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Abstract: Background: It is reported that a majority of the patients with knee osteoarthritis have cartilage degeneration in medial and patellofemoral compartments. A bi-compartmental knee replacement system was designed to treat osteoarthritis at medial and patellofemoral compartments. To date, there is very little information regarding the knee mechanics during gait after bi-compartmental knee replacement. The purpose of the study was to evaluate knee strength and mechanics during level walking after knee replacement. Methods: Ten healthy control subjects and eight patients with unilateral bi-compartmental knee replacement participated in the study. Maximal isokinetic concentric knee extension strength was evaluated. 3D kinematic and kinetic analyses were conducted for level walking. Paired Student t-test was used to determine difference between surgical and non-involved limbs. One way MANOVA was used to determine difference between surgical and control groups. Findings: The surgical knee exhibited less peak torque and initial abduction moment than both the non-involved and control limbs (P <0.05). The non-involved limb had less knee extension at stance and greater knee extensor moment during push-off than both the surgical and control limbs (P <0.05). No differences were found for other typical knee mechanics among the surgical, non-involved, and control limbs during walking (P >0.05). Interpretations: Patients with bi-compartmental knee replacement exhibited good frontal plane knee mechanics and were able to produce the same level of knee extensor moment as healthy control limbs during walking. While showing some compensatory patterns during walking, patients with bi-compartmental knee replacement largely exhibited normal gait patterns and knee mechanics. [Copyright &y& Elsevier]

Abstract: Background: Muscular tightness is a common clinical musculoskeletal disorder and is regarded as a predisposing factor for muscle injuries. In this study, a two-way mixed design ANOVA was applied to investigate the effects of the gastrocnemius tightness on the joint angle and joint work during walking. Methods: Twenty-two patients with muscular tightness of gastrocnemius muscle (<12° of ankle dorsiflexion with knee extended) and 22 age- and gender-matched subjects with normal gastrocnemius flexibility (>15° of ankle dorsiflexion with knee extended) participated in this study. The joint angle and work at hip, knee, and ankle joints during the stance phase were analyzed at two preset cadences of 100steps/min and 140steps/min. Findings: Significantly greater flexion angles at hip (P =0.025) and knee (P =0.001) were found in the tightness group at the time of maximal ankle dorsiflexion. Significantly less work generation at knee (P =0.034) and greater work absorption at ankle (P =0.024) were detected in the tightness group. Interpretation: The subjects with gastrocnemius tightness revealed a compensatory gait pattern, which included the changes in the joint angles and associated work productions. The potential disturbance of the knee control and strain injuries of plantar flexors might be crucial in the clinical considerations for subjects with gastrocnemius tightness. [Copyright &y& Elsevier]

Abstract: Background: The principle of specificity in muscle training requires the training mode to reflect the desired outcome. The observed similarity of lower limb movements during recumbent cycling to the functional movements sit-to-stand and step-up presents the possibility of using recumbent cycling in a rehabilitation context. This may reduce the need to practice the actual task which in some, less able, patients may be labour intensive and patient fatiguing. To date no studies have compared recumbent cycling to these functional movements. This study therefore aimed to compare the lower limb kinematics and muscle activity between recumbent cycling and both sit-to-stand and step-up movements. Methods: Electromyographic and kinematic signals from 12 young (mean age 42.1years) healthy participants were collected during the performance of three activities: (1) cycling at 60rpm, (2) sit-to-stand and (3) a single step-up. Only the extension phase of each movement was compared. Findings: Although the results demonstrated differences in joint movement and muscle activation, e.g., greater gastrocnemius activity during recumbent cycling (P <0.00), knee range of motion and average root mean square activity for rectus femoris, biceps femoris and the sum of the average activity for five muscles recorded showed no difference (P >0.05) suggesting that there was sufficient agreement to support the use of recumbent cycling as a specific training modality for the sit-to-stand and step-up movements. This finding may have positive implications for the rehabilitation of a wide range of patients in the early stages of rehabilitation. [Copyright &y& Elsevier]

