Quadriceps femoris muscle voluntary isometric force production and relaxation characteristics before and 6 months after unilateral total knee arthroplasty in women

The course of knee extensor strength after total knee arthroplasty: a systematic review with meta-analysis and -regression

PURPOSE

Muscular strength loss and atrophy are postoperative complications. This systematic review with meta-analysis investigated the course of on knee extensor mass and strength from pre-surgery over total knee arthroplasty to rehabilitation and recovery.

METHODS

A systematic literature search was conducted in PubMed (Medline), Cochrane Library (CINAHL, Embase) and Web of Science (until 29th of June 2022). Main inclusion criteria were  ≥ 1 preoperative and  ≥ 1 measurement  ≥ 3-months post-operation and ≥ 1 objective assessment of quadriceps strength, muscle mass or neuromuscular activity, measured at both legs. Studies were excluded if they met the following criteria: further impairment of treated extremity or of the contralateral extremity; further muscle affecting disease, or muscle- or rehabilitation-specific intervention. The Robins-I tool for non-randomized studies, and the Cochrane Rob 2 tool for randomized controlled studies were used for risk of bias rating. Pre-surgery, 3 months, 6 months and 1 year after surgery data were pooled using random effects meta-analyses (standardized mean differences, SMD, Hedge's g) in contrast to the pre-injury values.

RESULTS

1417 studies were screened, 21 studies on 647 participants were included. Thereof, 13 were non-randomized controlled trails (moderate overall risk of bias in most studies) and 7 were randomized controlled trials (high risk of bias in at least one domain in most studies). Three (k = 12 studies; SMD = - 0.21 [95% confidence interval = - 0.36 to - 0.05], I² = 4.75%) and six (k = 9; SMD = - 0.10 [- 0.28 to - 0.08]; I² = 0%) months after total knee arthroplasty, a deterioration in the strength of the operated leg compared with the strength of the non-operated leg was observed. One year after surgery, the operated leg was stronger in all studies compared to the preoperative values. However, this increase in strength was not significant compared to the non-operated leg (k = 6, SMD = 0.18 [- 0.18 to 0.54], I² = 77.56%).

CONCLUSION

We found moderate certainty evidence that deficits in muscle strength of the knee extensors persist and progress until 3 months post-total knee arthroplasty in patients with end-stage knee osteoarthritis. Very low certainty evidence exists that preoperatively existing imbalance of muscle strength and mass in favor of the leg not undergoing surgery is not recovered within 1 year after surgery.

Immunohistochemical analysis of the quadriceps femoris muscle before and after total knee arthroplasty

BACKGROUND

The number of total knee arthroplasties (TKA) has increased steadily with the aging of the population. This surgical procedure is recognized for its success in pain relief and restoration of knee function. However, decreased quadriceps femoris (QF) muscle strength after TKA is frequently observed but with unknown etiology. Evidence suggests that the location of the operative incision (i.e., surgical access) can influence QF muscle structure and function. The present study aimed to assess the fiber type composition, structure and assembly of the QF's vastus medialis (VM) and vastus lateralis (VL) muscles before and after TKA.

METHODS

Muscle biopsies (VM and VL muscles) were collected from patients previously submitted to TKA via the medial parapatellar route and undergoing TKA revision (main group, n = 9) and patients with osteoarthrosis (OA) who were due to undergo TKA (control group: n = 18). The biopsied muscle tissue was prepared, stored, and then sectioned in a cryostat at -25 °C. The tissue sections were evaluated using routine staining techniques in pathological anatomy and histochemistry.

RESULTS

The normal mosaic pattern of the medial and lateral knee muscles was observed in the main and control groups, with no evidence of peripheral nerve damage. Notably, 88.9 % of the patients exhibited mild to severe VL atrophy, while only 11.1 % of patients in the control group presented this feature (P < 0.001).

CONCLUSIONS

The medial parapatellar incision for TKA surgical access does not generate definitive morphological changes in the VM and VL muscle fibers but may contribute to VL atrophy.

Unilateral Strength Training Imparts a Cross-Education Effect in Unilateral Knee Osteoarthritis Patients

Background: Worldwide, 86 million individuals over the age of 20 were diagnosed with knee osteoarthritis (KOA) in 2020. Hallmark features of KOA are the loss in knee extensor strength, increasing knee pain severity, and deficits in functional performance. There is a critical need for the investigation into potential cost-effective therapeutic interventions in the treatment of KOA. A potential therapeutic option is the cross-education phenomenon. Methods: This was a non-blinded randomized control trial, with a 4-week intervention, with a pre, post and follow-up assessment (3 months post intervention). Outcome measures of isometric knee extensor strength, rectus femoris muscle thickness and neuromuscular activation were assessed at all-time points. Results: Compared to age-matched KOA controls, 4 weeks of unilateral strength training in end-stage KOA patients increased strength of the untrained affected KOA limb by 20% (p < 0.05) and reduced bilateral hamstring co-activation in the KOA intervention group compared to the KOA control group (p < 0.05). Conclusions: A 4-week-long knee extensor strength training intervention of the contralateral limb in a cohort with diagnosed unilateral KOA resulted in significant improvements to knee extensor strength and improved neuromuscular function of the KOA limb. Importantly, these results were maintained for 3 months following the intervention.

Normative Reference Values for Knee Extensor Muscle Rate of Torque Development and Torque Steadiness in Adolescents and Adults

OBJECTIVE

The aim of this study was to establish reference values for rate of torque development (RTD) and muscle torque steadiness (MTS) of knee extensors across the lifespan, and evaluate if these measures are independently associated with Osteoarthritis Research Society International (OARSI)-recommended performance-based measures (6-minute walk test, 30-second chair stand test, stair climb test) and other clinical variables.

