACLR.

METHODS

Ninety-five level I/II participants completed return-to-activity criteria testing (isometric quadriceps index, single-legged hop tests, Knee Outcome Survey-Activities of Daily Living Scale (KOS-ADLS) and Global Rating Score (GRS)) at 6 months after ACLR. The PASS group was defined as scoring >90% on all criteria and the FAIL group as scoring <90% on any criteria. At 12 and 24 months after ACLR, participants were asked if they had returned to participate in the same preinjury activity level or not. All return-to-activity criteria, except quadriceps index, were entered into the logistic regression model.

RESULTS

81% and 84.4% of the PASS group returned to participation in the same preinjury activity level, while only 44.2% and 46.4% of the FAIL group returned at 12 and 24 months, respectively, after ACLR. The 6-meter timed hop, single hop and triple hop limb symmetry indexes; GRS; and KOS-ADLS individually predicted the outcome of interest at 12 months after ACLR (range: R²: 0.12-0.22, p<0.024). In combination, they explained 27% of the variance (p=0.035). All hop tests, individually, predicted the outcome of interest at 24 months after ACLR (range: R²: 0.26-0.37; p<0.007); in combination they explained 45% of the variance (p<0.001).

CONCLUSION

Return to participation in the same preinjury activity level at 12 and 24 months after ACLR was higher in those who passed the criteria compared with those who failed. Individual and combined return-to-activity criteria predicted the outcomes of interest, with the hop tests as consistent predictors at 12 and 24 months after ACLR.

Eccentric Exercise to Enhance Neuromuscular Control

Context:

Neuromuscular alterations are a major causal factor of primary and secondary injuries. Though injury prevention programs have experienced some success, rates of injuries have not declined, and after injury, individuals often return to activity with functionality below clinical recommendations. Considering alternative therapies to the conventional concentric exercise approach, such as one that can target neuromuscular injury risk and postinjury alterations, may provide for more effective injury prevention and rehabilitation protocols.

Evidence Acquisition:

Peer-reviewed sources available on the Web of Science and MEDLINE databases from 2000 through 2016 were gathered using searches associated with the keywords eccentric exercise, injury prevention, and neuromuscular control.

Hypothesis:

Eccentric exercise will reduce injury risk by targeting specific neural and morphologic alterations that precipitate neuromuscular dysfunction.

Study Design:

Clinical review.

Level of Evidence:

Level 4.

Results:

Neuromuscular control is influenced by alterations in muscle morphology and neural activity. Eccentric exercise beneficially modifies several underlying factors of muscle morphology (fiber typing, cross-sectional area, working range, and pennation angle), and emerging evidence indicates that eccentric exercise is also beneficial to peripheral and central neural activity (alpha motorneuron recruitment/firing, sarcolemma activity, corticospinal excitability, and brain activation).

Conclusion:

There is mounting evidence that eccentric exercise is not only a therapeutic intervention influencing muscle morphology but also targets unique alterations in neuromuscular control, influencing injury risk.

Effects of quadriceps functional exercise with isometric contraction in the treatment of knee osteoarthritis

OBJECTIVE

This study aims to investigate the effects of a quadriceps isometric contraction exercise method in the treatment of knee osteoarthritis (OA).

METHODS

A total of 250 patients with a confirmed diagnosis of knee OA were enrolled. The patients were randomly divided into an exercise treatment test group (128 patients) and a traditional treatment control group (122 patients). Quadriceps isometric contraction exercise was used in the test group, and local physiotherapy and oral nonsteroidal anti-inflammatory drugs were used in the control group. Knee joint function was evaluated with a visual analog scale (VAS) score and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire before treatment, and 1 and 3 months after treatment.

RESULTS

VAS scoring and the WOMAC questionnaire showed significant relief in pain 1 month after treatment in the test group (P < 0.05), but minimal relief in the control group; at 1 month, there was also minimal joint function improvement in the test group (P > 0.05), but significant improvement in the control group (P < 0.05). However, 3 months after treatment, pain relief and knee joint function were more improved in the test group than in the control group, with a significant difference (P < 0.05).

CONCLUSION

Through our short-term observation, joint pain was effectively relieved and knee joint function was improved with systematic quadriceps isometric contraction exercise.

Anterior cruciate ligament reconstruction does not induce further gamma loop abnormalities on the intact side of the quadriceps femoris: A longitudinal study

This study aimed to investigate the effect of surgery on the gamma loop of the quadriceps on the side with an intact knee in patients with anterior cruciate ligament (ACL) injuries. We compared longitudinally the response of alpha motor neurons to vibration stimulation of the quadriceps on the side with an intact knee before and after ACL reconstruction. To evaluate alpha motor neuron response, we measured the maximal knee extension strength and integrated electromyography of the vastus medialis, vastus lateralis, and rectus femoris. After obtaining pre-vibration data from each subject, vibration stimulation was applied to the infrapatellar tendon, and the same measurements were performed immediately after stimulation. The results of this study showed that the response to prolonged vibration stimulation on the intact side of the quadriceps did not differ pre- and post-surgery. As vibration stimuli normally elicit a decrease in alpha motor neuron activity in normal individuals, abnormal responses to prolonged vibration stimulation of the quadriceps on the side with an intact knee might be observed in patients with ACL injuries. The abnormality of the gamma loop of the quadriceps on the side with an intact knee was probably induced by the rupture. Based on these results, we conclude that surgery does not induce further gamma loop abnormalities on the intact side of the quadriceps.

Do Patients Failing Return-to-Activity Criteria at 6 Months After Anterior Cruciate Ligament Reconstruction Continue Demonstrating Deficits at 2 Years?

BACKGROUND

The variability in outcomes after anterior cruciate ligament reconstruction (ACLR) might be related to the criteria that are used to determine athletes' readiness to return to their preinjury activity level. A battery of return-to-activity criteria (RTAC) that emphasize normal knee function and movement symmetry has been instituted to quantitatively determine athletes' readiness to return to preinjury activities.

PURPOSE

To investigate performance-based and patient-reported measures at 12 and 24 months after ACLR between patients who passed or failed RTAC at 6 months after ACLR.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A total of 108 patients who had participated in International Knee Documentation Committee level 1 or 2 sports activities completed RTAC testing at 6, 12, and 24 months after surgery. The RTAC included the isometric quadriceps strength index (QI), 4 single-legged hop tests, the Knee Outcome Survey-activities of daily living subscale (KOS-ADLS), and the global rating scale of perceived function (GRS). Patients who scored ≥90% on all RTAC were classified as the pass group, and those who scored <90% on any RTAC were classified as the fail group. At 12- and 24-month follow-ups, patients were asked if they had returned to the same preinjury activity level.

RESULTS

At the 6-month follow-up, there were 48 patients in the pass group and 47 in the fail group. At the 12-month follow-up, 31 patients (73.8%) from the pass group and 15 patients (39.5%) from the fail group passed RTAC, and at the 24-month follow-up, 25 patients (75.8%) from the pass group and 14 patients (51.9%) from the fail group passed RTAC. The rate of return to activities in the pass group was 81% and 84% at 12 and 24 months after ACLR, respectively, compared with only 44% and 46% in the fail group ( P ≤ .012), respectively; however, some patients in the fail group participated in preinjury activities without being cleared by their therapists. At 12 and 24 months, 60.5% and 48.1% of patients continued to fail again on the criteria, respectively. A statistically significant group × time interaction was found for the single hop and 6-m timed hop limb symmetry indices (LSIs) ( P ≤ .037), with only the fail group demonstrating a significant improvement over time. A main effect of group was detected for the QI and the crossover hop and triple hop LSIs ( P < .01), with patients in the pass group demonstrating higher performance. A main effect of time was detected for the crossover hop and triple hop LSIs and the GRS, with improvements seen in both groups ( P < .05).

CONCLUSION

Patients who passed the RTAC early after ACLR were more likely to demonstrate normal knee function and movement symmetry at 12 and 24 months postoperatively, while patients who failed the RTAC early were more likely to demonstrate impaired knee function and movement asymmetry at 12- and 24-month follow-ups. Patients in the pass group had a higher rate of return to their preinjury activity level compared with those in the fail group. A group of patients chose to return to their preinjury activities, even though they were functionally not ready.

An anterior cruciate ligament injury does not affect the neuromuscular function of the non-injured leg except for dynamic balance and voluntary quadriceps activation

PURPOSE

The function of the anterior cruciate ligament (ACL) patients' non-injured leg is relevant in light of the high incidence of secondary ACL injuries on the contralateral side. However, the non-injured leg's function has only been examined for a selected number of neuromuscular outcomes and often without appropriate control groups. We measured a broad array of neuromuscular functions between legs of ACL patients and compared outcomes to age, sex, and physical activity matched controls.

METHODS

Thirty-two ACL-deficient patients (208 ± 145 days post-injury) and active and less-active controls (N = 20 each) participated in the study. We measured single- and multi-joint neuromuscular function in both legs in each group and expressed the overall neuromuscular function in each leg by calculating a mean z-score across all neuromuscular measures. A group by leg MANOVA and ANOVA were performed to examine group and leg differences for the selected outcomes.

