Quadriceps femoris muscle weakness and activation failure in patients with symptomatic knee osteoarthritis

Piriformis Syndrome in Knee Osteoarthritis Patients after Wearing Rocker Bottom Shoes

Background

Rocker bottom shoes (RBS) are popular among patients with different foot, leg, or back problems in Korea. Patients with knee osteoarthritis concurrent weakness in the quadriceps femoris muscle, who wear these shoes, are often assumed to develop piriformis syndrome (PS). This study was performed to improve the understanding about the effect of wearing such shoes on duration of the syndrome in knee osteoarthritis.

Methods

We randomly assigned 150 patients with PS, who had used RBS daily for at least 6 months, to 2 groups, the S (stopped wearing) and K (kept wearing) groups. Both the groups were subdivided into the O and N groups, comprising patients with and without knee osteoarthritis, respectively. The effects of the treatment, including piriformis muscle injections and a home exercise program, were compared between the 2 groups by using a flexion-adduction-internal rotation (FAIR) test, a numeric rating scale (NRS), and the revised Oswestry disability index (ODI) during the 12-week follow-up.

Results

The positive FAIR test ratios, mean NRS scores, and revised ODIs were higher in the KO group than the SN group from 4?12 weeks after treatment.

Conclusions

RBS may extend duration of the PS in osteoarthritis patients.

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.

Effect of a high intensity quadriceps fatigue protocol on knee joint mechanics and muscle activation during gait in young adults

The purpose of this study was to determine the effect of impaired quadriceps function on knee joint biomechanics and neuromuscular function during gait. Surface electromyograms, three-dimensional motion and ground reaction forces were collected during gait before and after 20 healthy adults completed a high intensity quadriceps fatigue protocol. Pattern recognition techniques were utilized to examine changes in amplitude and temporal characteristics of all gait variables. The fatigue protocol resulted in decreased knee extensor torque generation and quadriceps median power frequencies for 18 of 20 participants (p < 0.05). The gait data from these 18 participants was analyzed. The knee external rotation angle increased (p < 0.05), the net external flexion and external rotation moments decreased (p < 0.05), and the net external adduction moment increased (p < 0.05). Post-fatigue changes in periarticular muscle activation patterns were consistent with the biomechanical changes, but were not significantly altered. Even for this low demand task of walking the knee motion and loading characteristics were altered following a high intensity fatigue protocol in a manner that may place the knee joint at greater risk for joint pathology and injury.

Prehabilitation before total knee arthroplasty increases strength and function in older adults with severe osteoarthritis

Preparing for the stress of total knee arthroplasty (TKA) surgery by exercise training (prehabilitation) may improve strength and function before surgery and, if effective, has the potential to contribute to postoperative recovery. Subjects with severe osteoarthritis (OA), pain intractable to medicine and scheduled for TKA were randomized into a usual care (UC) group (n = 36) or usual care and exercise (UC + EX) group (n = 35). The UC group maintained normal daily activities before their TKA. The UC + EX group performed a comprehensive prehabilitation program that included resistance training using bands, flexibility, and step training at least 3 times per week for 4-8 weeks before their TKA in addition to UC. Leg strength (isokinetic peak torque for knee extension and flexion) and ability to perform functional tasks (6-minute walk, 30 second sit-to-stand repetitions, and the time to ascend and descend 2 flights of stairs) were assessed before randomization at baseline (T1) and 1 week before the subject's TKA (T2). Repeated-measures analysis of variance indicated a significant group by time interaction (p < 0.05) for the 30-second sit-to-stand repetitions, time to ascend the first flight of stairs, and peak torque for knee extension in the surgical knee. Prehabilitation increased leg strength and the ability to perform functional tasks for UC + EX when compared to UC before TKA. Short term (4-8 weeks) of prehabilitation was effective for increasing strength and function for individuals with severe OA. The program studied is easily transferred to a home environment, and clinicians working with this population should consider prehabilitation before TKA.

Voluntary quadriceps activation deficits in patients with tibiofemoral osteoarthritis: a meta-analysis

The objective of this study was to assess the magnitude of quadriceps activation deficits in the involved extremity and contralateral extremity of patients with knee joint osteoarthritis (OA), as well as matched controls. An exhaustive search of the literature was performed using Web of Science between 1970 and February 24, 2010, using the search terms "osteoarthritis" AND "quadriceps activation" OR "quadriceps inhibition" and cross-referencing pertinent articles. Studies written in English reporting quadriceps activation means and standard deviations in patients with tibiofemoral OA via a method using an exogenous electrical stimulation were evaluated for methodological quality and were included for data analysis. Fourteen individual studies met the criteria for inclusion into data analysis. The number of participants and mean activation levels were used to calculate weighted means for the involved limb (14 studies), the contralateral limb (from a subset of 6 studies), and an involved limb subset from only the studies evaluating the contralateral limb and population of control subjects (5 studies). Weighted means from the involved limb (82.2; 95% CI = 81.4-83.3%), contralateral limb (81.7; 80.1-83.3%), and involved limb subset (76.8; 74.8-78.8%) groups were found to have lower volitional quadriceps activation compared with the control groups (90; 88.9-91.7%). Although the weighted involved limb mean was not different from that of the contralateral limb, the mean and 95% confidence intervals for the involved limb subset were lower than that of the contralateral limb group, suggesting that the involved limb had less volitional activation within OA subjects. This provides evidence that bilateral quadriceps volitional activation deficits are present in persons with knee OA.

