Quadriceps strength asymmetry predicts loading asymmetry during sit-to-stand task in patients with unilateral total knee arthroplasty

Reliability and validity of a method to measure trunk rotation angle from images using a camera and posture mirror

This study aimed to measure trunk rotation angle representations from images using a single camera combined with a posture mirror and to examine its reliability and validity. We applied a trunk rotation angle model using a tripod and markers simulating trunk rotation. We compared two methods of trunk rotation angle measurement: the conventional method from the superior aspect using a manual goniometer and a novel measurement method using images from a digital camera and a posture mirror. Measurement error was calculated as the average absolute error between the angle measured by the goniometer and that calculated from the camera and mirror image. The intraclass correlation coefficient (ICC 1, 1) and ICC (2, 1) were calculated as the intra-rater reliability and agreement between the measurement angles of the two methods, respectively. Systematic errors of the angles measured by the two methods were examined by a Bland‒Altman analysis. The mean (SD) of the mean absolute error was 1.17° (0.71°). ICC (1, 1) was 0.978, and ICC (2, 1) was 0.991. The Bland‒Altman analysis showed no systematic errors. The results suggest the validity and accuracy of our novel method to measure the angle of trunk rotation, which does not require high-cost equipment or a special environment.

Quadriceps Strength Loss Following Total Knee Arthroplasty as a Predictor of Three-Month Strength Recovery: A Secondary Analysis of a Randomized Controlled Trial

Background and objectives Patients often experience significant quadriceps muscle weakness immediately after total knee arthroplasty (TKA), which can persist and lead to reduced physical function, increased risk of falls, and reduced patient satisfaction. Immediate postoperative quadriceps weakness is commonly caused by several factors, such as preoperative quadriceps weakness related to knee osteoarthritis (OA) and TKA-induced quadriceps weakness. Although many interventions have focused on addressing knee OA-related quadriceps weakness, there may be fewer studies specifically investigating TKA-induced quadriceps weakness. This study aimed to clarify whether TKA-induced quadriceps weakness is a significant predictor of quadriceps strength at three months postoperatively, highlighting the clinical importance of preoperative interventions targeting this specific weakness. Methods This secondary analysis of a randomized controlled trial included patients aged 60-79 years with advanced knee OA who underwent unilateral TKA. The study used pooled data from two groups of 11 participants each: those receiving preoperative low-intensity resistance training with blood flow restriction and those performing low-intensity resistance training with slow movement and tonic force generation. Quadriceps strength was assessed using a pull-type handheld dynamometer preoperatively at six weeks and one week as well as postoperatively at four days, one month, and three months. TKA-induced quadriceps weakness was defined as a change in strength from one week preoperatively to four days postoperatively. Postoperative quadriceps strength gain, reflecting postoperative recovery, was defined as the strength change from four days to three months postoperatively. Correlation and multiple regression analyses were used to identify the predictors of postoperative quadriceps strength at three months. Statistical significance was set at p < 0.05. Results The analysis included 22 participants. The median preoperative quadriceps strength was 1.1 Nm/kg (IQR: 0.9-1.4) at six weeks and 1.3 Nm/kg (IQR: 1.1-1.4) at one week. Quadriceps strength significantly decreased immediately after TKA (median quadriceps strength dropped to 0.4 Nm/kg (IQR: 0.3-0.4) at four days postoperatively) and gradually improved over three months (median three-month postoperative quadriceps strength was 0.9 Nm/kg (IQR: 0.8-1.0)). TKA-induced quadriceps weakness was -72% (SD: 11%), and postoperative quadriceps strength gain was 210% (IQR: 98-324%). TKA-induced quadriceps weakness was strongly correlated with quadriceps strength at four days (r = 0.84, p < 0.01). The postoperative quadriceps strength at four days was significantly correlated with the quadriceps strength at three months (r = 0.51, p = 0.02). Regression analysis showed that one-week preoperative quadriceps strength, TKA-induced quadriceps weakness, and postoperative quadriceps strength gain significantly predicted quadriceps strength at three months (R² = 0.77, p < 0.001). Conclusions This study highlights TKA-induced quadriceps weakness as a key predictor of postoperative quadriceps strength at three months. Preoperative interventions targeting TKA-induced weakness may improve postoperative recovery of quadriceps strength and functional outcomes.

Abnormal gait pattern in downhill hiking is related to muscular deficits of the knee flexors and extensors in active patients with total knee arthroplasty

BACKGROUND

To assess the in-field walking mechanics during downhill hiking of patients with total knee arthroplasty five to 14 months after surgery and an age-matched healthy control group and relate them to the knee flexor and extensor muscle strength.

METHODS

Participants walked on a predetermined hiking trail at a self-selected, comfortable pace wearing an inertial sensor system for recording the whole-body 3D kinematics. Sagittal plane hip, knee, and ankle joint angles were evaluated over the gait cycle at level walking and two different negative slopes. The concentric and eccentric lower extremity muscle strength of the knee flexors and extensors isokinetically at 50 and 120°/s were measured.

FINDINGS

Less knee flexion angles during stance have been measured in patients in the operated limb compared to healthy controls in all conditions (level walking, moderate downhill, steep downhill). The differences increased with steepness. Muscle strength was lower in patients for both muscle groups and all measured conditions. The functional hamstrings to quadriceps ratio at 120°/sec correlated with knee angle during level and downhill walking at the moderate slope in patients, showing higher ratios with lower peak knee flexion angles.

INTERPRETATION

The study shows that even if rehabilitation has been completed successfully and complication-free, five to 14 months after surgery, the muscular condition was still insufficient to display a normal gait pattern during downhill hiking. The muscle balance between quadriceps and hamstring muscles seems related to the persistence of a stiff knee gait pattern after knee arthroplasty. LoE: III.

