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

Transcranial magnetic stimulation and volitional quadriceps activation

CONTEXT

Quadriceps-activation deficits have been reported after meniscectomy. Transcranial magnetic stimulation (TMS) in conjunction with maximal contractions affects quadriceps activation in patients after meniscectomy.

OBJECTIVE

To determine the effect of single-pulsed TMS on quadriceps central activation ratio (CAR) in patients after meniscectomy.

DESIGN

Randomized controlled clinical trial.

SETTING

University laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty participants who had partial meniscectomy and who had a CAR less than 85% were assigned randomly to the TMS group (7 men, 4 women; age  =  38.1 ± 16.2 years, height  =  176.8 ± 11.5 cm, mass  =  91.8 ± 27.5 kg, postoperative time  =  36.7 ± 34.9 weeks) or the control group (7 men, 2 women; age  =  38.2 ± 17.5 years, height  =  176.5 ± 7.9 cm, mass  =  86.2 ± 15.3 kg, postoperative time  =  36.6 ± 37.4 weeks).

INTERVENTION(S)

Participants in the experimental group received TMS over the motor cortex that was contralateral to the involved leg and performed 3 maximal quadriceps contractions with the involved leg. The control group performed 3 maximal quadriceps contractions without the TMS.

MAIN OUTCOME MEASURE(S)

Quadriceps activation was assessed using the CAR, which was measured in 70° of knee flexion at baseline and at 0, 10, 30, and 60 minutes posttest. The CAR was expressed as a percentage of full activation.

RESULTS

Differences in CAR were detected over time (F(4,72)  =  3.025, P  = .02). No interaction (F(4,72)  =  1.457, P  =  .22) or between-groups differences (F(1,18)  =  0.096, P  =  .76) were found for CAR. Moderate CAR effect sizes were found at 10 (Cohen d  =  0.54, 95% confidence interval [CI]  =  -0.33, 1.37) and 60 (Cohen d  =  0.50, 95% CI  =  -0.37, 1.33) minutes in the TMS group compared with CAR at baseline. Strong effect sizes were found for CAR at 10 (Cohen d  =  0.82, 95% CI  =  -0.13, 1.7) and 60 (Cohen d  =  1.06, 95% CI  =  0.08, 1.95) minutes in the TMS group when comparing percentage change scores between groups.

CONCLUSIONS

No differences in CAR were found between groups at selected points within a 60-minute time frame, yet moderate to strong effect sizes for CAR were found at 10 and 60 minutes in the TMS group, indicating increased activation after TMS.

Relationship between transcranial magnetic stimulation and percutaneous electrical stimulation in determining the quadriceps central activation ratio

OBJECTIVE

To determine the relationship between quadriceps central activation ratios (CARs) derived from a percutaneous electrical stimulation (CAR(SIB)) and a transcranial magnetic stimulation (CAR(TMS)) in healthy participants.

DESIGN

Nineteen healthy participants (5 men, 14 women, 23.7 ± 4.8 yrs, 66.8 ± 10.0 kg, and 170.1 ± 7.0 cm) qualified for this descriptive study. Muscle activation, using both methods (CAR(SIB) and CAR(TMS)), was measured at days 1, 14, and 28. All participants performed both methods in a counterbalanced order. Correlation coefficients and Bland-Altman plots were used to assess relationships and agreement between the two methods. For both methods, reliability was assessed at 14 and 28 days using Bland-Altman plots and intraclass correlation coefficients.

RESULTS

CAR(TMS) scores were higher than CAR(SIB) scores for all three sessions, with mean differences between CAR scores of -0.06 (95% confidence interval, -0.19-0.07), -0.03 (95% confidence interval, -0.14-0.08), and -0.03 (95% confidence interval, -0.11-0.05). There was a significant moderate positive correlation between CAR(SIB) and CAR(TMS) at 14 days from baseline (ρ = 0.45, P = 0.05). Intersession reliability was strong for CAR(SIB) at 14 and 28 days from baseline (intraclass correlation coefficients = 0.80 [P = 0.001] and 0.85 [P < 0.001], respectively). Intersession reliability for CAR(TMS) was moderate from baseline to 14 days (intraclass correlation coefficients = 0.68 [P = 0.01]).

CONCLUSIONS

It does not seem that the CAR(TMS) and CAR(SIB) methods are interchangeable measurements for evaluating volitional quadriceps activation; however, both measurements seem to have acceptable agreement at 14 and 28 days compared with day 1.

Relationship between quadriceps femoris muscle volume and muscle torque at least 18 months after anterior cruciate ligament reconstruction

The purpose of this study was to evaluate motor unit recruitment in the quadriceps femoris (QF) after anterior cruciate ligament (ACL) rupture and repair. Subjects included 24 patients at ≥ 18 months after ACL reconstruction and 22 control subjects with no history of knee injury. A series of cross-sectional magnetic resonance images were obtained to compare the QF of patients' injured side with that of their uninjured sides and that of uninjured control subjects. Muscle torque per muscle volume was calculated as isokinetic peak torque divided by QF muscle volume (cm(3)). The mean muscle torque per unit volume of the injured side of patients was not significantly different from that of the uninjured side or control subjects (one-way ANOVA) Results of the present study were contrary to the results of a previous study that evaluated patients at ≤ 12 months after ACL reconstruction. The present study found that high-threshold motor unit recruitment was restored at ≥ 18 months after ACL reconstruction. Thus, clinicians must develop techniques that increase the recruitment of high-threshold motor units in the QF from the period immediately after the injury until approximately 18 months after ACL reconstruction.

WITHDRAWN: Exercise for treating isolated anterior cruciate ligament injuries in adults

BACKGROUND

The anterior cruciate ligament (ACL) is the most frequently injured ligament of the knee. Injury causes pain, effusion and inflammation leading to the inability to fully activate the thigh muscles. Regaining muscular control is essential if the individual wishes to return to pre-injury level of function and patients will invariably be referred for rehabilitation.

OBJECTIVES

To present the best evidence for effectiveness of exercise used in the rehabilitation of isolated ACL injuries in adults, on return to work and pre-injury levels of activity.

SEARCH STRATEGY

We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (Feb 2005), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 1, 2005), MEDLINE (1996 to March 2005), EMBASE (1980 to March 2005), other databases and reference lists of articles.

SELECTION CRITERIA

Randomised controlled trials and quasi-randomised trials testing exercise programmes designed to rehabilitate adults with isolated ACL injuries. Trials where participants were randomised to receive any combination of the following: no care, usual care, a single-exercise intervention, and multiple-exercise interventions, were included. The primary outcome measures of interest were returning to work and return to pre-injury level of activity post treatment, at six months and one year.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. Study authors were contacted for additional information. Adverse effects information was collected from the trials.

MAIN RESULTS

Nine trials involving 391 participants were included. Only two trials, involving 76 participants, reported conservative rehabilitation and seven trials, involving 315 participants, evaluated rehabilitation following ACL reconstruction. Methodological quality scores varied considerably across the trials, with the nature of participant and assessor blinding poorly reported. Trial comparisons fell into six categories. Pooling of data was rarely possible due to lack of appropriate data as well as the wide variety in outcome measures and time points reported. Insufficient evidence was found to support the efficacy of one exercise intervention over another.

AUTHORS' CONCLUSIONS

This review has demonstrated an absence of evidence to support one form of exercise intervention against another and the use of supplementary exercises in the management of isolated ACL injuries. Further research in the form of large scale well designed randomised controlled trials with suitable outcome measures and surveillance periods, using standardised reporting should be considered.

Relationship between quadriceps femoris muscle volume and muscle torque after anterior cruciate ligament rupture

PURPOSE

The purpose of this study was to obtain evidence to support the hypothesis that motor unit recruitment is reduced in the quadriceps femoris (QF) of patients with ACL rupture.

METHODS

We compared muscle torque per unit volume in the QF from injured and uninjured sides to normal subjects. If high-threshold motor unit recruitment is reduced in patients with ACL rupture, this reduction will theoretically lead to a reduction in muscle torque per unit volume compared to the control group. The subjects included 22 patients with ACL rupture and 22 subjects with no history of knee injury. To identify the muscle torque per unit volume, the isokinetic peak torque was divided by QF volume which was obtained by MRI.

RESULTS

Tests revealed that the mean muscle torque per unit volume of the uninjured and injured sides was significantly lower than those of the control group.

