Improvements in knee biomechanics during walking are associated with increased physical activity after total knee arthroplasty

Maximal daily stepping cadence partially explains functional capacity of individuals with end-stage knee osteoarthritis

BACKGROUND

Individuals with end-stage knee osteoarthritis (OA) walk at a lower intensity (ie, slower step cadence) contributing to worse physical function. Previous literature reports daily step counts and sedentary time, with little information regarding stepping bouts or cadence. Determining relationships between daily higher stepping cadence duration and clinical outcomes can move the field toward optimal daily stepping prescription.

OBJECTIVE

To quantify daily physical activity patterns of individuals with end-stage knee OA and determine the contribution of high stepping cadence to explain functional capacity variability.

DESIGN

Cross-sectional analysis.

SETTING

Veterans Administration medical center.

PARTICIPANTS

U.S. military veterans (n = 104; age: 67.1 years [7.2]; mean [SD]; male [89.3%]) with end-stage knee OA were enrolled.

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURE

Functional capacity (6-Minute Walk Test [6MWT]). Physical activity (activPAL wearable sensor; cadence and time sitting, standing, and stepping), pain (Western Ontario and McMaster Universities Osteoarthritis Index-pain subscale) sociodemographic variables, and comorbidities (body mass index and Functional Comorbidity Index) are the main explanatory variables.

RESULTS

Participants' wake time was mainly sitting (11.0 h/day) in ≥60-minute bouts (29.7% ± 12.7 of sitting time). Standing (3.4 hours/day) and stepping (1.4 h/day) primarily occurred in 0-5 minute bouts (standing: 87.7% ± 14.4 of standing time, stepping: 98.7% ± 12.7 of stepping time) and stepping cadence was predominantly incidental (1-19 spm; 52.9% ± 9.6 of total stepping time). Backward elimination model results indicated shorter medium-to-brisk cadence bout duration, older age, and higher pain significantly explained shorter 6MWT distance (AdjR2=0.24, p < .01).

CONCLUSIONS

Individuals with knee OA spend most of their waking hours sitting, while standing and stepping occurs in short bouts at very low stepping cadence. Decreased time in high stepping cadence is associated with lower functional capacity. Future studies should explore if increasing the daily time spent in higher step cadence can improve functional capacity in this population.

Restoration of the native tibial joint line obliquity in total knee arthroplasty with inverse kinematic alignment does not increase knee adduction moments

PURPOSE

Patient-specific alignment in total knee arthroplasty (TKA) has shown promising patient-reported outcome measures; however, the clinical and biomechanical effects of restoring the native knee anatomy remain debated. The purpose of this study was to compare the gait pattern between a mechanically aligned TKA cohort (adjusted mechanical alignment-aMA) and a patient-specific alignment TKA cohort (inverse kinematic alignment-iKA).

METHODS

At two years postoperatively, the aMA and iKA groups, each with 15 patients, were analyzed in a retrospective case-control study. All patients underwent TKA with robotic assistance (Mako, Stryker) through an identical perioperative protocol. The patients' demographics were identical. The control group comprised 15 healthy participants matched for age and gender. Gait analysis was performed with a 3D motion capture system (VICON). Data collection was conducted by a blinded investigator. The primary outcomes were knee flexion during walking, knee adduction moment during walking and spatiotemporal parameters (STPs). The secondary outcomes were the Oxford Knee Score (OKS) and Forgotten Joint Score (FJS).

RESULTS

During walking, the maximum knee flexion did not differ between the iKA group (53.0°) and the control group (55.1°), whereas the aMA group showed lower amplitudes of sagittal motion (47.4°). In addition, the native limb alignment in the iKA group was better restored, and although more in varus, the knee adduction moments in the iKA group were not increased (225 N mm/kg) compared to aMA group (276 N mm/kg). No significant differences in STPs were observed between patients receiving iKA and healthy controls. Six of 7 STPs differed significantly between patients receiving aMA and healthy controls. The OKS was significantly better in patients receiving iKA than aMA: 45.4 vs. 40.9; p = 0.05. The FJS was significantly better in patients receiving iKA than aMA: 84.8 vs. 55.5; p = 0.002.

CONCLUSION

At two years postoperatively, the gait pattern showed greater resemblance to that in healthy controls in patients receiving iKA rather than aMA. The restoration of the native coronal limb alignment does not lead to increased knee adduction moments due to the restoration of the native tibial joint line obliquity.

LEVEL OF EVIDENCE

Level III.

Movement direction impacts knee joint kinematics during elliptical exercise at varying incline angles

BACKGROUND

Elliptical trainers are a popular cardiovascular exercise for individuals with injuries or those post-operation. There is currently limited data on the impacts of direction while on elliptical trainers for knee joint kinematic risk factors. This study compared lower extremity kinematics between the forward and reverse direction at varying inclines on an elliptical trainer modified with converging footpath and reduced inter-pedal distance.

