Acute influence of restricted ankle dorsiflexion angle on knee joint mechanics during gait

BackgroundRestrictions in range of ankle dorsiflexion (DF) motion can persist following ankle injuries. Ankle DF is necessary during terminal stance of gait, and its restricted range may affect knee joint kinematics and kinetics. The purpose of this study was to investigate the acute influence of varied levels of restricted ankle DF on knee joint sagittal and frontal plane kinematics and kinetics during gait.MethodsThirty healthy volunteers walked with a custom-designed ankle brace that restricted ankle DF. Kinematics and kinetics were collected using a 7-camera motion analysis system and two force plates. Ankle dorsiflexion was restricted in 10-degree increments, allowing for four conditions: Free, light (LR), moderate (MR) and severe restriction (SR). Knee angles and moments were measured during terminal stance.ResultsReal peak ankle DF for Free, LR, MR, and SR were 13.7 ± 4.8°, 11.6 ± 5.0°, 7.5 ± 5.3°, and 4.2 ± 7.2°, respectively. Peak knee extension angles under the same conditions were − 6.7 ± 6.7°, − 5.4 ± 6.4°, − 2.5 ± 7.5°, and 0.6 ± 7.8°, respectively, and the peak knee varus moment was 0.48 ± 0.17 Nm/kg, 0.47 ± 0.17 Nm/kg, 0.53 ± 0.20 Nm/kg, and 0.57 ± 0.20 Nm/kg. The knee varus moment was significantly increased from MR condition with an 8-degree restriction in ankle DF.ConclusionKnee joint kinematics and kinetics in the sagittal and frontal planes were affected by reduced ankle DF during terminal stance of gait. Differences were observed with restriction in ankle DF range of approximately 8°.Level of evidencelevel III     

Factors contributing to inherent varus alignment of lower limb in normal Asian adults: Role of tibial plateau inclination

PurposeThis prospective study aimed to evaluate radiographically, mechanical or hip–knee–ankle (HKA) axis in healthy, asymptomatic, Asian (Indian and Korean) adults between 20 and 40 years of age to determine the incidence of inherent varus (mechanical limb alignment of > 3° varus) and the factors influencing it.MethodsThree hundred and eighty-eight lower limbs were evaluated using full length, standing hip-to-ankle radiographs in 198 healthy, asymptomatic, Asian (Indian and Korean) adults between 20 and 40 years of age to assess the hip–knee–ankle (HKA) angle, medial proximal tibial angle (MPTA), femoral bowing and femoral neck–shaft angle to determine the incidence of inherent varus (mechanical limb alignment of > 3° varus) and the factors influencing it.ResultsOverall, the mean HKA angle was 177.6° ± 2.6° with 34.5% of limbs in inherent varus (mean HKA angle 174.9° ± 1.8°). The incidence of inherent varus was significantly higher (p = 0.01) in males (40%) compared to females (28%) but similar among Indian (34%) and Korean subjects (35%). The hip–knee–ankle (HKA) angle showed significant positive correlation (r = 0.82, p < 0.001) with only the medial proximal tibial angle (MPTA).ConclusionsInherent varus alignment of the lower limb is fairly common among asymptomatic, Asian adults. These results raise several pertinent questions regarding the role of inherent varus in the aetiopathogenesis of knee osteoarthritis and in lower limb realignment procedures.     

Effects of knee bracing on postural control after anterior cruciate ligament rupture