CONCLUSION

This study demonstrated that the values of the muscle torque per unit volume of both injured and uninjured sides of patients with ACL rupture were significantly lower than those of the control group, thereby providing indirect evidence of the hindrance of motor unit recruitment in these patients. The results of the present study also indicate that there may be bilateral QF weakness in patients with ACL rupture. Since persistent QF weakness is a significant barrier to effective rehabilitation in patients with ACL injuries, a better understanding of the underlying mechanisms will allow clinicians and scientists to develop more effective therapeutic strategies for patient rehabilitation.

Quadriceps activation following knee injuries: a systematic review

CONTEXT

Arthrogenic muscle inhibition is an important underlying factor in persistent quadriceps muscle weakness after knee injury or surgery.

OBJECTIVE

To determine the magnitude and prevalence of volitional quadriceps activation deficits after knee injury.

DATA SOURCES

Web of Science database.

STUDY SELECTION

Eligible studies involved human participants and measured quadriceps activation using either twitch interpolation or burst superimposition on patients with knee injuries or surgeries such as anterior cruciate ligament deficiency (ACLd), anterior cruciate ligament reconstruction (ACLr), and anterior knee pain (AKP).

DATA EXTRACTION

Means, measures of variability, and prevalence of quadriceps activation (QA) failure (<95%) were recorded for experiments involving ACLd (10), ACLr (5), and AKP (3).

DATA SYNTHESIS

A total of 21 data sets from 18 studies were initially identified. Data from 3 studies (1 paper reporting data for both ACLd and ACLr, 1 on AKP, and the postarthroscopy paper) were excluded from the primary analyses because only graphical data were reported. Of the remaining 17 data sets (from 15 studies), weighted mean QA in 352 ACLd patients was 87.3% on the involved side, 89.1% on the uninvolved side, and 91% in control participants. The QA failure prevalence ranged from 0% to 100%. Weighted mean QA in 99 total ACLr patients was 89.2% on the involved side, 84% on the uninvolved side, and 98.5% for the control group, with prevalence ranging from 0% to 71%. Thirty-eight patients with AKP averaged 78.6% on the involved side and 77.7% on the contralateral side. Bilateral QA failure was commonly reported in patients.

CONCLUSIONS

Quadriceps activation failure is common in patients with ACLd, ACLr, and AKP and is often observed bilaterally.

Functional performance and muscle strength phenotypes in men and women with Danon disease

Danon disease is a rare X-linked myopathy that is characterized clinically by a triad of cardiomyopathy, skeletal myopathy, and cognitive impairment. The purpose of this investigation was to quantify functional performance, muscle weakness, and quadriceps activation in individuals with Danon disease as compared with healthy individuals. Four males (ages 10-34 years) and 4 females (ages 16-50 years), with the genetic markers of Danon disease, were compared with 8 healthy males (ages 22-34 years) and 8 healthy females (ages 23-41 years) and previously reported norms. Affected males and females had decreased functional performance, significant generalized muscle weakness, and decreased quadriceps strength and activation when compared with healthy individuals. Affected males had larger deficits in function, strength, and activation when compared with affected females. The results indicate that, although the presentation of Danon disease is variable and is typically only described in males, muscle weakness patterns exist in both affected males and females.

Effects of joint effusion on proprioception in patients with knee osteoarthritis: a single-blind, randomized controlled clinical trial

OBJECTIVE

To assess the effects of joint effusion on proprioceptive status in patients with knee osteoarthritis (OA).

DESIGN

A single-blind, randomized, controlled clinical trial in 40 female subjects aged 50 years and over with painful knee OA. All subjects were randomly assigned to either the control or experimental group. A volume of 20 mL of normal saline was injected into the knee joint cavity of subjects in the experimental group under ultrasonographic guidance. Proprioceptive acuity was assessed by active repositioning of the lower limb using an electrogoniometer to measure knee joint position sense (JPS) under both non-weight-bearing (NWB) and weight-bearing (WB) conditions twice, with a 20-min rest interval. The experimental group performed the task twice (Test 1 and Test 2) before and within 5 min after joint infusion. The control group also performed Test 1 and Test 2 without joint infusion. The outcome of interest was the absolute angular error (AAE), ignoring the direction of the error, between the randomized target angle and the patient's reproduced angle of JPS values.

RESULTS

Compared with the control group, JPS was significantly compromised in the experimental group in the NWB test after joint infusion (P=0.025). However, no significant differences in the angular error were observed between Test 1 and Test 2 in the control group for the NWB or WB test or in the experimental group for the WB test after infusion (P>0.05).

CONCLUSIONS

This study showed that joint effusion impairs proprioceptive function in osteoarthritic knee joints.

Cryotherapy to treat persistent muscle weakness after joint injury

Cryotherapy is a widely used modality following acute joint injury. It is considered helpful in reducing pain and swelling, and there is a growing body of evidence to suggest that it may have additional benefits in muscle function. Following joint injury, it is common for patients to experience persistent muscle weakness that is resistant to traditional strengthening exercises. This may be due to a reflex inhibition of musculature surrounding the injured joint. The underlying cause of this reflex inhibition may arise from aberrant sensory information from the joints' neural receptors, which result in a neural inhibition of motor neurons. This inhibition is beyond conscious control, is ongoing, and impedes normal joint function via a disruption of normal muscle function. Cryotherapy treatments targeted at peripheral joints have been shown to result in transient resolution of reflex inhibition, which thereby provide an environment where injured patients can benefit from a more thorough motorneuron pool during controlled rehabilitation exercises. This article presents current evidence-based recommendations regarding the use of joint cryotherapy for maximizing the effectiveness of commonly used rehabilitation exercises in patients recovering from joint injury.

A clinical trial of neuromuscular electrical stimulation in improving quadriceps muscle strength and activation among women with mild and moderate osteoarthritis

BACKGROUND

Neuromuscular electrical stimulation (NMES) has demonstrated efficacy in improving quadriceps muscle strength (force-generating capacity) and activation following knee replacement and ligamentous reconstruction. Yet, data are lacking to establish the efficacy of NMES in people with evidence of early radiographic osteoarthritis.

OBJECTIVE

The purpose of this study was to determine whether NMES is capable of improving quadriceps muscle strength and activation in women with mild and moderate knee osteoarthritis.

DESIGN

This study was a randomized controlled trial.

METHODS

Thirty women with radiographic evidence of mild or moderate knee osteoarthritis were randomly assigned to receive either no treatment (standard of care) or NMES treatments 3 times per week for 4 weeks. The effects of NMES on quadriceps muscle strength and activation were evaluated upon study enrollment, as well as at 5 and 16 weeks after study enrollment, which represent 1 and 12 weeks after cessation of NMES among the treated participants. The Western Ontario and McMaster Universities Osteoarthritis Index and a 40-foot (12.19-m) walk test were used at each testing session.

RESULTS

Improvements in quadriceps muscle strength or activation were not realized for the women in the intervention group. Quadriceps muscle strength and activation were similar across testing sessions for both groups.

LIMITATIONS

Women were enrolled based on radiographic evidence of osteoarthritis, not symptomatic osteoarthritis, which could have contributed to our null finding. A type II statistical error may have been committed despite an a priori power calculation. The assessor and the patients were not blinded to group assignment, which may have introduced bias into the study.

CONCLUSIONS

Four weeks of NMES delivered to women with mild and moderate osteoarthritis and mild strength deficits was insufficient to induce gains in quadriceps muscle strength or activation. Future research is needed to examine the dose-response relationship for NMES in people with early radiographic evidence of osteoarthritis.

Heightened flexor withdrawal responses following ACL rupture are enhanced by passive tibial translation

OBJECTIVE

Hyperexcitability of nociceptive pathways has been demonstrated with several musculoskeletal conditions but not anterior cruciate ligament (ACL) injury. The purpose was to investigate flexor withdrawal reflex (FWR) excitability following ACL rupture and determine if painless stretch of knee joint structures enhanced reflexive responses.

METHODS

Ten subjects with and 10 subjects without unilateral ACL rupture were compared. FWRs were induced through sural nerve stimulus in symmetrical stance and recumbent positions, with the knee in relaxed and stressed condition. Latencies and amplitudes of hamstring electromyographic activity were analyzed.

RESULTS

FWR thresholds were significantly diminished (p=0.05) on the injured limb (11.8±8 mA) compared to non-injured limb (18.6±13 mA) and controls (22.5±3 mA). Anterior tibial translation resulted in increased (p=0.001) amplitude of EMG hamstring response on the injured limb (70±50%) versus control (-1±20%) and decreased latency (p=0.01) of hamstring activation (82.0±13 ms).