Inter-limb kinetic asymmetries during sit-to-stand performance persist following unilateral total knee arthroplasty: A systematic review and meta-analysis

BACKGROUND

Kinetic asymmetries during sit-to-stand have been consistently observed early after total knee arthroplasty; however, the longer-term outcomes are less clear. The purpose of this systematic review and meta-analysis was to analyze the results of studies examining inter-limb kinetic symmetry during sit-to-stand performance among individuals who were at least one-year post unilateral total knee arthroplasty.

METHODS

PubMed, SPORTDiscus, CINAHL, and Health Source databases were searched. Studies were included if they were published in a peer-reviewed journal, included subjects who had undergone unilateral total knee arthroplasty at least one-year prior, and examined vertical ground reaction forces and/or knee extension moments for the involved and uninvolved limbs during sit-to-stand performance. Data were transformed into a limb symmetry index, which expressed the ratio of the peak forces/moments for the involved limb, relative to the uninvolved limb (1.0 reflects perfect symmetry). These ratios were meta-analyzed using the ratio of means method.

FINDINGS

Seven studies were deemed eligible for inclusion. Ground reaction force data was pooled from seven studies and knee extension moment data was pooled from two studies. For the peak vertical ground reaction forces, the pooled limb symmetry index was 0.96 (CI95% = [0.93, 0.99]). For the peak knee extension moments, the pooled limb symmetry index was 0.91 (CI95% = [0.84, 0.98]). In both cases this reflects greater limb/knee loading for the uninvolved limb, relative to the involved limb.

INTERPRETATION

Asymmetries in limb/knee loading persist beyond the one-year post-operative period following total knee arthroplasty, potentially contributing to degenerative changes for the uninvolved limb.

Concurrent Force Feedback on Load Symmetry in Total Knee Arthroplasty Patients

Background and Purpose

Load asymmetry can be present before and after total knee arthroplasty (TKA), which may affect progress during knee rehabilitation in an outpatient sports medicine setting. Current rehabilitation primarily focuses on strength, pain, and range of motion deficits; however, recent evidence suggests the use of movement retraining strategies such as load feedback to address load asymmetry. Therefore, the purpose of this study was to examine how a single session of concurrent force feedback influences load symmetry during the leg-press and body-weight squat exercises in individuals following TKA. Additionally, a secondary purpose was to examine the retention of any changes over the course of a week.

Study design

Case-series study.

Methods

This observational, repeated-measures study design examined the effect of concurrent force feedback training on the mean and standard deviation of load symmetry index during the leg press and squat exercises in 26 patients with TKA in an outpatient sports medicine clinic.The load asymmetry was measured with loadpad sensors placed underneath the each extremity during leg press and squat (baseline), after one training session consisting of concurrent force feedback during these exercises within a single physical therapy session (post feedback), and after seven to ten days of a washout period (post retention). Separate 2 x 3 repeated measures analysis of variance was used to compare the mean and standard deviation of load symmetry across exercise (leg press and squat) and across time (baseline, post feedback and post retention).

Results

There was a time effect for the mean load symmetry index (p=0.027) but not for the standard deviation (p=0.441) during these exercises. The leg press showed a greater mean symmetry index compared to the squat regardless of time (p=0.001).

Conclusions

A reduction in the mean load symmetry index following concurrent feedback training suggests improved use of the surgical limb during both leg press and squat exercises during the same therapy session but the more symmetric loading pattern was not retained one week later. Overall, the leg press showed greater mean asymmetry than the squat. Standard deviation in the load symmetry index did not change across time or by exercise.

Level of Evidence

3©The Author(s).

Translation of surface electromyography to clinical and motor rehabilitation applications: The need for new clinical figures

Advanced sensors/electrodes and signal processing techniques provide powerful tools to analyze surface electromyographic signals (sEMG) and their features, to decompose sEMG into the constituent motor unit action potential trains, and to identify synergies, neural muscle drive, and EEG-sEMG coherence. However, despite thousands of articles, dozens of textbooks, tutorials, consensus papers, and European and International efforts, the translation of this knowledge into clinical activities and assessment procedures has been very slow, likely because of lack of clinical studies and competent operators in the field. Understanding and using sEMG-based hardware and software tools requires a level of knowledge of signal processing and interpretation concepts that is multidisciplinary and is not provided by most academic curricula in physiotherapy, movement sciences, neurophysiology, rehabilitation, sport, and occupational medicine. The chasm existing between the available knowledge and its clinical applications in this field is discussed as well as the need for new clinical figures. The need for updating the training of physiotherapists, neurophysiology technicians, and clinical technologists is discussed as well as the required competences of trainers and trainees. Indications and examples are suggested and provide a basis for addressing the problem. Two teaching examples are provided in the Supplementary Material.

No correlation between symmetry-based performance measures and patient-related outcome prior to and after total knee arthroplasty

PURPOSE

Standardized outcome measures are crucial for the evaluation of different treatment and rehabilitation regimes in patients after total knee arthroplasty (TKA). Performance-based measures are necessary to capture different aspects of physical function. High reliability and agreement of five performance-based measures were hypothesized to differentiate between measurement error and change in test performance. Secondary outcomes are the correlation of performance-based measurements to KSS and WOMAC prior to surgery (baseline) and 10 weeks thereafter (t3).

METHODS

The test-retest reliabilities and agreements of the 1-m walk test, the stair-climbing test, the timed-up-and-go test, the weight-balanced-chair-rising test and the isometric maximum knee extension force in patients undergoing total knee replacements were studied. The intraclass correlation coefficient was calculated and a Bland-Altman analysis performed.

RESULTS

The weight-balanced-chair-rising test showed a symmetry at baseline = 0.77, 5 ± 1 days after surgery (t1) = 0.50, 9 ± 1 days (t2) = 0.59 and (t3) = 0.80. All performance tests showed high intraclass correlation coefficients (ICC = 0.81-0.99). The 10-m walk test, stair climbing test, and the timed-up-and-go test showed high agreement in the Bland-Altman analysis. The Bland-Altman analysis for the weight-balanced-chair-rising test and isometric knee extension force indicated high agreement at 5 and 9 days postoperatively, but the relative measurement error increased pre- and 10 weeks postoperatively.