Study designRandomized clinical trial.ObjectivesTo investigate the effects of functional knee braces on postural control in patients with anterior cruciate ligament (ACL) rupture.BackgroundACL rupture leads to both mechanical knee instability and deficits in proprioception. Although elastic knee braces do not increase mechanical stability, patients report improved stability when wearing a brace. Elastic braces were found to reduce the loss of proprioception. It is, however, still unclear whether they also improve postural control, which involves the processing of proprioceptive input at a higher level.MethodsWe studied 58 patients with isolated unilateral ACL rupture using computerized dynamic posturography and compared overall stability index (OSI) scores for injured and uninjured legs with and without a knee brace. In addition, patients were classified as copers and non-copers depending on knee function.ResultsWithin subjects, OSI scores were 3.0 ± 1.1° for uninjured legs when unbraced, 2.8 ± 1.3° for uninjured legs when braced (p = 0.17), 3.7 ± 1.5° for unbraced injured legs, and 2.9 ± 1.3° for braced injured legs (p < 0.001). For the injured legs of copers and non-copers, OSI scores were 3.4° ± 1.2° for copers and 4.0° ± 1.6° for non-copers in the unbraced condition (p = 0.11) and 2.7 ± 1.0° for copers and 3.1 ± 1.4° for non-copers in the braced condition (p = 0.26).ConclusionElastic knee braces increase postural stability by approximately 22% in patients with ACL rupture. There was no difference in postural stability between uninjured and injured legs in the braced condition. One possible explanation is that bracing improves both proprioception and postural control.Level of evidenceControlled clinical trial, level 2a.     

3D in vivo femoro-tibial kinematics of tri-condylar total knee arthroplasty during kneeling activities

BackgroundKneeling position can serve as an important posture, providing stability and balance from a standing position to sitting on the floor or vice-versa. The purpose of the current study was to determine the kinematics during kneeling activities after subjects were implanted with a tri-condylar total knee arthroplasty.Materials and methodsKinematics was evaluated in 54 knees using fluoroscopy and a three-dimensional model fitting approach.ResultsThe average knee flexion at before contact status, at complete contact and at maximum flexion was 98.1 ± 9.0°, 107.2 ± 6.7°, and 139.6 ± 12.3°, respectively. On average, there was no gross anterior displacement from before contact status to complete contact. Only slight posterior rollback motion of both condyles from complete contact to maximum flexion was observed. Three of 39 (7.7%) knees experienced anterior movement of both condyles more than 2 mm from before contact status to complete contact. Reverse rotation pattern from before contact status to complete contact and then normal rotation pattern from complete contact to maximum flexion were observed. Condylar lift-off greater than 1.0 mm was observed in 45 knees (83.3%).ConclusionThe presence of the ball-and-socket joint articulation provides sufficient antero-posterior stability in these designs to enable the patients to kneel safely without the incidence of any dislocation.Clinical relevanceThis study suggests a safe implant design for kneeling.     

The in vivo relationship between anterior neutral tibial position and loss of knee extension after transtibial ACL reconstruction

BackgroundRestoration of anterior tibial stability while avoiding knee extension deficit are a common goal of anterior cruciate ligament (ACL) reconstruction. However, achieving this goal can be challenging. The purpose of this study was to determine whether side-to-side differences in anterior tibial neutral position and laxity are correlated with knee extension deficit in subjects 2 years after ACL reconstruction.MethodsIn the reconstructed and contralateral knees of 29 subjects with transtibial reconstruction, anterior tibiofemoral neutral position was measured with MRI and three-dimensional modeling techniques; terminal knee extension at heel strike of walking and during a seated knee extension were measured via gait analysis; and anterior laxity was measured using the KT-1000.ResultsKnees that approached normal anterior stability and anterior tibial position had increased extension deficit relative to the contralateral knee. On average the reconstructed knee had significantly less (2.1 ± 4.4°) extension during active extension and during heel strike of walking (3.0 ± 4.3º), with increased anterior neutral tibial position (2.5 ± 1.7 mm) and anterior laxity (1.8 ± 1.0 mm). There was a significant correlation between side-to-side difference in anterior neutral tibial position with both measures of knee extension (walking, r = − 0.711, p < 0.001); active knee extension, r = − 0.544, p = 0.002).ConclusionThe results indicate a relationship between the loss of active knee extension and a change in anterior neutral tibial position following non-anatomic transtibial ACL reconstruction. Given the increasing evidence of a link between altered kinematics and premature osteoarthritis, these findings provide important information to improve our understanding of in vivo knee function after ACL reconstruction.     