CONCLUSIONS

Individuals with ACL rupture demonstrated increased excitability of FWR responses indicated by decreased FWR threshold and reduced hamstring muscle latency. Responses were enhanced by passive stretch of the knee joint.

SIGNIFICANCE

Subjects with ACL rupture demonstrated hyperexcitability of nociceptive pathways on the injured limb which may trigger the FWR more readily and promote the sensation of instability at the knee.

Whole-body vibration strengthening compared to traditional strengthening during physical therapy in individuals with total knee arthroplasty

This study investigated the use of whole-body vibration (WBV) as an alternative strengthening regimen in the rehabilitation of individuals with total knee arthroplasty (TKA) compared with traditional progressive resistance exercise (TPRE). Individuals post TKA (WBV n = 8; TPRE n = 8) received physical therapy with WBV or with TPRE for 4 weeks. Primary dependent variables were knee extensor strength, quadriceps muscle activation, mobility, pain, and range of motion (ROM). There was a significant increase in knee extensor strength and improvements in mobility, as measured by maximal volitional isometric contraction and the Timed Up and Go Test (TUG), respectively, for both groups (p < 0.01). The WBV knee extensor strength improved 84.3% while TPRE increased 77.3%. TUG scores improved 31% in the WBV group and 32% for the TPRE group. There were no significant differences between groups for strength or muscle activation (Hotelling's T(2) = 0.42, p = 0.80) or for mobility (F = 0.54; p = 0.66). No adverse side effects were reported in either group. In individuals with TKA, both WBV and TPRE showed improved strength and function. Influence of WBV on muscle activation remains unclear, as muscle activation levels were near normal for both groups.

Time line for noncopers to pass return-to-sports criteria after anterior cruciate ligament reconstruction

STUDY DESIGN

Randomized clinical trial.

OBJECTIVES

Determine effective interventions for improving readiness to return to sports postoperatively in patients with complete, unilateral, anterior cruciate ligament (ACL) rupture who do not compensate well after the injury (noncopers). Specifically, we compared the effects of 2 preoperative interventions on quadriceps strength and functional outcomes.

BACKGROUND

The percentage of athletes who return to sports after ACL reconstruction varies considerably, possibly due to differential responses after acute ACL rupture and different management. Prognostic data for noncopers following ACL reconstruction is absent in the literature.

METHODS

Forty noncopers were randomly assigned to receive either progressive quadriceps strength-training exercises (STR group) or perturbation training in conjunction with strength-training exercises (PERT group) for 10 preoperative rehabilitation sessions. Postoperative rehabilitation was similar between groups. Data on quadriceps strength indices [(involved limb/uninvolved limb force) x 100], 4 hop score indices, and 2 self-report questionnaires were collected preoperatively and 3, 6, and 12 months postoperatively. Mann-Whitney U tests were used to compare functional differences between the groups. Chi-square tests were used to compare frequencies of passing functional criteria and reasons for differences in performance between groups postoperatively.

RESULTS

Functional outcomes were not different between groups, except a greater number of patients in the PERT group achieved global rating scores (current knee function expressed as a percentage of overall knee function prior to injury) necessary to pass return-to-sports criteria 6 and 12 months after surgery. Mean scores for each functional outcome met return-to-sports criteria 6 and 12 months postoperatively. Frequency counts of individual data, however, indicated that 5% of noncopers passed RTS criteria at 3, 48% at 6, and 78% at 12 months after surgery.

CONCLUSION

Functional outcomes suggest that a subgroup of noncopers require additional supervised rehabilitation to pass stringent criteria to return to sports.

LEVEL OF EVIDENCE

Therapy, level 2b.Note: If watching the first video, we recommend downloading and referring to the accompanying PowerPoint slides for any text that is not readable.

Surface neuromuscular electrical stimulation for quadriceps strengthening pre and post total knee replacement

BACKGROUND

Total knee replacement has been demonstrated to be one of the most successful procedures in the treatment of osteoarthritis. However quadriceps weakness and reductions in function are commonly reported following surgery. Recently Neuromuscular Electrical Stimulation (NMES) has been used as an adjunct to traditional strengthening programmes. This review considers the effectiveness of NMES as a means of increasing quadriceps strength in patients before and after total knee replacement.

OBJECTIVES

To assess the effectiveness of NMES as a means of improving quadriceps strength before and after total knee replacement.

SEARCH STRATEGY

We searched The Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (1950 to January week 1 2008), EMBASE (1980 to 2008 week 2), Cumulative Index to Nursing and Allied Health Literature (CINAHL)(1982 to 2007/11), AMED (1985 to Jan 2008), Web of Science, and Pedro (Jan 2008) (http://www.pedro.fhs.usyd.edu.au/index.html) for randomised controlled trials and controlled clinical trials. The electronic search was complimented by hand searches and experts in the area and companies supplying NMES equipment were also contacted.

SELECTION CRITERIA

Randomised controlled trials and controlled clinical trials were accepted that used NMES for the purpose of quadriceps strengthening either pre or post total knee replacement.

DATA COLLECTION AND ANALYSIS

Two review authors decided which studies were suitable for inclusion based on the inclusion and exclusion criteria in the protocol and the data was extracted using pre-developed data extraction forms. Two review authors (BM and BC) independently assessed the methodological quality of the included trials using a descriptive approach as advocated by the Musculoskeletal group. Only two studies were included in the review. Neither study presented results in a form suitable for meta-analysis. The authors of both studies were contacted to obtain the raw data but they were no longer available.The data from both studies are described in the review.

MAIN RESULTS

Two studies were identified for inclusion in the review. No significant differences were reported in either study for maximum voluntary isometric torque or endurance between the NMES group and the control group but significantly better quadriceps muscle activation was reported in the exercise and neuromuscular stimulation group compared with the exercise group alone in the second study. This difference was significant at the mid training (six week) time point but not at the twelfth week post training time point. Further analysis of both studies were not possible due to the absence of raw data scores. Both studies carried a high risk of bias. Mean values were not given for strength, endurance, cross sectional area or quality of life. Pain outcomes, patient satisfaction or adverse effects were not reported in either study. The results were presented as percentage improvements from baseline and the number of subjects in each group was unclear.

AUTHORS' CONCLUSIONS

The studies found in this review do not permit any conclusions to be made about the application of neuromuscular stimulation for the purposes of quadriceps strengthening before or after total knee replacement. At this time the evidence for the use of neuromuscular stimulation for the purposes of quadriceps strengthening in this patient group is unclear.

Quadriceps arthrogenic muscle inhibition: neural mechanisms and treatment perspectives

OBJECTIVES

Arthritis, surgery, and traumatic injury of the knee joint are associated with long-lasting inability to fully activate the quadriceps muscle, a process known as arthrogenic muscle inhibition (AMI). The goal of this review is to provide a contemporary view of the neural mechanisms responsible for AMI as well as to highlight therapeutic interventions that may help clinicians overcome AMI.

METHODS

An extensive literature search of electronic databases was conducted including AMED, CINAHL, MEDLINE, OVID, SPORTDiscus, and Scopus.

RESULTS

While AMI is ubiquitous across knee joint pathologies, its severity may vary according to the degree of joint damage, time since injury, and knee joint angle. AMI is caused by a change in the discharge of articular sensory receptors due to factors such as swelling, inflammation, joint laxity, and damage to joint afferents. Spinal reflex pathways that likely contribute to AMI include the group I nonreciprocal (Ib) inhibitory pathway, the flexion reflex, and the gamma-loop. Preliminary evidence suggests that supraspinal pathways may also play an important role. Some of the most promising interventions to counter the effects of AMI include cryotherapy, transcutaneous electrical nerve stimulation, and neuromuscular electrical stimulation. Nonsteroidal anti-inflammatory drugs and intra-articular corticosteroids may also be effective when a strong inflammatory component is present with articular pathology.

CONCLUSIONS

AMI remains a significant barrier to effective rehabilitation in patients with arthritis and following knee injury and surgery. Gaining a better understanding of AMI's underlying mechanisms will allow the development of improved therapeutic strategies, enhancing the rehabilitation of patients with knee joint pathology.

Sex differences in quadriceps and hamstrings EMG-moment relationships

PURPOSE

To evaluate sex differences in quadriceps and hamstrings muscle EMG-moment relationships when the muscles were acting as agonists and antagonists across the range of contraction intensity.