RESULTS

After an ACL injury, duration (-4.3 h/week) and level (Tegner activity score of -3.9) of sports activity decreased and was comparable to less-active controls. ACL patients showed bilateral impairments in the star excursion balance test compared to both control groups (P ≤ 0.004) and for central activation ratio compared to active controls (P ≤ 0.002). There were between-leg differences within each group for maximal quadriceps and hamstring strength, voluntary quadriceps activation, star excursion balance test performance, and single-leg hop distance (all P < 0.05), but there were no significant differences in quadriceps force accuracy and variability, knee joint proprioception, and static balance. Overall neuromuscular function (mean z-score) did not differ between groups, but ACL patients' non-injured leg displayed better neuromuscular function than the injured leg (P < 0.05).

CONCLUSIONS

Except for poorer dynamic balance and reduced quadriceps activation, ACL patients had no bilateral neuromuscular deficits despite reductions in physical activity after injury. Therapists can use the non-injured leg as a reference to assess the injured leg's function for tasks measured in the present study, excluding dynamic balance and quadriceps activation. Rehabilitation after an ACL injury should be mainly focused on the injured leg.

LEVEL OF EVIDENCE

III.

Cellular and Morphological Alterations in the Vastus Lateralis Muscle as the Result of ACL Injury and Reconstruction

BACKGROUND

Individuals who have had an anterior cruciate ligament (ACL) tear and reconstruction continue to experience substantial knee extensor strength loss despite months of physical therapy. Identification of the alterations in muscle morphology and cellular composition are needed to understand potential mechanisms of muscle strength loss, initially as the result of the injury and subsequently from surgery and rehabilitation.

METHODS

We performed diffusion tensor imaging-magnetic resonance imaging and analyzed muscle biopsies from the vastus lateralis of both the affected and unaffected limbs before surgery and again from the reconstructed limb following the completion of rehabilitation. Immunohistochemistry was done to determine fiber type and size, Pax-7-positive (satellite) cells, and extracellular matrix (via wheat germ agglutinin straining). Using the diffusion tensor imaging data, the fiber tract length, pennation angle, and muscle volume were determined, yielding the physiological cross-sectional area (PCSA). Paired t tests were used to compare the effects of the injury between injured and uninjured limbs and the effects of surgery and rehabilitation within the injured limb.

RESULTS

We found significant reductions before surgery in type-IIA muscle cross-sectional area (CSA; p = 0.03), extracellular matrix (p < 0.01), satellite cells per fiber (p < 0.01), pennation angle (p = 0.03), muscle volume (p = 0.02), and PCSA (p = 0.03) in the injured limb compared with the uninjured limb. Following surgery, these alterations in the injured limb persisted and the frequency of the IIA fiber type decreased significantly (p < 0.01) and that of the IIA/X hybrid fiber type increased significantly (p < 0.01).

CONCLUSIONS

Significant and prolonged differences in muscle quality and morphology occurred after ACL injury and persisted despite reconstruction and extensive physical therapy.

CLINICAL RELEVANCE

These results suggest the need to develop more effective early interventions following an ACL tear to prevent deleterious alterations within the quadriceps.

Quadriceps function relates to muscle size following ACL reconstruction

It remains unclear what role reduced volume and cross-section area (CSA) of individual quadriceps muscles may play in persistent quadriceps weakness and more global dysfunction following ACL reconstruction (ACLR). The purpose of this investigation was to establish the relationship between cross-sectional area of the quadriceps muscle group and measures of knee related and quadriceps function following ACLR. Thirty participants with a history of primary, unilateral ACLR experiencing persistent quadriceps activation failure participated in this cohort study. Clinical factors including International Knee Documentation Committee (IKDC) score, normalized knee extension MVIC torque (Nm/kg) and quadriceps central activation ratio (CAR, %) were assessed in addition to CSA. Quadriceps CSA was measured via magnetic resonance imaging (MRI; Siemens Avanto 1.5T). Quadriceps CSA (cm(2) ) and quadriceps volume (cm(3) ) as well as individual muscle estimates were identified within a 10 cm mid-thigh capture area. Pearson's product-moment correlation coefficients (r) established relationships between CSA and all other variables. Stepwise linear regression established which CSA factors were able to successfully predict clinical factors. Knee extension MVIC torque was strongly correlated with Vastus Intermedius (VI; r =  0.857, p < 0.001) CSA as well as partial VI (r = 0.849, p < 0.001) and quadriceps (r = 0.830, p < 0.001) volume. Partial VI (r = 0.365, p = 0.047) volume was weakly correlated with IKDC score. Knee extension MVIC torque was strongly predicted using VI CSA alone (R(2)  = 0.725) or in combination with Vastus Medialis CSA (VM; R(2)  = 0.756). Statement of Clinical Significance: Atrophy of the VI and VM muscles negatively impacts knee extension strength following ACLR. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1656-1662, 2016.

Anterior cruciate ligament (ACL) loading in a collegiate athlete during sidestep cutting after ACL reconstruction: A case study

BACKGROUND

Athletes with anterior cruciate ligament (ACL) injuries usually undergo ACL-reconstruction (ACLR) in order to restore joint stability, so that dynamic maneuvers such as the sidestep cut can be performed. Despite restoration of joint stability after ACLR, many athletes do not return to pre-injury levels and may be at a high risk of a second ACL injury. The purpose of this study was to determine whether or not ACL loading, would increase after ACLR.

METHODS

One female Division I collegiate athlete performed bilateral unanticipated sidestep cuts both before ACL injury and 27months after ACLR. Musculoskeletal simulations were used to calculate ACL loading during the deceleration phase of the sidestep cuts.

RESULTS

Twenty-seven months after ACLR, the athlete demonstrated higher total ACL loading in the ipsilateral limb as well as altered joint kinematics, moments, and quadriceps muscle force production. In the contralateral limb, there were no increases in total ACL loading or muscle force production yet altered lower extremity joint kinematics and moments were present after ACLR.

CONCLUSIONS

Higher total ACL loading in the ipsilateral limb of this athlete may suggest an increased risk of second ACL injury. The results of this study provide an initial step in understanding the effects of ACLR on the risk of second ACL injury in an elite athlete and suggest that it is important to develop a better understanding of this surgical intervention on knee joint loading, in order to reduce the risk of second ACL injury while performing dynamic maneuvers.

Gait analysis of national athletes after anterior cruciate ligament reconstruction following three stages of rehabilitation program: Symmetrical perspective

This study aimed to objectively evaluate changes in gait kinematics, kinetics and symmetry among anterior cruciate ligament (ACL) reconstructed athletes during rehabilitation. Twenty-two national athletes with ACL reconstruction and 15 healthy athletes were recruited for the study. Gait data were collected between the weeks 4-5, 8-9, and 12-13 post-operation using three-dimensional motion analysis system. Five separate components, including knee range of motion (ROM), vertical ground reaction force (VGRF), their symmetries and knee extension moment were evaluated. One way and repeated measure multivariate analysis of variance (MANOVA) were used to analyze the knee ROMs. The VGRF and extension moment were tested using repeated measure ANOVA and independent sample t-test. Findings indicated significant alterations in all measured components between patients' Test 1 and control group. Repeated measure analysis revealed significant effect for time in components of knee angular and VGRF (P<0.001), their symmetry index (P=0.03) and knee extension moment (P=0.045). Univariate outcomes demonstrated significant improvement in the injured limb's stance and swing (P<0.001), and single-stance (P=0.005) ROMs over time. Symmetry indexes of stance and swing ROM, and VGRF reduced significantly by 26.3% (P=0.001), 17.9% (P<0.001), and 31.9% (P=0.03) respectively. After three months, symmetry indexes of single-stance ROM and VGRF along with operated knee extension moment were the only variables which showed significant differences with control group. The rehabilitation program allowed national athletes to restore the operated limb's gait parameters except knee extension moment by 12-13 weeks post-reconstruction; however, more time is required to normalize single-stance ROM and VGRF asymmetries.

Impact of quadriceps strengthening on response to fatiguing exercise following ACL reconstruction

OBJECTIVES

Patients commonly experience altered response to fatiguing exercise after ACL reconstruction (ACLR). The objective of this study was to assess the impact of quadriceps strengthening on response to exercise after ACLR.

DESIGN

Clinical trial.

METHODS

Ten participants with a history of primary, unilateral ACLR (sex=9F/1M, age=21.0±2.8 years, BMI=23.7±2.7kg/m²) and 10 healthy participants (sex=9F/1M, age=22.2±3.2 years, BMI=23.8±3.9kg/m²) participated. ACLR participants completed a 2-week quadriceps strengthening intervention including 14 progressive strengthening exercise sessions. Normalized knee extension maximum voluntary isometric contraction (MVIC) torque (Nm/kg) and quadriceps central activation ratio (%, CAR) were measured before and after a 30-minute fatiguing exercise protocol. ACLR participants completed testing before and after the 2-week intervention while control participants completed a single testing session.

RESULTS

The intervention significantly improved normalized knee extension MVIC torque (pre-intervention=1.85±0.67Nm/kg, post-intervention=2.09±0.81Nm/kg, p=0.04) and quadriceps CAR in the ACLR involved limb (pre-intervention=86.51±5.03%, post-intervention=92.94±5.99%, p=0.02). Quadriceps CAR (pre-intervention=1.13±9.04%, post-intervention=-3.97±4.59%, p=0.16) and normalized knee extension MVIC torque (pre-intervention=0.26±20.90%, post-intervention=-8.02±12.82%, p=0.30) response to exercise did not significantly change from pre-intervention to post-intervention conditions.