CONCLUSION

In conclusion, symmetry, as an important outcome after TKA, is a reliable and rather unique item that should unquestionably be added to established measurements like walking tests or survey-based function assessment. The implementation of standardized performance-based measures to assess physical function in rehabilitation procedures will help to improve the more objectively based assessment of different rehabilitation protocols.

LEVEL OF EVIDENCE

II.

Sit-to-Stand Weight-Bearing Symmetry Performance in Total Knee Arthroplasty: Recovery Curves, Correlates, and Predictive Validity With Gait Speed

OBJECTIVE

After total knee arthroplasty, the ability to weight bear symmetrically during the sit-to-stand task provides important information regarding altered movement patterns. Despite this, comprehensive recovery curves and validity data for sit-to-stand weight-bearing symmetry are lacking in the total knee arthroplasty population. Our study aimed to (1) develop recovery curves with reference ranges, (2) identify the correlates of standard and constrained sit-to-stand weight-bearing symmetry, and (3) evaluate their predictive validity with gait speed.

DESIGN

We performed a retrospective longitudinal study of 706 patients with primary unilateral total knee arthroplasty. Monthly, for 4 mos after surgery, sit-to-stand weight-bearing symmetry, knee pain, knee range of motion, quadriceps strength, and gait speed were quantified.

RESULTS

Standard and constrained sit-to-stand weight-bearing symmetry measures improved nonlinearly over time. Standard sit-to-stand weight-bearing symmetry was most strongly associated with bilateral quadriceps strength, whereas constrained sit-to-stand weight-bearing symmetry was most strongly associated with ipsilateral quadriceps strength. Knee range of motion and contralateral knee pain were additional correlates. Both standard sit-to-stand and constrained sit-to-stand weight-bearing symmetry were independently and nonlinearly associated with gait speed in multivariable models.

CONCLUSIONS

Our study provided recovery curves and validity data to support routine clinical measurement of sit-to-stand weight-bearing symmetry in total knee arthroplasty. Our results also indicate that constrained sit-to-stand may promote greater use of the operated limb than standard sit-to-stand.

Gait mechanics are influenced by quadriceps strength, age, and sex after total knee arthroplasty

Although most patients are satisfied with outcomes after total knee arthroplasty (TKA), many retain preoperative altered gait mechanics. Identifying patient characteristics associated with gait mechanics will improve rehabilitation strategies and enhance our understanding of movement disorders. Therefore, the purpose of this study was to identify which patient characteristics are related to gait mechanics in the surgical limb during walking post-TKA. Patient characteristics included age, body mass, sex, quadriceps strength, self-reported function, and knee pain. General linear regression was used to compare patient characteristics associated with gait mechanics, after controlling for gait speed, functional capacity and time from surgery. We tested 191 patients cross-sectionally at 6-24 months after primary, unilateral TKA. Quadriceps weakness in the surgical limb was associated with less peak vertical ground reaction force (PvGRF) (β = .245, p = .044), knee extension moment (β = .283, p = .049), and knee extension excursion (β = .298, p = .038). Older age (β = .168, p = .050) was associated with less PvGRF. Quadriceps strength in the nonsurgical limb (β = -.357, p = .021) was associated with greater knee extension excursion in the surgical limb. Females with TKA (β = -.276, p = .007) had less knee flexion excursion compared to males. Faster gait speed was also associated with greater PvGRF (β = .585, p < .001), knee extensor moment (β = .481, p < .001), and knee flexion excursion (β = .318, p < .001). Statement of Clinical Significance: This study showed quadriceps weakness, slower gait speed, older age and being female were related to altered gait mechanics post-TKA. These findings will help clinicians better educate patients and develop targeted interventions for improving care in patients post-TKA.

A Novel Simplified System to Estimate Lower-Limb Joint Moments during Sit-to-Stand

To provide effective diagnosis and rehabilitation, the evaluation of joint moments during sit-to-stand is essential. The conventional systems for the evaluation, which use motion capture cameras, are quite accurate. However, the systems are not widely used in clinics due to their high cost, inconvenience, and the fact they require lots of space. To solve these problems, some studies have attempted to use inertial sensors only, but they were still inconvenient and inaccurate with asymmetric weight-bearing. We propose a novel joint moment estimation system that can evaluate both symmetric and asymmetric sit-to-stands. To make a simplified system, the proposal is based on a kinematic model that estimates segment angles using a single inertial sensor attached to the shank and a force plate. The system was evaluated with 16 healthy people through symmetric and asymmetric weight-bearing sit-to-stand. The results showed that the proposed system (1) has good accuracy in estimating joint moments (root mean square error < 0.110 Nm/kg) with high correlation (correlation coefficient > 0.99) and (2) is clinically relevant due to its simplicity and applicability of asymmetric sit-to-stand.

Effects of preoperative low-intensity training with slow movement on early quadriceps weakness after total knee arthroplasty in patients with knee osteoarthritis: a retrospective propensity score-matched study

Background

Severe and early quadriceps weakness (QW) after total knee arthroplasty (TKA), which is caused by acute inflammation resulting from surgical trauma and tourniquet-induced ischemia-reperfusion (IR) injury, can be especially problematic. We focused on tourniquet-induced IR injury, because it has been shown to be preventable through ischemic and exercise preconditioning. Low-intensity resistance exercise with slow movement and tonic force generation (LST) share some similarities with ischemic and exercise preconditioning. The present study primarily aimed to clarify the efficacy of preoperative LST program as prehabilitation for early QW among patients with TKA using propensity score matching analysis.