METHODS

Twenty-two age- and activity-level-matched young people (11 females, 11 males) with no history of serious lower extremity injuries participated in this study. Muscle-specific EMG-moment relationships were determined for the quadriceps and hamstrings muscles when acting as agonists and antagonists during isometric target matching at 10 loads ranging from 10% to 100% peak moment. Sex differences in quadriceps and hamstrings muscle activation were assessed across the normalized moment spectrum.

RESULTS

Females had significantly higher vastus medialis activity than males during knee extension trials at 10%, 20%, and 30% peak moment (P < or = 0.05). Significant sex differences were broadly observed in the subjects' quadriceps muscle EMG-moment relationships (females displayed higher activity) during knee flexion trials (P < 0.05). Conversely, no sex differences were observed in the subjects' hamstrings muscle EMG-moment relationships. The shape of the EMG-moment relationships in agonist contractions were variable with linear patterns observed in the rectus femoris, semitendinosus, and biceps femoris muscles, and nonlinear patterns observed in the vastus medialis and vastus lateralis muscles. Antagonistic muscle activity increased with increases in moment magnitude.

CONCLUSIONS

The results of this study provide evidence of some sex differences in quadriceps muscle EMG-moment relationships. Conversely, the activation patterns for the hamstrings muscles were similar between the sexes. The consistent association between antagonist activity patterns and moment magnitudes supports the idea that the control of agonist-antagonist activity in the thigh muscles is linked.

Effect of baseline quadriceps activation on changes in quadriceps strength after exercise therapy in subjects with knee osteoarthritis

OBJECTIVE

To examine whether pretreatment magnitude of quadriceps activation (QA) helps predict changes in quadriceps strength after exercise therapy in subjects with knee osteoarthritis (OA). We hypothesized that subjects with lower magnitudes of QA (greater failure of muscle activation) would have smaller gains in strength compared with those with higher magnitudes of QA following exercise therapy.

METHODS

One hundred eleven subjects with knee OA (70 women) participated. Baseline measures included demographic information, quadriceps muscle strength, and QA using a burst-superimposition isometric torque test. Following baseline testing, subjects underwent a 6-week supervised exercise program designed to improve strength, range of motion, balance and agility, and physical function. On completion of the program, quadriceps strength and QA were reassessed. Multiple regression analysis was used to determine whether baseline QA predicted quadriceps strength scores at the 2-month followup.

RESULTS

Bivariate correlations demonstrated that baseline QA was significantly associated with quadriceps strength at baseline (rho = 0.30, P < 0.01) and 2-month followup (rho = 0.23, P = 0.01). Greater magnitude of baseline QA correlated with higher strength. While controlling for baseline quadriceps strength and type of exercise therapy, the level of QA did not predict quadriceps strength at the 2-month followup (beta = -0.04, P = 0.18).

CONCLUSION

Baseline QA did not predict changes in quadriceps strength following exercise therapy. Measurement of QA using the central activation ratio method does not appear to be helpful in identifying subjects with knee OA who will have difficulty improving quadriceps strength with exercise therapy.

Sit-to-stand 3 months after unilateral total knee arthroplasty: comparison of self-selected and constrained conditions

After unilateral total knee arthroplasty (TKA), rehabilitation specialists often constrain knee angles or foot positions during sit-to-stand, to encourage increased weight bearing through the operated limb. Biomechanical studies often constrain limb position during sit-to-stand in an effort to reduce variability. Differences between self-selecting or constraining position are unknown in persons after TKA. Twenty-six subjects with unilateral TKA participated in motion analysis. Subjects performed the sit-to-stand using a self-selected position (ssSTS); next, trials were collected in a constrained condition (ccSTS), where both knees were positioned with the tibia vertical, perpendicular to the floor. Repeated measures ANOVA (limb x condition) assessed differences between limbs and between conditions. Subjects used greater hip flexion bilaterally during ccSTS (91 degrees) compared to ssSTS (87 degrees; p=0.001) and knee flexion on the non-operated limb was greater during ssSTS (84 degrees) compared to ccSTS (82 degrees; p=0.018). The ccSTS resulted in larger extensor moments on the non-operated limb at the hip (ssSTS -0.473, ccSTS -0.521; p=0.021) and knee (ssSTS -0.431, ccSTS -0.457; p=0.001) compared to the operated limb. The ccSTS exacerbated the asymmetries at the hip and knee compared to ssSTS, and did not improve use of the operated limb. Reliance on the non-operated limb may put them at risk for progression of osteoarthritis in other joints of the lower extremities.

Perturbation training prior to ACL reconstruction improves gait asymmetries in non-copers

We investigated whether preoperative perturbation training would help anterior cruciate ligament (ACL) deficient individuals who complain of knee instability ("non-copers") regain quadriceps strength and walk normally after ACL reconstruction. Nineteen non-copers with acute ACL injury were randomly assigned into a perturbation group (PERT) or a strengthening group (STR). The PERT group received specialized neuromuscular training and progressive quadriceps strength training, whereas the STR group received progressive quadriceps strength training only. We compared quadriceps strength indexes and knee excursions during the mid-stance phase of gait preoperatively to data collected 6 months after ACL reconstruction. Analyses of Variance with repeated measures (time/limb) were conducted to compare quadriceps strength index values over time (time x group) and differences in knee excursions in limbs between groups over time (limb x time x group). If significance was found, post hoc analyses were performed using paired and independent t-tests. Quadriceps strength indexes before intervention (Pert: 87.2%; Str: 75.8%) improved 6 months after ACL reconstruction in both groups (Pert: 97.1%; Str: 94.4%). Non-copers who received perturbation training preoperatively had no differences in knee excursions between their limbs 6 months after ACL reconstruction (p = 0.14), whereas those who received just strength training continued to have smaller knee excursions during the mid-stance phase of gait (p = 0.007). Non-copers strength and knee excursions were more symmetrical 6 months postoperatively in the group that received perturbation training and progressive quadriceps strength training than the group who received strength training alone.

Improved function from progressive strengthening interventions after total knee arthroplasty: a randomized clinical trial with an imbedded prospective cohort

OBJECTIVE

To determine the effectiveness of progressive quadriceps strengthening with or without neuromuscular electrical stimulation (NMES) on quadriceps strength, activation, and functional recovery after total knee arthroplasty (TKA), and to compare progressive strengthening with conventional rehabilitation.

METHODS

A randomized controlled trial was conducted between July 2000 and November 2005 in an academic outpatient physical therapy clinic. Two hundred patients who had undergone primary, unilateral TKA for knee osteoarthritis were randomized to 1 of 2 interventions 4 weeks after surgery, and 41 patients eligible for enrollment who did not participate in the intervention were tested 12 months after surgery (standard of care group). All randomized patients received 6 weeks of outpatient physical therapy 2 or 3 times per week through 1 of 2 intervention protocols: an exercise group (volitional strength training) or an exercise-NMES group (volitional strength training and NMES). Treatment effects were evaluated by a burst superimposition test to assess quadriceps strength and volitional activation 3 and 12 months postoperatively. The Medical Outcomes Study Short Form 36 and Knee Outcome Survey were completed. Knee range of motion, Timed Up and Go, Stair-Climbing Test, and 6-Minute Walk were also measured.

RESULTS

Strength, activation, and function were similar between the exercise and exercise-NMES groups at 3 and 12 months. The standard of care group was weaker and exhibited worse function at 12 months compared with both treatment groups.

CONCLUSION

Progressive quadriceps strengthening with or without NMES enhances clinical improvement after TKA, achieving similar short- and long-term functional recovery and approaching the functional level of healthy older adults. Conventional rehabilitation does not yield similar outcomes.

Patella fracture during rehabilitation after bone-patellar tendon-bone anterior cruciate ligament reconstruction: 2 case reports

STUDY DESIGN

Case report.

BACKGROUND

Patellar fracture is a rare but significant complication following anterior cruciate ligament (ACL) reconstruction when using a bone-patellar tendon-bone (BPTB) autograft. The purpose of these case reports is to describe 2 cases in which patellar fracture occurred during rehabilitation after ACL reconstruction using a BPTB.

CASE DESCRIPTION

Both patients were 23-year-old males referred for rehabilitation after ACL reconstruction using a BPTB autograft. They were both progressing satisfactorily in rehabilitation until sustaining a fracture of the patella. One fracture occurred during the performance of the eccentric phase of a knee extension exercise during the sixth week of rehabilitation (7 weeks postsurgery), whereas the other fracture occurred during testing of the patient is quadriceps maximum voluntary isometric contraction in the ninth week of rehabilitation (10 weeks postsurgery). Both patients were subsequently treated with open reduction and internal fixation of the patella.

