BackgroundPatients undergoing total knee arthroplasty (TKA) often experience strength deficits both pre- and post-operatively. As these deficits may have a direct impact on functional recovery, strength assessment should be performed in this patient population. For these assessments, reliable measurements should be used. This study aimed to determine the inter- and intrarater reliability of hand-held dynamometry (HHD) in measuring isometric knee strength in patients awaiting TKA.MethodsTo determine interrater reliability, 32 patients (81.3% female) were assessed by two examiners. Patients were assessed consecutively by both examiners on the same individual test dates. To determine intrarater reliability, a subgroup (n = 13) was again assessed by the examiners within four weeks of the initial testing procedure. Maximal isometric knee flexor and extensor strength were tested using a modified Citec hand-held dynamometer. Both the affected and unaffected knee were tested. Reliability was assessed using the Intraclass Correlation Coefficient (ICC). In addition, the Standard Error of Measurement (SEM) and the Smallest Detectable Difference (SDD) were used to determine reliability.ResultsIn both the affected and unaffected knee, the inter- and intrarater reliability were good for knee flexors (ICC range 0.76-0.94) and excellent for knee extensors (ICC range 0.92-0.97). However, measurement error was high, displaying SDD ranges between 21.7% and 36.2% for interrater reliability and between 19.0% and 57.5% for intrarater reliability. Overall, measurement error was higher for the knee flexors than for the knee extensors.ConclusionsModified HHD appears to be a reliable strength measure, producing good to excellent ICC values for both inter- and intrarater reliability in a group of TKA patients. High SEM and SDD values, however, indicate high measurement error for individual measures. This study demonstrates that a modified HHD is appropriate to evaluate knee strength changes in TKA patient groups. However, it also demonstrates that modified HHD is not suitable to measure individual strength changes. The use of modified HHD is, therefore, not advised for use in a clinical setting.
MULTIFILE
BackgroundGait analysis has been used for decades to quantify knee function in patients with knee osteoarthritis; however, it is unknown whether and to what extent inter-laboratory differences affect the comparison of gait data between studies. Therefore, the aim of this study was to perform an inter-laboratory comparison of knee biomechanics and muscle activation patterns during gait of patients with knee osteoarthritis.MethodsKnee biomechanics and muscle activation patterns from patients with knee osteoarthritis were analyzed, previously collected at Dalhousie University (DAL: n = 55) and Amsterdam UMC, VU medical center (VUmc: n = 39), using their in-house protocols. Additionally, one healthy male was measured at both locations. Both direct comparisons and after harmonization of components of the protocols were made. Inter-laboratory comparisons were quantified using statistical parametric mapping analysis and discrete gait parameters.ResultsThe inter-laboratory comparison showed offsets in the sagittal plane angles, moments and frontal plane angles, and phase shifts in the muscle activation patterns. Filter characteristics, initial contact identification and thigh anatomical frame definitions were harmonized between the laboratories. After this first step in protocol harmonization, the offsets in knee angles and sagittal plane moments remained, but the inter-laboratory comparison of the muscle activation patterns improved.ConclusionsInter-laboratory differences obstruct valid comparisons of gait datasets from patients with knee osteoarthritis between gait laboratories. A first step in harmonization of gait analysis protocols improved the inter-laboratory comparison. Further protocol harmonization is recommended to enable valid comparisons between labs, data-sharing and multicenter trials to investigate knee function in patients with knee osteoarthritis.
MULTIFILE
Purpose: Instability of the knee joint is reported by a majority (>65%) of patients with knee osteoarthritis (KOA) and is hypothesized to play a crucial role in the initiation and progression of KOA. A generally accepted objective metric of knee joint stability is lacking, making development of diagnostics and treatment options for knee joint instability more difficult. Such a metric should be based on how gait biomechanics and muscle activation in the unstable knee joint differ from those in a stable knee joint. To challenge knee joint instability, external perturbations during gait are needed to replicate the situations in daily life that require stability of the knee joint. Therefore, the aim of this study was to compare the responses in knee biomechanics and muscle activation patterns to different types of external perturbations during gait of patients with self-reported knee joint instability (KOA-I) versus patients reporting stable knees (KOA-S) and healthy control subjects.Methods: Forty patients (60% female) were included in this study with a mean age of 66 years (range: 52-82), body mass index of 26 (range: 19-32) and Kellgren and Lawrence grade of 2.5 (range 0-4). Patients were dichotomized in a KOA-I group (n=20) and KOA-S group (n=20) based on if they had perceived an episode of knee joint instability in the past four weeks. Furthermore, twenty age-, gender- and BMI-matched healthy control subjects were measured. The participants walked on a dual-belt instrumented treadmill while different external perturbations were applied, triggered by heel strike of the most affected leg (figure 1). The external perturbations consisted of sway left (SL) or sway right (SR) translations (4 cm) or accelerations (AC) or decelerations (DC) of one belt (1.6 m/s walking speed change in 0.23 seconds). Knee kinematics and muscle activation patterns of the perturbed gait cycles were collected using a motion capture system and surface electromyography. The three groups were compared using statistical parametric mapping (SPM) and discrete values by analysis of variance. The discrete values of the knee angles (initial contact, peak and range of motion (ROM) values) and muscle activation patterns (peak, mean and co-contraction index (CCI) values) were corrected for walking speed.Results: The SPM analysis results (example provided in figure 2) showed that in response to the SL perturbations the KOA-I group walked with greater knee flexion angles (KFA) during pre-swing compared to the control group (SPM, p<0.01) and during mid-swing compared to the KOA-S group and control group (SPM, p<0.01). Moreover, during the SR perturbed gait cycles the KOA-I group had greater KFA during mid-swing compared to the KOA-S group (SPM, p=0.01). In response to the AC perturbations the KOA-I group walked with a greater KFA during late terminal stance compared to the control group (SPM, p<0.01). Furthermore, the KOA-I group had greater KFA during the pre-swing phase of the DC perturbed gait cycles compared to the control group (SPM, p<0.01). The significant results from the comparison of the discrete values are presented in table 1. The KOA-I group had greater peak KFA during the swing phase of all perturbed gait cycles (independent of perturbation type) compared to the KOA-S group and control group (p<0.01). Moreover, during both sway perturbations (SL, SR) higher KFA ROM were observed in the KOA-I group compared to the KOA-S group (p<0.05). Besides this, the KOA-I group presented higher CCI of the medial muscles (vastus medialis and medial hamstring) compared to the KOA-S group during the DC perturbation (p=0.03). Furthermore, changes in vastus medialis and gluteus medius muscle activation in response to different external perturbations were observed in the KOA-S group compared to the control group and the KOA-I group (p<0.05).Conclusions: Patients with KOA-I walked with greater knee flexion angles during peak stance, late-terminal stance, pre-swing and mid-swing in response to different external perturbations, which could be a distinctive strategy of these patients to maintain stability of the knee joint during these phases of gait. Besides this, only few alterations were observed in the knee muscle activation patterns between the groups. This could be explained by the large variation between subjects in the muscle activations patterns which might indicate different neuromuscular strategies to respond to the external perturbations. Future studies with larger sample sizes are required to test the reliability and validity of the knee flexion angle as a candidate for the objective measurement of knee joint stability and to further investigate neuromuscular control of the unstable osteoarthritic knee.