Methods

This single-center retrospective observational study used data from patients with knee osteoarthritis (n = 277) who were scheduled to undergo unilateral TKA between August 2015 and January 2017. Those with missing outcome data due to their inability to perform tests were excluded. The LST group included participants who performed LST and aerobic exercise (LST session) more than seven times for three months prior to surgery. The control group included participants who performed less than eight LST sessions, a general and light exercise or had no exercise for three months prior to surgery. Knee circumference, thigh volume, knee pain during quadriceps strength test (QST) and timed up and go test (TUG), quadriceps strength, and TUG were measured before and 4 days after surgery. Knee swelling, thigh swelling, Δknee pain, QW, and ΔTUG were determined by comparing pre- and postoperative measurements.

Results

Propensity score matching generated 41 matched pairs who had nearly balanced characteristics. The LST group had a significantly lower knee and thigh swelling, QW, and ΔTUG compared to the control group (all, p < 0.05). No significant differences in Δknee pain during the QST and TUG were observed between both groups (both, p > 0.05).

Conclusions

The present study demonstrated the beneficial effects of preoperative LST program on knee swelling, thigh swelling, QW, and walking disability immediately after TKA.

Which Patients Require a Contralateral Total Knee Arthroplasty Within 5 Years of Index Surgery?

Osteoarthritis (OA) of the knee often presents bilaterally. However, not all patients with severe bilateral knee OA require bilateral total knee arthroplasty (TKA). This study aims to identify predictive factors for contralateral TKA in patients presenting with severe bilateral knee OA undergoing unilateral TKA. We prospectively collected perioperative data from 209 consecutive patients of a single surgeon who had severe bilateral OA knees at presentation. All patients underwent unilateral TKA on the more symptomatic knee. Patients were then stratified by their need for a contralateral TKA within the next 5 years. Using regression analysis, we compared patients who underwent contralateral knee surgery within 5 years (n = 115) against patients who did not (n = 94), so as to create a predictive model. Significant factors identified by the multiple regression models were incorporated into a decision tree using classification and regression tree analysis. Body mass index (BMI), degree of varus angulation, and Oxford knee scores were identified as significant predictive factors. The generated decision tree model was able to stratify patients according to their BMI and Oxford scores into four subgroups, the highest with more than 90% odds of contralateral surgery and the lowest with less than 40% odds of contralateral surgery. BMI, degree of varus angulation, and preoperative Oxford knee scores seem to predict the need for contralateral TKA in patients with severe bilateral OA knees undergoing unilateral TKA. These patients should be counseled on their requirement for the second TKA based on these factors.

Improvements in Isokinetic Quadriceps and Hamstring Strength Testing After Focused Therapy in Patients With Flexion Instability

BACKGROUND

There is a paucity of literature to guide non-operative treatment for patients with problems after total knee arthroplasty (TKA). We sought to quantify how quadriceps and hamstring strength could improve with focused physical therapy (PT) and whether improving leg strength may prevent revision surgery for patients with flexion instability (FI) after TKA.

METHODS

This retrospective study included patients diagnosed with FI by one of the 4 fellowship-trained arthroplasty surgeons at a single academic institution. Patients with FI were referred for strength measurements and a focused PT program. In total, 166 patients completed isokinetic testing to quantify their relative quadriceps and hamstring power, torque, and work measures compared to their contralateral leg. Fifty-five (33.5%) patients subsequently completed post-PT isokinetic testing. Statistical analysis was conducted to evaluate strength deficits in the knee with FI.

RESULTS

Patients with FI were found to be 20.5%-38.4% weaker in all strength domains compared to the contralateral leg (P < .001). Patients who completed PT and pre-isokinetic and post-isokinetic testing demonstrated statistically significant gains in all extension metrics by a net range of 24.7%-34.2% (P = .011-.029) and their flexion strength metrics improved by 32.5%-40.2% (P = .002-.005). About 81.9% of patients in this subgroup did not undergo revision TKA. Those subjects who went on to revision did not statistically improve in any strength domain (P = .063-.121).

CONCLUSION

Patients with FI after TKA have significantly weaker quadriceps and hamstrings in the operative compared to contralateral leg. Patients who did not undergo revision knee arthroplasty and completed a formal PT program improved quadriceps and hamstring strength by 30%.

LEVEL OF EVIDENCE

IV (Case series).

Are TKA Kinematics During Closed Kinetic Chain Exercises Associated with Patient-reported Outcomes? A Preliminary Analysis

BACKGROUND

Kinematic patterns after TKA can vary considerably from those of the native knee. It is unknown, however, if there is a relationship between a given kinematic pattern and patient satisfaction after TKA.

QUESTIONS/PURPOSES

Is there an association between kinematic patterns as measured by AP translation during open kinetic chain flexion-extension and closed kinetic chain exercises (rising from a chair and squatting) and a custom aggregate of patient-reported outcome measures (PROMs) that targeted symptoms, pain, activities of daily living (ADL), sports, quality of life (QOL), and patient satisfaction after TKA?

METHODS

Thirty patients who underwent TKA between 2014 and 2016 were tested at a minimum follow-up of 6 months. As three different implants were used, per implant the first 10 patients who presented themselves at the follow-up consultations and were able to bend the knee at least 90°, were recruited. Tibiofemoral kinematics during an open kinetic chain flexion-extension and closed kinetic chain exercises-rising from a chair and squatting-were analyzed using fluoroscopy. A two-step cluster analysis was performed, resulting in two clusters of patients who answered the Knee Injury and Osteoarthritis Outcome Score and the satisfaction subscore of the Knee Society Score questionnaires. Cluster 1 (CL1) consisted of patients with better (good-to-excellent) patient-reported outcome measures scores (high-PROMs cluster); Cluster 2 (CL2) consisted of patients with poorer scores (low-PROMs cluster). Tibiofemoral kinematics were compared between patients in these clusters by performing a Mann-Whitney U test with Bonferroni correction.