METHODS

In this cross-sectional observational study, knee extensor strength of 764 participants (12-89 years) from the 1000 Norms Project was assessed via fixed dynamometry. Age- and sex-stratified normative RTD (Nms-1 kg-1) and MTS (Nm kg-1) values were presented as means and 95% confidence intervals. Correlations and multiple regression analyses were calculated to identify factors (age, sex, height, weight, OARSI-recommended performance-based measures, Knee Injury and Osteoarthritis Outcome Score, vertical jump, long jump, grip strength, basic gait-related knee biomechanics) independently associated with RTD or MTS.

RESULTS

Age- and sex-stratified normative RTD and MTS reference values were generated. Male subjects exhibited higher RTD but poorer MTS (less steady) than female subjects across all age groups. Better performance in OARSI-recommended performance-based measures, vertical jump, long jump, and grip strength were associated with greater RTD but poorer MTS. Thirty-second chair stand test, stair climb test, vertical jump, long jump, and grip strength were independent determinants of RTD and MTS.

CONCLUSIONS

The RTD and MTS demonstrated associations with clinical variables relevant to knee osteoarthritis. The normative reference values generated may help identify the presence and extent of impairments in RTD and MTS associated with knee osteoarthritis and assist in developing responsive outcome measures for therapeutic trials.

Muscle loaded stability reflects ligament-based stability in TKA: a cadaveric study

PURPOSE

This paper aims at evaluating the effects of muscle load on knee kinematics and stability after TKA and second at evaluating the effect of TKA surgery on knee kinematics and stability; and third, at correlating the stability in passive conditions and the stability in active, muscle loaded conditions.

METHODS

Fourteen fresh frozen cadaveric knee specimens were tested under passive and active condition with and without external loads involving a varus/valgus and internal/external rotational torque before and after TKA surgery using two in-house developed and previously validated test setups.

RESULTS

Introduction of muscle force resulted in increased valgus (0.98°) and internal rotation of the femur (4.64°). TKA surgery also affected the neutral path kinematics, resulting in more varus (1.25°) and external rotation of the femur (5.22°). All laxities were significantly reduced by the introduction of the muscle load and after implantation of the TKA. The presence of the implant significantly affects the active varus/valgus laxity. This contrasts with the rotational laxity, in which case the passive laxity is the main determinant for the active laxity. For the varus/valgus laxity, the passive laxity is also a significant predictor of the active laxity.

CONCLUSION

Knee stability is clearly affected by the presence of muscle load. This points to the relevance of appropriate rehabilitation with focus on avoiding muscular atrophy. At the same time, the functional, muscle loaded stability strongly relates to the passive, ligament-based stability. It remains therefore important to assess knee stability at the time of surgery, since the passive laxity is the only predictor for functional stability in the operating theatre.

LEVEL OF EVIDENCE

Case series, Level IV.

Familiarization and Reliability of the Isometric Knee Extension Test for Rapid Force Production Assessment

Despite the rising interest in the use of portable force sensors during isometric exercises to inform on neuromuscular performance, the design of practical field-based methods to obtain reliable measures is an ongoing challenge. We aim at identifying the intra-session and test-retest reliability of a rapid, isometric knee extension test to evaluate the maximal voluntary concentric force (MVC), rate of force development (RFD) and impulse following a field-based approach. On two occasions, 14 athletes unfamiliar with the test completed three sets of 2 s ballistic contractions (as fast and hard as possible) with 30 s rest. Raw and filtered data were collected in real time using a portable force sensor. RFD and impulse were highly reliability during “late” phases of the contraction (0–250 ms) since the first session (coefficient of variation (CV) < 9.8%). Earlier phases (0–150 ms) achieved a moderate reliability after one familiarization session (CV < 7.1%). Measures at 0–50 ms did not reach sufficient reliability (CV~14%). MVC was accurately assessed. Dominant limbs were not importantly altered by the familiarization. In opposite, non-dominant limbs showed large variations. New evidence is provided about the positive effects of a single familiarization session to improve the reliability the isometric knee extension test for rapid force production assessment. Coaches and practitioners may benefit of from these findings to conduct practical and reliable assessments of the rapid force production using a portable force sensor and a field-based approach.

Neurostructural correlates of strength decrease following total knee arthroplasty: A systematic review of the literature with meta-analysis

Recent literature suggests that alterations in both neural and structural components of the neuromuscular system are major determinants of knee extensor muscle weakness after total knee arthroplasty (TKA). Therefore, the goal of this study was to investigate the maximal voluntary strength (MVS), voluntary muscle activation (VMA), and the cross-sectional area (CSA) of the muscle, up to 33 months after the TKA.  We searched relevant scientific databases and literature for outcomes of interest, including quadriceps MVS, VMA, and CSA. Ten studies met the inclusion criteria and involved a total of 289 patients. The quality of the studies was evaluated by Methodological Index for Non-Randomized Studies (MINORS). Results showed that quadriceps MVS markedly declines in the early postoperative period, after which it slowly and linearly recovers over time. However, the same phenomenon was not observed for VMA and CSA, which were not significantly altered after the TKA. Furthermore, a meta-regression analysis revealed that the change in VMA accounted for 39% of the relative change in quadriceps strength (R2=0.39; p=0.015) in the early postoperative period. Patients treated with TKA had considerable weakness of the quadriceps muscle, which was detectable up to 3 months after surgery. Although the change in VMA largely explains quadriceps weakness, this change and CSA differences were not significant, suggesting that other neural correlates, such as hamstrings coactivation, might alter quadriceps muscle function. Thus, more attention should be paid to address VMA failure and coactivation of antagonist muscles.  More comprehensive rehabilitation approaches may be required to target the whole neural circuit controlling the motor action.

Relationship Between Strength Parameters and Functional Performance Tests in Patients With Severe Knee Osteoarthritis

BACKGROUND

Decreased leg muscle strength is a major determinant of reduced function in patients with knee osteoarthritis (OA). The identification of a strength parameter that is best correlated with functional performance is important for monitoring rehabilitation results.