Estimation of frontal alignment error of the extramedullary tibial guide on the bi-malleolar technique: A simulation study with magnetic resonance imaging

PurposeThe bi-malleolar technique for the extramedullary tibial guide is a representative method for determining the ankle center in total knee arthroplasty (TKA). The purpose of this study is to estimate three-dimensionally the lateral errors (difference between the real ankle center and the bi-malleolar center) and the varus angular errors of this technique under the condition that the malleolar prominences were correctly identified.MethodsMagnetic resonance images of 51 lower limbs from 51 healthy volunteers were analyzed. The lateral errors were measured, including or excluding the subcutaneous thickness, along the line perpendicular to the transmalleolar axis (TMA) or along the tibial anteroposterior (AP) axis. Furthermore, we evaluated the effects of the tibial torsion and the difference between the subcutaneous thicknesses on the malleoli on the lateral error.ResultsWhen including the skin, the mean lateral errors of the ankle center observed along the line perpendicular to the TMA and along the tibial AP axis were 3.7 ± 1.4 mm and 1.2 ± 1.5 mm, respectively. The mean angular errors were 0.6 ± 0.2° and 0.2 ± 0.3°, respectively. A significant correlation between the tibial torsion and the lateral error was noted when observed along the tibial AP axis. The difference between the subcutaneous thicknesses on the malleoli affected the lateral error.ConclusionThe errors were small enough to determine the mechanical axis of the tibia if the tibial guide could catch the bi-malleolar prominences of the ankle accurately and align along the tibial AP axis.     

Partial harvesting technique in anterior cruciate ligament reconstruction with autologous semitendinosus tendon to prevent a postoperative decrease in deep knee flexion torque

BackgroundA significant decrease in deep knee flexion torque has been reported after harvesting the semitendinosus tendon for anterior cruciate ligament (ACL) reconstruction. Thus, we have developed a partial harvesting technique that leaves part of the width of the insertion of semitendinosus tendon by splitting it. Our hypothesis was that the partial harvesting technique would reduce postoperative functional deficits in deep knee flexion by achieving regeneration of harvested tendon without shortening.MethodsA total of 36 patients who underwent ACL reconstruction with an autologous semitendinosus tendon by means of either the conventional whole harvesting technique (whole-ST group, n = 16) or the partial harvesting technique (partial-ST group, n = 20) were included in this study. Clinical outcome, semitendinosus muscle length, and deep knee flexion torque were assessed 2 years after surgery.ResultsNo significant group differences were found in terms of range of motion, Lysholm score, or anterior knee laxity. Shortening of the semitendinosus muscle was significantly less in the partial-ST group (mean 8 mm) than in the whole-ST group (mean 36 mm; P < 0.001). The side-to-side ratio of isometric knee flexion torque in the prone position with 90° of knee flexion was statistically different between the partial-ST (87.0 ± 20.4%) and whole-ST (55.3 ± 13.9%; P < 0.001) groups.ConclusionsThe present partial harvesting technique not only prevented shortening of the semitendinosus muscle, but also reduced the deficit in the maximum knee flexion angle in the standing position and a decrease in the deep knee flexion torque in the prone position with the partial harvesting technique compared to the nonoperated side with good clinical outcomes.Level of evidenceCase–control study, Level III.     

The immediate effects of open kinetic chain knee extensor exercise at different loads on knee anterior laxity in the uninjured

BackgroundThere is evidence that anterior laxity may be affected by knee extensor open kinetic chain (OKC) exercise with responses being load-dependent. The aim of this study is to evaluate the immediate and short-term changes in passive knee anterior laxity following a single session of OKC knee extensor exercise.MethodsThirty two participants were randomly allocated to perform either high load (20 sets of 2 repetitions) or low load (2 sets of 20 repetitions) knee extensor OKC exercise with knee anterior laxity assessed before exercise, immediately after exercise and 45 and 90 min after exercise with a KT-2000 arthrometer using a 133 N force.ResultsA significant effect of time was observed on knee laxity (p < 0.001). However, a significant interaction of time and group was not found (p = 0.54) and so the results presented here are for the combined (low and high load) group mean ± standard deviation knee anterior laxity (mm) in the exercised leg: 7.2 ± 2.2 (baseline), 8.2 ± 2.3 (immediate post exercise, 14% change from baseline), 8.1 ± 2.3 (45 min post exercise, 12% change from baseline), and 7.7 ± 2.2/0.29 (6.9) (90 min post exercise, 7% change from baseline).ConclusionOKC knee extensor exercise at high loads and low loads causes an immediate increase in knee laxity that begins to decrease within 90 min.     