RESULTS

Concerning open kinetic chain flexion-extension, there was no difference in kinematic patterns between the patients in the high-PROMs cluster and those in the low-PROMs cluster, with the numbers available. However, during the closed-chain kinetic exercises, medially, initial anterior translation (femur relative to tibia) was found in patients in Cluster 1 during early flexion, but in those in Cluster 2, translation was steeper and ran more anteriorly (CL1 -1.5 ± 7.3%; CL2 -8.5 ± 4.4%); mean difference 7.0% [95% CI 0.1 to 13.8]; p = 0.046). In midflexion, the femur did not translate anterior nor posterior in relation to the tibia, resulting in a stable medial compartment in Cluster 1, whereas Cluster 2 had already started translating posteriorly (CL1 -0.7 ± 3.5%; CL2 3.4 ± 3.6%; mean difference -4.1% [95% CI -7.0 to -1.2]; p = 0.008). There was no difference, with the numbers available, between the two clusters with respect to posterior translation in deep flexion. Laterally, there was small initial anterior translation in early flexion, followed by posterior translation in midflexion that continued in deep flexion. Patients in Cluster 1 demonstrated more pronounced posterior translation in deep flexion laterally than patients in Cluster 2 did (CL1 8.3 ± 5.2%; CL2 3.5 ± 4.5%); mean difference 4.9% [95% CI 0.6 to 9.1]; p = 0.026).

CONCLUSIONS

This study of total knee kinematics suggests that during closed kinetic chain movements, patients with poor PROM scores after TKA experience more anterior translation on the medial side followed by a medial mid-flexion instability and less posterior translation on the lateral side in deep flexion than patients with good PROM scores. The relationship of kinematic variations with patient-reported outcomes including satisfaction must be further elaborated and translated into TKA design and position. Reproduction of optimal kinematic patterns during TKA could be instrumental in improving patient satisfaction after total knee replacement. Future expansion of the study group is needed to confirm these findings.Level of Evidence Level II, therapeutic study.

Association between serum n-3 polyunsaturated fatty acids and quadriceps weakness immediately after total knee arthroplasty

Objectives

Quadriceps weakness (QW) following total knee arthroplasty (TKA) can be elicited by tourniquet-induced ischaemia reperfusion (IR), which causes a vigorous acute inflammatory response. Dietary n-3 polyunsaturated fatty acids (PUFA) are important determinants of organ and tissue protection from IR. This study aimed to examine the association between serum n-3 PUFA levels and QW, knee pain, and knee swelling immediately after TKA.

Methods

A total of 32 patients who underwent unilateral TKA participated in this prospective study. On Postoperative Day 1, serum n-3 PUFA (eicosapentaenoic acid and docosahexaenoic acid) levels were measured. Preoperatively and on Postoperative Day 4, quadriceps strength, knee pain during quadriceps testing, and knee circumference were measured. QW, knee pain, and knee swelling were defined as changes in quadriceps strength, knee pain during quadriceps testing, and knee circumference, respectively, between the preoperative to the postoperative measurement.

Results

Mean serum n-3 PUFA levels were 192 μg/mL (standard deviation, 58 μg/mL) on Postoperative Day 1. All measured variables changed significantly between the preoperative and the postoperative measurement time-points (P <0.01). Quadriceps strength decreased from 1.2 to 0.4 Nm/kg (QW = −65%). Knee pain during quadriceps testing increased from 1.1 to 6.0 (knee pain = 4.0). Knee circumference increased from 40 to 44 cm (knee swelling = 10%). Multivariate analysis showed that lower serum n-3 PUFA levels were independently associated with an increased QW after adjusting for the Kellgren-Lawrence grade and the tourniquet time (P = 0.04). No significant relationship was observed between serum n-3 PUFA levels and knee pain or knee swelling.

Conclusion

Higher serum n-3 PUFA are independently associated with a lower increase in the QW immediately after TKA.

Toward clinically-relevant joint moment estimation during sit to stand: a feasibility study

Conventional motion analysis system to measure joint moment during sit to stand is impractical to be used in clinics. Inertial sensor-based motion analysis system has been proposed to improve usability. In this study, we propose a simple system that can predict joint moment, especially maximum joint moment, with a minimum number of an inertial sensor attached and force plate; shank and thigh angles were estimated with a kinematic model and an effective joint moment analysis period. Through a validation experiment with eight subjects, the estimated joint moments were comparable to be actual joint moment measured by the conventional system, also the previous study with the inertial system.

Musculoskeletal Symptomatic Areas After Total Knee Replacement for Osteoarthritis

OBJECTIVE

The objective of this study was to measure cumulative incidence and incidence rate and identify factors associated with new musculoskeletal (MSK) symptomatic areas after total knee replacement (TKR) for osteoarthritis (OA).

METHODS

Using data from a randomized controlled trial of patients undergoing elective TKR for OA, we assessed for MSK symptomatic areas by region (neck, hands/wrists/arms/shoulders, back, hips, nonindex knee, and ankles/feet) at baseline (pre-TKR), and at 3, 6, 12, 24, 36, and 48 months post-TKR. Cumulative incidence and incidence rates were calculated for each region. Factors associated with incident MSK symptomatic areas were identified using generalized linear mixed models. Time to incident symptomatic area was assessed using Cox proportional hazards regression.

RESULTS

Among 293 subjects, the cumulative incidence of any new MSK symptomatic area over 4 years was 45%; the incidence rate was 19.2 per 100 person-years. Body site-specific cumulative incidence and incidence rates were highest for nonindex knee and back. Predictors of incident MSK symptomatic areas included female sex (relative risk [RR] 1.64; 95% confidence interval [CI] 1.15-2.34), body mass index of 35 or higher (RR 1.27; 95% CI 0.88-1.85), Charlson Comorbidity Index 2 or more (RR 1.28; 95% CI 0.92-1.78), baseline index knee Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain score greater than 40 (RR 1.39; 95% CI 0.99-1.95), and anxiety/depression (measured by the five-item Mental Health Index) (RR 1.70; 95% CI 1.20-2.40).