OBJECTIVE

To determine which muscle strength measurements show the highest correlation with functional capacity in patients with severe knee OA shortly before total knee arthroplasty (TKA).

DESIGN

Cross-sectional exploratory study.

SETTING

Outpatient rehabilitation department at a university teaching hospital.

PATIENTS

The sample included 75 patients (51 female) scheduled for primary TKA, recruited through multistage sampling.

METHODS OR INTERVENTIONS

Independent variables were peak isometric, isokinetic concentric, and eccentric leg extensor strength measured on the leg press, as well as peak isometric knee extensor strength measured on the strength chair. Two multiple regression analyses were performed, one including all strength measures and the other including all of the strength ratios. Pearson correlation coefficients were calculated between the strength measures and functional test scores.

MAIN OUTCOME MEASUREMENTS

Dependent variables were the Timed Up and Go Test (TUG) and the Stair Test (ST).

RESULTS

The regression analysis including all strength measures could explain 11.9% of the variance of the TUG (P = .068, not significant [NS]) and 21.5% of the variance of the ST (P = .009, significant). The regression model for the strength ratios explained 11.8% of the variance of the TUG (P = .090, NS) and 6.3% of the ST (P = .217, NS).

CONCLUSIONS

Although univariate analysis confirmed significant correlations between strength measurements and functional tests, multiple regression analysis revealed a higher predictive value for the ST than for the TUG. The use of both muscle strength tests and performance-based function tests is advisable to evaluate functional impairments of patients with knee OA.

LEVEL OF EVIDENCE

III.

Quadriceps Rate of Torque Development and Disability in Persons With Tibiofemoral Osteoarthritis

Background Declines in the ability to rapidly generate quadriceps muscle torque may underlie disability in individuals with tibiofemoral osteoarthritis. Objective To determine whether quadriceps rate of torque development (RTD) predicts self-reported disability and physical performance outcomes in individuals with tibiofemoral osteoarthritis. Methods This controlled laboratory, cross-sectional study assessed quadriceps strength and RTD in 76 individuals (55% female; mean ± SD age, 61.83 ± 7.11 years) with symptomatic and radiographic tibiofemoral osteoarthritis. Early (0-50 milliseconds), late (100-200 milliseconds), and overall peak RTDs were quantified in the symptomatic (involved) and contralateral limbs and used to calculate bilateral average values. Disability was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) function subscale and 3 physical performance tests, including the (1) 20-m fast-paced walk, (2) 30-second chair stand, and (3) timed stair climb. Separate univariate regression models were used to determine the unique associations among measures of quadriceps RTD, WOMAC function score, and physical performance outcomes after accounting for quadriceps strength (change in R²). Results Greater involved-side late RTD and greater bilateral average early RTD were associated with faster walking (change in R² = 0.05, P = .013 and change in R² = 0.05, P = .043, respectively). Greater bilateral average late RTD was associated with faster walking (change in R² = 0.20, P<.001) and faster stair climb (change in R² = 0.11, P = .001). No quadriceps RTD variable was significantly associated with WOMAC function score (change in R² range, <0.01-0.017). Conclusion Involved-limb quadriceps RTD was weakly associated with physical performance outcomes, but not self-reported disability, in individuals with tibiofemoral osteoarthritis. Bilateral average quadriceps RTD was moderately associated with walking speed. Level of Evidence Prognosis, level 2b. J Orthop Sports Phys Ther 2018;48(9):694-703. Epub 22 May 2018. doi:10.2519/jospt.2018.7898.

Short-term functional advantages after medial unicompartmental versus total knee arthroplasty

BACKGROUND

There are many uncertainties about the advantages and disadvantages of using unicompartmental (UKA) versus total knee arthroplasty (TKA) to treat patients with knee osteoarthritis. It is important to have sufficient early postoperative quadriceps strength for long-term, self-reported and gait-related outcomes after knee arthroplasty, but very limited comparative data exist regarding UKA and TKA patients.

METHODS

This study assessed isometric quadriceps strength, spatio-temporal gait parameters (walking speed, step length, single-limb support phase) and self-reported outcomes (pain, function, stiffness) in 18 TKA and 18 UKA patients six months after surgery, as well as in 18 healthy controls.

RESULTS

Quadriceps strength of TKA, but not of UKA patients, was lower than that of controls (P < 0.05). UKA patients demonstrated better gait function in terms of a longer single-limb support phase than TKA patients (P < 0.01), which agreed with better self-reported pain (P < 0.05), function (P < 0.01) and stiffness (P < 0.05) scores compared to TKA patients.

CONCLUSIONS

Six months after surgery, UKA patients showed better short-term quadriceps strength and gait function compared to TKA patients, together with less self-reported knee pain and stiffness. Patients eligible for UKA may experience less functional impairments compared to those who require TKA.

The mental representation of the human gait in patients with severe knee osteoarthrosis: a clinical study to aid understanding of impairment and disability

OBJECTIVE

Objectives were (1) to explore differences in gait-specific long-term memory structures and gait performance between knee osteoarthrosis patients and healthy subjects and (2) to identify the extent to which the gait-specific mental representation is associated with gait performance.

DESIGN

Cross-sectional study.

SUBJECTS

In total, 18 knee osteoarthrosis patients and 18 control subjects.

METHODS

Spatio-temporal (gait speed, step length) and temporophasic (stance time, swing time, single support time, total double support time) gait parameters and gait variability were measured with an electronic walkway (OptoGait). The mental representation was assessed using the structural dimensional analysis of mental representations (SDA-M).

RESULTS

(1) Patients showed significantly longer stance times ( P < 0.002) and total double support times, shorter swing times and single support times, a decreased gait speed ( P-values < 0.001) and structural differences in the gait-specific mental representation as compared with the healthy controls. (2) Correlation analyses revealed the mental representation of the human gait to be associated with actual gait performance in osteoarthrosis patients. Double support times were positively associated with the structural quality of the mental representation and step length variability was positively associated with the number of sequencing errors in the representation.