CONCLUSIONS

Two weeks of quadriceps strengthening reduced this between group difference in the involved limb which may indicate restoration of more optimal quadriceps neuromuscular function and increased demand on the quadriceps during physical activity.

Quadriceps strength affects patient satisfaction after total knee arthroplasty

BACKGROUND

Total knee arthroplasty is one of the most successful surgeries with respect to relieving pain and restoring function of the knee. However, some studies have reported that patients are not always satisfied with their results after total knee arthroplasty. The aim of this study was to determine whether the muscle strength around the knee joint and the walking status influence patients' expectations and satisfaction before and after total knee arthroplasty.

METHODS

We evaluated 28 patients who underwent 30 primary total knee arthroplasties from March 2012 to June 2013. We assessed patient-reported scores using the 2011 Knee Society Scoring System, knee extensor and flexor strength, the 10-m walking test, and the timed up-and-go test. All assessments were performed preoperatively and 1 year after total knee arthroplasty. We determined the correlation between the patient-reported scores and each variable.

RESULTS

Preoperative patient satisfaction was significantly correlated with knee symptoms and functional activities, but not with muscle strength or walking status. Postoperative patient satisfaction was significantly correlated with knee symptoms, functional activities, knee extensor strength, and walking status, including the 10-m walking test and timed up-and-go test, after total knee arthroplasty. In stepwise regression analysis, predictors of patient satisfaction with total knee arthroplasty were knee symptoms, functional ability, and knee extensor strength.

CONCLUSIONS

Our study demonstrates that pain relief and restoration of functional activity are highly correlated with increasing patient satisfaction after total knee arthroplasty. The results also indicate that the quadriceps is important for patient satisfaction and restoration of functional activity following total knee arthroplasty.

Quadriceps Strength, Muscle Activation Failure, and Patient-Reported Function at the Time of Return to Activity in Patients Following Anterior Cruciate Ligament Reconstruction: A Cross-sectional Study

STUDY DESIGN

Cross-sectional.

OBJECTIVES

To determine if quadriceps activation failure (QAF) moderates the relationship between quadriceps strength and physical function in individuals following anterior cruciate ligament (ACL) reconstruction.

BACKGROUND

Quadriceps activation failure may impair the recovery of physical function after ACL reconstruction, given that QAF reduces strength and strength is related to physical function. Evidence of this relationship has been found in individuals with knee osteoarthritis, wherein patients with lower strength and greater QAF had lower levels of physical function.

METHODS

Participants consisted of 52 individuals who were cleared for return to activity at an average ± SD of 7.4 ± 1.2 months post-ACL reconstruction. Quadriceps activation failure was assessed using the superimposed burst technique, and quadriceps strength was assessed using concentric isokinetic contractions (Newton meters per kilogram). Physical function was quantified using a combined variable of a physical measure (single-leg hop for distance) and a self-reported function measure (International Knee Documentation Committee [IKDC] Subjective Knee Evaluation Form), calculated using a principal-component analysis. Simple correlations were then performed to determine the order in which variables were entered into the regression model to evaluate if QAF moderates the relationship between quadriceps strength and physical function.

RESULTS

The combination of quadriceps strength and the interaction of strength by QAF predicted 30% of the variance in physical function (R(2) = 0.30, P<.001; principal-component analysis, -0.61(strength) + 0.02(interaction) -1.896); however, the interaction of strength by QAF only accounted for 7% of the capabilities of the model (P = .023).

CONCLUSION

Physical function is largely influenced by the recovery of quadriceps strength and minimally attenuated by QAF. These data suggest that QAF may affect individuals post-ACL reconstruction differently, and to a lesser extent, than individuals with knee osteoarthritis. This trial was prospectively registered in a public registry (NCT01555567).

Electromechanical delay of the knee flexor muscles after anterior cruciate ligament reconstruction using semitendinosus tendon

The purpose of the study was to evaluate whether using only the semitendinosus as a tripled short graft would affect the electromechanical delay (EMD) of the knee flexors. EMD was evaluated in volunteers (N = 15) after they had undergone surgery for anterior cruciate ligament (ACL) reconstruction where the semitendinosus tendon alone was used as a graft. The results were compared with the intact leg and healthy controls (N = 15). After warming up, each subject performed four maximally explosive isometric contractions on an isokinetic dynamometer. Torques were measured by the dynamometer, while the electrical activity of the semitendinosus and biceps femoris muscles was detected using surface electromyography. EMD was found to be significantly increased (p = 0.001) in patients who had undergone ACL reconstruction compared to the controls. On the contrary, no significant differences (p = 0.235) were found for the biceps femoris muscle between the two groups. Similar results were found when the study group was compared with the intact leg group (p = 0.027 for semitendinosus and p = 0.859 for biceps femoris). Harvesting the semitendinosus tendon increases the EMD for the semitendinosus muscle but does not influence the EMD outcomes for the biceps femoris muscle.

Femoral quadriceps neuromuscular electrical stimulation after total knee arthroplasty: a systematic review

The purpose of this study was to evaluate the effects of neuromuscular electrical stimulation in patients submitted to total knee arthroplasty. This was a systematic review with no language or publication status restriction. Our search was made in Cochrane Library, MEDLINE, Embase and LILACS. Randomized or quasi-randomized clinical trials evaluating neuromuscular electrical stimulation after total knee arthroplasty were included. Four studies with moderate risk of bias and low statistical power were included, totalizing 376 participants. There was no statistically significant difference in knee function, pain and range of motion during 12 month follow-up. This review concluded that neuromuscular electrical stimulation was less effective than traditional rehabilitation in function, muscular strength and range of motion. However, this technique was useful for quadriceps activation during the first days after surgery.

Does concomitant meniscectomy or meniscal repair affect the recovery of quadriceps function post-ACL reconstruction?

PURPOSE

The purpose of this study was to determine the effect of concomitant meniscal surgery on the recovery of quadriceps activation and strength at a time when individuals return to sport following anterior cruciate ligament (ACL) reconstruction.

METHODS

Forty-six individuals that were cleared for participation following ACL reconstruction were invited to participate in this study. Participants were placed into groups according to surgical reports (ACL-only, n = 24; meniscal repair, n = 12; meniscectomy, n = 10). Quadriceps strength was quantified using isokinetic and isometric measures. Isokinetic strength was collected at 60°/s in concentric mode. Isometric strength was collected at 90° of knee flexion. Quadriceps activation was assessed using the burst superimposition technique and quantified via the central activation ratio. One-way ANOVAs were utilized to detect whether differences existed in quadriceps activation and strength between groups. Where appropriate, post hoc Bonferroni multiple comparison procedures were used.

RESULTS

Quadriceps activation (P = n.s.) and strength (isokinetic: P = n.s.; isometric: P = n.s.) were not different between groups.

CONCLUSION

Concomitant meniscectomy or meniscal repair did not affect the recovery of quadriceps activation and strength at a time when individuals return to sport following ACL reconstruction. Though group differences in quadriceps function were not detected, all participants demonstrated levels of quadriceps activation failure that are below healthy individuals at a time when they were returned to sport. Given that persistent quadriceps activation failure is detrimental to knee function, rehabilitation protocols that target quadriceps activation failure should be developed and employed post-reconstruction.

Effect of whole body vibration frequency on neuromuscular activity in ACL-deficient and healthy males

Whole-body vibration (WBV) has been shown to enhance muscle activity via reflex pathways, thus having the potential to contrast muscle weakness in individuals with rupture of the anterior cruciate ligament (ACL). The present study aimed to compare the magnitude of neuromuscular activation during WBV over a frequency spectrum from 20 to 45 Hz between ACL-deficient and healthy individuals. Fifteen males aged 28±4 with ACL rupture and 15 age-matched healthy males were recruited. Root mean square (RMS) of the surface electromyogram from the vastus lateralis in both limbs was computed during WBV in a static half-squat position at 20, 25, 30, 35, 40 and 45 Hz, and normalized to the RMS while maintaining the half-squat position without vibration. The RMS of the vastus lateralis in the ACL-deficient limb was significantly greater than in the contralateral limb at 25, 30, 35 and 40 Hz (P<0.05) and in both limbs of the healthy participants (dominant limb at 25, 30, 35, 40 and 45 Hz, P<0.05; non dominant limb at 20, 25, 30, 35, 40 and 45 Hz, P<0.05). The greater neuromuscular activity in the injured limb compared to the uninjured limb of the ACL-deficient patients and to both limbs of the healthy participants during WBV might be due to either augmented excitatory or reduced inhibitory neural inflow to motoneurons of the vastus lateralis through the reflex pathways activated by vibratory stimuli. The study provides optimal WBV frequencies which might be used as reference values for ACL-deficient patients.

Quadriceps Strength Asymmetry After Anterior Cruciate Ligament Reconstruction Alters Knee Joint Biomechanics and Functional Performance at Time of Return to Activity

BACKGROUND

Quadriceps strength deficits are observed clinically after anterior cruciate ligament (ACL) injury and reconstruction and are often not overcome despite rehabilitation. Given that quadriceps strength may be important for achieving symmetrical joint biomechanics and promoting long-term joint health, determining the magnitude of strength deficits that lead to altered mechanics is critical.