The Influence of Radiographic Severity on the Relationship between Muscle Strength and Joint Loading in Obese Knee Osteoarthritis Patients

Objective. To investigate the relationship between knee muscle strength and the external knee adduction moment during walking in obese knee osteoarthritis patients and whether disease severity influences this relationship. Methods. This cross-sectional study included 136 elderly obese (BMI > 30) adults with predominant medial knee osteoarthritis. Muscle strength, standing radiographic severity as measured by the Kellgren and Lawrence scale, and the peak external knee adduction moment were measured at self-selected walking speed. Results. According to radiographic severity, patients were classified as “less severe” (KL 1-2, N = 73) or “severe” (KL 3-4, N = 63). A significant positive association was demonstrated between the peak knee adduction moment and hamstring muscle strength in the whole cohort (P = .047). However, disease severity did not influence the relationship between muscle strength and dynamic medial knee joint loading. Severe patients had higher peak knee adduction moment and more varus malalignment (P < .001). Conclusion. Higher hamstring muscle strength relates to higher estimates of dynamic knee joint loading in the medial compartment. No such relationship existed for quadriceps muscle strength. Although cross sectional, the results suggest that hamstrings function should receive increased attention in future studies and treatments that aim at halting disease progression.

Gait patterns during different walking conditions in older adults with and without knee osteoarthritis--results from the Baltimore Longitudinal Study of Aging

Biomechanical analysis of lower extremity activities while walking at different speeds and in challenging conditions may help to identify specific gait patterns associated with knee osteoarthritis (knee-OA). We hypothesized that individuals with asymptomatic knee-OA have lower ankle activity, while individuals with symptomatic knee-OA have similar or higher ankle activity compared to individuals without knee-OA, and that such differences are enhanced during challenging gait tasks. We tested this hypothesis by examining gait characteristics in multiple gait tasks using data from 153 Baltimore Longitudinal Study of Aging (BLSA) participants (112 without knee-OA, 41 with knee-OA; 53-87 years, 52% women). All participants who could walk unassisted were evaluated in the BLSA gait lab while walking at self-selected speed (usual-walking), at maximum speed (fast-walking) and again at self-selected speed after 30-min of walking activities (usual-walking-after-30 min). Knee range of motion was lower for knee-OA participants in the fast-walking and usual-walking-after-30 min tasks (p<0.030). Ankle range of motion for symptomatic knee-OA was greater compared to asymptomatic knee-OA for all walking tasks (p<0.050). Symptomatic knee-OA had greater generative MWE of the ankle compared to asymptomatic knee-OA (p=0.034), while keeping similar absorptive MWE of the knee when compared to no-OA controls (p=0.151). Symptomatic knee-OA individuals seem to adapt an ankle kinematic gait pattern aimed at avoiding knee pain, by enhancing forward propulsion so to minimize knee joint load. Whether these conditions represent subsequent steps in the causal pathway from knee-OA to changes in gait is still not clear.

Effects of transcutaneous electrical nerve stimulation and therapeutic exercise on quadriceps activation in people with tibiofemoral osteoarthritis

STUDY DESIGN

Blinded, randomized controlled trial.

OBJECTIVES

To determine if the combination of transcutaneous electrical nerve stimulation (TENS) set to a sensory level and therapeutic exercise would be more effective than the combination of placebo TENS and therapeutic exercises or therapeutic exercises only to increase quadriceps activation in individuals with tibiofemoral osteoarthritis.

BACKGROUND

Quadriceps activation deficits are common in those with tibiofemoral osteoarthritis, and TENS has been reported to immediately increase quadriceps activation. Yet the long-term benefits of TENS for motor neuron activation have yet to be determined.

METHODS

Thirty-six individuals with radiographically assessed tibiofemoral osteoarthritis were randomly assigned to the TENS and exercise, placebo and exercise, and exercise only groups. All participants completed a supervised 4-week lower extremity exercise program. TENS and placebo TENS were worn throughout the therapeutic exercise sessions, as well as during daily activities. Our primary outcome measures, quadriceps central activation ratio, and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were evaluated at baseline and at 2 weeks and 4 weeks of the intervention.

RESULTS

Quadriceps activation was significantly higher in the TENS with exercise group compared to the exercise only group at 2 weeks (0.94 ± 0.04 versus 0.82 ± 0.12, P<.05) and the placebo and exercise group at 4 weeks (0.94 ± 0.06 versus 0.81 ± 0.15, P<.05). WOMAC scores improved in all 3 groups over time, with no significant differences among groups.

CONCLUSION

This study provides evidence that TENS applied in conjunction with therapeutic exercise and daily activities increases quadriceps activation in patients with tibiofemoral osteoarthritis and, while function improved for all participants, effects were greatest in the group treated with a combination of TENS and therapeutic exercises.

LEVEL OF EVIDENCE

Therapy, level 1b-.

Treatment and Prevention of Osteoarthritis through Exercise and Sports

Osteoarthritis (OA) is a degenerative joint disease with a high prevalence among older people. To date, the pathogenesis of the disease and the link between muscle function and OA is not entirely understood. As there is no known cure for OA, current research focuses on prevention and symptomatic treatment of the disorder. Recent research has indicated that muscle weakness precedes the onset of OA symptoms. Furthermore, several studies show a beneficial effect of land-based aerobic and strengthening exercises on pain relief and joint function. Therefore, current research focuses on the possibility to employ exercise and sports in the prevention and treatment of OA.

Alterations in neuromuscular patterns between pre and one-year post-total knee arthroplasty

BACKGROUND

Total knee arthroplasty is a common treatment for severe knee osteoarthritis. Objective measures are needed to evaluate the effect of arthroplasty surgery on function and joint loading, in particular given the rise in younger adults receiving this intervention. The objective was to compare neuromuscular activation patterns of the knee musculature during level walking one-week prior to and one-year following total knee arthroplasty.

METHODS

Surface electromyograms from seven periarticular muscles were recorded from 43 patients with severe medial compartment knee osteoarthritis during walking one-week prior to and one-year following total knee arthroplasty. Principal component analysis extracted patterns from the electromyographic waveforms and assigned scores for these patterns, which were statistically compared between test times and between medial and lateral sites within a muscle group.

FINDINGS

Significantly lower overall activation amplitudes were found for the quadriceps and hamstrings, with decreased activity during mid-late stance following surgery. Significant increases in gastrocnemius activity were found late stance, along with altered waveform shapes.