CONCLUSION

The gait-specific mental representation and actual gait performance differ between patients with severe knee osteoarthrosis and healthy controls, and both are linked to one another. This finding suggests that musculoskeletal disorders can lead to changes in the mental representation of the gait, and as such the SDA-M could provide useful information to improve the rehabilitation following osteoarthrosis.

Neuromuscular function of the quadriceps muscle during isometric maximal, submaximal and submaximal fatiguing voluntary contractions in knee osteoarthrosis patients

INTRODUCTION

Knee osteoarthrosis (KOA) is commonly associated with a dysfunction of the quadriceps muscle which contributes to alterations in motor performance. The underlying neuromuscular mechanisms of muscle dysfunction are not fully understood. The main objective of this study was to analyze how KOA affects neuromuscular function of the quadriceps muscle during different contraction intensities.

MATERIALS AND METHODS

The following parameters were assessed in 20 patients and 20 healthy controls: (i) joint position sense, i.e. position control (mean absolute error, MAE) at 30° and 50° of knee flexion, (ii) simple reaction time task performance, (iii) isometric maximal voluntary torque (IMVT) and root mean square of the EMG signal (RMS-EMG), (iv) torque control, i.e. accuracy (MAE), absolute fluctuation (standard deviation, SD), relative fluctuation (coefficient of variation, CV) and periodicity (mean frequency, MNF) of the torque signal at 20%, 40% and 60% IMVT, (v) EMG-torque relationship at 20%, 40% and 60% IMVT and (vi) performance fatigability, i.e. time to task failure (TTF) at 40% IMVT.

RESULTS

Compared to the control group, the KOA group displayed: (i) significantly higher MAE of the angle signal at 30° (99.3%; P = 0.027) and 50° (147.9%; P < 0.001), (ii) no significant differences in reaction time, (iii) significantly lower IMVT (-41.6%; P = 0.001) and tendentially lower RMS-EMG of the rectus femoris (-33.7%; P = 0.054), (iv) tendentially higher MAE of the torque signal at 20% IMVT (65.9%; P = 0.068), significantly lower SD of the torque signal at all three torque levels and greater MNF at 60% IMVT (44.8%; P = 0.018), (v) significantly increased RMS-EMG of the vastus lateralis at 20% (70.8%; P = 0.003) and 40% IMVT (33.3%; P = 0.034), significantly lower RMS-EMG of the biceps femoris at 20% (-63.6%; P = 0.044) and 40% IMVT (-41.3%; P = 0.028) and tendentially lower at 60% IMVT (-24.3%; P = 0.075) and (vi) significantly shorter TTF (-51.1%; P = 0.049).

CONCLUSION

KOA is not only associated with a deterioration of IMVT and neuromuscular activation, but also with an impaired position and torque control at submaximal torque levels, an altered EMG-torque relationship and a higher performance fatigability of the quadriceps muscle. It is recommended that the rehabilitation includes strengthening and fatiguing exercises at maximal and submaximal force levels.

Long-term data of gait characteristics and moment-knee angle relations in female total knee arthroplasty patients

BACKGROUND

Despite the clinical success of total knee arthroplasty, impaired gait patterns and quadriceps and hamstring maximal voluntary force production might persist years post-surgery. Long-term data of gait patterns and quadriceps and hamstring maximal force production are rarely published with total knee arthroplasty patients. This work examined gait characteristics and the moment-knee angle relations of the knee extensors and flexors about 10 years post-total knee arthroplasty.

METHODS

About a decade post-surgery, 10 female total knee arthroplasty patients (64 years, mobile-bearing inlay) and 10 age-matched female controls were examined. Sagittal plane kinematics in the hip and knee joint during treadmill walking at 2 kilometres per hour were recorded using motion analysis. Spatiotemporal gait parameters were analyzed at self-selected walking speeds with a pressure-platform. The unilateral isometric moment-knee angle relations of the knee extensors and flexors and the electromyographic knee angle relation of the quadriceps were studied using dynamometry. Due to group differences for body mass index values, univariate analysis of variance (main effect: group, secondary effect: body mass index) was used for statistical analysis.

FINDINGS

Total knee arthroplasty patients demonstrated significant (P<0.05) gait deficits during constant and self-selected walking speeds and lower average absolute values in the moment-knee angle relations of the knee extensors and flexors. Significant (P<0.05) lower body-mass-normalized knee extension moments were detected at all knee joint positions for the patients.

INTERPRETATION

Long-term impairments of gait characteristics and maximal voluntary force production, especially for the knee extensors, might persist after total knee arthroplasty.

Knee extensor and flexor muscle power explains stair ascension time in patients with unilateral late-stage knee osteoarthritis: a cross-sectional study

OBJECTIVES

To determine the extent of asymmetrical deficits in knee extensor and flexor muscles, and to examine whether asymmetrical muscle deficits are associated with mobility limitations in persons with late-stage knee osteoarthritis (OA).

DESIGN

Cross-sectional.

SETTING

Research laboratory.

PARTICIPANTS

A clinical sample (N=56; age range, 50-75y) of eligible persons with late-stage knee OA awaiting knee replacement.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Knee extensor and flexor power and torque assessed isokinetically; thigh muscle cross-sectional area (CSA) assessed by computed tomography; mobility limitation assessed by walking speed and stair ascension time; and pain assessed with the Western Ontario and McMaster Universities Osteoarthritis Index questionnaire.