Pre-operative analysis of lower limb coronal alignment — A comparison of supine MRI versus standing full-length alignment radiographs

BackgroundIn this study we compare the results of pre-operative standing full-length alignment (SFLA) radiographs with supine MRI assessment of the lower limb alignment prior to MRI based patient specific total knee arthroplasty (TKA).MethodsImaging was performed in 45 knees (45 patients). Assessment of SFLA radiographs was performed by three independent assessors. Inter-observer correlation was high and so the mean values were calculated. This data was then compared to MRI alignment data used to create the patient specific cutting jigs.ResultsThe range of alignment on SFLA radiographs ranged from + 25° to − 13° versus + 20° to − 11° with MRI. The mean difference between techniques was 2° (range 0–8°, SD ± 3°). Supine MRI under-estimated the degree of deformity in 31/45 (69%) cases. In 25/45 (56%) cases the supine MRI result was within ± 2° of the value on SFLA radiographs, 31/45 (69%) were within ± 3° and 38/45 (84%) within ± 5°. There was no correlation between the degree of varus/valgus deformity and the magnitude of the difference between imaging modalities (Spearman's r² = 0.02, p = 0.41).ConclusionsThe findings from this study would indicate that supine MRI underestimates the degree of deformity at the knee joint, a conclusion which may be important for pre-operative planning or follow-up of corrective osteotomy or TKA.     

Efficacy of passive extension mobilization in addition to exercise in the osteoarthritic knee: An observational parallel-group study

Study designPretest post-test observational parallel-group design.ObjectivesTo evaluate the efficacy of passive knee extension mobilization in addition to exercise therapy on extension range of motion (ROM) in patients with osteoarthritis (OA) of the knee. Secondary objectives were to determine changes in pain and functional abilities.BackgroundPatients with knee OA complain of pain, limited range of motion, and impaired activities. Efficacy of mobilization as a treatment option next to exercises has not been studied rigorously.Methods and measuresThirty-four participants with persistent knee pain, a positive radiography for knee OA, and a passive extension deficit were included. Seventeen participants (mean age ± SD, 59.8 ± 6.1 years) were treated with an exercise protocol and were additionally given manual mobilizations to improve passive extension ROM. The other group (mean age ± SD, 61.5 ± 7.3 years) with equal characteristics was treated with an identical exercise therapy protocol only. Prior to participation, detailed ROM measurements were recorded next to muscle function tests, pain (VAS), six-minute walking tests (6MWTs), a condition-specific questionnaire, and the patient-specific function scale (PSFS). Participants in both groups completed 16 treatment sessions each.ResultsPassive mobilization significantly improved extension ROM in the intervention group (5.2 versus 8.6°, p = .017). The manually mobilized group also had better physical capacities as assessed by 6MWT, less pain, and a lower PSFS score.ConclusionA combined protocol including exercise therapy and passive mobilization was beneficial for patients with OA of the knee complaining of pain, decreased extension ROM and decreased limited abilities.Level of evidenceTherapy, 2b.     

Knee joint laxity and passive stiffness in meniscectomized patients compared with healthy controls

BackgroundPassive mechanical behavior of the knee in the frontal plane, measured as angular laxity and mechanical stiffness, may play an important role in the pathogenesis of knee osteoarthritis (OA). Little is known about knee laxity and stiffness prior to knee OA onset. We investigated knee joint angular laxity and passive stiffness in meniscectomized patients at high risk of knee OA compared with healthy controls.MethodsSixty patients meniscectomized for a medial meniscal tear (52 men, 41.4 ± 5.5 years, 175.3 ± 7.9 cm, 83.6 ± 12.8 kg, mean ± SD) and 21 healthy controls (18 men, 42.0 ± 6.7 years, 176.8 ± 5.7 cm, 77.8 ± 13.4 kg) had their knee joint angular laxity and passive stiffness assessed twice ~ 2.3 years apart. Linear regression models including age, sex, height and body mass as covariates in the adjusted model were used to assess differences between groups.ResultsGreater knee joint varus (− 10.1 vs. − 7.3°, p < 0.001), valgus (7.1 vs. 5.6°, p = 0.001) and total (17.2 vs. 12.9°, p < 0.001) angular laxity together with reduced midrange passive stiffness (1.71 vs. 2.36 Nm/°, p < 0.001) were observed in patients vs. healthy controls. No differences were observed in change in stiffness over time between patients and controls, however a tendency towards increased laxity in patients was seen.ConclusionsMeniscectomized patients showed increased knee joint angular laxity and reduced passive stiffness ~ 3 months post surgery compared with controls. In addition, the results indicated that knee joint laxity may increase over time in meniscectomized patients.     