DISCUSSION

During rehabilitation following ACL reconstruction using BPTB autograft, clinicians should consider the need to balance the sometimes-competing goals of improving quadriceps strength while providing protection to the healing graft, minimization of patellofemoral pain, and protection of the patellar donor site.

Effect of cross exercise on quadriceps acceleration reaction time and subjective scores (Lysholm questionnaire) following anterior cruciate ligament reconstruction

BACKGROUND

Anterior cruciate ligament (ACL) injury or reconstruction can cause knee impairments and disability. Knee impairments are related to quadriceps performance - accelerated reaction time (ART) - and disability to performance of daily living activities which is assessed by questionnaires such as the Lysholm knee score. The purposes of this study were to investigate the effect of cross exercise, as supplementary rehabilitation to the early phase of ACL reconstruction: a) on quadriceps ART at the angles 45 degrees , 60 degrees and 90 degrees of knee flexion and, b) on the subjective scores of disability in ACL reconstructed patients.

METHODS

42 patients who underwent ACL reconstruction were randomly divided into 3 groups, two experimental and one control. All groups followed the same rehabilitation program. The experimental groups followed 8 weeks of cross eccentric exercise (CEE) on the uninjured knee; 3 d/w, and 5 d/w respectively.Quadriceps ART was measured at 45 degrees , 60 degrees and 90 degrees of knee flexion pre and nine weeks post-operatively using an isokinetic dynamometer. Patients also completed pre and post operatively the Lysholm questionnaire whereby subjective scores were recorded.

RESULTS

Two factor ANOVA showed significant differences in ART at 90 degrees among the groups (F = 4.29, p = 0.02, p < 0.05). Post hoc Tukey HSD analysis determined that the significant results arose from the first experimental group in comparison to the control (D = -0.83, p = 0.01). No significant differences were revealed at 45 degrees and 60 degrees .Significant differences were also found in the Lysholm score among the groups (F = 4.75, p = 0.01, p < 0.05). Post hoc analysis determined that the above significant results arose from the first experimental group in comparison with the control (D = 7.5, p < 0.01) and from the second experimental in comparison with the control (D = 3.78, p = 0.03).

CONCLUSION

CEE showed improvements on quadriceps ART at 90 degrees at a sequence of 3 d/w and in the Lysholm score at a sequence of 3 d/w and 5 d/w respectively on ACL reconstructed patients.

Development of a mathematical model for predicting electrically elicited quadriceps femoris muscle forces during isovelocity knee joint motion

Background

Direct electrical activation of skeletal muscles of patients with upper motor neuron lesions can restore functional movements, such as standing or walking. Because responses to electrical stimulation are highly nonlinear and time varying, accurate control of muscles to produce functional movements is very difficult. Accurate and predictive mathematical models can facilitate the design of stimulation patterns and control strategies that will produce the desired force and motion. In the present study, we build upon our previous isometric model to capture the effects of constant angular velocity on the forces produced during electrically elicited concentric contractions of healthy human quadriceps femoris muscle. Modelling the isovelocity condition is important because it will enable us to understand how our model behaves under the relatively simple condition of constant velocity and will enable us to better understand the interactions of muscle length, limb velocity, and stimulation pattern on the force produced by the muscle.

Methods

An additional term was introduced into our previous isometric model to predict the force responses during constant velocity limb motion. Ten healthy subjects were recruited for the study. Using a KinCom dynamometer, isometric and isovelocity force data were collected from the human quadriceps femoris muscle in response to a wide range of stimulation frequencies and patterns. % error, linear regression trend lines, and paired t-tests were used to test how well the model predicted the experimental forces. In addition, sensitivity analysis was performed using Fourier Amplitude Sensitivity Test to obtain a measure of the sensitivity of our model's output to changes in model parameters.

Results

Percentage RMS errors between modelled and experimental forces determined for each subject at each stimulation pattern and velocity showed that the errors were in general less than 20%. The coefficients of determination between the measured and predicted forces show that the model accounted for ~86% and ~85% of the variances in the measured force-time integrals and peak forces, respectively.

Conclusion

The range of predictive abilities of the isovelocity model in response to changes in muscle length, velocity, and stimulation frequency for each individual make it ideal for dynamic applications like FES cycling.

The effect of neuromuscular electrical stimulation of the infraspinatus on shoulder external rotation force production after rotator cuff repair surgery

BACKGROUND

Muscle weakness, particularly of shoulder external rotation, is common after rotator cuff repair surgery. Neuromuscular electrical stimulation has been shown to be an effective adjunct in the enhancement of muscle recruitment.

HYPOTHESIS

Shoulder external rotation peak force can be enhanced by neuromuscular electrical stimulation after rotator cuff repair surgery.

STUDY DESIGN

Controlled laboratory study.

METHODS

Thirty-nine patients (20 men, 19 women) who had undergone rotator cuff repair surgery were tested a mean of 10.5 days after surgery. Testing consisted of placing patients supine with the shoulder in 45 degrees of abduction, neutral rotation, and 15 degrees of horizontal adduction. Neuromuscular electrical stimulation was applied to the infraspinatus muscle belly and inferior to the spine of the scapula. Placement was confirmed by palpating the muscle during a resisted isometric contraction of the external rotators. Patients performed 3 isometric shoulder external rotation contractions with and without neuromuscular electrical stimulation, each with a 5-second hold against a handheld dynamometer. Neuromuscular electrical stimulation was applied at maximal intensity within comfort at 50 pulses per second, symmetrical waveform, and a 1-second ramp time. The 3 trials under each condition were recorded, and an average was taken. The order of testing was randomized for each patient tested. A paired samples t test was used to determine significant differences between conditions (P < .05). Each group was also divided based on age, rotator cuff tear size, number of days postoperative, and neuromuscular electrical stimulation intensity. Analysis of variance models were used to determine the influence of these variables on external rotation force production (P < .05).

RESULTS

Peak force production was significantly greater (P < .001) when tested with neuromuscular electrical stimulation (3.75 kg) as opposed to without neuromuscular electrical stimulation (3.08 kg) for all groups tested. There was no significant difference based on the size of the tear, age of the patient, number of days after surgery, or level of neuromuscular electrical stimulation intensity.

CONCLUSION

Peak shoulder external rotation force was significantly increased by 22% when tested with neuromuscular electrical stimulation after rotator cuff repair surgery. Neuromuscular electrical stimulation significantly increased force production regardless of the age of the patient, size of the tear, intensity of the current, or the number of days postoperative.

CLINICAL RELEVANCE

Neuromuscular electrical stimulation may be used concomitantly with exercises to enhance the amount of force production and potentially minimize the inhibition of the rotator cuff after repair surgery.

Postoperative management of pigmented villonodular synovitis in a single subject

STUDY DESIGN

Case report.

BACKGROUND

Pigmented villonodular synovitis (PVNS) is a rare, benign disorder characterized by idiopathic proliferation affecting the synovium of joints, tendon sheaths, and bursae. Diagnosing PVNS in the knee is difficult because the clinical presentation and symptoms mimic those of more common disorders at the joint, such as internal derangements or arthritis. Operative treatment of PVNS typically consists of arthroscopic or open synovectomy, but no reports of postoperative rehabilitation exist.

CASE DESCRIPTION

This case describes the postoperative rehabilitation of a 46-year-old female who had left knee surgery secondary to PVNS. Rehabilitation consisted of combined manual therapy, exercise, and gait training to improve function and gait, and cognitive-behavioral techniques to improve self-efficacy.

OUTCOMES

All impairments improved in 2.5 months of physical therapy to normal, and the patient estimated 80% to 90% return to function.

DISCUSSION

This patient obtained excellent outcomes in 2.5 months of physical therapy following surgery for PVNS. Although no firm conclusions can be drawn from a case report, this patient responded well to a biopsychosocial approach that combined physical therapy with cognitive-behavioral techniques.

LEVEL OF EVIDENCE

Therapy, level 4.