RESULTS

The asymmetrical deficits in knee extensor and flexor power and torque were between 18% and 29% (P<.001). Regarding the thigh muscle CSA, the asymmetrical deficit was 4% (P<.001). Larger asymmetrical knee extensor power deficits and weaker knee extensor and flexor power on the contralateral side were associated with slower stair ascension times. Moreover, weaker knee extensor and flexor power on the ipsilateral side were associated with slower stair ascension times. Greater knee pain in the OA joint was independently associated with slower stair ascending time in both models.

CONCLUSIONS

The knee extensor and flexor muscle power of both the ipsilateral and contralateral sides and the pain in the OA knee were independently associated with stair ascension times. These results highlight the importance of assessing muscle power on both sides and knee pain in the prevention of mobility limitations in patients with knee OA.

Better quadriceps recovery after minimally invasive total knee arthroplasty

PURPOSE

The proponents of minimally invasive total knee arthroplasty (TKA) have reported better functional recovery than conventional TKA. In most of the previous studies, the results were shown with the relatively subjective methods. We investigated the objective results with a dynamometry in this prospective randomized study. It was hypothesized that minimally invasive TKA would have a better and earlier recovery of quadriceps force in terms of the objective numeric data.

METHODS

Sixty-six TKAs were prospectively randomized into two groups. Thirty-three knees underwent minimally invasive TKA using mini-midvastus approach and 33 knees underwent conventional TKA using medial parapatellar approach. The quadriceps force was assessed using a dynamometer. The data were collected preoperatively and at postoperative 6 weeks, 3 months, 6 months and 1 year consecutively.

RESULTS

The mean of quadriceps force in minimally invasive TKA group at postoperative 6 weeks was greater than conventional TKA after removing the covariate (preoperative quadriceps force) with analysis of covariance (P = 0.002), but thereafter, the difference was not significant till 1 year. Meanwhile, with repeated measures analysis of variance, conventional TKA group had greater quadriceps recovery than minimally invasive TKA group during postoperative 6 weeks to 3 months (P = 0.035). The proportion of patients unable to recover the quadriceps force to their preoperative levels by 1 year postoperatively was similar in two groups.

CONCLUSION

Minimally invasive TKA has benefit in quadriceps recovery at earlier rehabilitation period although catch-up recovery in conventional TKA was accelerated from the postoperative 6 weeks to 3 months. It may support the concept of early return to full activity after minimally invasive TKA, and patients might get back early to normal life.

Lower limb strength following total knee arthroplasty: a systematic review

BACKGROUND

Total knee arthroplasty (TKA) is commonly performed for end-stage knee osteoarthritis to relieve pain and improve quality of life. Understanding specific muscle weakness following TKA is required in order to develop targeted rehabilitation programmes for TKA patients. The aim of this systematic review was to determine whether TKA patients have reduced strength in lower limb muscle groups compared to controls.

METHODS

A search of common scientific databases was conducted. A modified published checklist was used to assess the risk of bias. A meta-analysis was completed for each lower limb muscle group in three separate post-operative time periods (4-6 months, 1-3 years, and >3 years). The GRADE approach was used to determine the quality of the evidence.

RESULTS

Fifteen studies met the inclusion criteria for this review. There was low quality evidence for all meta-analyses. The meta-analyses showed that TKA patients had weaker quadriceps than the controls at every post-operative time (pooled effect sizes between -2.81 and -0.53). The meta-analyses of hamstring strength for patients 1-3 years post-operatively also showed patient weakness (pooled effect size=-1.87) and no significant difference at >3 years post-operatively (pooled effect size=-0.20).

CONCLUSION

There was low quality evidence of quadriceps and hamstring weakness following TKA. Further research is required to determine if other lower limb muscles also display similar muscle weakness. Strategies that specifically target strengthening of these muscle groups may need to be incorporated in rehabilitation to improve outcomes from TKA.

LEVEL OF EVIDENCE

I.

Lengthening the moment arm of the patella confers enhanced extensor mechanism power following total knee arthroplasty

We investigated whether a postulated biomechanical advantage conferred to the extensor mechanism by a change in knee implant design was detectable in patients by direct physical testing. 212 TKA patients were enrolled in a double blind randomized controlled trial to receive either a traditional implant or one which incorporated new design features. Extensor mechanism power output and physical performance on a battery of timed functional activities was assessed pre-operatively and then at 6, 26, and 52 weeks post-operatively. Significantly enhanced power output was observed in both groups post-arthroplasty; however, the new design implant group demonstrated a greater change in power output than the traditional implant group. Posthoc testing of between group differences highlighted greater improvement at all post-operative assessments. At 52 weeks, patients receiving the implant with the postulated biomechanical advantage achieved 116% of the power output of their contralateral limb, whereas patients with the traditional design achieved 90%. No between group difference was detected in the patient's time to complete functional tasks. Thus, patients receiving a knee implant of a modern design (theoretically able to confer a mechanical advantage to the extensor mechanism) were found to generate significantly greater extensor power than those receiving a traditional implant without the postulated mechanical advantage.

Quadriceps femoris muscle function prior and after total knee arthroplasty in women with knee osteoarthritis

PURPOSE

The aim of the present study was to evaluate an isometric voluntary force generation and relaxation capacity of the quadriceps femoris (QF) muscle prior and after total knee arthroplasty (TKA).

METHODS

Isometric maximal voluntary contraction force, rate of force development, voluntary activation, half-relaxation time, and latency of contraction of the QF muscle were recorded in 12 female patients (aged 49-68 years) with knee osteoarthritis one day before, 3 and 6 months following TKA in the operated and nonoperated leg. Knee pain intensity was assessed by visual analog scale, and Knee injury and Osteoarthritis Outcome Score (KOOS) questionnaire was used to assess knee problems during daily living.

RESULTS

A significant decrease in knee pain and significant increase in KOOS were established after TKA. Maximal voluntary isometric force in the operated leg was lower (P < 0.05) before, 3 and 6 months after TKA as compared to the nonoperated leg. Rate of force development of the QF muscle in the operated leg compared to the nonoperated leg was significantly lower (P < 0.05) 3 and 6 months after TKA. Voluntary activation, latency of contraction, and half-relaxation time of the QF muscle did not differ significantly before, 3 and 6 months after TKA.