Does flexion of the femoral implant in total knee arthroplasty increase knee flexion: A randomised controlled trial

IntroductionProsthetic and operative modifications in total knee arthroplasty (TKA) have been proposed to maximise post-operative knee flexion as it is essential in routine functional activities.MethodsWe performed a double blind randomised controlled trial to compare clinical outcomes of primary cruciate-retaining TKA for osteoarthritis with the femoral component implanted in either 4° flexion in the sagittal plane (F) or in a neutral position (C). The primary outcome of knee flexion and secondary outcomes knee extension, quadriceps strength, WOMAC, SF-12v2, timed stand test, stair climb test and satisfaction were assessed at 1 year. Knee flexion and extension were also assessed intra-operatively. Implant flexion was measured from true lateral radiographs.ResultsThirty-nine participants (40 knees) were recruited, 20 knees per group. Three subjects from the control group and two from the flexed group were lost to 1 year follow-up but numbers were sufficient to satisfy the sample size calculation. Significant differences were found between the groups in knee flexion (F: 113.6 ± 8.8° pre-operative, 122.4 ± 6.0° intra-operative, 110.2 ± 7.5° 1 year, C: 117.4 ± 11.7°, 117.4 ± 7.6°, 103.5 ± 10.7°. p = 0.031) and mental component score of the SF12-v2 (F 53.3 ± 13.2, C 61.1 ± 7.3, p = 0.009) but there were no significant differences in other outcomes and patients were equally satisfied.ConclusionFlexing the femoral implant in this cruciate retaining TKA system provided a significant difference in knee flexion compared to a neutral position. The improvement appears to occur predominantly at surgery and was not associated with a clinical or functional benefit at 1 year. (ACTRN12606000325505). Level of evidence: Level 1; randomised controlled trial.     

Dynamic foot function changes following total knee replacement surgery

BackgroundIndividuals with knee osteoarthritis (OA) have flatter/more pronated feet than those without OA, but it is unclear whether altered foot posture and function are a cause or consequence of knee OA. The purpose of this study was to examine whether changes in foot posture and function occur after realignment of the knee following total knee replacement (TKR).Materials and methodsNineteen patients with predominantly medial compartment knee OA were tested prior to and 12 months after TKR. The Foot Posture Index (FPI) and Arch Index (AI) were measured as well as motion of the tibia, rearfoot and forefoot using a 3D motion analysis system incorporating a multisegment foot model.ResultsThere were no significant changes in FPI or AI following TKR, however gait analysis revealed significant increases in tibial external rotation (? 18.7 ± 7.0° vs ? 22.5 ± 8.7°, p = 0.002), tibial transverse plane range of motion (? 9.1 ± 4.6° vs ? 11.4 ± 6.1°, p = 0.0028) and rearfoot range of motion in the frontal plane (8.6 ± 2.6° vs 10.4 ± 2.7°, p = 0.002), and a decrease in rearfoot transverse plane range of motion (8.7 ± 5.3° vs 5.9 ± 4.1°, p = 0.038) following the procedure.ConclusionsTKR produces no change in static foot posture, but results in significant changes in rearfoot kinematics during gait. These findings suggest that rearfoot motion compensates for changes in the alignment of the knee, highlighting the ability of the foot to accommodate for proximal skeletal malalignment.     

Comparative postural stability in patients with lateral meniscus versus medial meniscus tears

Background

Types of mechanoreceptors may differ between the medial and lateral menisci, suggesting that postural stability may differ between patients with medial and lateral meniscus tears. However, to date, postural stability has not been compared in patients with medial and lateral meniscus tears. This study used stabilometry to compare postural stability in patients with medial and lateral meniscus tears.