PURPOSE

To determine if the magnitude of quadriceps strength asymmetry alters knee and hip biomechanical symmetry as well as functional performance and self-reported function.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A total of 73 patients were tested at the time they were cleared for return to activity after ACL reconstruction. Quadriceps strength and activation, scores on the International Knee Documentation Committee form, the hop for distance test, and sagittal plane lower extremity biomechanics were recorded while patients completed a single-legged hop.

RESULTS

Patients with high and moderate quadriceps strength symmetry had larger central activation ratios as well as greater limb symmetry indices on the hop for distance compared with patients with low quadriceps strength symmetry (P < .05). Similarly, knee flexion angle and external moment symmetry were higher in the patients with high and moderate quadriceps symmetry compared with those with low symmetry (P < .05). Quadriceps strength was found to be associated with sagittal plane knee angle and moment symmetry (P < .05).

CONCLUSION

Patients with low quadriceps strength displayed greater movement asymmetries at the knee in the sagittal plane. Quadriceps strength was related to movement asymmetries and functional performance. Rehabilitation after ACL reconstruction needs to focus on maximizing quadriceps strength, which likely will lead to more symmetrical knee biomechanics.

Effect of knee angle on quadriceps strength and activation after anterior cruciate ligament reconstruction

Quadriceps strength and activation deficits after anterior cruciate ligament (ACL) injury or surgery are typically evaluated at joint positions that are biomechanically advantageous to the quadriceps muscle. However, the effect of knee joint position and the associated changes in muscle length on strength and activation is currently unknown in this population. Here, we examined the effect of knee angle on quadriceps strength, activation, and electrically evoked torque in individuals with ACL reconstruction. Furthermore, we evaluated whether knee angle mediated the relationship between quadriceps weakness and functional performance after ACL reconstruction. Knee strength and activation were tested bilaterally at 90° and 45° of knee flexion in 11 subjects with ACL reconstruction using an interpolated triplet technique. The magnitude of electrically evoked torque at rest was used to quantify peripheral muscle contractile property changes, and the single-leg hop for distance test was used to evaluate functional performance. The results indicated that although quadriceps strength deficits were similar between knee angles, voluntary activation deficits were significantly higher in the reconstructed leg at 45° of knee flexion. On the contrary, the side-to-side evoked torque at rest ratio [i.e., (reconstructed/nonreconstructed) × 100] was significantly lower at 90° than at 45° of knee flexion. The association between quadriceps strength and functional performance was stronger at 45° of knee flexion. The results provide novel evidence that quadriceps activation is selectively affected at 45° of knee flexion and emphasize the importance of assessing quadriceps strength and activation at this position when feasible because it better captures activation deficits.

Isokinetic dynamometer evaluation of the effects of early thigh diameter difference on thigh muscle strength in patients undergoing anterior cruciate ligament reconstruction with hamstring tendon graft

After anterior cruciate ligament (ACL) reconstruction, which muscle groups are more affected from frequently developing thigh muscle atrophy is a matter of debate. We evaluate the effect of thigh circumference difference between patients' knees who were administered the ACL reconstruction with hamstring tendon autograft and intact knees, on torque between the hamstring and quadriceps muscles. Fifty-five patients at least 6 months follow-up period available were included in our study. Power measurements of quadriceps and hamstring muscle groups in patients' extremities were done by using isokinetic dynamometer. The maximum torque values at 60°/sec, 240°/sec in frequency, positions of flexion and extension were determined. In accordance with our findings it is still possible to encounter the thigh atrophy in average 28 months after ACL reconstruction surgery even under physical rehabilitation programs and appropriate follow-up. It is inevitable for the clinician to consider these changes in diagnosis and rehabilitation stages. It can't be ignored that muscle weakness mechanisms developing in the thigh circumference vary according to the thigh muscle group and knee flexors play an important role in thigh atrophy when determining an appropriate rehabilitation program after reconstruction application.

Non-operative management of a complete anterior cruciate ligament injury in an English Premier League football player with return to play in less than 8 weeks: applying common sense in the absence of evidence

This case report illustrates and discusses the non-operative management of a complete anterior cruciate ligament (ACL) injury in an English Premier League football player, his return to play within 8 weeks and problem-free follow-up at 18 months post injury. When non-operative verses surgical ACL reconstruction is considered there are many fundamental gaps in our knowledge and currently, at elite level, there are no cases in cutting sports within the literature to guide these decisions. When the norm is for all professional footballers to be recommended surgery, it will be very challenging when circumstances and patient autonomy dictate a conservative approach, where prognosis, end points and risk are unclear and assumed to be high. This case challenges current dogma and provides a starting point for much needed debate about best practice, treatment options, research direction and not just at the elite level of sport.

Neural Excitability Alterations After Anterior Cruciate Ligament Reconstruction

CONTEXT

Neuromuscular dysfunction is common after anterior cruciate ligament reconstruction (ACL-R). However, little is known about quadriceps spinal-reflex and descending corticomotor excitability after ACL-R. Understanding the effects of ACL-R on spinal-reflex and corticomotor excitability will help elucidate the origins of neuromuscular dysfunction.

OBJECTIVE

To determine whether spinal-reflex excitability and corticomotor excitability differed between the injured and uninjured limbs of patients with unilateral ACL-R and between these limbs and the matched limbs of healthy participants.

DESIGN

Case-control study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 28 patients with unilateral ACL-R (9 men, 19 women; age = 21.28 ± 3.79 years, height = 170.95 ± 10.04 cm, mass = 73.18 ± 18.02 kg, time after surgery = 48.10 ± 36.17 months) and 29 participants serving as healthy controls (9 men, 20 women; age = 21.55 ± 2.70 years, height = 170.59 ± 8.93 cm, mass = 71.89 ± 12.70 kg) volunteered.

MAIN OUTCOME MEASURE(S)

Active motor thresholds (AMTs) were collected from the vastus medialis (VM) using transcranial magnetic stimulation. We evaluated VM spinal reflexes using the Hoffmann reflex normalized to maximal muscle responses (H : M ratio). Voluntary quadriceps activation was measured with the superimposed-burst technique and calculated using the central activation ratio (CAR). We also evaluated whether ACL-R patients with high or low voluntary activation had different outcomes.

RESULTS

The AMT was higher in the injured than in the uninjured limb in the ACL-R group (t27 = 3.32, P = .003) and in the matched limb of the control group (t55 = 2.05, P = .04). The H : M ratio was bilaterally higher in the ACL-R than the control group (F1,55 = 5.17, P = .03). The quadriceps CAR was bilaterally lower in the ACL-R compared with the control group (F1,55 = 10.5, P = .002). The ACL-R group with low voluntary activation (CAR < 0.95) had higher AMT than the control group (P = .02), whereas the ACL-R group with high voluntary activation (CAR ≥ 0.95) demonstrated higher H : M ratios than the control group (P = .05).

CONCLUSIONS

The higher VM AMT in the injured limbs of ACL-R patients suggested that corticomotor deficits were present after surgery. Higher bilateral H : M ratios in ACL-R patients may be a strategy to reflexively increase excitability to maintain voluntary activation.

Ponseti casting for severe club foot deformity: are clinical outcomes promising?

Between 2007 and 2010, a prospective study was done on 85 patients with severe idiopathic nonsyndromic clubfeet, in our center. Demographic features, severity of the deformity before and after serial casting according to Diméglio classification, and complications were assessed. The mean age of the patients was 8 days and 69% were male. The mean follow-up period was 26 months. The average number of castings used to correct the deformity was 5.7 times (range: 4 to 8). Tenotomy was performed in 76 (89.4%) of the feet. In all patients, plantigrade foot was achieved. Tenotomy occurred more in patients with higher Diméglio scores. Although patients who underwent Achilles tenotomy began to walk later than those who did not (13 ± 7.2 versus 9.2 ± 18), it was not significant (P = 0.06). Relapse rate, at the end of follow-up, was 27.1%. Diméglio score before casting was 16 ± 3.4 and at the end of follow-up it was 1.6 ± 6.2. The patients with bilateral clubfeet had inferior final outcome compared to those with unilateral clubfoot. Eighty percent of parents' were completely satisfied with their child's gait and foot appearance (94.1%). Ponseti method of manipulation and casting is a valuable technique in severe club foot as well as in common types.

Neuromechanical characteristics in the knees of patients who had primary conservative treatment for a torn cruciate ligament and reconstruction afterward

BACKGROUND/PURPOSE

To compare the neuromechanical characteristics and subjective outcomes for knees of patients with a cruciate ligament tear and reconstruction with those for knees of controls at three time intervals, and to determine correlations between the characteristics and subjective outcomes.

METHODS

Ten participants with a cruciate ligament tear and at least a 12-week conservative treatment prior to ligament reconstruction were prospectively measured prior to and 3 months and 6 months after surgery. Ten healthy individuals were recruited as controls. Questionnaire surveys regarding the injured knee were conducted, as were bilateral measurements of root mean square electromyography (EMG), the rate of EMG rise, the median frequency in the vastus medialis of the quadriceps muscles and antagonist coactivation from the semitendinosus muscle, and force capacities, including peak torque, rate of force development, and total works of the knee extension. Correlations between the EMG variables (of the vastus medialis and semitendinosus) and the force capacities, and between the EMG variables and the knee injury and osteoarthritis outcome scores (KOOS), and between force capacities and the KOOS were assessed in the participants with a ligament reconstruction.

RESULTS

Pre- and postoperative results of EMG variable and force capacities were lower in both knees of the experimental group participants than in the control group participants (all p < 0.05). Correlations between EMG and force capacities, and between these parameters and the KOOS were found.