Abstract: Background: Surgical reconstruction of the medial patellofemoral ligament used to stabilize the patella against lateral dislocation may concomitantly produce alteration of the patellofemoral contact pressure distribution. Two different tendon transfer techniques of reconstructing the medial patellofemoral ligament, one dynamic and one static, as well as a proximal soft tissue realignment of the patella were investigated. Methods: Eight human knee specimens were mounted in a kinematic knee simulator and isokinetic extension motion was simulated. Patellofemoral pressure was measured using a pressure sensitive film while a 100N laterally directed dislocation load was applied to the patella. The specimens were evaluated in a physiologic state, as well as after dynamic reconstruction of the medial patellofemoral ligament using a distal transfer of the semitendinosus tendon, following static reconstruction using a semitendinosus autograft, and following proximal soft tissue realignment of the patella. Findings: Following both reconstruction techniques of the medial patellofemoral ligament patellofemoral contact pressure was not significantly (P =0.49) altered. In contrast, after proximal realignment a trend (P =0.07) towards higher contact pressure near knee extension was observed. In the absence of a lateral dislocation load dynamic and static reconstruction resulted in a medialization (P =0.04) of the center of pressure, whereas under the application of a 100N dislocation load the center of pressure showed no significant alteration. Following proximal realignment the center of pressure was significantly medialized without (P <0.01) and with a dislocation load (P =0.01) throughout the entire range of knee motion. Interpretation: Static and dynamic ligament reconstruction of the medial patellofemoral ligament did not alter patellofemoral pressure. Proximal realignment, on the other hand, resulted in a constant medialization of the patellofemoral pressure. The data suggest that the reconstruction techniques would be associated with a low risk of causing premature cartilage degeneration due to excessive patellofemoral contact pressure, whereas proximal realignment could cause medial overload of the patellofemoral joint. [Copyright &y& Elsevier]

Abstract: Background: The aim of this study was to assess the effects of static stretching on hamstring passive stiffness calculated using different data reduction methods. Methods: Subjects performed a maximal range of motion test, five cyclic stretching repetitions and a static stretching intervention that involved five 30-s static stretches. A computerised dynamometer allowed the measurement of torque and range of motion during passive knee extension. Stiffness was then calculated as the slope of the torque–angle relationship fitted using a second-order polynomial, a fourth-order polynomial, and an exponential model. The second-order polynomial and exponential models allowed the calculation of stiffness indices normalized to knee angle and passive torque, respectively. Findings: Prior to static stretching, stiffness levels were significantly different across the models. After stretching, while knee maximal joint range of motion increased, stiffness was shown to decrease. Stiffness decreased more at the extended knee joint angle, and the magnitude of change depended upon the model used. After stretching, the stiffness indices also varied according to the model used to fit data. Thus, the stiffness index normalized to knee angle was found to decrease whereas the stiffness index normalized to passive torque increased after static stretching. Interpretation: Stretching has significant effects on stiffness, but the findings highlight the need to carefully assess the effect of different models when analyzing such data. [Copyright &y& Elsevier]

Abstract: Detailed understanding of the knee joint loading requires the calculation of muscle and joint forces in different conditions. In these applications the patellar tendon moment arm length is essential for the accurate estimation of the tibiofemoral joint loading. In this article, different methods that have been used to determine the patellar tendon moment arm length under in vivo and in vitro conditions are reviewed. The limitations and advantages associated with each of the methods are evaluated together with their applications in the different loading conditions that the musculoskeletal system is subjected to. The three main measurement methods that this review considers are the geometric method, the tendon excursion method and the direct load method. A comparison of relevant quantitative results is presented to asses the impact of the errors of each method on the quantification of the patellar tendon moment arm and the implications for joint loading assessment in clinical applications. [Copyright &y& Elsevier]

Background. Patients with genu varum of the knee and moderate to severe osteoarthritis often suffer from additional symptoms of the patello-femoral joint. These patients have a poor prognosis following high tibial osteotomy. It is unclear whether varus knees with only mild femoro-tibial osteoarthritis are also associated with alterations of patella biomechanics, and affect the prognosis of intended high tibial osteotomy.Methods. Fifteen patients with genu varum and mild osteoarthritis and 15 healthy volunteers were assessed in an open MRI-scanner. 3D-GRE sequences of the knee were obtained in 0°, 30° and 90° with and without activity of the extensor muscles. After segmentation of patella, femur, tibia and the adjacent cartilage, a patella-based local coordinate system was established. Femoral and tibial reference points allowed definition of the spatial position of the patella. Contact areas were defined by intersection of opposing cartilage volumes.Findings. No significant differences in patella kinematics and patello-femoral contact areas could be found (P>0.05) between varus knees with mild osteoarthritis and healthy knees either at different flexion angles or under extending muscle activity.Interpretation. In knees with genu varum and mild medial osteoarthritis we could detect no alterations in patello-femoral kinematics. Since the alterations of patients with genu varum and mild osteoarthritis are restricted to the medial femoro-tibial joint high tibial osteotomy might be successful. [Copyright &y& Elsevier]