In vivo kinematic analysis of posterior-stabilized total knee arthroplasty for the valgus knee operated by the gap-balancing technique

BackgroundMost in vivo kinematic studies of total knee arthroplasty (TKA) report on the varus knee. The objective of the present study was to evaluate in vivo kinematics of a posterior-stabilized fixed-bearing TKA operated on a valgus knee during knee bending in weight-bearing (WB) and non-weight-bearing (NWB).MethodsA total of sixteen valgus knees in 12 cases that underwent TKA with Scorpio NRG PS knee prosthesis and that were operated on using the gap balancing technique were evaluated. We evaluated the in vivo kinematics of the knee using fluoroscopy and femorotibial translation relative to the tibial tray using a 2-dimensional to 3-dimensional registration technique.ResultsThe average flexion angle was 111.3° ± 7.5° in WB and 114.9° ± 8.4° in NWB. The femoral component demonstrated a mean external rotation of 5.9° ± 5.8° in WB and 7.4° ± 5.2° in NWB. In WB and NWB, the femoral component showed a medial pivot pattern from 0° to midflexion and a bicondylar rollback pattern from midflexion to full flexion. The medial condyle moved similarly in the WB condition and in the NWB condition. The lateral condyle moved posteriorly at a slightly earlier angle during the WB condition than during the NWB condition.ConclusionsWe conclude that similar kinematics after TKA can be obtained with the gap balancing technique for the preoperative valgus deformity when compared to the kinematics of a normal knee, even though the magnitude of external rotation was small. Level of evidence: IV.     

Osteochondral autologous graft transfer system in the knee; mid-term results

IntroductionThe purpose of this study was to determine the effectiveness of the osteochondral autologous graft transfer system in the treatment of chondral and osteochondral lesions of the knee.MethodsSixty five knees of sixty four patients who underwent autologous osteochondral graft transfer were evaluated with clinical scores and imaging techniques.ResultsThe average follow up was 82.2 (51–145) months. The patients were evaluated according to Tegner activity scale, Lysholm scale and IKDC subjective knee evaluation form. According to all these scales, all patients showed increasing results in various rates in the last follow up. Accordingly, mean increases of 59.2 ± 15.9 points, 3.6 ± 1.4 points, and 42.6 ± 11.5 points were achieved in Lysholm knee scores, Tegner activity scale scores, and IKDC subjective knee evaluation form, respectively (p ≤ .0001). Moreover, we found no significant correlation between functional results and age, functional results and localization of osteochondral defect, functional results and additional knee pathologies.ConclusionIn our study we achieved significant increases in all the scales in the last follow up. Furthermore, we found no significant correlation between functional results and age, defect localization and additional knee pathologies.     

Anterior tibiofemoral intersegmental forces during landing are predicted by passive restraint measures in women

BackgroundPassive restraint capabilities may influence sagittal plane knee joint mechanics during activity. This study aimed to determine if measures associated with passive restraint of anterior translation of the tibia are predictive of peak anterior knee shear force during landing.MethodsPassive restraint measures were assessed via joint arthrometry and during 40% body weight simulated weight acceptance using recreationally active students (73 F, 42 M; 21.8 ± 2.9 yr, 1.69 ± 0.1 m, 68.9 ± 14.1 kg). Anterior knee laxity (mm) at 133 N and initial (0–20 N) and terminal (100–130 N) anterior stiffnesses (N/mm) were calculated from arthrometer data. Peak anterior tibial acceleration (m?s^?2) relative to the femur was assessed via electromagnetic position sensors during 40% body weight acceptance trials. Peak knee shear force was assessed during double-leg drop jumps.ResultsSex specific linear stepwise regressions revealed that in females, increasing peak tibial acceleration (5.1 ± 1.8 m·s^? 2) (R²? = 7.3%, P? = 0.021), increasing initial anterior stiffness (31.0 ± 14.0 N/mm) (R²? = 5.9%, P? = 0.032), and decreasing terminal anterior stiffness (43.4 ± 17.4 N/mm) (R²? = 4.9%, P? = 0.046) collectively predicted greater peak knee shear forces (66.6 ± 12.03% BW) (multiple R² = 18.1%). No male regressions were significant.ConclusionsSagittal laxity measures are associated with anterior knee shear loads during landing in females. Greater tibial acceleration during early axial load along with greater initial and lesser terminal anterior stiffnesses predicted increasing anterior knee shear forces. Future work should investigate the combined contribution of passive and active restraints to high-risk ACL biomechanics.     