CONCLUSION

There were bilateral neuromechanical defects in the knees of the participants who had undergone conservative treatment as well as reconstruction after a cruciate ligament tear.

Persistent neuromuscular and corticomotor quadriceps asymmetry after anterior cruciate ligament reconstruction

CONTEXT

Return to activity in the presence of quadriceps dysfunction may predispose individuals with anterior cruciate ligament reconstruction (ACLR) to long-term joint degeneration. Asymmetry may manifest during movement and result in altered knee-joint-loading patterns; however, the underlying neurophysiologic mechanisms remain unclear.

OBJECTIVE

To compare limb symmetry of quadriceps neuromuscular function between participants with ACLR and participants serving as healthy controls.

DESIGN

Descriptive laboratory study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 22 individuals with ACLR (12 men, 10 women) and 24 individuals serving as healthy controls (12 men, 12 women).

MAIN OUTCOME MEASURE(S)

Normalized knee-extension maximal voluntary isometric contraction (MVIC) torque (Nm/kg), quadriceps central activation ratio (CAR) (%), quadriceps motor-neuron-pool excitability (Hoffmann reflex to motor wave ratio), and quadriceps active motor threshold (AMT) (% 2.0 T) were measured bilaterally and used to calculate limb symmetry indices for comparison between groups. We used analyses of variance to compare quadriceps Hoffmann reflex to motor wave ratio, normalized knee-extension MVIC torque, quadriceps CAR, and quadriceps AMT between groups and limbs.

RESULTS

The ACLR group exhibited greater asymmetry in knee-extension MVIC torque (ACLR group = 0.85 ± 0.21, healthy group = 0.97 ± 0.14; t44 = 2.26, P = .03), quadriceps CAR (ACLR group = 0.94 ± 0.11, healthy group = 1.00 ± 0.08; t44 = 2.22, P = .04), and quadriceps AMT (ACLR group = 1.13 ± 0.18, healthy group = 1.02 ± 0.11; t34 = -2.46, P = .04) than the healthy control group.

CONCLUSIONS

Asymmetries in measures of quadriceps function and cortical excitability were present in patients with ACLR. Asymmetry in quadriceps strength, activation, and cortical excitability persisted in individuals with ACLR beyond return to recreational activity. Measuring the magnitude of asymmetry after ACLR represents an important step in understanding long-term reductions in self-reported function and increased rate of subsequent joint injury in otherwise healthy, active individuals after ACLR.

Muscle atrophy contributes to quadriceps weakness after anterior cruciate ligament reconstruction

OBJECTIVES

Quadriceps weakness persists after anterior cruciate ligament reconstruction. Muscle atrophy and activation failure may contribute. This study examined the roles of atrophy and activation failure in quadriceps weakness after anterior cruciate ligament reconstruction.

DESIGN

Case series.

METHODS

Twenty patients six months post-anterior cruciate ligament reconstruction participated. Atrophy was determined as peak quadriceps cross sectional area from magnetic resonance images. Quadriceps activation was quantified via the central activation ratio, while muscle strength was measured isometrically. All testing was performed bilaterally. Hierarchical linear regression and one-way ANOVAs were performed to examine the relation of muscle strength with activation and atrophy.

RESULTS

Cross sectional area (R(2)=0.307; p=0.011) explained more of the variance in quadriceps strength than central activation ratio (R(2)<0.001; p=0.987). Strength and cross sectional area were lower in the injured (strength: 2.03±0.51Nm/kg; cross sectional area: 68.81±17.80cm(2)) versus uninjured limb (strength: 2.89±0.81Nm/kg; cross sectional area: 81.10±21.58cm(2); p<0.001). There were no side-to-side differences in central activation ratio; however, quadriceps activation failure was present bilaterally (injured: 0.87±0.12; uninjured: 0.85±0.14; p=0.571).

CONCLUSIONS

Quadriceps cross sectional area was strongly related to muscle strength six months after anterior cruciate ligament reconstruction and substantial injured versus uninjured limb deficits were demonstrated for strength and cross sectional area. Patients may benefit from exercises aimed at improving quadriceps cross sectional area post-operatively.

Quantitative and qualitative MR-imaging assessment of vastus medialis muscle volume loss in asymptomatic patients after anterior cruciate ligament reconstruction

BACKGROUND

To quantitatively and qualitatively assess vastus medialis muscle atrophy in asymptomatic patients with anterior cruciate ligament reconstruction, using the nonoperated leg as control.

METHODS

Prospective Institutional Review Board approved study with written informed patient consent. Thirty-three asymptomatic patients (men, 21; women,12) with ACL-reconstruction underwent MR imaging of both legs (axial T1-weighted spin-echo and 3D spoiled dual gradient-echo sequences). Muscle volume and average fat-signal fraction (FSF) of the vastus medialis muscles were measured. Additionally, Goutallier classification was used to classify fatty muscle degeneration. Significant side differences were evaluated using the Wilcoxon test and, between volumes and FSF, using student t-tests with P-value < 0.05 and < 0.025, respectively.

RESULTS

The muscle volume was significantly smaller in the operated (mean ± SD, 430.6 ± 119.6 cm(3) ; range, 197.3 to 641.7 cm(3) ) than in the nonoperated leg (479.5 ± 124.8 cm(3) ; 261.4 to 658.9 cm(3) ) (P < 0.001). Corresponding FSF was 6.3 ± 1.5% (3.9 to 9.2%) and 5.8 ± 0.9% (4.0 to 7.4%), respectively, with a nonsignificant (P > 0.025) difference. The relative muscle-volume and FSF differences were -10.1 ± 8.6% (7.1 to -30.1%) and 10.9 ± 29.4% (39.7 to 40.1%). The qualitative assessment revealed no significant differences (P > 0.1).

CONCLUSION

A significant muscle volume loss of the vastus medialis muscle does exist in asymptomatic patients with ACL-reconstruction, but without fatty degeneration.

Knee contact force asymmetries in patients who failed return-to-sport readiness criteria 6 months after anterior cruciate ligament reconstruction

BACKGROUND

After anterior cruciate ligament (ACL) injury, contact forces are decreased in the injured knee when compared with the uninjured knee. The persistence of contact force asymmetries after ACL reconstruction may increase the risk of reinjury and may play an important role in the development of knee osteoarthritis in these patients. Functional performance may also be useful in identifying patients who demonstrate potentially harmful joint contact force asymmetries after ACL reconstruction.

HYPOTHESIS

Knee joint contact force asymmetries would be present during gait after ACL reconstruction, and performance on a specific set of validated return-to-sport (RTS) readiness criteria would discriminate between those who demonstrated contact force asymmetries and those who did not.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A total of 29 patients with ACL ruptures participated in gait analysis and RTS readiness testing 6 months after reconstruction. Muscle and joint contact forces were estimated using an electromyography (EMG)-driven musculoskeletal model of the knee. The magnitude of typical limb asymmetry in uninjured controls was used to define limits of meaningful limb asymmetry in patients after ACL reconstruction. The RTS testing included isometric quadriceps strength testing, 4 unilateral hop tests, and 2 self-report questionnaires. Paired t tests were used to assess limb symmetry for peak medial and tibiofemoral contact forces in all patients, and a mixed-design analysis of variance was used to analyze the effect of passing or failing RTS testing on contact force asymmetry.

RESULTS

Among all patients, neither statistically significant nor meaningful contact force asymmetries were identified. However, patients who failed RTS testing exhibited meaningful contact force asymmetries, with tibiofemoral contact force being significantly lower for the involved knee. Conversely, patients who passed RTS testing exhibited neither significant nor meaningful contact force asymmetries.

CONCLUSION

Joint contact force asymmetries during gait are present in some patients 6 months after ACL reconstruction. Patients who demonstrated poor functional performance on RTS readiness testing exhibited significant and meaningful contact force asymmetries.

CLINICAL RELEVANCE

When assessing all patients together, variability in the functional status obscured significant and meaningful differences in contact force asymmetry in patients 6 months after ACL reconstruction. These specific RTS readiness criteria appear to differentiate between those who demonstrate joint contact force symmetry after ACL reconstruction and those who do not.

Cross-education strength and activation after eccentric exercise

CONTEXT

After injury, eccentric exercise of the injured limb is often contraindicated. Cross-education training, whereby the uninvolved limb is exercised, is an alternative that may improve quadriceps muscle strength and activation in the unexercised limb.

OBJECTIVE

To determine the effect of eccentric exercise on quadriceps strength and activation gains in the unexercised limb.

PATIENTS OR OTHER PARTICIPANTS

Eighteen healthy individuals were randomly assigned to an eccentric training group or a control group.

INTERVENTION(S)

Quadriceps strength and activation measures were collected at preintervention, midintervention, and postintervention. Eccentric training participants exercised their dominant limb with a dynamometer in eccentric mode at 60°/s, 3 times per week for 8 weeks.

MAIN OUTCOME MEASURE(S)

Quadriceps strength was quantified at 30° and 60°/s in concentric and eccentric modes. Quadriceps activation was assessed using the burst superimposition technique and quantified via the central activation ratio. A 2 × 3 repeated-measures analysis of variance was used to detect the effects of group and testing session on quadriceps strength and activation. Where appropriate, post hoc Bonferroni multiple-comparisons procedures were used.