INTERPRETATION

In general, the post-surgical changes moved toward more typical asymptomatic patterns, supporting improved neuromuscular strategies during walking. Given that improvements would not be expected to occur naturally in severe osteoarthritic knees the positive changes in neuromuscular characteristics during specific phases of the gait cycle can be explained in part by the altered mechanical environment and reduction in pain from the surgical intervention. These objective findings are directly relevant to the joint loading environment and can be valuable for evaluating surgical techniques, different prostheses and pre-post surgical management.

Muscle weakness, afferent sensory dysfunction and exercise in knee osteoarthritis

Lower-extremity muscle strength and afferent sensory dysfunction, such as reduced proprioceptive acuity, are potentially modifiable putative risk factors for knee osteoarthritis (OA). Findings from current studies suggest that muscle weakness is a predictor of knee OA onset, while there is conflicting evidence regarding the role of muscle weakness in OA progression. In contrast, the literature suggests a role for afferent sensory dysfunction in OA progression but not necessarily in OA onset. The few pilot exercise studies performed in patients who are at risk of incident OA indicate a possibility for achieving preventive structure or load modifications. In contrast, large randomized controlled trials of patients with established OA have failed to demonstrate beneficial effects of strengthening exercises. Subgroups of individuals who are at increased risk of knee OA (such as those with previous knee injuries) are easily identified, and may benefit from exercise interventions to prevent or delay OA onset.

Do worsening knee radiographs mean greater chances of severe functional limitation?

OBJECTIVE

Development of functional limitation is thought to be unrelated to changes in severity of radiographic osteoarthritis (OA) of the knee. We evaluated the relationship of change in radiographic OA to the incidence of severe functional limitation.

METHODS

Participants of the Multicenter Osteoarthritis Study, a cohort study of persons with or at high risk of knee OA, were evaluated at 0 and 30 months. Subjects were classified as having no, incident, stable, or worsening radiographic OA. Incidence of severe functional limitation was defined by Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) physical function scores (≥36.1/68) and walking speed (≤1.0 meter/second) at 30 months. The relationship of the change in radiographic OA to the incidence of severe functional limitation was evaluated by calculating risk ratios adjusted for potential confounders.

RESULTS

Of the 2,210 subjects included (mean age 62 years, mean body mass index 30 kg/m², 60% women), 53% had no, 6% had incident, 14% had stable, and 27% had worsening radiographic OA. Persons with incident radiographic OA had 1.9 and 1.8 times the risk by WOMAC physical function score and walking speed, respectively, to have incident severe functional limitation compared with those with no radiographic OA over 30 months. Compared with those with stable radiographic OA, persons with worsening radiographic OA had 2.2 and 2.3 times the risk of incident severe functional limitation, respectively.

CONCLUSION

Changes in structural disease are associated with the development of severe functional limitations in persons with or even at high risk of knee OA.

Joint kinetics and muscle activity while walking on ballast

OBJECTIVE

This study examined the impact of two common sizes of ballast on gait biomechanics. The terrain was designed to simulate a railroad work setting to investigate the variation in gait kinetics and muscle activation while walking.

BACKGROUND

Research and epidemiology suggest a potential link between walking surface characteristics and injury. However, few studies have investigated the impact of ballast surfaces, which is a surface of interest in the railroad and construction industries, on gait dynamics.

METHOD

For this study, 20 healthy adult men walked along three distinct pathways (no ballast [NB], walking ballast [WB], and mainline ballast [MB]). WB and MB consisted of rock with an average size of 0.75 to I in. and 1.25 to 1.5 in., respectively. Full-body motion, ground reaction forces, and electromyographic (EMG) signals from lower extremity muscles were collected, and three dimensional joint moments were calculated. Parameters of interest were moment trajectories and ranges, EMG activity, and temporal gait measures.

RESULTS

Joint-specific differences indicate significant variations between surface conditions. Joint moment ranges were generally smaller for MB and WB compared with NB. EMG activity, in particular, co-contraction levels, was found to be significantly greater on ballast compared with NB. Temporal gait parameters were significantly different for MB than for either WB or NB.

CONCLUSION

Walking on ballast increases muscle activation to control the moments of the lower extremity joints.

APPLICATION

The results suggest that ballast has an effect on muscles and joints; thus, the findings provide insight to improve and develop new work practices and methods for injury prevention.

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.

Quadriceps and hamstrings muscle dysfunction after total knee arthroplasty

BACKGROUND/RATIONALE

Although TKA reliably reduces pain from knee osteoarthritis, full recovery of muscle strength and physical function to normal levels is rare. We presumed that a better understanding of acute changes in hamstrings and quadriceps muscle performance would allow us to enhance early rehabilitation after TKA and improve long-term function.

QUESTIONS/PURPOSES

The purposes of this study were to (1) evaluate postoperative quadriceps and hamstrings muscle strength loss after TKA and subsequent recovery using the nonoperative legs and healthy control legs for comparison, and (2) measure hamstrings coactivation before and after TKA during a maximal isometric quadriceps muscle contraction and compare with nonoperative and healthy control legs.

METHODS

We prospectively followed 30 patients undergoing TKA at 2 weeks preoperatively and 1, 3, and 6 months postoperatively and compared patient outcomes with a cross-sectional cohort of 15 healthy older adults. Bilateral, isometric strength of the quadriceps and hamstrings was assessed along with EMG measures of hamstrings coactivation during a maximal isometric quadriceps contraction.

RESULTS

There were no differences in strength loss or recovery between the quadriceps and hamstrings muscles of the operative leg throughout the followup, although differences existed when compared with nonoperative and healthy control legs. Hamstrings muscle coactivation in the operative leg during a maximal quadriceps effort was elevated at 1 month (144.5%) compared to the nonoperative leg.