CONCLUSION

Incident MSK symptomatic areas occurred in roughly half of recipients of TKR in the 4 years after the operation. Further study is needed to examine the long-term impact of MSK symptomatic areas on postoperative pain, function, and quality of life.

Weight-bearing radiography depends on limb loading

PURPOSE

The mechanical axis of the lower limb has shown to vary between different weight-bearing conditions and change after total knee arthroplasty (TKA). The purpose of this study was to investigate the correlation between mechanical axis alignment in standing long-leg radiographs and limb loading after TKA.

METHODS

Mechanical axis of the lower limb and limb loading have been prospectively evaluated in 115 patients 10 days and 3 months after TKA. By the moment of standing long-leg radiography for analysis of the mechanical leg axis, two digital scales separately captured the load of each limb.

RESULTS

Mechanical axis changed from an initial - 1° ± 2° valgus alignment to a varus axis of + 1° ± 2° (p < 0.01). This change in alignment was associated with an increase of limb loading from 89.9 ± 10.7 to 93.0 ± 7.0% (p < 0.01). The mechanical axis strongly correlated with relative limb loading at the first and second measurements (r = 0.804, p < 0.001, respectively, r = 0.562, p < 0.001). A significant change in the rate of outliers was registered within the observation period. These alterations and distinctions were much more pronounced in patients with postoperative incomplete extension (n = 15).

CONCLUSIONS

The postoperative mechanical axis correlates with limb loading. A clinical relevant change in frontal alignment of the lower limb is associated with increased limb loading after TKA. The actual mechanical axis can only be assessed at physiological limb loading in long-leg radiographs with complete extension at full weight bearing.

LEVEL OF EVIDENCE

Diagnostic study, Level II.

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.

The relationship between lower extremity swelling, quadriceps strength, and functional performance following total knee arthroplasty

BACKGROUND

The relationships between swelling after total knee arthroplasty (TKA) and quadriceps strength and functional performance are poorly understood. Therefore, the aim of this study was to examine the relationships between lower extremity swelling, measured using bioelectrical impedance assessment (SF-BIA), and quadriceps strength and timed up and go (TUG) times following TKA.

METHODS

53 participants (64 ± 9.5 y/o, 43% male) undergoing primary unilateral TKA were recruited for the longitudinal observational study with repeated measures. Quantities of swelling were examined for contribution to two and six-week outcomes of strength and TUG time using hierarchical regression controlling for age, sex, and the baseline value of the dependent variable. Swelling was assessed using bioelectrical impedance assessment and quantified as the peak level of swelling and cumulative swelling (integral) over the post-TKA time window. Maximum isometric quadriceps strength (MVIC) was measured using a electromechanical dynamometer and participant functional performance measured using the TUG.

RESULTS

Neither peak swelling nor cumulative swelling significantly contributed to the variance of two-week quadriceps strength. At six weeks, peak swelling significantly improved the variance in maximal quadriceps strength by an additional four percent (p = 0.05), while cumulative swelling did not significantly contribute. Peak swelling significantly contributed to the variance in two-week (16%) and six-week (five percent) TUG times (p < 0.05), but the cumulative swelling did not.

CONCLUSIONS

Peak swelling represents a value of post-TKA swelling that is associated with strength and function. Reducing the peak level of swelling, occurring early after surgery, may improve patient functional recovery.

LEVEL OF EVIDENCE

Level II - Prospective observational study.

Stiff knee gait may increase risk of second total knee arthroplasty

Osteoarthritis (OA) progression in the contralateral limb after unilateral total knee arthroplasty (TKA) may be related to altered and asymmetrical movement patterns that overload the contralateral joints. The purpose of this study was to determine if biomechanical factors after unilateral TKA were associated with future contralateral TKA. One hundred and fifty-eight individuals who underwent unilateral TKA completed three dimensional motion analysis 6-24 months after unilateral TKA (baseline). Subjects were re-contacted for follow-up (mean 5.89 years after baseline testing) to determine if they had undergone a contralateral TKA. Biomechanical variables from gait at baseline were compared between those who did and did not undergo contralateral TKA at follow-up using one-way ANOVAs. Odds ratios were calculated for variables found to be significant in the ANOVA models. Individuals who underwent contralateral TKA had less knee flexion excursion (10.5° vs. 12.1°; p = 0.032) and less knee extension excursion (8.2° vs. 9.6°; p = 0.035) at baseline on the operated side during walking. Individuals who underwent contralateral TKA also had less knee flexion excursion on the contralateral limb at baseline (11.9° vs. 14.0°; p = 0.017). For every additional degree of knee flexion excursion on the contralateral knee at baseline, there was a 9.1% reduction in risk of future contralateral TKA. Individuals who walked with stiffer gait patterns were more likely to undergo future contralateral TKA. Clinical Significance: Altered movement patterns after surgery may increase the risk for contralateral TKA. Knee excursion is an important metric to include in outcome studies and may serve as a target of rehabilitation after TKA. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:397-402, 2019.

Improved walking distance and range of motion predict patient satisfaction after TKA

PURPOSES

The focus in the evaluation of total knee arthroplasty has shifted from objective measures of implant position and knee function, to patient-reported outcome measures (PROMs). The relation between these two measures was investigated and the possibility of prediction of the patient satisfaction level was evaluated by defining thresholds for improvement of (1) range of motion (ROM), (2) 6-min walk test (6MWT), (3) sit-to-stand test (STS) and (4) quadriceps force after TKA?

METHODS

Fifty-seven patients were prospectively tested at preoperative and 6 months postoperative intervals. The ROM, 6MWT, STS-test and quadriceps force were evaluated. Two clusters were created based on the postoperative KOOS, OKS and the satisfaction subscore of the new KSS, cluster 1 consisted of patients with good to excellent PROMs, cluster 2 of patients with poorer PROMs. Patients in each cluster were more similar to each other than to those in the other cluster. Receiver operating characteristic (ROC)-curve analysis was used to identify thresholds for the functional outcomes that established cluster allocation. Multiple logistic regression was used to define a model to predict cluster allocation.