RESULTS

We found greater eccentric strength in the unexercised limbs of eccentric training participants between preintervention and midintervention and between preintervention and postintervention (preintervention to midintervention: 30°/s P = .05; preintervention to postintervention: 30°/s P = .02, 60°/s P = .02). No differences were noted in concentric strength (P > .05). An overall trend toward greater quadriceps activation in the unexercised knee was detected between preintervention and postintervention (P = .063), with the eccentric training group demonstrating a strong effect (Cohen d = 0.83). Control strength did not change (P > .05).

CONCLUSIONS

Exercising with eccentric actions resulted in mode-specific and velocity-specific gains in quadriceps strength in the unexercised limb. A trend toward greater quadriceps activation in the unexercised knee was noted, suggesting that strength gains may have occurred because of enhanced neural activity. This type of therapy may be a useful addition to rehabilitation programs designed to improve quadriceps strength.

Sensory response following knee joint damage in rabbits

BACKGROUND

Altered sensory information arising from damaged knee joint structures has been hypothesized as a contributing factor to persistent muscle dysfunction following injury.

METHODS

Composite femoral nerve sensory signal was measured in 24 rabbits randomly allocated (8 per group) to receive surgical anterior cruciate ligament (ACL) transection with or without autograft reconstruction or nothing (control). Two-weeks after the intervention composite afferent signals were recorded from the femoral nerve. Side-to-side ratios (surgical side vs contralateral healthy side) for peak femoral nerve afferent composite signal were used for comparison.

RESULTS

Femoral nerve afferent signal ratios were significantly higher in the ACL-R (2.21 ± 0.74) group when compared to the ACL-T (1.28 ± 0.61, P=0.02) group and Control group (1.31 ± 0.78, P=0.03).

CONCLUSION

The magnitude of sensory information recorded on the femoral nerve is increased following ACL injury and reconstruction surgery, but not after an isolated ACL injury in rabbits.

Manual therapy directed at the knee or lumbopelvic region does not influence quadriceps spinal reflex excitability

Manual therapies, directed to the knee and lumbopelvic region, have demonstrated the ability to improve neuromuscular quadriceps function in individuals with knee pathology. It remains unknown if manual therapies may alter impaired spinal reflex excitability, thus identifying a potential mechanism in which manual therapy may improve neuromuscular function following knee injury.

AIM

To determine the effect of local and distant mobilisation/manipulation interventions on quadriceps spinal reflex excitability.

METHODS

Seventy-five individuals with a history of knee joint injury and current quadriceps inhibition volunteered for this study. Participants were randomised to one of five intervention groups: lumbopelvic manipulation (grade V), lumbopelvic manipulation positioning (no thrust), grade IV patellar mobilisation, grade I patellar mobilisation, and control (no treatment). Changes in spinal reflex excitability were quantified by assessing the Hoffmann reflex (H-reflex), presynaptic, and postsynaptic excitability. A hierarchical linear-mixed model for repeated measures was performed to compare changes in outcome variables between groups over time (pre, post 0, 30, 60, 90 min).

RESULTS

There were no significant differences in H-reflex, presynaptic, or postsynaptic excitability between groups across time.

CONCLUSIONS

Manual therapies directed to the knee or lumbopelvic region did not acutely change quadriceps spinal reflex excitability. Although manual therapies may improve impairments and functional outcomes the underlying mechanism does not appear to be related to changes in spinal reflex excitability.

Closed chain assessment of quadriceps activation using the superimposed burst technique

The superimposed burst technique is used to estimate quadriceps central activation ratio during a maximal voluntary isometric contraction, which is calculated from force data during an open-chain knee extension task. Assessing quadriceps activation in a closed-chain position would more closely simulate the action of the quadriceps during activity. Our aim was to determine the test-retest reliability of the quadriceps central activation ratio in the closed chain.

METHODS

Twenty-two healthy, active volunteers (13M/12F; age=23.8±3; height=72.7±14.5cm; mass=175.3±9.6kg) were recruited to participate. Knee extension MVIC torque and the peak torque during a superimposed electrical stimulus delivered to the quadriceps during an MVIC were measured to estimate quadriceps CAR. Interclass correlation coefficients were used to assess test-retest reliability between sessions, and Bland-Altman plots to graphically assess agreement between sessions.

RESULTS

Test-retest reliability was fair for CAR (ICC2,k=0.68; P=0.005), with a mean difference of -2.8±10.3%, and limits of agreement ranging -23.1-18.1%.

CONCLUSIONS

CAR calculated using the superimposed burst technique is moderately reliable in a closed-chain position using technique-based instruction. Although acceptable reliability was demonstrated, wide limits of agreement suggest high variability between sessions.

Functional electrical stimulation for equine epaxial muscle spasms: retrospective study of 241 clinical cases

A retrospective study of 241 clinical cases, utilising over 1,800 functional electrical stimulation (FES) treatments to alleviate epaxial muscle spasms, showed that almost 80% (191) of the horses had a 1-grade improvement in muscle spasms after 2 FES treatments, based on the Modified Ashworth Scale adapted to horses. In addition, 60% (142) of these horses showed a sustained improvement for a minimum of 2 months.

Kinesiophobia after anterior cruciate ligament rupture and reconstruction: noncopers versus potential copers

STUDY DESIGN

Secondary-analysis, longitudinal cohort study.

OBJECTIVES

To compare kinesiophobia levels in noncopers and potential copers at time points spanning pre- and post-anterior cruciate ligament (ACL) reconstruction and to examine the association between changes in kinesiophobia levels and clinical measures.

BACKGROUND

After ACL injury, a screening examination may be used to classify patients as potential copers or noncopers based on dynamic knee stability. Quadriceps strength, single-leg hop performance, and self-reported knee function are worse in noncopers. High kinesiophobia levels after ACL reconstruction are associated with poorer self-reported knee function and lower return-to-sport rates. Kinesiophobia levels have not been examined before ACL reconstruction, across the transition from presurgery to postsurgery, or based on potential coper and noncoper classification.

METHODS

Quadriceps strength indexes, single-leg hop score indexes, self-reported knee function (Knee Outcome Survey activities of daily living subscale, global rating scale), and kinesiophobia (Tampa Scale of Kinesiophobia [TSK-11]) scores were compiled for potential copers (n = 50) and noncopers (n = 61) from 2 clinical trial databases. A repeated-measures analysis of variance was used to compare TSK-11 scores between groups and across 4 time points (before preoperative treatment, after preoperative treatment, 6 months post-ACL reconstruction, and 12 months post-ACL reconstruction). Correlations determined the association of kinesiophobia levels with other clinical measures.

RESULTS

Presurgery TSK-11 scores were significantly higher in noncopers than in potential copers. Postsurgery, no group differences existed. TSK-11 scores in both groups decreased across all time points; however, TSK-11 scores decreased more in noncopers in the interval between presurgery and postsurgery. In noncopers, the decreases in TSK-11 scores from presurgery to postsurgery and after surgery were related to improvements in the Knee Outcome Survey activities of daily living subscale, whereas the association was only present in potential copers after surgery.

CONCLUSION

Kinesiophobia levels were high in both noncopers and potential copers preoperatively. Restoration of mechanical knee stability with surgery might have contributed to decreased kinesiophobia levels in noncopers. Kinesiophobia is related to knee function after surgery, regardless of preoperative classification as a potential coper or noncoper.

Tibial displacement and rotation during seated knee extension and wall squatting: a comparative study of tibiofemoral kinematics between chronic unilateral anterior cruciate ligament deficient and healthy knees

BACKGROUND

Following anterior cruciate ligament (ACL) rupture, the knee becomes unstable with alterations in joint kinematics including anterior tibial displacement (ATD), and internal tibial rotation. Therapeutic exercises that promote faulty kinematics should be discouraged, especially early post-reconstruction, to avoid graft stretching and possibly longer-term osteoarthritis. Our study aimed to compare ATD and tibial rotation during two commonly prescribed exercises, namely: open kinetic chain (OKC) seated extension and closed kinetic chain (CKC) single leg wall squatting in ACL-deficient and healthy knees.

METHODS

Eight ACL-deficient patients and eight healthy subjects matched for age, gender and sports history were assessed using Qualisys 3D-Motion Analysis System to track 17 infrared markers while performing a seated knee extension with 3kg weight and a unilateral wall squat. We developed a model to measure joint kinematics through 70° of knee flexion and extension. ANOVA and paired t-tests compared relative ATD and tibial rotation between exercises and groups at 10° increments of flexion and extension.

RESULTS

We found increased ATD in the wall squat compared to the seated extension (p=0.049). There was no difference in ATD between the healthy and ACL-deficient knees but overall the tibia was significantly more internally rotated (p=0.003) in ACL-deficient knees, irrespective of the exercise, possibly interfering with the screw-home mechanism.

CONCLUSIONS

CKC exercises, in particular wall squats, are not necessarily safer for patients with ACL-deficiency and possibly ACL-reconstruction; although generalization should only be made with appropriate caution. Clinicians require a detailed knowledge of the effect of exercise on knee joint kinematics.