Objective. To analyze the influence of knee bracing on the tension of the medial and lateral collateral ligaments in anterior cruciate ligament deficiency.Design. The tension of the collateral ligaments in anterior cruciate ligament deficient knees was measured with and without knee bracing using an in vitro model.Background. Anterior cruciate ligament deficiency increases the tension in both collateral ligaments at the knee joint. Therefore knee braces should reduce that tension increase. However, that effect has never been proven quantitatively.Methods. After anterior cruciate ligament-transection, the forces of the medial (anterior/posterior part) and lateral collateral ligament were measured in ten fresh human cadaver knees at 0°, 20°, 40°, 60°, 80° and 100° of flexion, with and without application of a mono-centric knee brace. To quantify the ligament forces, strain gauges were fixed at the bony origins of the ligaments.Results. Bracing led to a significant decrease of ligament forces (20–100°: P<0.0001) in the anterior part of the medial collateral ligament in all joint positions. In the posterior aspect, this effect was observed only at 40° (P<0.0001) and 80° (P=0.001) of flexion. In the lateral collateral ligament, bracing caused a strain reduction from 60° to 100° of flexion (P<0.0001). Therefore a flexion angle dependent effect of knee bracing on the strain was seen in the posterior aspect of the medial and in the lateral collateral ligament in anterior cruciate ligament deficient knee joints.Conclusions. Application of a mono-centric knee brace leads to a significant position dependent reduction of collateral ligament tension after anterior cruciate ligament-rupture.vsp sp="1">RelevanceThe over-all force reducing effect of applying a mono-centric knee brace may contribute to counteract the increasing knee laxity seen in some conservatively treated anterior cruciate ligament-patients over time. [Copyright &y& Elsevier]

Objective. To establish the range of forces and moments applied to lower limb orthoses during ambulation by routine users.Design. Well-established gait analysis techniques were used to determine the loading at the major joints. It was assumed that the joint moments were transmitted by the orthosis encompassing any particular joint. Two hundred and five assessments of 164 patients were successfully completed by a consortium of four gait laboratories in Europe. The orthosis specification and patient clinical data were also recorded.Background. The design and development of orthoses has occurred largely by evolution rather than by formal engineering methods. In particular, formal design has been hampered by a lack of information on the forces and moments applied during ambulation.Methods. A standard gait analysis procedure was employed to capture the data. In-house biomechanical models were used to calculate the joint loading. Data were normalised with respect to patient weight and leg length.Results. It was found that the median maximum normalised ankle moment transmitted by an ankle foot orthosis was 0.15 and the maximum knee moment was 0.09. The greatest moment transmitted by the hip joint of a hip knee ankle foot orthosis was also 0.09. There was a wide variation in the data due to differences in the impairments of the test subjects.Conclusion. It is possible to estimate the loads transmitted by an orthosis using established gait analysis procedures without the need for load measurement transducers. There is now a need both to collect a larger representative dataset and to perform validation studies with transducers.vsp sp="1">RelevanceThe methodology developed in this project has formed an important step in the development of standards and the incorporation of new materials and technologies into orthotic design. [Copyright &y& Elsevier]

Objective. The objective of this study was to assess the effect of localized leg muscle fatigue on tibial acceleration following impact.Background. Peak tibial accelerations measured just distal to the knee joint during running have been shown to increase with general body fatigue. However, the role that local leg muscle fatigue plays in shock attenuation is not clear.Methods. The unshod, dominant foot of 24 healthy women in two different age groups was impacted into a vertical force plate, using a human pendulum method. Impact velocity and force approximated that found in running. EMG activity of the gastrocnemius and tibialis anterior muscles was monitored during fatiguing isometric exercise to assess fatigue, and quantified at impact as a measure of muscle activation level. A skin-mounted uni-axial accelerometer, was located at the tibial tubercle under pre-load, to measure tibial acceleration at impact.Results. There was a significant decrease in peak tibial acceleration (P=0.008) and acceleration slope (P=0.033) following fatigue. There were no significant main effects or interactions for age group or muscle group for all tibial response variables.Conclusion. The reduction in peak tibial acceleration following fatigue (for the test performed) is contrary to the response documented following whole-body fatigue.vsp sp="1">RelevanceA decrease in tibial acceleration transmission may have a protective effect on the weight-bearing joints proximal to the ankle. Thus, local muscle fatigue may not be detrimental to the joints in those people participating in weight-bearing, ballistic activities or for those with neurological peripheral weakness. [Copyright &y& Elsevier]