Whole body coordination and knee movement control during five rehabilitation exercises

Knee rehabilitation exercises to improve motor control, target movement fluency and displacement variability. Although knee movement in the frontal plane during exercise is routinely assessed in clinical practice, optimal knee control remains poorly understood. In this study, twenty-nine healthy participants (height: 1.73±0.11 m, mass: 73.5±16.4 kg, age: 28.0±6.9 years) performed four repetitions of five rehabilitation exercises whilst motion data were collected using the VICON PlugInGait full body marker set. Fluency and displacement variability were calculated for multiple landmarks, including Centre of Mass (CoM) and knee joint centres. Fluency was calculated as the inverse of the average number of times a landmark velocity in the frontal plane crossed zero. Variability was defined as the standard deviation of the frontal plane movement trajectories. CoM fluency and displacement variability were significantly different between tasks (p<0.001). CoM displacement variability was consistently smallest compared to the constituent landmarks (p<0.005). This was interpreted as a whole body strategy of compensatory variability constraining CoM frontal plane movement. Ipsilateral knee fluency (p<0.01) and displacement variability (p<0.001) differed substantially between tasks. The role of the weight-bearing knee seemed dependent on task constraints of the overall movement and balance, as well as constraints specific for knee joint stability

Motor control strategies during double leg squat following anterior cruciate ligament rupture and reconstruction: an observational study

Background: Anterior cruciate ligament (ACL) injured individuals often show asymmetries between the injured and non-injured leg. A better understanding of the underlying motor control could help to improve rehabilitation. Double leg squat exercises allow for compensation strategies. This study therefore investigated motor control strategies during a double leg squat with the aim to investigate if individuals with ACL rupture (ACLD), ACL reconstruction (ACLR) and healthy control subjects (CONT) used different strategies. Methods: 20 ACLD and 21 ACLR were compared to 21 CONT subjects. Participants performed eight continuous double leg squats to their maximum depth, while kinematic and kinetic data were collected. Outcome measures were calculated to quantify the behavior of the injured and non-injured legs and the asymmetry between these legs. Results: Squat depth was significantly reduced in ACLR and ACLD compared to CONT (p < 0.05; 106 ± 17°; 105 ± 21°; 113 ± 21°). Peak knee extensor moments (Mkn(mx)) were significantly reduced in ACLR and ACLD compared to CONT in the injured leg only (p < 0.05; 0.045 ± 0.015; 0.046 ± 0.016; 0.059 ± 0.022 body weight.height respectively). There was no significant correlation between symmetry of the support moment (SYMMsup) and of the % support moment by the knee (SYM%supkn) in CONT (R2 = -0.07). Data distribution average indicated good symmetry. ACLR showed a significant correlation between SYMMsup and SYM%supkn (R2 = 0.561) when two participants who did not recover as well were excluded. ACLR controlled knee moment magnitude using two strategies; 1) transfer of support moment to non-injured leg; 2) transfer of support moment from knee to ankle and/or hip of injured leg. These were combined in different proportions, but with the same effect on the knee moment. ACLD showed no significant correlation between SYMMsup and SYM%supkn (R2 = 0.015). Data distribution average indicated reduced symmetry. ACLD therefore used an avoidance strategy: reducing squat depth and subsequently the support moment in the injured leg and the knee contribution. Conclusions: ACLD and ACLR individuals used different squatting strategies compared to controls, with ACLR using controlled and ACLD using avoidance behavior regarding knee loading. This has major implications for rehabilitation as these kinetic strategies cannot be observed, but result in the injured leg not being exercised as intended

Activity progression for anterior cruciate ligament injured individuals

Background: Functional exercises such as distance hop, squatting and gait are important in the rehabilitation of anterior cruciate ligament deficient and reconstructed individuals but movement compensations and incomplete recovery persist. This study aimed to; 1. Identify how these tasks pose different challenges; 2. Evaluate if these activities challenge anterior cruciate ligament groups differently compared to controls. Methods: Motion and force data were collected during distance hop, squatting and gait for 20 anterior cruciate ligament deficient, 21 reconstructed and 21 controls. Findings: For all groups knee range of motion was greatest during squatting, intermediate during hopping and smallest during gait (p < 0.01). Peak internal knee extensor moments were greatest during distance hop (p < 0.01). The mean value of peak knee moments were reduced in squatting and gait (p < 0.01) compared to hop. Peak internal extensor moments were significantly larger during squatting and external adductor moments during gait (p < 0.01). Fluency was highest during squatting (p < 0.01). Anterior cruciate ligament demonstrated good recovery of gait but anterior cruciate ligament deficient adopted a strategy of increased fluency (p < 0.01). During squatting knee range of motion and peak internal knee extensor moment were reduced in anterior cruciate ligament (p < 0.01). Both anterior cruciate ligament groups hopped a shorter distance (p < 0.01) and had reduced knee range of motion (p < 0.025). Anterior cruciate ligament reconstructed had reduced fluency (p < 0.01). Interpretation: Distance hop was the most challenging activity; squatting and gait were of similar difficulty but challenged patients in different ways. Despite squatting being an early, less challenging exercise, anterior cruciate ligament groups demonstrated numerous compensation strategies, indicating that this may be more challenging for anterior cruciate ligament than gait