The role of muscle activation in cruciate disease

Traditional investigations into the etiopathogenesis of canine cranial cruciate ligament (CCL) disease have focused primarily on the biological and mechanical insults to the CCL as a passive stabilizing structure of the stifle. However, with recent collaboration between veterinarians and physical therapists, an increased focus on the role of muscle activity and aberrant motor control mechanisms associated with anterior cruciate ligament (ACL) injuries and rehabilitation in people has been transferred and applied to dogs with CCL disease. Motor control mechanisms in both intact and cruciate-deficient human knees may have direct translation to canine patients, because the sensory and motor components are similar, despite moderate anatomic and biomechanical differences. Components of motor control, such as muscle recruitment and the coordination and amplitudes of activation are strongly influenced by afferent proprioceptive signaling from peri- and intra-articular structures, including the cruciate ligaments. In people, alterations in the timing or amplitude of muscle contractions contribute to uncoordinated movement, which can play a critical role in ACL injury, joint instability and the progression of osteoarthritis (OA). A better understanding of motor control mechanisms as they relate to canine CCL disease is vitally important in identifying modifiable risk factors and applying preventative measures, for development of improved surgical and rehabilitative treatment strategies. The purpose of this review article is to analyze the influence of altered motor control, specifically pelvic limb muscle activation, in dogs with CCL disease as evidenced by mechanisms of ACL injury and rehabilitation in people.

Muscle morphometric effect of anterior cruciate ligament injury measured by computed tomography: aspects on using non-injured leg as control

Background

Anterior cruciate ligament (ACL) tears are common, functionally disabling, and predispose to subsequent injuries and early onset of osteoarthritis in the knee. Injuries result in muscular atrophy and impaired muscular activation. To optimize surgical methods and rehabilitation strategies, knowledge of the effects of ACL injuries on muscles size and function is needed. Asymmetry due to limb dominance implies that the effect of ACL-injury might be different in right-sided and left-sided injuries which, should be taken in account when evaluating the effect of an injury. Evaluation of the effects of injuries is usually made with the contralateral leg as control. The aim of this study is to describe the effect of ACL-injuries on thigh muscle size and also to analyze feasibility of using contralateral limb as control.

Methods

Sixty-two patients scheduled to undergo ACL reconstruction were examined with computed tomography (CT). Muscle cross sectional area (CSA) was recorded for quadriceps, hamstrings, gracilis and sartorius 15 cm above the knee joint. Comparisons were made between the injured and non-injured side and between individuals separated by gender and side of injury. Comparisons were also made for patients with or without concomitant meniscal tear, for patients differing in time between injury and examinations and for patients with different level of physical activity after the injury.

Results

Quadriceps CSA was 5% smaller on the injured side. There was an indication that the muscles of the right thigh were generally bigger than those of the left thigh. The difference between the injured and the non-injured side was larger for right-sided injuries than for left-sided. There was also a greater difference in semimembranosus for women than for men. There were no differences related to meniscal injury, time since injury or physical activity.

Conclusion

The use of contralateral leg for evaluating the effect of ACL-injury is often the only available alternative but our study indicates that the difference in CSA between injured and non-injured side does not necessarily reflect the true degree of atrophy, as there are side differences both in muscle size in general and in the effect of an ACL-injury on muscle size.

Association between Disability and Psychological Factors and Dose of Neuromuscular Electrical Stimulation in Subjects with Rheumatoid Arthritis

BACKGROUND

The therapeutic effect of neuromuscular electrical stimulation (NMES) on muscle strengthening and hypertrophy depends on its dose. Patients must tolerate high doses of NMES to maximize gains in muscle function. It is unknown why some patients are able to achieve high NMES dose while others are not. Disability and psychological attributes may play a role in a patient's tolerance of NMES dose.

PURPOSE

To explore if disability and psychological attributes associate with the ability to achieve high doses of NMES in patients with rheumatoid arthritis (RA).

METHODS

Cross-sectional study. Forty subjects with RA participated in 2 sessions of NMES intervention to the quadriceps muscles. The highest NMES dose achieved by each subject was recorded. Dose was defined as the torque produced by the NMES as a percentage of the torque produced during a maximum voluntary isometric contraction. Subjects were then grouped in high or low NMES dose. Variables investigated in this study included disability, pain coping strategies, pain acceptance, sense of mastery or control, anxiety, and depression. Correlations were sought between these factors and NMES dose.

MAIN RESULTS

In unadjusted models, disability, coping self-statements, catastrophizing, and anxiety were predictors of NMES dose. In adjusted models only disability (OR = 0.17 [95% CI: 0.04, 0.77]) and catastrophizing (OR = 0.85 [95% CI: 0.72, 0.99]) predicted NMES dose.

CONCLUSION

Patients with RA with lower disability and lower catastrophising achieve higher doses of NMES. Identifying factors associated with achieving high NMES dose may guide strategies to improve effectiveness of this intervention.

Intramuscular adipose tissue and central activation in older adults

INTRODUCTION

Intramuscular adipose tissue (IMAT) is a potential contributor to declining force production and may be related to impaired central activation; therefore, the purpose of this report is to describe IMAT composition and its association with central activation in older adults. The central activation ratio (CAR) of the knee extensors was assessed using a superimposition technique in 15 older adults (29 legs) along with the cross-sectional area of IMAT and lean tissue.

RESULTS

IMAT and CAR are inversely related in older adults (r = -0.51, P = 0.005), and many subjects with high IMAT have deficits in central activation, whereas those with low IMAT have normal central activation.

CONCLUSIONS

These novel findings may assist in unraveling why muscle force production and lean tissue cross-sectional area are not strongly linked, as the ability to centrally activate muscle appears to be unrelated to lean muscle area and may be dependent in part on IMAT levels.

Relationship between muscle volume and muscle torque of the hamstrings after anterior cruciate ligament lesion

PURPOSE

This study was conducted to identify factors other than morphological muscle strength factors that affect injured and uninjured sides of knee flexors with anterior cruciate ligament (ACL) lesions.

METHODS

The study population consisted of 22 patients with ACL lesions. Their hamstring muscle volume was measured on MRI, and muscle torque per muscle volume was calculated as the peak torque of knee flexion divided by hamstring muscle volume.

RESULTS

The mean muscle torque per unit volume of hamstrings in patients with ACL rupture was 0.09 ± 0.02 Nm/cm(3) at 60°/s and 0.08 ± 0.01 Nm/cm(3) at 180°/s on the injured side, and 0.11 ± 0.02 Nm/cm(3) at 60°/s and 0.08 ± 0.01 Nm/cm(3) at 180°/s on the uninjured side. The mean muscle torque per unit volume of hamstrings in control subjects was 0.11 ± 0.02 Nm/cm(3) at 60°/s and 0.08 ± 0.03 Nm/cm(3) at 180°/s. One-factor ANOVA analysis found no significant differences between the three groups at either flexion velocity.

CONCLUSIONS

Neurological dysfunction does not appear to exist in knee flexor muscles after ACL injury, unlike the quadriceps. Since the mechanism of muscle weakness will differ depending on the muscle, it is important for clinicians to take this discrepancy into consideration.

LEVEL OF EVIDENCE

II.

Within- and between-session reliability of the maximal voluntary knee extension torque and activation

A ratio between the torque generated by maximal voluntary isometric contraction (MVIC) and exogenous electrical stimulus, central activation ratio (CAR), has been widely used to assess quadriceps function. To date, no data exist regarding between-session reliability of this measurement. Thirteen neurologically sound volunteers underwent three testing sessions (three trials per session) with 48 hours between-session. Subjects performed MVICs of the quadriceps with the knee locked at 90° flexion and the hip at 85°. Once the MVIC reached a plateau, an electrical stimulation from superimposed burst technique (SIB: 125 V with peak output current 450 mA) was manually delivered and transmitted directly to the quadriceps via stimulating electrodes. CAR was calculated by using the following equation: CAR = MVIC torque/MVIC + SIB torque. Intraclass correlation coefficients (ICC) were calculated within- (ICC((2,1))) and between-session (ICC((2,k))) for MVIC torques and CAR values. Our data show that quadriceps MVIC and CAR are very reliable both within- (ICC((2,1)) = 0.99 for MVIC; 0.94 for CAR) and between-measurement sessions (ICC((2,k)) = 0.92 for MVIC; 0.86 for CAR) in healthy young adults. For clinical research, more data of the patients with pathological conditions are required to ensure reproducibility of calculation of CAR.

Relationship between intensity of quadriceps muscle neuromuscular electrical stimulation and strength recovery after total knee arthroplasty

BACKGROUND

Neuromuscular electrical stimulation (NMES) can facilitate the recovery of quadriceps muscle strength after total knee arthroplasty (TKA), yet the optimal intensity (dosage) of NMES and its effect on strength after TKA have yet to be determined.

OBJECTIVE

The primary objective of this study was to determine whether the intensity of NMES application was related to the recovery of quadriceps muscle strength early after TKA. A secondary objective was to quantify quadriceps muscle fatigue and activation immediately after NMES to guide decisions about the timing of NMES during rehabilitation sessions.

DESIGN

This study was an observational experimental investigation.

METHODS

Data were collected from 30 people who were 50 to 85 years of age and who received NMES after TKA. These people participated in a randomized controlled trial in which they received either standard rehabilitation or standard rehabilitation plus NMES to the quadriceps muscle to mitigate strength loss. For the NMES intervention group, NMES was applied 2 times per day at the maximal tolerable intensity for 15 contractions beginning 48 hours after surgery over the first 6 weeks after TKA. Neuromuscular electrical stimulation training intensity and quadriceps muscle strength and activation were assessed before surgery and 3.5 and 6.5 weeks after TKA.