CONCLUSIONS

Although quadriceps dysfunction after TKA typically is recognized and addressed in postoperative therapy protocols, hamstrings dysfunction also is present and should be addressed.

CLINICAL RELEVANCE

Quadriceps and hamstrings muscle strengthening should be the focus of future rehabilitation programs to optimize muscle function and long-term outcomes.

Effects of disinhibitory transcutaneous electrical nerve stimulation and therapeutic exercise on sagittal plane peak knee kinematics and kinetics in people with knee osteoarthritis during gait: a randomized controlled trial

Objective: To determine whether sensory transcutaneous electrical nerve stimulation (TENS) augmented with therapeutic exercise and worn for daily activities for four weeks would alter peak gait kinetics and kinematics, compared with placebo electrical stimulation and exercise, and exercise only.

Design: Randomized controlled trial.

Setting: Motion analysis laboratory.

Subjects: Thirty-six participants with radiographically assessed knee osteoarthritis and volitional quadriceps activation below 90% were randomly assigned to electrical stimulation, placebo and comparison (exercise-only) groups.

Interventions: Participants in all three groups completed a four-week quadriceps strengthening programme directed by an experienced rehabilitation clinician. Active electrical stimulation units and placebo units were worn in the electrical stimulation and placebo groups throughout the rehabilitation sessions as well as during all activities of daily living.

Main measures: Peak external knee flexion moment and angle during stance phase were analysed at a comfortable walking speed before and after the intervention.

Findings: Comfortable walking speed increased for all groups over time (TENS 1.16 ± 0.15 versus 1.32 ± 0.16 m/s; placebo 1.21 ± 0.34 versus 1.3 ± 0.24 m/s; comparison 1.27 ± 0.18 versus 1.5 ± 0.14 m/s), yet no group differences in speed were found. No differences were found for peak flexion moment or angle between groups overtime.

Conclusions: TENS in conjunction with therapeutic exercise does not seem to affect peak flexion moment and angle during stance over a four-week period in participants with tibiofemoral osteoarthritis.

Internal kinetic changes in the knee due to high tibial osteotomy are well-correlated with change in external adduction moment: an osteoarthritic knee model

In-vivo quantification of loads in the constitutive structures of the osteoarthritic knee can provide clinical insight, particularly when planning a surgery like the opening-wedge high tibial osteotomy (HTO). A computational knee model was created to estimate internal kinetics during walking gait. An optimization approach partitioned loads between the muscles, ligaments, medial and lateral contact surfaces of the tibial-femoral joint. Three kinetic measures were examined in 30 HTO patients: external knee adduction moment (EKAM), medial compartment load (ML) and the medial-to-lateral compartment loads ratio (MLR). Three time points were compared: immediately pre-HTO, 6 and 12 months post-HTO. Three hypotheses were tested: (1) HTO reduces an EKAM, an ML and an MLR, (2) these measures are not significantly different at 6 and 12 months post-HTO, and (3) the change in the impulse of EKAM due to a HTO is well-correlated with the impulse of an MLR. The three hypotheses were confirmed. First peak of an EKAM during stance phase was reduced significantly by 1.70% BW-ht. ML and MLR at the same instance were reduced significantly by 0.56%BW and 1.0, respectively. These measures were not significantly different between 6 and 12 months post-HTO. Changes in impulse of an EKAM and an MLR were moderately well-correlated between the pre-HTO and 6 months post-HTO time points (R(2)=0.5485). Therefore, the external measure EKAM-impulse is a good proxy of the internal kinetic measure of an MLR-impulse, explaining about 55% of the variance in the change due to a HTO intervention.

Lack of quadriceps dysfunction in women with early knee osteoarthritis

Quadriceps dysfunction, specifically weakness and central activation failure (CAF), has been implicated in the development and progression of knee osteoarthritis (OA), though few data are available to confirm its presence in early OA. The purpose of this study was to determine the presence and magnitude of quadriceps dysfunction in those with and without early knee OA. Thirty-five female volunteers were classified into two groups, OA (n=22) and control (n=13), based on the presence [Kellgren-Lawrence (K-L) grade 2] or absence (K-L grade 0-1) of mild OA, respectively. Isometric quadriceps strength and central activation ratio (CAR) were assessed and compared between groups utilizing a one-way ANOVA. Frequency statistics and Fisher's exact test were used to compare the percentage of women with and without CAF between groups. Quadriceps strength (control: 1.47+/-0.62 Nm/kg; OA: 1.30+/-0.62 Nm/kg; p=0.45) was not significantly different for women with and without mild OA. Further, the CAR (control: 0.91+/-0.07; OA: 0.87+/-0.12; p=0.19) did not differ between groups; however, women in both groups presented with CAF (control: 54%; OA: 73%; p=0.29). Our results suggest that the women with mild osteoarthritis do not present with quadriceps dysfunction.

Error associated with antagonist muscle activity in isometric knee strength testing

The purpose of this study was to determine the measurement error associated with antagonist muscle activity in isometric knee strength testing at 60 degrees of knee flexion in both sexes. Muscle specific EMG-contraction intensity relationships were obtained from 22 young people by having them match moment targets ranging from 10% to 100% peak moment. The moments attributed to each of the quadriceps and hamstrings muscles were partitioned using a practical mathematical model. Subject specific EMG-moment relationships were defined for each muscle using second-order polynomial equations. These equations were subsequently used to predict the countermoment associated with antagonist muscle activity. Error during strength testing was calculated by expressing net antagonist moments as a percentage of net agonist moments. The net antagonist moments associated with quadriceps and hamstrings muscle activity were 11.0% and 8.7% of the peak moment values recorded when the same muscle groups were acting as agonists. The error associated with antagonist activity was significantly higher in knee flexion (20.1%) than in knee extension (4.5%). Females displayed significantly higher error in knee flexor testing (P < 0.001). Limb symmetry indices did not change significantly when the countermoments generated by the antagonist muscles were accounted for (P > 0.05). The results of this study indicate that the error associated with antagonist activity in knee extensor testing is relatively small, whereas the error in knee flexor testing is larger. This is due to the quadriceps being much stronger than the hamstrings muscles while displaying similar levels of antagonist activity.