CONCLUSIONS

The present study indicated reduced maximal and explosive strength of quadriceps femoris muscle in the operated leg 3 and 6 months after TKA with no significant changes in voluntary activation, and capacity for rapid contraction and relaxation.

LEVEL OF EVIDENCE

Prospective comparative study, Level II.

Muscle impairments in patients with knee osteoarthritis

Context:

Muscle impairments associated with knee osteoarthritis (OA) are the primary underlying cause of functional limitations. Understanding the extent of muscle impairments, its relationship with physical function and disease progression, and the evidence behind exercise therapy that targets muscle impairments is crucial.

Evidence Acquisition:

An electronic search for relevant articles using MEDLINE and CINHAL databases up to September 2011 was performed. In addition to the electronic search, retrieved articles were searched manually for relevant studies.

Results:

Quadriceps, hamstrings, and hip muscles are significantly impaired in subjects with knee OA compared with age-matched controls. Muscle strength, especially quadriceps, is a major determinant of both performance-based and self-reported physical function. Whether stronger quadriceps is protective against knee OA onset and progression is not clear. Exercise therapy, including global and targeted resistance training, is effective in reducing pain and improving function in subjects with knee OA.

Conclusions:

Subjects with knee OA have significant muscle impairments. These muscle impairments affect physical function and should be targeted in therapy. Further research is needed to explore the relationship between quadriceps strength and knee OA initiation and progression and to determine the optimal exercise prescription that augments outcomes in this patient population.

Inibição muscular dos extensores do joelho em sujeitos acometidos por condromalácia patelar e osteoartrite do joelho - um estudo de revisão sistemática

A inibição muscular (IM) tem sido reportada como um dos fatores associados à fraqueza muscular presente na osteoartrite (OA) e condromalácia patelar (CP), sendo inclusive associada com a etiologia e a progressão. Entretanto, parece existir uma lacuna na literatura em relação a estudos de revisão que avaliaram o grau de IM de sujeitos acometidos por CP e OA. O objetivo do estudo foi reunir os resultados de estudos que investigaram o grau de IM na OA e CP e identificar possíveis diferenças na IM que estejam associadas aos estágios do processo degenerativo. Foram incluídos nesta revisão sistemática estudos transversais e/ou experimentais publicados nas bases de dados PubMed, Scopus, SciELO e Cochrane entre 1990 e 2010 que avaliaram a IM por meio da técnica de interpolação de abalo publicados. Os dados referentes à população, protocolo de IM, qualidade dos estudos e resultados de IM foram sumariados e apresentados em Tabelas. Para análise da qualidade, utilizou-se a escala de PEDro. Após a aplicação dos critérios de inclusão, 13 artigos foram incluídos na revisão sistemática (OA=9 e CP=4). A partir da análise dos dados, observou-se uma IM maior na CP em comparação à OA. Contudo, a variabilidade metodológica e a falta de informações sobre os protocolos de IM indicam a necessidade de novos estudos experimentais a fim de que se possa determinar com maior precisão a relação entre a IM e as doenças degenerativas articulares.

Maximal voluntary isokinetic knee flexion torque is associated with femoral shaft bone strength indices in knee replacement patients

It is currently unknown whether knee replacement-associated bone loss is modified by rehabilitation programs. Thus, a sample of 45 (18 men and 25 women) persons with unilateral knee replacement were recruited; age 66 years (sd 6), height 169 cm (sd 8), body mass 83 kg (sd 15), time since operation 10 months (sd 4) to explore the associations between maximal torque/power in knee extension/flexion and femoral mid-shaft bone traits (Cortical cross-sectional area (CoA, mm(2)), cortical volumetric bone mineral density (CoD, mg/mm(3)) and bone bending strength index (SSI, mm(3))). Bone traits were calculated from a single computed tomography slice from the femoral mid-shaft. Pain in the operated knee was assessed with the WOMAC questionnaire. Stepwise regression models were built for the operated leg bone traits, with knee extension and flexion torque and power, age, height, body mass, pain score and time since operation as independent variables. CoA was 2.3% (P=0.015), CoD 1.2% (P<0.001) and SSI 1.6% (P=0.235) lower in the operated compared to non-operated leg. The overall proportions of the variation explained by the regression models were 50%, 29% and 55% for CoA, CoD and SSI, respectively. Body mass explained 12% of Coa, 11% of CoD and 11% of SSI (P≤0.003). Maximal knee flexion torque explained 38% of Coa, 7% of CoD and 44% of SSI (p≤0.047). For CoD time since operation also became a significant predictor (11%, P=0.045). Knee flexion torque of the operated leg was positively associated with bone strength in the operated leg. Thus, successful rehabilitation may diminish bone loss in the operated leg.

Early high-intensity rehabilitation following total knee arthroplasty improves outcomes

STUDY DESIGN

Prospective cohort study with an age-matched and sex-matched control group.

OBJECTIVES

To assess the clinical outcomes of a high-intensity rehabilitation program (HI) compared to those of a group of age-matched and sex-matched controls who underwent a lower intensity rehabilitation program.

BACKGROUND

Total knee arthroplasty (TKA) successfully alleviates pain from knee osteoarthritis; but deficits in function can persist long term. Despite these well-known deficits, there is little evidence supporting the use of rehabilitation interventions following TKA.

METHODS

Eight patients, who participated in the HI program, were compared to 8 age-matched and sex-matched patients who participated in a lower intensity rehabilitation program (control group). Patients were assessed preoperatively, and at 3.5, 6.5, 12, 26, and 52 weeks postoperatively. Assessment of patients included measures of pain, range of motion (ROM), functional performance, and quadriceps strength and activation.