RESULTS

Patients with high postoperative PROMs (cluster 1 allocation) showed higher postoperative functional outcomes (p < 0.05). Thresholds for the improvement of ROM (≥ 5°, OR 6.3, 95% CI 1.23-31.84), 6MWT (≥ 50 m, OR 8.2, 95% CI 1.61-42.18) STS (≥ 1.05 s, OR 3, 95% CI 0.56-16.07) and normalized Q4 force (≥ 1.5 N/BMI, OR 2.5, 95% CI 0.49-12.89) were found to be predictors of cluster allocation. A model to predict the cluster allocation contained gender, ROM improvement and 6MWT improvement (sensitivity 91.1%, specificity 75%).

CONCLUSIONS

Thresholds for improvement of functional parameters can predict the patient satisfaction cluster. Patients, who are male, improve on the 6-min walk test with 50 m or more and have an increased range of motion of 5° or more, compared to the preoperative situation, are 6-8 times more likely of being satisfied after TKA. These tests are easy to use in clinical practice and can predict the level of patient satisfaction after TKA.

LEVEL OF EVIDENCE

Level II, prognostic study.

Quadriceps weakness preferentially predicts detrimental gait compensations among common impairments after total knee arthroplasty

Patients with total knee arthroplasty (TKA) have large deficits in physical performance in comparison to their healthy age-matched peers. Limb asymmetry stemming from less relative load borne by the surgical limb during daily mobility is associated with diminished performance and worsens with greater mobility demands. How common targets of postoperative care, such as muscle weakness, lower limb extension power, residual knee pain, and poor balance confidence can influence asymmetrical limb loading remains unclear. Forty-six patients with unilateral TKA underwent testing of impairments and motion analysis during 10° decline walking at 3 and 6 months postoperatively. At 3 months, only quadriceps femoris strength asymmetry was found to be significantly related to both total support moment (M_T ) (β = 0.431; p < 0.001) and knee extensor moment (M_K ) (β = 0.493; p < 0.001) asymmetry. Again at 6 months, only quadriceps strength asymmetry was related to M_T (β = 0.432; p < 0.001) and M_K (β = 0.534; p < 0.001) asymmetry. Quadriceps strength significantly improved over time in both limbs, however, deficits between limbs remained. Persistent quadriceps weakness is a key factor associated with walking compensation patterns that are limiting the capacity for greater physical performance of patients with TKA. The pronounced asymmetry in limb and knee loading at 3 months remains unchanged until at least 6 months after surgery, and its association with quadriceps strength asymmetry does not substantially change over time. While other factors may also prompt gait compensations, emphasis on improved quadriceps strength should be a focus of efforts to resolve gait compensations and enhance physical performance outcomes. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2355-2363, 2018.

Restoring physical function after knee replacement: a cross sectional comparison of progressive strengthening vs standard physical therapy

Objective: The purpose of this study is to compare the functional status of patients 12 months after total knee arthroplasty (TKA) who underwent progressive strengthening or standard of care rehabilitation to older adults without knee joint pain. Methods: This cross-sectional design study included 165 participants in the progressive strengthening group, 40 participants in the standard of care group, and 88 older adults (control group). The Knee Outcome Survey - Activity of Daily Living, knee active range of motion (ROM), quadriceps strength, and performance tests were compared between groups using a one-way ANOVA. The proportions of participants in both TKA groups who achieved the lower bound of the 95% confidence interval of the control group were compared using a Fisher's exact test. Results: Significant between-group effects were found for all variables (p < 0.001). The control group had better outcomes than both the progressive strengthening and standard of care groups (p < 0.001). Compared to the standard of care group, a higher proportion of participants in the progressive strengthening group achieved the lower bound cutoff for active knee extension ROM (p = 0.042), quadriceps strength (p = 0.032), and stair climbing time (p = 0.029). Conclusion: More participants in the progressive strengthening group had physical function that was similar to the healthy control group, when compared to the standard of care group. Progressive strengthening rehabilitation may be more effective in restoring normative levels of function after TKA than standard of care.

The centre of mass trajectory is a sensitive and responsive measure of functional compensations in individuals with knee osteoarthritis performing the five times sit-to-stand test

This study aimed to evaluate whether the trajectory of the body's Centre of Mass (CoM) is a sensitive and responsive measure of functional compensations in individuals with knee osteoarthritis (OA) performing the Five Times Sit-to-Stand test (5STS). This prospective study included 21 individuals with OA and 21 age- and gender-matched controls. Motion analysis data was collected while participants performed the 5STS, one month prior and one year after total knee arthroplasty (TKA). Pain was evaluated using a visual analogue scale. Repeated measures ANOVAs were used to evaluate (1) differences in the area under the curve (AUC) of CoM trajectories, and (2) the effect of number of sit-to-stand cycles on the AUC. Preoperatively, individuals with OA displayed a larger contralateral shift (p = 0.009) and forward displacement of the CoM (p < 0.004) than controls. Postoperatively, CoM trajectories of OA individuals were not statistically different from controls. However, upon comparison of specific cycles, OA individuals displayed a larger forward displacement during the final cycle. Pain was significantly reduced postoperatively (p = 0.001). The CoM trajectory appears to be a sensitive and responsive measure of functional compensations. The increased contralateral shift of the CoM represents a strategy to reduce pain by unloading the affected knee. Postoperatively, when pain was substantially reduced, OA individuals were comparable to controls. The increased forward CoM displacement characterises a strategy to reduce muscular effort by reducing the required knee extension moment. Postoperatively, OA individuals were comparable to controls in all cycles but the last, possibly suggesting residual muscle weakness.