Alterations in quadriceps and hamstrings coordination in persons with medial compartment knee osteoarthritis

Altered muscle coordination strategies in persons with knee osteoarthritis (OA) result in an increase in co-contraction of the quadriceps and hamstrings during walking. While this may increase intersegmental joint contact force and expedite disease progression, it is not currently known whether the magnitude of co-contraction increases with a progressive loss of joint space or whether the level of co-contraction is dependent on walking speed. The purposes of this study were to (1) determine if co-contraction increased with OA severity and (2) discern whether differences in co-contraction were a result of altered freely chosen walking speeds or rather an inherent change associated with disease progression. Forty-two subjects with and without knee osteoarthritis were included in the study. Subjects were divided into groups based on disease severity. When walking at a controlled speed of 1.0m/s, subjects with moderate and severe knee OA showed significantly higher co-contraction when compared to a healthy control group. At freely chosen walking speeds only the moderate OA group had significantly higher co-contraction values. Increased walking speed also resulted in a significant increase in co-contraction, regardless of group. The results of this study demonstrate that persons with knee OA develop higher antagonistic muscle activity. This occurs despite differences in freely chosen walking speed. Although subjects with OA had higher co-contraction than the control group, co-contraction may not increase with disease severity.

Knee extension and flexion weakness in people with knee osteoarthritis: is antagonist cocontraction a factor?

STUDY DESIGN

Controlled laboratory study, cross-sectional data.

OBJECTIVES

To investigate isometric knee flexion and extension strength, failure of voluntary muscle activation, and antagonist cocontraction of subjects with knee osteoarthritis (OA) compared with age-matched asymptomatic control subjects.

BACKGROUND

Quadriceps weakness is a common impairment in individuals with knee OA. Disuse atrophy, failure of voluntary muscle activation, and antagonist muscle cocontraction are thought to be possible mechanisms underlying this weakness; but antagonist cocontraction has not been examined during testing requiring maximum voluntary isometric contraction.

METHODS

Fifty-four subjects with knee OA (mean +/- SD age, 65.6 +/- 7.6 years) and 27 similarly aged control subjects (age, 64.2 +/- 5.1 years) were recruited for this study. Isometric knee flexion and extension strength were measured, and electromyographic data were recorded, from 7 muscles crossing the knee and used to calculate cocontraction ratios during maximal effort knee flexion and extension trials. The burst superimposition technique was used to measure failure of voluntary activation.

RESULTS

Knee extension strength of subjects with knee OA (mean +/- SD, 115.9 +/- 6.7 Nm) was significantly lower than for those in the control group (152.3 +/- 9.6 Nm). No significant between-group difference was found for failure of voluntary muscle activation, or the cocontraction ratios during maximum effort knee flexion or extension.

CONCLUSION

These results demonstrate that the reduction in isometric extension strength, measured with a 90 degrees knee flexion angle, in subjects with knee OA is not associated with increased antagonist cocontraction.

No difference between home-based strength training and home-based balance training on pain in patients with knee osteoarthritis: a randomised trial

QUESTION

Is four weeks of home-based balance training more effective than four weeks of home-based strength training at decreasing pain in patients with knee osteoarthritis?

DESIGN

Randomised trial with concealed allocation and assessor blinding.

PARTICIPANTS

48 community volunteers with knee osteoarthritis.

INTERVENTION

Two groups undertook home-based exercise programs: one group performed balance training and the other performed strength training. Participants performed 30 repetitions/leg/day, 5 days/week for four weeks.

OUTCOME MEASURES

The Knee injury and Osteoarthritis Outcome Score was used to evaluate pain, which was the primary outcome. Secondary outcomes were the other subscales of the Knee injury and Osteoarthritis Outcome Score (other symptoms, function in daily living, function in sport and recreation, knee-related quality of life), strength, and mobility.

RESULTS

There was no significant difference between groups for pain (mean difference -3 points out of 100, 95% CI -10 to 5). The only between-group difference in the Knee injury and Osteoarthritis Outcome Score was in knee-related quality of life, where the strength group improved 17 points out of 100 (95% CI 5 to 28) more than the balance group. There was no significant difference between groups for strength. The only between-group difference in mobility was in the time taken to walk downstairs, where the strength group improved by 2 s (95% CI 0 to 3) more than the balance group.

CONCLUSION

There was no difference in pain between home-based strength training and home-based balance training in patients with knee osteoarthritis.

TRIAL REGISTRATION

NCT 00687726.

Effect of thigh strength on incident radiographic and symptomatic knee osteoarthritis in a longitudinal cohort

OBJECTIVE

To assess whether knee extensor strength or hamstring:quadriceps (H:Q) ratio predicts risk for incident radiographic tibiofemoral and incident symptomatic whole knee osteoarthritis (OA) in adults ages 50-79 years.

METHODS

We followed 1,617 participants (2,519 knees) who, at the baseline visit of the Multicenter Osteoarthritis (MOST) Study, did not have radiographic tibiofemoral OA and 2,078 participants (3,392 knees) who did not have symptomatic whole knee OA (i.e., did not have the combination of radiographic OA and frequent knee symptoms). Isokinetic strength was measured at baseline, and participants were followed for development of incident radiographic tibiofemoral OA, or incident symptomatic whole knee OA at 30 months. Generalized estimating equations accounted for 2 knees per subject, and multivariable models adjusted for age, body mass index (BMI), hip bone mineral density, knee surgery or pain, and physical activity score.