METHODS

Twenty-four college age participants exercised on the modified elliptical in both directions at four ramp inclines: 6°, 12°, 25°, and 35°. Three-dimensional kinematics were collected for each direction and ramp incline. A 2 × 4 (direction × incline) repeated measures analysis of variance was run with an alpha of 0.05. Simple effects analysis was run with Bonferroni correction for significant interaction or main effect of ramp incline.

RESULTS

The reverse direction had significantly greater peak knee valgus at 6° incline (mean difference [MD] = 1.35°, p < 0.014, d = 0.31) and 12° (MD = 2.41°, p < 0.001, d = 0.55), peak hip abduction at 6° (MD = 2.86°, p = 0.002, d = 0.49) and 12° (MD = 2.91°, p < 0.001, d = 0.51), but decreased peak knee flexion angles (p = 0.032) at all inclines.

CONCLUSIONS

Individuals with knee pathologies such as knee osteoarthritis or anterior knee pain should exercise in the reverse direction at lower inclines. However, switching to the forward direction and/or increasing incline may increase quadriceps strength during a safe activity such as elliptical trainers.

Physical Therapist Management of Total Knee Arthroplasty

A clinical practice guideline on total knee arthroplasty was developed by an American Physical Therapy (APTA) volunteer guideline development group that consisted of physical therapists, an orthopedic surgeon, a nurse, and a consumer. The guideline was based on systematic reviews of current scientific and clinical information and accepted approaches to management of total knee arthroplasty.

Lower extremity gait kinematics outcomes after knee replacement demonstrate arthroplasty-specific differences between unicondylar and total knee arthroplasty: A pilot study

BACKGROUND

The aim of the present study is to compare sagittal gait kinematics of ankle, knee and hip joints between subjects with unicondylar and total knee arthroplasty and age matched healthy controls. Since unicondylar knee replacement is a less invasive procedure, which more closely preserves knee joint anatomy, we hypothesized that one year post unicondylar knee arthroplasty patients would demonstrate more normal gait patterns than patients with total knee arthroplasty.

RESEARCH QUESTION

Do unicondylar and total knee arthroplasty patients display similar gait kinematics one year after surgery?

METHODS

Fourteen subjects (8 posterior stabilized and 6 medial unicondylar knee replacements) that were one year post surgery, and 6 healthy control subjects underwent a 3D gait analysis and a physical examination (range of motion, muscle strength). Statistical parametric mapping was used to compare gait kinematics of the lower limbs between groups. Additionally, differences in peak angles and clinical outcomes were assessed using a one-way ANOVA between subjects analysis.

RESULTS

Both knee replacement groups showed reduced knee flexion range of motion and reduced muscle strength at the operated leg compared to the control group. Subjects with TKA demonstrated reduced knee flexion at loading response and midstance of the gait cycle. Both UKA and TKA demonstrated significantly less knee flexion during swing.

SIGNIFICANCE

The results of this study demonstrate arthroplasty-specific differences in muscle strength, range of motion and gait kinematics of the lower limb one year after knee surgery. Future planning of post-surgery follow-up should addresses these arthroplasty-specific weaknesses and gait deviations.

Kinematic alignment in total knee arthroplasty better reproduces normal gait than mechanical alignment

PURPOSE

Kinematic alignment technique for TKA aims to restore the individual knee anatomy and ligament tension, to restore native knee kinematics. The aim of this study was to compare parameters of kinematics during gait (knee flexion-extension, adduction-abduction, internal-external tibial rotation and walking speed) of TKA patients operated by either kinematic alignment or mechanical alignment technique with a group of healthy controls. The hypothesis was that the kinematic parameters of kinematically aligned TKAs would more closely resemble that of healthy controls than mechanically aligned TKAs.

METHODS

This was a retrospective case-control study. Eighteen kinematically aligned TKAs were matched by gender, age, operating surgeon and prosthesis to 18 mechanically aligned TKAs. Post-operative 3D knee kinematics analysis, performed with an optoelectronic knee assessment device (KneeKG®), was compared between mechanical alignment TKA patients, kinematic alignment TKA patients and healthy controls. Radiographic measures and clinical scores were also compared between the two TKA groups.

RESULTS

The kinematic alignment group showed no significant knee kinematic differences compared to healthy knees in sagittal plane range of motion, maximum flexion, abduction-adduction curves or knee external tibial rotation. Conversely, the mechanical alignment group displayed several significant knee kinematic differences to the healthy group: less sagittal plane range of motion (49.1° vs. 54.0°, p = 0.020), decreased maximum flexion (52.3° vs. 57.5°, p = 0.002), increased adduction angle (2.0-7.5° vs. - 2.8-3.0°, p < 0.05), and increased external tibial rotation (by a mean of 2.3 ± 0.7°, p < 0.001). The post-operative KOOS score was significantly higher in the kinematic alignment group compared to the mechanical alignment group (74.2 vs. 60.7, p = 0.034).