Isokinetic quadriceps and hamstring muscle strength and knee function 5 years after anterior cruciate ligament reconstruction: comparison between bone-patellar tendon-bone and hamstring tendon autografts

Existing clinical studies have not proven which graft is to be preferred in anterior cruciate ligament (ACL) reconstruction. In recent years, bone-patellar tendon-bone and hamstring tendons have been the most frequently used graft types. Muscle strength deficit is one of the consequences after ACL reconstruction. The aim of this study was to evaluate possible differences in hamstring and quadriceps muscle strength and knee function 5 years after ACL reconstruction between the BPTB and the STG groups. The study group consisted of 288 patients (132 women, 156 men) with a unilateral ACL rupture who had received a BPTB (175 patients) or STG (113 patients) ACL reconstruction. Lower extremity concentric isokinetic peak extension and flexion torques were assessed at the angular velocities of 60 degrees /s and 180 degrees /s. The International Knee Documentation Committee (IKDC), the Tegner activity level, the Lysholm knee and the Kujala patellofemoral scores were also collected. Isokinetic quadriceps peak torque (percentage of the contralateral side) was 3.9% higher in the STG group than in the BPTB group at the velocity of 60 degrees /s and 3.2% higher at the velocity of 180 degrees /s and the isokinetic hamstring peak torque 2% higher in the BPTB group than in the STG group at the velocity of 60 degrees /s and 2.5% higher at the velocity of 180 degrees /s. In both groups the subjects had weaker quadriceps and hamstring muscle strength in the injured extremity compared with the uninjured one. In the single-leg hop test (according to the IKDC recommendations) there was a statistically significant difference (P = 0.040) between the groups. In the STG group, 68% of the patients had the single-leg hop ratio (injured vs. uninjured extremity) > or =90%, 31% of the patients 75-89% and 1% of the patients <75%, while in the BPTB group the corresponding percentages were 72, 21 and 7%. However, no statistically significant differences in clinical outcome were found between the groups as determined by the IKDC, Tegner activity level, Lysholm knee and Kujala patellofemoral scores.

Effects of lumbopelvic joint manipulation on quadriceps activation and strength in healthy individuals

Lumbopelvic joint manipulation has been shown to increase quadriceps force output and activation, but the duration of effect is unknown. It is also unknown whether lower grade joint mobilisations may have a similar effect. Forty-two healthy volunteers (x+/-SD; age=28.3+/-7.3 yr; ht=172.8+/-9.8 cm; mass=76.6+/-21.7 kg) were randomly assigned to one of three groups (lumbopelvic joint manipulation, 1 min lumbar passive range of motion (PROM), or prone extension on elbows for 3 min). Quadriceps force and activation were measured using the burst-superimposition technique during a seated isometric knee extension task before and at 0, 20, 40, and 60 min following intervention. Collectively, all groups demonstrated a significant decrease (p<0.001) in quadriceps force output without changes in activation (p>0.05) at all time intervals following intervention. The group that received a lumbopelvic joint manipulation demonstrated a significant increase in quadriceps force (3%) and activation (5%) (p<0.05) immediately following intervention, but this effect was not present after the 20 min interval. Since participants in this study were free of knee joint pathology, it is possible that they did not have the capacity to allow for large changes in quadriceps muscle activation to occur.

Decreased quadriceps activation measured hours prior to a noncontact anterior cruciate ligament tear

STUDY DESIGN

Case report.

BACKGROUND

Decreased quadriceps activation has been shown to be present following anterior cruciate ligament (ACL) injury, but its presence prior to ACL injury is unknown. The purpose of this case report was to describe the level of quadriceps activation measured hours before a noncontact ACL injury in an individual who previously demonstrated known biomechanical risk factors for ACL injury.

CASE DESCRIPTION

A 23-year-old female (height, 176.9 cm; mass, 72.4 kg), sustained a left noncontact ACL injury while landing from a jump stop during a recreational basketball game. This case was unique because data regarding landing biomechanics and quadriceps force and activation were gathered in 2 separate, unrelated studies prior to injury.

OUTCOMES

Peak external knee abduction moment (-65.3 Nm) during a drop jump landing 8 months prior to injury indicated elevated risk for ACL injury. Involved quadriceps central activation ratios (CAR) were obtained 1 week (CAR, 0.81) and 4 hours (CAR, 0.77) prior to injury. Strength and CAR (0.76) measurements changed very little within 36 hours of injury and both strength, and activation (CAR, 0.90) improved following surgical reconstruction and formal rehabilitation.

DISCUSSION

An individual with known biomechanical risk factors for ACL injury may compound risk for noncontact ACL injury if decreased quadriceps activation is also present.

LEVEL OF EVIDENCE

Prognosis, level 4.

Persistence of altered movement patterns during a sit-to-stand task 1 year following unilateral total knee arthroplasty

BACKGROUND AND PURPOSE

Following total knee arthroplasty (TKA), quadriceps femoris muscle strength (force-generating capacity) and functional test scores improve but continue to be lower than those in people without injury. Analysis of the sit-to-stand (STS) task demonstrated side-to-side differences in subjects with TKA, as well as differences between subjects with TKA and control subjects. It was hypothesized that, when using a self-selected starting position, subjects 1 year following TKA would show improvements in strength and movement patterns but would continue to show asymmetries of angles and moments at the hips and knees.

SUBJECTS AND METHODS

Twenty-four subjects (12 subjects with unilateral TKA and 12 control subjects) were recruited; those with TKA were tested 3 months and 1 year following surgery. Motion analysis of an STS task was synchronized with 2 force platforms and electromyography. Outcome measures included joint angles and moments, electromyography, vertical ground reaction forces, muscle strength, and functional performance tests.

RESULTS

Subjects with TKA showed improvements in symmetry of motion, strength, and functional performance from 3 months to 1 year following TKA. Compared with control subjects, subjects with TKA relied on increased hip flexion and a larger hip extensor moment to perform the STS task.

DISCUSSION AND CONCLUSION

The increased hip extensor moment demonstrated that subjects adopted a strategy to avoid the use of the quadriceps femoris muscle, yet this strategy persisted as quadriceps femoris muscle strength improved. This pattern may be a learned movement pattern that may not resolve without retraining.

Total knee arthroplasty: muscle impairments, functional limitations, and recommended rehabilitation approaches

The number of total knee arthroplasty (TKA) surgeries performed each year is predicted to steadily increase. Following TKA surgery, self-reported pain and function improve, though individuals are often plagued with quadriceps muscle impairments and functional limitations. Postoperative rehabilitation approaches either are not incorporated or incompletely address the muscular and functional deficits that persist following surgery. While the reason for quadriceps weakness is not well understood in this patient population, it has been suggested that a combination of muscle atrophy and neuromuscular activation deficits contribute to residual strength impairments. Failure to adequately address the chronic muscle impairments has the potential to limit the long-term functional gains that may be possible following TKA. Postoperative rehabilitation addressing quadriceps strength should mitigate these impairments and ultimately result in improved functional outcomes. The purpose of this paper is to describe these quadriceps muscle impairments and discuss how these impairments can contribute to the related functional limitations following TKA. We will also describe the current concepts in TKA rehabilitation and provide recommendations and clinical guidelines based on the current available evidence.

LEVEL OF EVIDENCE

Therapy, level 5.

Isokinetic Dynamometry in Anterior Cruciate Ligament Injury and Reconstruction

The use of isokinetic dynamometry has often been criticised based on the face-validity argument that isokinetic movements poorly resemble the everyday multi-segmented, dynamic activities of human movements. In the anterior cruciate ligament (ACL) reconstruction or deficiency population where muscle deficits are ubiquitous, this review paper has made a case for using isokinetic dynamometry to isolate and quantify these deficits in a safe and controlled manner. More importantly, the usefulness of isokinetic dynamometry, as applied in individuals with ACL reconstruction or deficiency, is attested by its established known-group and convergent validity. Known-group validity is demonstrated by the extent to which a given isokinetic measure is able to identify individuals who could and could not resume pre-morbid athletic or strenuous activities with minimal functional limitations following an ACL injury. Convergent validity is demonstrated by the extent to which a given isokinetic measure closely associates with self-report measures of knee function in individuals with ACL reconstruction. A basic understanding of the measurement properties of isokinetic dynamometry will guide the clinicians in providing reasoned interventions and advancing the clinical care of their clients. Key words: Biomechanics, Knee, Validity

Influence of age, gender, and injury mechanism on the development of dynamic knee stability after acute ACL rupture

STUDY DESIGN

Cross-sectional study.

OBJECTIVES

To determine whether the distribution of those with and without dynamic knee stability after anterior cruciate ligament (ACL) rupture differs by age, gender, and contact versus non-contact injury mechanisms.

BACKGROUND

There is a differential return to preinjury activities after ACL rupture. It is unknown if there are specific patient groups who are more or less likely to experience good dynamic knee stability after ACL rupture.