RESULTS

In the studies of incident radiographic and incident symptomatic knee OA, mean +/- SD ages were 62.4 +/- 8.0 years and 62.3 +/- 8.0 years, respectively, and mean +/- SD BMI scores were 30.6 +/- 5.8 kg/m(2) and 30.2 +/- 5.5 kg/m(2), respectively. Knee extensor strength and H:Q ratio at baseline significantly differed between men and women. Neither knee extensor strength nor the H:Q ratio was predictive of incident radiographic tibiofemoral OA. Compared with the lowest tertile, the highest tertile of knee extensor strength protected against development of incident symptomatic whole knee OA in both sexes (adjusted odds ratio 0.5-0.6). H:Q ratio was not predictive of incident symptomatic whole knee OA in either sex.

CONCLUSION

Thigh muscle strength does not appear to predict incident radiographic OA, but does seem to predict incident symptomatic knee OA.

Muscle weakness causes joint degeneration in rabbits

OBJECTIVE

The objective of this study was to investigate the effects of botulinum toxin type-A (BTX-A) induced quadriceps weakness on micro-structural changes in knee cartilage of New Zealand White (NZW) rabbits.

DESIGN

Fifteen rabbits were divided randomly into an experimental and a sham control group. Each group received a unilateral single quadriceps muscle injection either with saline (sham control; n=4) or BTX-A (experimental; n=11).

RESULTS

BTX-A injection produced significant quadriceps muscle weakness (P<0.05) and loss of quadriceps muscle mass (P<0.05). Degenerative changes of the knee cartilage, assessed with the Mankin grading system, were the same for the injected and non-injected hind limbs of the experimental group animals. Sham injection had no effect on joint degeneration but all control animals showed some degenerative changes in the knee. Degenerative changes of the retro-patellar cartilage were more severe in the experimental compared to sham control group rabbits (P<0.05). The distal region of the retro-patellar cartilage was more degenerated than the proximal part in the experimental and control group rabbits (P<0.05). The Mankin grades for the tibiofemoral region were not significantly different between experimental and control group rabbits (P>0.05).

CONCLUSION

Quadriceps muscle weakness caused increased degeneration in the retro-patellar cartilage of NZW rabbits, providing evidence that muscle weakness might be a risk factor for the onset and progression of osteoarthritis (OA). Future work needs to delineate whether muscle weakness directly affects joint degeneration, or if changes in function and movement execution associated with muscle weakness are responsible for the increased rate of OA onset and progression observed here.

Co-activation differences in lower limb muscles between asymptomatic controls and those with varying degrees of knee osteoarthritis during walking

BACKGROUND

Increased muscle co-activation during gait has been identified as a neuromuscular alteration associated with knee osteoarthritis, however levels of co-activation among different osteoarthritis severity have not been established. The purpose of this study was to determine if differences in co-activation could be detected among asymptomatic controls, those with moderate and those with severe osteoarthritis using a co-activation index and a pattern recognition technique.

METHODS

Surface electromyograms from vastus lateralis and medialis, lateral and medial hamstring and gastrocnemius pairs were recorded from 63 asymptomatic, 59 moderate and 48 severe osteoarthritic subjects during self-selected walking. A co-activation index was calculated over the initial stance for four medial and lateral muscle pairs. The four co-activation indices were tested among groups using a one factor ANOVA (alpha=0.05). Gait waveform pattern recognition procedures were applied to yield a principal pattern, scored for each muscle site and subject. A mixed model ANOVA (group-muscle) tested for principal pattern score differences.

FINDINGS

A significant group effect was found (P<0.05) for all four co-activation indices. Principal pattern one captured the amplitude and general shape of activity throughout the entire stance phase. ANOVA revealed a significant (P<0.05) group by muscle interaction for the principal pattern scores. Significant differences were found among all three groups and between the two osteoarthritic groups for both measures.

INTERPRETATION

The co-activation indices and principal patterns identified that lateral site differences occurred among all three groups with medial site differences between the two osteoarthritic groups. These findings suggest that measures of muscle co-activity provide additional information related to knee osteoarthritis severity.

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.

Linking biomechanics to mobility and disability in people with knee osteoarthritis

Knee osteoarthritis is the leading cause of chronic disability among community-dwelling adults. The factors resulting in this disability extend beyond pathology. Therefore, understanding disability requires assessment of both pathology and the day-to-day consequences of knee osteoarthritis. This review develops a novel osteoarthritis construct, "careful mobility," by linking qualitative and quantitative methods to study both patient experience and biomechanics.

Quadriceps strength and the risk of cartilage loss and symptom progression in knee osteoarthritis

OBJECTIVE

To determine the effect of quadriceps strength in individuals with knee osteoarthritis (OA) on loss of cartilage at the tibiofemoral and patellofemoral joints (assessed by magnetic resonance imaging [MRI]) and on knee pain and function.

METHODS

We studied 265 subjects (154 men and 111 women, mean+/-SD age 67+/-9 years) who met the American College of Rheumatology criteria for symptomatic knee OA and who were participating in a prospective, 30-month natural history study of knee OA. Quadriceps strength was measured at baseline, isokinetically, during concentric knee extension. MRI of the knee at baseline and at 15 and 30 months was used to assess cartilage loss at the tibiofemoral and patellofemoral joints, with medial and lateral compartments assessed separately. At baseline and at followup visits, knee pain was assessed using a visual analog scale, and physical function was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index.

RESULTS

There was no association between quadriceps strength and cartilage loss at the tibiofemoral joint. Results were similar in malaligned knees. However, greater quadriceps strength was protective against cartilage loss at the lateral compartment of the patellofemoral joint (for highest versus lowest tertile of strength, odds ratio 0.4 [95% confidence interval 0.2, 0.9]). Those with greater quadriceps strength had less knee pain and better physical function over followup (P<0.001).

CONCLUSION

Greater quadriceps strength had no influence on cartilage loss at the tibiofemoral joint, including in malaligned knees. We report for the first time that greater quadriceps strength protected against cartilage loss at the lateral compartment of the patellofemoral joint, a finding that requires confirmation. Subjects with greater quadriceps strength also had less knee pain and better physical function over followup.