Comparative analysis of quadriceps and hamstrings strength in knee osteoarthritis before and after total knee arthroplasty: a cross-sectional study

Objective

Compare the maximal isokinetic muscle strength of knee extensor and flexor muscles between patients with knee osteoarthritis and patients submitted to total knee arthroplasty.

Methods

Volunteers were divided into five groups (n = 20): Control; Ahlbäck I and II; Ahlbäck IV; six months after total knee arthroplasty; 12 months after total knee arthroplasty. An isokinetic knee strength evaluation was conducted for the quadriceps and hamstrings at 60°/s.

Results

Significant differences in the peak torque of the quadriceps and hamstrings were found among the groups (p < 0.001). The Ahlbäck IV, six-month, and 12-month postoperative groups demonstrated lower values when compared to the Control and Ahlbäck I and II groups. When percentage values were compared to the Control group, mean differences ranged from 7% to 41%.

Conclusion

Patients with healthy knees or early stage osteoarthritis have higher quadriceps and hamstrings strengths than those with a more advanced stage of the disease, even after knee replacement. These findings suggest that the traditional rehabilitation programs do not recover strength to levels observed in individuals without knee osteoarthritis.

Visual knee-kinetic biofeedback technique normalizes gait abnormalities during high-demand mobility after total knee arthroplasty

BACKGROUND

Abnormal knee mechanics frequently follow total knee arthroplasty (TKA) surgery with these deficits amplifying as task demands increase. Knee-kinetic biofeedback could provide a means of attenuating gait abnormalities. The purposes of this study were as follows: (1) to describe the gait characteristic differences between patients with TKA and non-TKA adults during level (low-demand) and decline (high-demand) walking; and (2) where differences existed, to determine the impact of knee-kinetic biofeedback on normalizing these abnormalities.

METHODS

Twenty participants six months following a primary TKA and 15 non-TKA peers underwent gait analysis testing during level and decline walking. Knee-kinetic biofeedback was implemented to patients with TKA to correct abnormal gait characteristics if observed.

RESULTS

Patients with TKA had lower knee extensor angular impulse (p<0.001), vGRF (p=0.001) and knee flexion motion (p=0.005) compared to the non-TKA group during decline walking without biofeedback. Patients with TKA normalized their knee extensor angular impulse (p=0.991) and peak vGRF (p=0.299) during decline walking when exposed to biofeedback. No between-group differences were observed during level walking. Groups were similar in age, gender, body mass index, physical activity level, pain interference and depression scores (p>0.05).

CONCLUSION

Patients with TKA demonstrate abnormal gait characteristics during a high-demand walking task when compared to non-TKA peers. Our findings indicate that knee-kinetic biofeedback can induce immediate improvements in gait characteristics during a high-demand walking task. There may be a potential role for the use of visual knee-kinetic biofeedback techniques to improve gait abnormalities during high-demand tasks following TKA.

Unilateral Discomfort Increases the Use of Contralateral Side during Sit-to-Stand Transfer

Individuals with unilateral impairment perform symmetrical movements asymmetrically. Restoring symmetry of movements is an important goal of rehabilitation. The aim of the study was to evaluate the effect of using discomfort-inducing devices on movement symmetry. Fifteen healthy individuals performed the sit-to-stand (STS) maneuver using devices inducing unilateral discomfort under the left sole and left thigh or right sole and right thigh and without them. 3D body kinematics, ground reaction forces, electrical activity of muscles, and the level of perceived discomfort were recorded. The center of mass (COM), center of pressure (COP), and trunk displacements as well as the magnitude and latency of muscle activity of lower limb muscles were calculated during STS and compared to quantify the movement asymmetry. Discomfort on the left and right side of the body (thigh and feet) induced statistically significant displacement of the trunk towards the opposite side. There was statistically significant asymmetry in the activity of the left and right Tibialis Anterior, Medial Gastrocnemius, and Biceps Femoris muscles when discomfort was induced underneath the left side of the body (thigh and feet). The technique was effective in causing asymmetry and promoted the use of the contralateral side. The outcome provides a foundation for future investigations of the role of discomfort-inducing devices in improving symmetry of the STS in individuals with unilateral impairment.

Deficits in functional performance and gait one year after total knee arthroplasty despite improved self-reported function

PURPOSE

The current literature lacks sufficient information about improvements in gait patterns and function after total knee arthroplasty (TKA) and whether patients return to full function. This study evaluated change in gait, performance-based function, and self-reported function 1 year after TKA in patients with symptomatic knee osteoarthritis and how these aspects interrelate.

METHODS

A total of 28 patients (64 % female) with knee osteoarthritis, with a mean age of 66 (±7) years, and 25 age- and gender-matched controls participated in this prospective cohort study. Three-dimensional gait analysis generated comprehensive measures of kinematic and kinetic gait deviations, respectively. Participants completed the Five Times Sit-to-Stand (5STS) test, and the self-reported questionnaire Knee Injury and Osteoarthritis Outcome Score (KOOS), at baseline prior to surgery and 1 year after TKA.

RESULTS

Kinetic gait deviations of both the operated and non-operated limb persisted in patients with knee osteoarthritis at 1 year after surgery, while kinematic gait patterns were comparable to controls. Performance on the 5STS and KOOS scores in patients with knee osteoarthritis improved significantly 1 year after surgery (effect size 0.5-1.5), but did not reach the level of controls. Ten patients with knee osteoarthritis (36 %) exceeded the minimally detectable change on the 5STS.

CONCLUSION

Measures of overall gait patterns and the 5STS revealed improvements in function 1 year after TKA, but were not restored to the level of healthy controls. Based on change in 5STS performance, we identified patients with substantial improvements in gait patterns. Self-reported measures of function could not detect differences between patients improving in 5STS performance and those who did not. These findings highlight the use of the 5STS in clinical practice since improvement on this test seems to follow the reduction in gait pattern deviations.

LEVEL OF EVIDENCE

II.