Identification of ankle plantar-flexors dynamics in response to electrical stimulation

Modeling the muscle response to functional electrical stimulation (FES) is an essential step in the design of closed-loop controlled neuroprostheses. This study was aimed at identifying the dynamic response of ankle plantar-flexors to FES during quiet standing. Thirteen healthy subjects stood in a standing frame that locked the knee and hip joints. The ankle plantar-flexors were stimulated bilaterally through surface electrodes and the generated ankle torque was measured. The pulse amplitude was sinusoidally modulated at five different frequencies. The pulse amplitude and the measured ankle torque fitted by a sine function were considered as input and output, respectively. First-order and critically-damped second-order linear models were fitted to the experimental data. Both models fitted similarly well to the experimental data. The coefficient of variation of the time constant among subjects was smaller in the case of the second-order model compared to the first-order model (18.1% vs. 79.9%, p < 0.001). We concluded that the critically-damped second-order model more consistently described the relationship between isometric ankle torque and surface FES pulse amplitude, which was applied to the ankle plantar-flexors during quiet standing.     

Gender analysis of the anterior femoral condyle geometry of the knee

BackgroundNo study has used 3-D anatomic knee models to investigate the gender differences in anterior femoral condyles. Therefore, this study aims to determine the morphologic differences between genders in anterior femoral condyles of the knees using 3-D anatomic knee models.MethodsNinety-six male and sixty-five female 3D anatomic knee models were used to measure lateral and medial anterior condyle heights, anterior trochlear groove heights, and anterior condyle width, which were normalized by the anterior–posterior and medial–lateral dimensions of the knee, respectively. The shape of anterior condyle groove was also analyzed.ResultsThe mean lateral anterior condyle height, medial anterior condyle height and anterior condyle width of females were 6.6 ± 1.8 mm, 2.0 ± 2.3 mm, and 44.7 ± 4.2 mm, respectively. These data were significantly smaller (p < 0.05) than those of males (7.7 ± 1.8 mm, 2.9 ± 2.0 mm and 50.0 ± 3.4 mm). However, after normalizing by the femur size, the aspect ratios had no gender differences. Both the ranges of lateral and medial condyle of females were significantly smaller than those of males, and the geometry curve of anterior condyle was different between genders.ConclusionAlthough the gender differences in anterior femoral condyle sizes no longer existed after normalization with the femur size, the shape and the peak position of anterior condyle groove still have gender differences. The data may have important implications on the current debate of gender-specific TKAs.Clinical relevanceThis study provides a better understanding of gender differences in anterior femoral condyle geometry.     

Leg general muscle moment and power patterns in able-bodied subjects during recumbent cycle ergometry with ankle immobilization

Rehabilitation of persons with pareses commonly uses recumbent pedalling and a rigid pedal boot that fixes the ankle joint from moving. This study was performed to provide general muscle moments (GMM) and joint power data from able-bodied subjects performing recumbent cycling at two workloads.Twenty-six able-bodied subjects pedalled a stationary recumbent tricycle at 60 rpm during passive cycling and at two workloads (low 15 W and high 40 W per leg) while leg kinematics and pedal forces were recorded. GMM and power were calculated using inverse dynamic equations.During the high workload, the hip and knee muscles produced extensor/flexor moments throughout the extensions/flexions phases of the joints. For low workload, a prolonged (crank angle 0–258°) hip extension moment and a shortened range (350–150°) of knee extension moment were observed compared to the corresponding extension phases of each joint. The knee and hip joints generated approximately equal power. At the high workload the hip and knee extensors generated increased power in the propulsion phase.For the first time, this study provides GMM and power patterns for able-bodied subjects performing recumbent cycling with an immobilized ankle. The patterns showed greater similarities to upright cycling with a free ankle, than previously supposed.