Multiple ligament knee reconstruction clinical follow-up and gait analysis

Multiple ligament knee injuries are serious and rare injures that have not been studied using advanced gait analysis techniques. The purpose of this study was to perform clinical follow-up and gait analysis on patients with multiple knee ligament reconstruction. Twenty-four patients who underwent a multi-ligament knee reconstruction by a single surgeon volunteered to participate in this study. We performed complete clinical exam including instrumented ACL exam (KT-1000), and radiological exam including weight-bearing and PCL stress radiographs (TELOS) at minimum 2 years post index surgery. In addition, we performed complete three-dimensional gait analysis on 18 patients. We used a 10-camera, high speed (120 Hz) motion analysis system in conjunction with a multi-axis strain-gage force plate which calculated knee joint kinetics and kinematics while subjects performed flat-ground walking and stair-descent tasks. Kinematic and kinetic variables were compared between reconstructed and contralateral knees and unmatched, healthy control knees. All knee joint moments were normalized to subjects' weight. Clinical: Average knee joint flexion/extension 123.6 +/- 15.5/1.7 +/- 3.5, respectively. Average KT-1000 side-to-side difference was 1.2 +/- 2.0 mm, TELOS side-to-side difference on stress radiographs was 4.0 +/- 3.1 mm. Median IKDC score was 67 (range 13-94). Fifty-three percent of patients exhibited radiographic evidence of osteoarthritis (OA) on the operative side; one patient on the contralateral knee. During gait analysis, patients exhibited significantly reduced total knee joint range of motion, and external knee flexion moment in the reconstructed knee compared to the contralateral knee and healthy control knees. The magnitude of these differences was greater while descending a step. Finally, patients who had radiographic evidence of knee joint OA had significantly lower magnitude external knee flexion moment compared to those who did not have OA at the time of follow-up. Greater than 2 years after reconstruction, patients with multi-ligament knee injuries are able to return to daily activities. Gait analysis data suggests that patients may be experiencing higher magnitude changes in sagittal plane kinematics and kinetics during demanding functional tasks (stair decent). Changes in walking gait biomechanics may help explain why this group is experiencing unilateral knee joint degeneration.

The feasibility of measuring the activation of the trunk muscles in healthy older adults during trunk stability exercises

BACKGROUND

As the older adult population increases, the potential functional and clinical burden of trunk muscle dysfunction may be significant. An evaluation of risk factors including the impact of the trunk muscles in terms of their temporal firing patterns, amplitudes of activation, and contribution to spinal stability is required. Therefore, the specific purpose of this study was to assess the feasibility of measuring the activation of trunk muscles in healthy older adults during specific leg exercises with trunk stabilization.

METHODS

12 asymptomatic adults 65 to 75 years of age were included in the study. Participants performed a series of trunk stability exercises, while bilateral activation of abdominal and back extensor muscles was recorded by 24 pairs of Meditrace surface electrodes. Maximal voluntary isometric contractions (MVIC) were performed for electromyographic (EMG) normalization purposes. EMG waveforms were generated and amplitude measures as a percentage of MVIC were calculated along with ensemble average profiles. 3D kinematics data were also recorded, using an electromagnetic sensor placed at the left lateral iliac crest. Furthermore, a qualitative assessment was conducted to establish the participant's ability to complete all experimental tasks.

RESULTS

Excellent quality abdominal muscle activation data were recorded during the tasks. Participants performed the trunk stability exercises with an unsteady, intermittent motion, but were able to keep pelvic motion to less than 10 degrees . The EMG amplitudes showed that during these exercises, on average, the older adults recruited their abdominal muscles from 15-34% of MVIC and back extensors to less than 10% of MVIC. There were similarities among the abdominal muscle profiles. No participants reported pain during the testing session, although 3 (25%) of the participants reported delayed onset muscle soreness during follow up that was not functionally limiting.

CONCLUSION

Older adults were able to successfully complete the trunk stability protocol that was developed for younger adults with some minor modifications. The collected EMG amplitudes were higher than those reported in the literature for young healthy adults. The temporal waveforms for the abdominal muscles showed a degree of synchrony among muscles, except for the early activation from the internal oblique prior to lifting the leg off the table.

Physical function and properties of quadriceps femoris muscle in men with knee osteoarthritis

OBJECTIVES

To examine the objective physical function of the lower extremities, to measure the properties of quadriceps femoris muscle (QFM), and to assess subjective disabilities in men with knee osteoarthritis (OA) and to compare the results with those obtained from age- and sex-matched control subjects.

DESIGN

Cross-sectional study.

SETTING

Rehabilitation clinic in a university hospital.

PARTICIPANTS

Male volunteers (n=54) (age range, 50-69y) with knee OA and randomly selected healthy, age- and sex-matched control subjects (n=53).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Physical function evaluated with a test battery including the QFM composition measurement, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and the RAND 36-Item Short-Form Health Survey, version 1.0.

RESULTS

Knee OA patients had 13% to 26% poorer (P range, .050-.001) physical function and muscle strength compared with the controls. There were also significant differences in QFM composition. WOMAC (P range, .050-.001) and muscle strength (P<.001) associated with physical function tests, but subjective pain correlated with neither physical function nor muscle strength in knee OA patients. The radiographic knee OA grade did not have any significant effect on physical function, but passive knee motion, knee extension strength, and WOMAC were related to the severity of the disease (P<.05).

CONCLUSIONS

The patients with knee OA exhibited impaired physical function and muscle strength and QFM composition compared with healthy controls. The severity of radiographic knee OA clearly had adverse effects on functional ability at the later stages of the disease. The results highlight the effect of QFM strength on physical function as well as the importance of patient's subjective and objective physical function when deciding on knee OA treatment policy.

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.

Mechanisms underlying quadriceps weakness in knee osteoarthritis

PURPOSE

To identify determinants of quadriceps weakness among persons with end-stage knee osteoarthritis (OA).