METHODS AND MEASURES

The study sample consisted of 345 consecutive, highly active patients with complete, isolated ACL insufficiency. Based on the results of a screening examination, patients were categorized as having either good (potential coper) or poor (noncoper) dynamic knee stability. Descriptive and chi-square statistics were calculated to describe patient characteristics and identify the proportion of potential copers and noncopers based on age, gender, and injury mechanism.

RESULTS

The groups with the greatest proportion of noncopers were women (P=0.002), mid-aged adults (35-44 years old) (P<0.001), and individuals who sustained a noncontact ACL injury (P=0.011).

CONCLUSIONS

Women who sustain an ACL rupture, and those who sustain an ACL rupture via a noncontact mechanism frequently experience dynamic knee instability. A profile of demographic characteristics of those most likely to experience knee instability after ACL rupture may facilitate improved patient outcomes.

Insufficient recovery of neuromuscular activity around the knee after experimental anterior cruciate ligament reconstruction

BACKGROUND

Operative and nonoperative treatment of anterior cruciate ligament (ACL) injuries is often associated with a lack of proprioception and persistent muscle weakness of unknown origin.

METHODS

This long-term study in the cat experimentally compares both neural and muscular activity in the articular nerves of the knee (PAN and MAN), quadriceps and hamstrings, in the chronic unstable knee, and in the reconstructed knee. We also investigated changes in neuromuscular response due to the mechanical competence of the graft, comparing stable and unstable reconstructed knees.

RESULTS

We found increased periarticular muscle activity during anterior tibial translation in chronically unstable knees. Both reconstructed and non-reconstructed knees lost fast reactive activity in the articular nerves. When stability was recovered after reconstruction, the knees showed a more adjusted - although incomplete - muscular reaction.

INTERPRETATION

ACL-injured knees in the cat, with or without reconstruction, show definite abnormalities in neuromuscular reaction in the long term. Regaining stability with a competent graft in the reconstructed knee is crucial for reduction of this anomalous reaction.

Landing mechanics between noninjured women and women with anterior cruciate ligament reconstruction during 2 jump tasks

BACKGROUND

Women with anterior cruciate ligament reconstruction have different neuromuscular strategies than noninjured women during functional tasks after ligament reconstruction and rehabilitation.

HYPOTHESIS

Landing from a jump creates high loads on the knee creating dynamic instability in women with anterior cruciate ligament reconstruction, whereas noninjured women have stable knee landing mechanics.

STUDY DESIGN

Controlled laboratory study.

METHODS

Fifteen noninjured women and 13 women with anterior cruciate ligament reconstruction performed 5 trials of a single-legged 40-cm drop jump and 2 trials of a 20-cm up-down hop task. Multivariate analyses of variance were used to compare hip and knee joint kinematics, knee joint moments, ground-reaction forces, and electromyographic findings between the dominant leg in noninjured women and reconstructed leg in women with anterior cruciate ligament reconstruction.

RESULTS

No statistically significant differences between groups were found for peak hip and knee joint angles for the drop jump task. Statistically significant differences in neuromuscular activity (P = .001) and anterior-posterior knee shear forces (P < .001) were seen in women with anterior cruciate ligament reconstruction compared with noninjured women in the drop jump task. However, no statistically significant differences (P > .05) between groups were found for either peak hip and knee joint angles, peak joint kinetics, or electromyographic findings during the up-down hop task.

CONCLUSION

Women with anterior cruciate ligament reconstruction have neuromuscular strategies that allow them to land from a jump similar to healthy women, but they exhibit joint moments that could predispose them to future injury if they participate in sports that require jumping and landing.

A 10-year prospective trial of a patient management algorithm and screening examination for highly active individuals with anterior cruciate ligament injury: Part 1, outcomes

BACKGROUND

A treatment algorithm and screening examination have been developed to guide patient management and prospectively determine potential for highly active individuals to succeed with nonoperative care after anterior cruciate ligament rupture.

OBJECTIVE

To prospectively characterize and classify the entire population of highly active individuals over a 10-year period and provide final outcomes for individuals who elected nonoperative care.

METHODS

Inclusion criteria included presentation within 7 months of the index injury and an International Knee Documentation Committee level I or II activity level before injury. Concomitant injury, unresolved impairments, and a screening examination were used as criteria to guide management and classify individuals as noncopers (poor potential) or potential copers (good potential) for nonoperative care.

RESULTS

A total of 832 highly active patients with subacute anterior cruciate ligament tears were seen over the 10-year period; 315 had concomitant injuries, 87 had unresolved impairments, and 85 did not participate in the classification algorithm. The remaining 345 patients (216 men, 129 women) participated in the screening examination a mean of 6 weeks after the index injury. There were 199 subjects classified as noncopers and 146 as potential copers. Sixty-three of 88 potential copers successfully returned to preinjury activities without surgery, with 25 of these patients not undergoing anterior cruciate ligament reconstruction at the time of follow-up.

CONCLUSION

The classification algorithm is an effective tool for prospectively identifying individuals early after anterior cruciate ligament injury who want to pursue nonoperative care or must delay surgical intervention and have good potential to do so.

A 10-year prospective trial of a patient management algorithm and screening examination for highly active individuals with anterior cruciate ligament injury: Part 2, determinants of dynamic knee stability

OBJECTIVE

To clarify the determinants of dynamic knee stability early after anterior cruciate ligament injury.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 1.

METHODS

Three hundred forty-five consecutive patients who were regular participants in International Knee Documentation Committee level I/II sports before injury and had an acute isolated anterior cruciate ligament injury from the practice of a single orthopaedic surgeon underwent a screening examination including clinical measures, knee laxity, quadriceps strength, hop testing, and patient self-reported knee function a mean of 6 weeks after injury when impairments were resolved. Independent t tests were performed to evaluate differences in quadriceps strength and anterior knee laxity between potential copers and noncopers. Hierarchical regression was performed to determine the influence of quadriceps strength, preinjury activity level, and anterior knee laxity on hop test performance, as well as the influence of timed hop, crossover hop, quadriceps strength, preinjury activity level, and anterior knee laxity on self-assessed global function.

RESULTS

Neither anterior knee laxity nor quadriceps strength differed between potential copers and noncopers. Quadriceps strength influenced hop test performance more significantly than did preinjury activity level or anterior knee laxity, but the variance accounted for by quadriceps strength was low (range, 4%-8%). Timed hop performance was the only variable that affected self-assessed global function.

CONCLUSION

Traditional surgical decision making based on passive anterior knee laxity and preinjury activity level is not supported by the results, as neither is a good predictor of dynamic knee stability. A battery of clinical tests that capture neuromuscular adaptations, including the timed hop test, may be useful in predicting function and guiding individualized patient management after anterior cruciate ligament injury.

Relationship between stimulation train characteristics and dynamic human skeletal muscle performance

AIM

The purpose of the present study was to investigate the effect of activation frequency on dynamic human muscle performance for a range of train durations and number of pulses during free limb movement.

METHODS

The quadriceps femoris muscles of 10 subjects were activated with stimulation trains with different activation frequency, train durations and number of pulses. The peak excursion produced in response to each train was the dependent measure of muscle performance.

RESULTS

The excursion-frequency (for a 300-ms train duration) and excursion-train duration (for trains with frequencies of 10, 30 or 59 Hz) relationships could each be fit with a two-parameter exponential equation (R(2) values > 0.97). Because the number of pulses in a stimulation train is a function of both train duration and frequency, the excursion produced as a function of the number of pulses was characterized by a three-parameter exponential equation that represented this combined relationship. The relationship between the measured and predicted excursions in response to a wide range of stimulation trains had a R(2) = 0.96. In addition, one-way repeated measures analyses of variance (anovas) showed that the frequency at which the maximum excursion was produced increased with an increase in the number of pulses in the trains tested.

CONCLUSION

These results show the importance of train duration and the number of pulses contained within a train on the relationship between activation frequency and human skeletal muscle performance.

Relationship between quadriceps femoris muscle volume and muscle torque after anterior cruciate ligament repair

This study was performed to obtain evidence regarding bilateral hindrance of motor unit (MU) recruitment in the quadriceps femoris (QF) of patients with anterior cruciate ligament (ACL) reconstruction. The subjects included 70 patients who underwent ACL reconstruction and 35 healthy subjects. To identify the muscle torque per unit volume (MTPUV), the peak torque of each velocity of isokinetic performance was divided by muscle volume of the QF measured by a series of cross-sectional images obtained by magnetic resonance imaging scans. Tests revealed that the mean MTPUV of the uninjured (0.113+/-0.03 N m/cm3 at 60 degrees /s, 0.081+/-0.02 N m/cm3 at 180 degrees /s) and injured sides (0.109+/-0.03 N m/cm3 at 60 degrees /s, 0.079+/-0.023 N m/cm3 at 180 degrees /s) were significantly lower than those of the control group (0.144+/-0.05 N m/cm3 at 60 degrees /s, 0.096+/-0.04 N m/cm3 at 180 degrees /s). Previous studies suggested that MU recruitment in the QF of patients with ACL injury was hindered bilaterally. However, the design of their studies could not provide evidence of bilateral hindrance of MU recruitment in the QF. The results of the present study demonstrated that the MTPUV of both injured and uninjured sides of patients were significantly lower than those of the control group.