RESULTS

There were no differences in knee ROM and pain between the HI and control groups at any postoperative time point. At the 3.5-week and 12-week (end of rehabilitation) time points, the HI group had better functional performance and quadriceps strength compared to the control group (P<.05). At the 52-week time point, the HI group continued to demonstrate better functional performance compared to the control group (P<.05), along with greater quadriceps strength (P = .08).

CONCLUSION

A HI program leads to better short- and long-term strength and functional performance outcomes compared to a lower intensity rehabilitation program. The HI program did not impair knee ROM and did not result in any musculoskeletal injuries in this small group of patients.

LEVEL OF EVIDENCE

Therapy, level 2b.

Effects of spatially targeted transcutaneous electrical nerve stimulation using an electrode array that measures skin resistance on pain and mobility in patients with osteoarthritis in the knee: a randomized controlled trial

A novel device was developed that measured local electrical skin resistance and generated pulsed local electrical currents that were delivered across the skin around the knee for patients with osteoarthritis (termed eBrace TENS). Currents were delivered using an electrode array of 16 small circular electrode elements so that stimulation could be spatially targeted. The aim of this study was to investigate the effects of spatially targeted transcutaneous electrical nerve stimulation (TENS) to points of low skin resistance on pain relief and mobility in osteoarthritis of the knee (OAK). A randomised, controlled, 3-arm, parallel-group trial was designed that compared pain and function following a 30 to 45 minute intervention of TENS at specific locations depending on the local electrical skin resistance. Pain intensity by the visual analogue scale (VAS), 6-minute walk test, maximum voluntary contraction (MVC), and range-of-motion (ROM) were the primary outcomes. Lowest-resistance TENS reduced pain intensity during walking relative to resting baseline compared with random TENS (95% confidence interval of the difference: -20.8mm, -1.26 mm). There were no statistically significant differences between groups in distance during the walk test, maximum voluntary contraction (MVC) or range-of-motion (ROM) measures or WOMAC scores. In conclusion, we provide evidence that use of a matrix electrode that spatially targets strong nonpainful TENS for 30 to 45 minutes at sites of low resistance can reduce pain intensity at rest and during walking.

Mechanisms of quadriceps muscle weakness in knee joint osteoarthritis: the effects of prolonged vibration on torque and muscle activation in osteoarthritic and healthy control subjects

INTRODUCTION

A consequence of knee joint osteoarthritis (OA) is an inability to fully activate the quadriceps muscles, a problem termed arthrogenic muscle inhibition (AMI). AMI leads to marked quadriceps weakness that impairs physical function and may hasten disease progression. The purpose of the present study was to determine whether γ-loop dysfunction contributes to AMI in people with knee joint OA.

METHODS

Fifteen subjects with knee joint OA and 15 controls with no history of knee joint pathology participated in this study. Quadriceps and hamstrings peak isometric torque (Nm) and electromyography (EMG) amplitude were collected before and after 20 minutes of 50 Hz vibration applied to the infrapatellar tendon. Between-group differences in pre-vibration torque were analysed using a one-way analysis of covariance, with age, gender and body mass (kg) as the covariates. If the γ-loop is intact, vibration should decrease torque and EMG levels in the target muscle; if dysfunctional, then torque and EMG levels should not change following vibration. One-sample t tests were thus undertaken to analyse whether percentage changes in torque and EMG differed from zero after vibration in each group. In addition, analyses of covariance were utilised to analyse between-group differences in the percentage changes in torque and EMG following vibration.

RESULTS

Pre-vibration quadriceps torque was significantly lower in the OA group compared with the control group (P = 0.005). Following tendon vibration, quadriceps torque (P < 0.001) and EMG amplitude (P ≤0.001) decreased significantly in the control group but did not change in the OA group (all P > 0.299). Hamstrings torque and EMG amplitude were unchanged in both groups (all P > 0.204). The vibration-induced changes in quadriceps torque and EMG were significantly different between the OA and control groups (all P < 0.011). No between-group differences were observed for the change in hamstrings torque or EMG (all P > 0.554).

CONCLUSIONS

γ-loop dysfunction may contribute to AMI in individuals with knee joint OA, partially explaining the marked quadriceps weakness and atrophy that is often observed in this population.

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.

Effects of aging on muscle mechanical function and muscle fiber morphology during short-term immobilization and subsequent retraining

Very little attention has been given to the combined effects of aging and disuse as separate factors causing deterioration in muscle mechanical function. Thus the purpose of this study was to investigate the effects of 2 wk of immobilization followed by 4 wk of retraining on knee extensor muscle mechanical function (e.g., maximal strength and rapid force capacity) and muscle fiber morphology in 9 old (OM: 67.3 ± 1.3 yr) and 11 young healthy men (YM: 24.4 ± 0.5 yr) with comparable levels of physical activity. Following immobilization, OM demonstrated markedly larger decreases in rapid force capacity (i.e., rate of force development, impulse) than YM (∼ 20-37 vs. ∼ 13-16%; P < 0.05). In contrast, muscle fiber area decreased in YM for type I, IIA, and IIx fibers (∼ 15-30%; P < 0.05), whereas only type IIa area decreased in OM (13.2%; P < 0.05). Subsequent retraining fully restored muscle mechanical function and muscle fiber area in YM, whereas OM showed an attenuated recovery in muscle fiber area and rapid force capacity (tendency). Changes in maximal isometric and dynamic muscle strength were similar between OM and YM. In conclusion, the present data reveal that OM may be more susceptible to the deleterious effects of short-term muscle disuse on muscle fiber size and rapid force capacity than YM. Furthermore, OM seems to require longer time to recover and regain rapid muscle force capacity, which may lead to a larger risk of falling in aged individuals after periods of short-term disuse.

Outcomes before and after total knee arthroplasty compared to healthy adults

STUDY DESIGN

Prospective cohort study.