METHODS

One-hundred twenty-three individuals (mean age 64.9 +/- 8.5 yr) with Kellgren/Lawrence grade IV knee OA participated. Quadriceps strength (MVIC) and volitional muscle activation (CAR) were measured using a burst superimposition test. Muscle composition (lean muscle cross-sectional area (LMCSA) and fat CSA (FCSA)) were quantified using magnetic resonance imaging. Specific strength (MVIC/LMCSA) was computed. Interlimb differences were analyzed using paired-sample t-tests. Regression analysis was applied to identify determinants of MVIC. An alpha level of 0.05 was adopted.

RESULTS

The OA limb was significantly weaker, had lower CAR, and had smaller LMCSA than the contralateral limb. CAR explained 17% of the variance in the contralateral limb's MVIC compared with 40% in the OA limb. LMCSA explained 41% of the variance in the contralateral limb's MVIC compared with 27% in the OA limb.

CONCLUSION

Both reduced CAR and LMCSA contribute to muscle weakness in persons with knee OA. Similar to healthy elders, the best predictor of strength in the contralateral, nondiseased limb was largely determined by LMCSA, whereas CAR was found to be the primary determinant of strength in the OA limb. Deficits in CAR may undermine the effectiveness of volitional strengthening programs in targeting quadriceps weakness in the OA population.

Combined application of neuromuscular electrical stimulation and voluntary muscular contractions

Electromyostimulation (EMS) and voluntary muscle contraction (VC) constitute different modes of muscle activation and induce different acute physiological effects on the neuromuscular system. Long-term application of each mode of muscle activation can produce different muscle adaptations. It seems theoretically possible to completely or partially cumulate the muscle adaptations induced by each mode of muscle activation applied separately. This work consisted of examining the literature concerning the muscle adaptations induced by long-term application of the combined technique (CT) [i.e. EMS is combined with VC - non-simultaneously] compared with VC and/or EMS alone in healthy subjects and/or athletes and in post-operative knee-injured subjects. In general, CT induced greater muscular adaptations than VC whether in sports training or rehabilitation. This efficiency would be due to the fact that CT can facilitate cumulative effects of training completely or partially induced by VC and EMS practiced alone. CT also provides a greater improvement of the performance of complex dynamic movements than VC. However, EMS cannot improve coordination between different agonistic and antagonistic muscles and thus does not facilitate learning the specific coordination of complex movements. Hence, EMS should be combined with specific sport training to generate neuromuscular adaptations, but also allow the adjustment of motor control during a voluntary movement. Likewise, in a therapeutic context, CT was particularly efficient to accelerate recovery of muscle contractility during a rehabilitation programme. Strength loss and atrophy inherent in a traumatism and/or a surgical operation would be more efficiently compensated with CT than with VC. Furthermore, CT also restored more functional abilities than VC. Finally, in a rehabilitation context, EMS is complementary to voluntary exercise because in the early phase of rehabilitation it elicits a strength increase, which is necessary to perform voluntary training during the later rehabilitation sessions.

Implications of increased medio-lateral trunk sway for ambulatory mechanics

The purposes of this study was to test a mechanism to reduce the knee adduction moment by testing the hypothesis that increased medio-lateral trunk sway can reduce the knee adduction moment during ambulation in healthy subjects, and to examine the possibility that increasing medio-lateral trunk sway can produce similar potentially adverse secondary gait changes previously associated with reduced knee adduction moments in patients with knee osteoarthritis. Nineteen healthy adults performed walking trials with normal and increased medio-lateral trunk sway at a self-selected normal walking speed. Standard gait analysis was used to calculate three-dimensional lower extremity joint kinematics and kinetics. Knee and hip adduction moments were lower (-65.0% and -57.1%, respectively) for the increased medio-lateral trunk sway trials than for the normal trunk sway trials. Knee flexion angle at heel-strike was 3 degrees higher for the increased than for the normal trunk sway trials. Knee and hip abduction moments were higher for the increased medio-lateral trunk sway trials, and none of the other variables differed between the two conditions. Walking with increased medio-lateral trunk sway substantially reduces the knee adduction moment during walking in healthy subjects without some of the adverse secondary effects such as increased axial loading rates at the major joints of the lower extremity. This result supports the potential of using gait retraining for walking with increased medio-lateral trunk sway as treatment for patients with degenerative joint disease such as medial compartment knee osteoarthritis.

Muscle co-activation patterns during walking in those with severe knee osteoarthritis

BACKGROUND

Sensory and motor impairments have been found for those with knee osteoarthritis; however, how these impairments are manifested during functional movements such as walking is not well established. A few studies suggest an increase in co-activity among lower limb muscles. The objective of this study was to characterize the neuromuscular patterns of knee joint muscles during walking for those with severe knee osteoarthritis using pattern recognition techniques on the entire waveform.

METHODS

Fifty-one subjects received a gait assessment within one-week prior to total knee replacement surgery. Subjects walked along a 6-m walkway at their preferred walking speed while surface electromyograms from seven muscles were recorded. The electromyographic data were entered into a pattern recognition procedure that captured both the amplitude and shape characteristics of electromyographic waveforms. ANOVA models tested whether differences existed both among and within muscle groups for these waveform characteristics.

FINDINGS

Four principal patterns explained 97% of the variance in the waveform data, with principal pattern one explaining 86% of the total variance. There were statistically significant differences (P<0.05) among muscle sites for all principal pattern scores. The analyses supported the hypothesis that similarities existed in patterns among muscles from different groups indicating (i) a general co-activity pattern and (ii) differential recruitment between muscles within a muscle group.

INTERPRETATION

In addition to the roles during impact loading and propulsion, the muscle responses were consistent with attempts to (i) decrease medial knee joint loading, (ii) decrease peak knee joint loading during push off and (iii) increase stiffness during stance phase to improve joint stability. The technique employed provides a novel approach to quantify synergistic co-activity.