CONCLUSIONS

The knee kinematics of patients with kinematically aligned TKAs more closely resembled that of normal healthy controls than that of patients with mechanically aligned TKAs. This may be the result of a better restoration of the individual's knee anatomy and ligament tension. A return to normal gait parameters post-TKA will lead to improved clinical outcomes and greater patient satisfaction.

LEVEL OF EVIDENCE

III.

Which osteoarthritic gait features recover following total knee replacement surgery?

Background

Gait analysis can be used to measure variations in joint function in patients with knee osteoarthritis (OA), and is useful when observing longitudinal biomechanical changes following Total Knee Replacement (TKR) surgery. The Cardiff Classifier is an objective classification tool applied previously to examine the extent of biomechanical recovery following TKR. In this study, it is further developed to reveal the salient features that contribute to recovery towards healthy function.

Methods

Gait analysis was performed on 30 patients before and after TKR surgery, and 30 healthy controls. Median TKR follow-up time was 13 months. The combined application of principal component analysis (PCA) and the Cardiff Classifier defined 18 biomechanical features that discriminated OA from healthy gait. Statistical analysis tested whether these features were affected by TKR surgery and, if so, whether they recovered to values found for the controls.

Results

The Cardiff Classifier successfully discriminated between OA and healthy gait in all 60 cases. Of the 18 discriminatory features, only six (33%) were significantly affected by surgery, including features in all three planes of the ground reaction force (p<0.001), ankle dorsiflexion moment (p<0.001), hip adduction moment (p = 0.003), and transverse hip angle (p = 0.007). All but two (89%) of these features remained significantly different to those of the control group after surgery.

Conclusions

This approach was able to discriminate gait biomechanics associated with knee OA. The ground reaction force provided the strongest discriminatory features. Despite increased gait velocity and improvements in self-reported pain and function, which would normally be clinical indicators of recovery, the majority of features were not affected by TKR surgery. This TKR cohort retained pre-operative gait patterns; reduced sagittal hip and knee moments, decreased knee flexion, increased hip flexion, and reduced hip adduction. The changes that were associated with surgery were predominantly found at the ankle and hip, rather than at the knee.

Effects of sex and obesity on gait biomechanics before and six months after total knee arthroplasty: A longitudinal cohort study

BACKGROUND

Gait biomechanics, sex, and obesity can contribute to suboptimal outcomes from primary total knee arthroplasty. The aims of this study were to i) determine if sex and/or obesity influence the amount of change in gait biomechanics from pre-surgery to six months post-surgery and; ii) assess if gait returns to normal in men and women.

METHODS

Three-dimensional gait analysis was performed on 43 patients undergoing primary total knee arthroplasty for knee osteoarthritis (pre- and six months post-operative) and 40 asymptomatic controls. Mixed linear regression models were fit to assess which factors influenced change in gait biomechanics within the arthroplasty cohort, and interaction terms were included to assess if biomechanics returned to normal following surgery.

FINDINGS

Male peak knee adduction moment (p < 0.001) and impulse (p < 0.001) decreased six months following arthroplasty, whilst gait in women remained unchanged after surgery. Obesity did not influence gait changes in men or women. Gait of female arthroplasty participants did not differ from female controls after surgery except for sagittal plane knee range of motion (p = 0.003), whilst men differed from controls for peak knee adduction moment (p = 0.011), knee range of motion (p < 0.001), and peak knee flexion moment (p < 0.001).

INTERPRETATION

Sex, but not obesity, influenced changes in gait biomechanics after arthroplasty. Men retained abnormal gait patterns after surgery, whilst women did not. Further research should determine the long-term implications of gait abnormalities seen in men after arthroplasty.

Postoperative Increased Loading Leads to an Alteration in the Radiological Mechanical Axis After Total Knee Arthroplasty

BACKGROUND

Standing long-leg radiographs allow assessment of the mechanical axis in the frontal plane before and after total knee arthroplasty (TKA). An alteration in loading, and hence in the forces acting on the knee joint, occurs postoperatively. We therefore postulated that the mechanical axis measured in the long-leg standing radiograph would change within the first year after TKA.

METHODS

Standing long-leg radiographs of 156 patients were performed 7 days, 3 months, and 12 months after TKA with determination of mechanical axis of the lower limb.

RESULTS

Seven days after surgery, the mechanical axis amounted 0.8° ± 1.7° valgus. Three months after the operation, at 1.3° ± 1.3° varus, it was significantly different (P < .001) from the primary measurement. No further alteration in the mechanical axis occurred during the first year after TKA. This difference was even more pronounced (P < .001) in patients with a postoperative lack of complete extension. Seven days after surgery, they had a valgus axis deviation of 1.6° ± 1.6°; after 3 months, the measurement amounted 1.2° ± 1.3° varus.

CONCLUSION

Measured by a standing long-leg radiograph, the frontal mechanical axis after TKA changes over time. The predictive power of a standing long-leg radiograph in the first week after surgery is limited because limb loading is altered because of pain and is therefore nonphysiological. The actual mechanical axis resulting after TKA can only be assessed in a standing long-leg radiograph at physiological loading.