Patellofemoral joint compression forces in backward and forward running

AbstractPatellofemoral pain (PFP) is a common injury and increased patellofemoral joint compression forces (PFJCF) may aggravate symptoms. Backward running (BR) has been suggested for exercise with reduced PFJCF.The aims of this study were to (1) investigate if BR had reduced peak PFJCF compared to forward running (FR) at the same speed, and (2) if PFJCF was reduced in BR, to investigate which biomechanical parameters explained this. It was hypothesized that (1) PFJCF would be lower in BR, and (2) that this would coincide with a reduced peak knee moment caused by altered ground reaction forces (GRFs).Twenty healthy subjects ran in forward and backward directions at consistent speed. Kinematic and ground reaction force data were collected; inverse dynamic and PFJCF analyses were performed.PFJCF were higher in FR than BR (4.5±1.5; 3.4±1.4BW; p<0.01). The majority of this difference (93.1%) was predicted by increased knee moments in FR compared to BR (157±54; 124±51Nm; p<0.01). 54.8% of differences in knee moments could be predicted by the magnitude of the GRF (2.3±0.3; 2.4±0.2BW), knee flexion angle (44±6; 41±7) and center of pressure location on the foot (25±11; 12±6%) at time of peak knee moment. Results were not consistent in all subjects.It was concluded that BR had reduced PFJCF compared to FR. This was caused by an increased knee moment, due to differences in magnitude and location of the GRF vector relative to the knee. BR can therefore be used to exercise with decreased PFJCF

Assessing participation in the ACL injured population: selecting a patient reported outcome measure on the basis of measurement properties

Background/aim A return to pre injury activity participation remains a common but often elusive goal following ACL injury. Investigations to improve our understanding of participation restrictions are limited by inconsistent use of insufficiently investigated measurement tools. The aim of this study was to follow the consensus based standards for the selection of health measurement instruments (COSMIN) guideline to provide a comparative evaluation of four patient reported outcomes (PROMs) on the basis of measurement properties. This will inform recommendations for measuring participation of ACL injured subjects, particularly in the United Kingdom (UK) National Health Service (NHS). Methods Thirteen criteria were compiled from the COSMIN guideline. These included reliability, measurement error, content validity, construct validity, responsiveness and interpretability. Data from 51 subjects collected as part of a longitudinal observational study of recovery over the first year following ACLR was used in the analysis. Results Of the thirteen criteria, the required standard was met in 11 for Tegner, 11 for International Knee Documentation Committee (IKDC), 6 for Cincinnati Sports Activity Scale (CSAS) and 6 for Marx. The two weaknesses identified for the Tegner are more easily compensated for during interpretation than those in the IKDC; for this reason the Tegner is the recommended PROM. Conclusions The Tegner activity rating scale performed consistently well in respect of all measurement properties in this sample, with clear benefits over the other PROMs. The measurement properties presented should be used to inform implementation and interpretation of this outcome measure in clinical practice and research

Altered biomechanical strategies and medio-lateral control of the knee represent incomplete recovery of individuals with injury during single leg hop

Anterior Cruciate Ligament (ACL) injury can result in failure to return to pre-injury activity levels and future osteoarthritis predisposition. Single leg hop is used in late rehabilitation to evaluate recovery and inform treatment but biomechanical understanding of this activity is insufficient. This study investigated single leg hop for distance aiming to evaluate if ACL patients had recovered: 1) landing strategies and 2) medio-lateral knee control. We hypothesized that patients with reconstructive surgery (ACLR) would have more similar landing strategies and knee control to healthy controls than patients treated conservatively (ACLD). 16 ACLD and 23 ACLR subjects were compared to 20 healthy controls (CONT). Kinematic and ground reaction force data were collected while subjects hopped their maximum distance. The main output parameters were hop distance, peak knee flexor angles and extensor moments and Fluency (a measure introduced to represent medio-lateral knee control). Statistical differences between ACL and control groups were analyzed using a general linear model univariate analysis, with COM velocity prior to landing as covariate. Hop distanced was smallest for ACLD and largest for CONT (p<0.001; ACLD 57.1±14.1; ACLR 75.1±17.8; CONT 77.7±14.07%height). ACLR used a similar kinematic strategy to CONT, but had a reduced peak knee extensor moment (P<0.001; ACLD 0.32±0.14; ACLR 0.31±0.16; CONT 0.42±0.13 BW.height). Fluency was reduced in both ACLD and ACLR (p=0.006; ACLD 0.13±0.34; ACLR 0.14±0.34; CONT 0.17±0.41 seconds). Clinical practice uses hopping distance to evaluate ACL patients’ recovery. This study demonstrated that aspects such as movement strategies and knee control need to be evaluated

A novel clinical approach for assessing hop landing strategies: a 2D telescopic inverted pendulum (TIP) model

Purpose Single leg hop for distance is used to inform rehabilitation and return to sport following anterior cruciate ligament reconstruction. However, impairment of landing mechanics may persist after the recommended performance parameter (hop distance) has been met; therefore, alternative methods are required. This study follows the COSMIN guideline to investigate the measurement properties of data from a new instrument (2D TIP). This is a simple motion analysis instrument to assess landing strategy based on more complex biomechanical modelling. Methods Data collected in the clinical setting from 30 subjects with chronic ACL deficiency (mean 15.5, SD 4.3 months following injury) before and 6 months after ACL reconstruction and a healthy control group were analysed. Reliability and measurement error were calculated using two repeated measures from three independent raters. Construct validity was assessed by hypothesis testing, and known groups validity and responsiveness were defined by differences between groups. Results The data demonstrate excellent inter-rater (ICC = 0.81–1.00) and intra-rater (ICC = 0.85–1.00) reliability with low measurement error. Of the eight construct validity hypothesis, six were fully and two partially supported. Between-group differences were significant (P < 0.05) supporting the validity and responsiveness hypothesis. Conclusion 2D TIP is a simple and inexpensive instrument for assessing landing strategy that has demonstrated appropriate reliability, validity and responsiveness in the ACL-injured population. The instrument will now be used to identify altered movement strategies and develop novel rehabilitation interventions that target strategy and performance. Level of evidence Prospective diagnostic study, Level II