OBJECTIVES

To measure changes in muscle strength, range of motion, and function from 2 weeks before to 6 months after total knee arthroplasty (TKA) and compare outcomes with data from a control group consisting of healthy adults.

BACKGROUND

Total knee arthroplasty successfully alleviates pain from knee osteoarthritis, but deficits in function can persist long term. How impairments and functional limitations change over the first 6 months after TKA, compared to data from healthy adults, has not been well reported in the literature.

METHODS

Twenty-four patients who underwent a primary unilateral TKA were compared to healthy adults (n = 17). All patients participated in a standardized rehabilitation program following surgery. Isometric quadriceps torque was assessed using an electromechanical dynamometer. Range of motion was measured actively and passively. Functional performance was assessed using the stair-climbing test, timed up-and-go test, 6-minute walk test, and single-limb stance time. Patients underwent testing at 2 weeks preoperatively and at 1, 3, and 6 months postoperatively.

RESULTS

Compared to healthy older adults, patients performed significantly worse at all times for all measures (P<.05), except for single-limb stance time at 6 months (P>.05). One month postoperatively, patients experienced significant losses from preoperative levels in all outcomes. Patients recovered to preoperative levels by 6 months postoperatively on all measures, except knee flexion range of motion, but still exhibited the same extent of limitation they did prior to surgery.

CONCLUSION

The persistent impairments and functional limitations 6 months after TKA with standard rehabilitation suggest that more intensive therapeutic approaches may be necessary to restore function of patients following TKA to the levels of healthy adults.

Asymmetry in quadriceps rate of force development as a functional outcome measure in TKA

Quadriceps muscle strength is an important predictor of functional abilities in patients having TKA. However, because several daily activities are characterized by a limited time to generate force, it has been suggested that rate of force development (RFD) could better predict functional difficulties than maximal strength. We therefore hypothesized the side-to-side asymmetry would be larger for RFD than for maximal strength, and RFD asymmetry relates to subjective symptoms and/or functional daily living activities. We studied 31 subjects (17 women, 14 men) 6 +/- 1 months after undergoing TKA for unilateral osteoarthritis. Symptoms and limitations during activities of daily living were quantified using the knee outcome survey-activities of daily living scale (KOS-ADLS). Quadriceps maximal strength and RFD at different times (50 to 200 ms from contraction onset) were quantified during unilateral maximal voluntary isometric actions. Side-to-side asymmetries (involved versus uninvolved side) were larger for RFD (approximately 36%) than for maximal strength (approximately 24%). Subjective knee function related to all RFD asymmetry variables, but not to maximal strength asymmetry. In addition to maximal strength, quadriceps RFD in the first 100 to 200 ms from contraction onset provides an alternative functional outcome measure for individuals undergoing TKA.

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.

Muscle deficits persist after unilateral knee replacement and have implications for rehabilitation

BACKGROUND

Knee joint arthritis causes pain, decreased range of motion, and mobility limitation. Knee replacement reduces pain effectively. However, people with knee replacement have decreases in muscle strength ("force-generating capacity") of the involved leg and difficulties with walking and other physical activities.

OBJECTIVE AND DESIGN

The aim of this cross-sectional study was to determine the extent of deficits in knee extensor and flexor muscle torque and power (ability to perform work over time) and in the extensor muscle cross-sectional area (CSA) after knee joint replacement. In addition, the association of lower-leg muscle deficits with mobility limitations was investigated.

METHODS

Participants were 29 women and 19 men who were 55 to 75 years old and had undergone unilateral knee replacement surgery an average of 10 months earlier. The maximal torque and power of the knee extensor and flexor muscles were measured with an isokinetic dynamometer. The knee extensor muscle CSA was measured with computed tomography. The symmetry deficit between the knee that underwent replacement surgery ("operated knee") and the knee that did not undergo replacement surgery ("nonoperated knee") was calculated. Maximal walking speed and stair-ascending and stair-descending times were assessed.

RESULTS

The mean deficits in knee extensor and flexor muscle torque and power were between 13% and 27%, and the mean deficit in the extensor muscle CSA was 14%. A larger deficit in knee extension power predicted slower stair-ascending and stair-descending times. This relationship remained unchanged when the power of the nonoperated side and the potential confounding factors were taken into account.

LIMITATIONS

The study sample consisted of people who were relatively healthy and mobile. Some participants had osteoarthritis in the nonoperated knee.

CONCLUSIONS

Deficits in muscle torque and power and in the extensor muscle CSA were present 10 months after knee replacement, potentially causing limitations in negotiating stairs. To prevent mobility limitations and disability, deficits in lower-limb power should be considered during rehabilitation after knee replacement.

The Chitranjan Ranawat Award: functional outcome after total knee replacement varies with patient attributes

Total knee replacement effectively relieves arthritis pain but improvement in physical function varies. A clearer understanding of the patient attributes associated with differing levels of functional gain after TKR is critical to surgical decision making. We reviewed 8050 primary, unilateral TKR patients enrolled in a prospective registry between 2000 and 2005 who had complete data. We evaluated associations between 12-month function (SF12/PCS) and preoperative gender, age, BMI, emotional health (MCS), knee diagnosis, quadriceps strength, and physical function (PCS). More than 98% of patients reported pain relief (KS pain score). At 12 months, mean PCS gain was 13.6 points, but the distribution was bimodal. The mean gain in PCS in the 63% of patients with greater improvement was 21 (SD = 7), and 4.1 (SD = 7) in the remaining 37%. Increased likelihood of poor functional gain was associated with older age, body mass index (BMI) over 40, lower MCS, and poor quadriceps strength. While two-thirds of patients reported functional gain well above national average at 12 months post-TKR, 37% reported limited functional improvement. Further understanding of the patient attributes associated with limited improvement will guide the design of innovative strategies to improve functional outcomes.

LEVEL OF EVIDENCE

Level II, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

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.