RESULTS

At 3.5 weeks, there was a significant association between NMES training intensity and a change in quadriceps muscle strength (R(2)=.68) and activation (R(2)=.22). At 6.5 weeks, NMES training intensity was related to a change in strength (R(2)=.25) but not to a change in activation (R(2)=.00). Furthermore, quadriceps muscle fatigue occurred during NMES sessions at 3.5 and 6.5 weeks, whereas quadriceps muscle activation did not change.

LIMITATIONS

Some participants reached the maximal stimulator output during at least 1 treatment session and might have tolerated more stimulation.

CONCLUSIONS

Higher NMES training intensities were associated with greater quadriceps muscle strength and activation after TKA.

Quadriceps activation failure after anterior cruciate ligament rupture is not mediated by knee joint effusion

STUDY DESIGN

Descriptive prospective cohort study.

OBJECTIVES

To investigate the relationships between knee joint effusion, quadriceps activation, and quadriceps strength. These relationships may help clinicians better identify impaired quadriceps activation.

BACKGROUND

After anterior cruciate ligament (ACL) injury, the involved quadriceps may demonstrate weakness. Experimental data have shown that quadriceps activation and strength may be directly mediated by intracapsular joint pressure created by saline injection. An inverse relationship between quadriceps activation and the amount of saline injected has been reported. This association has not been demonstrated for traumatic effusion. We hypothesized that traumatic joint effusion due to ACL rupture and postinjury quadriceps strength would correlate well with quadriceps activation, allowing clinicians to use effusion and strength measurement as a surrogate for electrophysiological assessment of quadriceps activation.

METHODS

Prospective data were collected on 188 patients within 100 days of ACL injury (average, 27 days) referred from a single surgeon. A complete clinical evaluation of the knee was performed, including ligamentous assessment and assessment of range of motion and effusion. Quadriceps function was electrophysiologically assessed using maximal volitional isometric contraction and burst superimposition techniques to quantify both strength and activation.

RESULTS

Effusion grade did not correlate with quadriceps central activation ratio (CAR) (zero effusion: mean ± SD CAR, 93.5% ± 5.8%; trace effusion: CAR, 93.8% ± 9.5%; 1+ effusion: CAR, 94.0% ± 7.5%; 2+/3+ effusion: CAR, 90.6% ± 11.1%). These values are lower than normative data from healthy subjects (CAR, 98% ± 3%).

CONCLUSION

Joint effusion after ACL injury does not directly mediate quadriceps activation failure seen after injury. Therefore, it should not be used as a clinical substitute for electrophysiological assessment of quadriceps activation. Patients presenting to physical therapy after ACL injury should be treated with high-intensity neuromuscular electrical stimulation to help normalize this activation.

The effect of anterior cruciate ligament rupture on the timing and amplitude of gastrocnemius muscle activation: a study of alterations in EMG measures and their relationship to knee joint stability

Changes in hamstring and quadriceps activity are well known in individuals with anterior cruciate ligament deficiency (ACLD) to potentially compensate for knee joint instability. However, few studies have explored gastrocnemius activity or its relationship to knee stability. The purpose of this study was therefore to examine the activation characteristics of medial gastrocnemius (MG) in ACLD subjects and relate any changes to knee joint laxity. Two subject cohorts were assessed: those with unilateral ACLD (n=15) and uninjured control subjects (n=11). Surface EMG of the left and right MG were recorded during a controlled single leg hop on each limb. Onset and offset of MG activation relative to take-off, during flight and landing were calculated as well as muscle activity (RMS). Passive antero-posterior knee laxity was measured with a KT1000 arthrometer during a maximal manual displacement test. Medial gastrocnemius activity on the injured side of ACLD participants demonstrated significantly prolonged activation in preparation to hop, minimal muscle inactivity prior to take-off, and increased duration of overall muscle activity when compared to the uninjured side and control subjects (p<0.05). Significant positive correlations were found between passive knee joint laxity and prolonged activation prior to knee bend. RMS of the muscle signal was not significantly different between limbs. Overall, MG on the ACLD side demonstrated longer activation, with minimal rest during the hop test, which may be an attempt to maintain knee stability. Furthermore, the strong relationship between knee laxity and prolonged muscle activation suggests that individuals with a loss of knee stability are more reliant on active control of the gastrocnemius muscle.

Early neuromuscular electrical stimulation to improve quadriceps muscle strength after total knee arthroplasty: a randomized controlled trial

BACKGROUND

The recovery of quadriceps muscle force and function after total knee arthroplasty (TKA) is suboptimal, which predisposes patients to disability with increasing age.

OBJECTIVE

The purpose of this investigation was to evaluate the efficacy of quadriceps muscle neuromuscular electrical stimulation (NMES), initiated 48 hours after TKA, as an adjunct to standard rehabilitation.

DESIGN

This was a prospective, longitudinal randomized controlled trial.

METHODS

Sixty-six patients, aged 50 to 85 years and planning a primary unilateral TKA, were randomly assigned to receive either standard rehabilitation (control) or standard rehabilitation plus NMES applied to the quadriceps muscle (initiated 48 hours after surgery). The NMES was applied twice per day at the maximum tolerable intensity for 15 contractions. Data for muscle strength, functional performance, and self-report measures were obtained before surgery and 3.5, 6.5, 13, 26, and 52 weeks after TKA.

RESULTS

At 3.5 weeks after TKA, significant improvements with NMES were found for quadriceps and hamstring muscle strength, functional performance, and knee extension active range of motion. At 52 weeks, the differences between groups were attenuated, but improvements with NMES were still significant for quadriceps and hamstring muscle strength, functional performance, and some self-report measures.

LIMITATIONS

Treatment volume was not matched for both study arms; NMES was added to the standard of care treatment. Furthermore, testers were not blinded during testing, but used standardized scripts to avoid bias. Finally, some patients reached the maximum stimulator output during at least one treatment session and may have tolerated more stimulation.

CONCLUSIONS

The early addition of NMES effectively attenuated loss of quadriceps muscle strength and improved functional performance following TKA. The effects were most pronounced and clinically meaningful within the first month after surgery, but persisted through 1 year after surgery.

Lumbopelvic joint manipulation and quadriceps activation of people with patellofemoral pain syndrome

CONTEXT

Quadriceps weakness and inhibition are impairments associated with patellofemoral pain syndrome (PFPS). Lumbopelvic joint manipulation has been shown to improve quadriceps force output and inhibition, but the duration of the effect is unknown.

OBJECTIVE

To determine whether quadriceps strength and activation are increased and maintained for 1 hour after high-grade or low-grade joint mobilization or manipulation applied at the lumbopelvic region in people with PFPS.

DESIGN

Randomized controlled clinical trial.

SETTING

University laboratory.

PATIENTS OR OTHER PARTICIPANTS

Forty-eight people with PFPS (age = 24.6 ± 8.9 years, height = 174.3 ± 11.2 cm, mass = 78.4 ± 16.8 kg) participated.

INTERVENTION(S)

Participants were randomized to 1 of 3 groups: lumbopelvic joint manipulation (grade V), side-lying lumbar midrange flexion and extension passive range of motion (grade II) for 1 minute, or prone extension on the elbows for 3 minutes.

MAIN OUTCOME MEASURE(S)

Quadriceps force and activation were measured using the burst superimposition technique during a seated isometric knee extension task. A 2-way repeated-measures analysis of variance was performed to compare changes in quadriceps force and activation among groups over time (before intervention and at 0, 20, 40, and 60 minutes after intervention).

RESULTS

We found no differences in quadriceps force output (F(5.33,101.18) = 0.65, P = .67) or central activation ratio (F(4.84,92.03) = 0.38, P = .86) values among groups after intervention. When groups were pooled, we found differences across time for quadriceps force (F(2.66,101.18) = 5.03, P = .004) and activation (F(2.42,92.03) = 3.85, P = .02). Quadriceps force was not different at 0 minutes after intervention (t(40) = 1.68, P = .10), but it decreased at 20 (t(40) = 2.16, P = .04), 40 (t(40) = 2.87, P = .01) and 60 (t(40) = 3.04, P = .004) minutes after intervention. All groups demonstrated decreased quadriceps activation at 0 minutes after intervention (t(40) = 4.17, P < .001), but subsequent measures were not different from preintervention levels (t(40) range, 1.53-1.83, P > .09).

CONCLUSIONS

Interventions directed at the lumbopelvic region did not have immediate effects on quadriceps force output or activation. Muscle fatigue might have contributed to decreased force output and activation over 1 hour of testing.

Measuring functional improvement after total knee arthroplasty requires both performance-based and patient-report assessments: a longitudinal analysis of outcomes

The purpose was to explore the responsiveness of both patient-report and performance-based outcome measures to determine functional changes during the acute and long-term postoperative recovery after total knee arthroplasty (TKA). One hundred patients scheduled for unilateral TKA underwent testing preoperatively and at 1 and 12 months postoperatively using the Delaware Osteoarthritis Profile. All physical performance measures decreased initially after surgery then increased in the long term; however, the perceived function did not follow the same trend, and some showed an increase immediately after surgery. Patient-report measures were variable, with no to small response early, but had excellent long-term responsiveness that was twice as large as performance measures. Patient perception fails to capture the acute functional declines after TKA and may overstate the long-term functional improvement with surgery.