Effects of stimulation frequency versus pulse duration modulation on muscle fatigue

During functional electrical stimulation (FES), both the frequency and intensity can be increased to increase muscle force output and counteract the effects of muscle fatigue. Most current FES systems, however, deliver a constant frequency and only vary the stimulation intensity to control muscle force. This study compared muscle performance and fatigue produced during repetitive electrical stimulation using three different strategies: (1) constant pulse-duration and stepwise increases in frequency (frequency-modulation); (2) constant frequency and stepwise increases in pulse-duration (pulse-duration-modulation); and (3) constant frequency and pulse-duration (no-modulation). Surface electrical stimulation was delivered to the quadriceps femoris muscles of 12 healthy individuals and isometric forces were recorded. Muscle performance was assessed by measuring the percent changes in the peak forces and force-time integrals between the first and the last fatiguing trains. Muscle fatigue was assessed by measuring percent declines in peak force between the 60Hz pre- and post-fatigue testing trains. The results showed that frequency-modulation showed better performance for both peak forces and force-time integrals in response to the fatiguing trains than pulse-duration-modulation, while producing similar levels of muscle fatigue. Although frequency-modulation is not commonly used during FES, clinicians should consider this strategy to improve muscle performance.

Effects of activation pattern on nonisometric human skeletal muscle performance

During volitional muscle activation, motor units often fire with varying discharge patterns that include brief, high-frequency bursts of activity. These variations in the activation rate allow the central nervous system to precisely control the forces produced by the muscle. The present study explores how varying the instantaneous frequency of stimulation pulses within a train affects nonisometric muscle performance. The peak excursion produced in response to each stimulation train was considered as the primary measure of muscle performance. The results showed that at each frequency tested between 10 and 50 Hz, variable-frequency trains that took advantage of the catchlike property of skeletal muscle produced greater excursions than constant-frequency trains. In addition, variable-frequency trains that could achieve targeted trajectories with fewer pulses than constant-frequency trains were identified. These findings suggest that similar to voluntary muscle activation patterns, varying the instantaneous frequency within a train of pulses can be used to improve muscle performance during functional electrical stimulation.

Reliability of electromyographic normalization methods for evaluating the hip musculature

The purpose of this study was to determine the reliability of three normalization methods for analyzing hip abductor activation during rehabilitation exercises. Thirteen healthy subjects performed three open kinetic chain and three closed kinetic chain hip abductor exercises. Surface EMG activity for the gluteus medius was collected during each exercise and normalized based on a maximum voluntary isometric contraction (MVIC), mean dynamic (m-DYN), and peak dynamic activity (pk-DYN). Intraclass coefficient correlations (ICCs), intersubject coefficients of variation (CVs), and intrasubject CVs were then calculated for each normalization method. MVIC ICCs exceeded 0.93 for all exercises. M-DYN and pk-DYN ICCs exceeded 0.85 for all exercises except for the sidelying abduction exercise. Intersubject CVs ranged from 55% to 77% and 19% to 61% for the MVIC and dynamic methods, respectively. Intrasubject CVs ranged from 11% to 22% for all exercises under all normalization methods. The MVIC method provided the highest measurement reliability for determining differences in activation amplitudes between hip abductor exercises in healthy subjects. Future research should determine if these same results would apply to a symptomatic patient population.

Reconstrução do ligamento cruzado anterior: impacto do desempenho muscular e funcional no retorno ao mesmo nível de atividade pré-lesão

INTRODUÇÃO: A reconstrução do LCA objetiva restabelecer a biomecânica e minimizar a instabilidade do joelho. OBJETIVO: comparar performance muscular, funcional e frouxidão ligamentar, entre voluntários que retornaram ao mesmo nível de atividade pré-lesão e aqueles que não retornaram, após a reconstrução ligamentar. MÉTODOS: 25 homens, operados pelo mesmo cirurgião, com o ligamento patelar, via artroscopia e mais de dois anos de pós-operatório. Utilizou-se a Cincinnati Knee Rating System para divisão em: grupo adaptado - 15 indivíduos - retornaram ao mesmo nível pré-lesão e grupo não adaptado - 10 indivíduos - não retornaram ao mesmo nível. Todos realizaram o hop test e a corrida em oito para avaliação do desempenho funcional. A performance muscular foi avaliada pelo dinamômetro isocinético (Biodex System 3 Pro®) e a frouxidão ligamentar determinada pelo artrômetro KT-1000 (Medmetric®). Utilizou-se o teste t independente e ANOVA para análise de associação. RESULTADOS: não houve diferença significativa entre os grupos em nenhuma das variáveis testadas e não houve diferença entre os membros - operado e não operado. CONCLUSÃO: O não retorno ao mesmo nível funcional pré-lesão não pode ser explicado pela frouxidão ligamentar residual ou pelas diferenças do desempenho muscular e funcional.

Changes in fascicle length from rest to maximal voluntary contraction affect the assessment of voluntary activation

The purpose of this study was to investigate the effect of the differences between the actual fascicle length during a voluntary contraction and the fascicle length at rest of the triceps surae muscle on the determination of the voluntary activation (VA) by using the interpolated twitch technique. Twelve participants performed isometric voluntary maximal (MVC) and submaximal (20%, 40%, 60% and 80% MVC) contractions at two different ankle angles (75 degrees and 90 degrees ) under application of the interpolated twitch technique. Two ultrasound probes were used to determine the fascicle length of soleus, gastrocnemius medialis and gastrocnemius lateralis muscles. Further, the MVCs and the twitches were repeated for six more ankle angles (85 degrees , 95 degrees , 100 degrees , 105 degrees , 110 degrees and 115 degrees ). The VA of the triceps surae muscle were calculated (a) using the rest twitch force (RTF) measured during the same trial as the interpolated twitch force (ITF; traditional method) and (b) using the RTF at an ankle angle where the fascicle length showed similar values between ITF and RTF (fascicle length consideration method). The continuous changes in fascicle length from rest to MVC affect the accuracy of the assessment of the VA. The traditional method overestimates the assessment of the VA on average 4% to 12%, especially at 90 degrees ankle angle (i.e. short muscle length). The reason for this influence is the unequal force-length potential of the muscle at twitch application by the measure of ITF and RTF. These findings provide evidence that the fascicle length consideration method permits a more precise prediction (an improvement of 4-12%) of the voluntary contraction compared to the traditional method.

Effect of frequency and pulse duration on human muscle fatigue during repetitive electrical stimulation

Different combinations of stimulation frequency and intensity can generate a targeted force during functional electrical stimulation (FES). This study compared isometric performance and muscle fatigue during repetitive stimulation with three different combinations of frequency and pulse duration that produced the same initial peak forces: protocol 1 used long pulse duration (fixed at 600 micros) and 11.5 +/- 1.2 Hz (low frequency); protocol 2 used 30 Hz (medium frequency) and medium pulse duration (150 +/- 21 micros); and protocol 3 used 60 Hz (high frequency) and short pulse duration (131 +/- 24 micros). Twenty and 60 Hz pre- and postfatigue testing trains were delivered at the pulse duration used by the fatiguing trains and at 600 micros pulse duration. The percentage decline in peak force between the first and last fatiguing train of each protocol was the measure of muscle performance. The declines in peak force of the 60 Hz testing trains were used to measure muscle fatigue. The 20 Hz:60 Hz peak force ratio was used as a measure of low-frequency fatigue. The results showed that protocol 1 produced the least decline in peak force in response to the fatiguing trains, as well as the least muscle fatigue and low-frequency fatigue when the pulse duration was maintained at the level used by the fatiguing trains. Interestingly, protocol 2 produced the least muscle fatigue, and there were no differences in the levels of low-frequency fatigue across protocols when a comparable motor unit population was tested using 600 micros pulse duration. The results suggest that if the frequency and intensity are kept constant during FES, using the lowest frequency and longest pulse duration may maximize performance.