The effect of wedge and tibial slope angles on knee contact pressure and kinematics following medial opening-wedge high tibial osteotomy

BackgroundHigh tibial osteotomy is a surgical procedure to treat medial compartment osteoarthritis in varus knees. The reported success rates of the procedure are inconsistent, which may be due to sagittal plane alignment of the osteotomy. The objective of this study was to determine the effect of changing tibial slope, for a range of tibial wedge angles in high tibial osteotomy, on knee joint contact pressure location and kinematics during continuous loaded flexion/extension.MethodsSeven cadaveric knee specimens were cycled through flexion and extension in an Oxford knee-loading rig. The osteotomy on each specimen was adjusted to seven clinically relevant wedge and slope combinations. We used pressure sensors to determine the position of the centre of pressure in each compartment of the tibial plateau and infrared motion capture markers to determine tibiofemoral and patellofemoral kinematics.FindingsIn early knee flexion, a 5° increase in tibial slope shifted the centre of pressure in the medial compartment anteriorly by 4.5 mm (P ≤ 0.001), (from the neutral slope/wedge position). Increasing the tibial slope also resulted in the tibia translating anteriorly (P ≤ 0.001).InterpretationChanges to the tibial slope during high tibial osteotomy for all tested wedge angles shifted the centre of pressure in both the medial and lateral compartments substantially and altered knee kinematics. Tibial slope should be controlled during high tibial osteotomy to prevent unwanted changes in tibial plateau contact loads.     

Relationship between medial plica and medial femoral condyle—a three-dimensional dynamic finite element model

BackgroundMany researches reported that the pathologic medial plica impinges on the facing medial femoral condyle during knee motion and leads to erosive changes of the articular cartilage. The purpose of this study was to construct a simplified three-dimensional dynamic finite element human knee model to evaluate the dynamics behaviour between different types of medial plicae with the facing medial femoral condyles during knee motion.MethodsA three-dimensional dynamic finite element model composed of femur, tibia, covering cartilage and medial plica was developed. The kinematics of this simulation model was verified by previous findings during arthroscopic examination. The validated model was used to investigate and compare the magnitudes of the cyclic pressures acting on the cartilage of the medial femoral condyles by three different types of medial plicae with various Young’s moduli.FindingsAll types of plicae remained in contact with the medial femoral condyles and shifted medially when the knees moved from extension to flexion. The contact pressures were positively correlated with the Young’s moduli of the medial plicae. During the whole range of motion, the maximum contact pressures of all simulation scenarios occurred when the knees moved beyond 50° of flexion. When the Young’s moduli of medial plicae were set greater than 60 MPa, all types of medial plicae would elicit contact pressures greater than 10 MPa on the medial femoral condyles.InterpretationThe close relationship and possible high contact pressure between fibrotic medial plica and medial femoral condyle during knee motion might be a cause of cartilage damage on the medial femoral condyle and warrants further investigation.     

Femorotibial kinematics and load patterns after total knee arthroplasty: An in vitro comparison of posterior-stabilized versus medial-stabilized design

BackgroundFemorotibial kinematics and contact patterns vary greatly with different total knee arthroplasty (TKA) designs. Therefore, guided motion knee systems were developed to restore natural knee kinematics and make them more predictable. The medial stabilized TKA design is supposed to replicate physiological kinematics more than the posterior-stabilized TKA system. We conducted this study to compare a newly developed medial stabilized design with a conventional posterior-stabilized design in terms of femorotibial kinematics and contact patterns in vitro.MethodsTwelve fresh-frozen knee specimens were tested in a weight-bearing knee rig after implantation of a posterior stabilized and medial-stabilized total knee arthroplasty under a loaded squat from 20° to 120° of flexion. Femorotibial joint contact pressures in the medial and lateral compartments were measured by pressure sensitive films and knee kinematics were recorded by an ultrasonic 3-dimensional motion analysis system.FindingsThe medial stabilized design showed a reduction of medial femorotibial translation compared to posterior-stabilized design (mean 3.5 mm compared to 15.7 mm, P < 0.01). In the lateral compartment, both designs showed a posterior translation of the femur with flexion, but less in the medial stabilized design (mean 14.7 mm compared to 19.0 mm, P < 0.01). In the medial femorotibial compartment of medial stabilized design, we observed an enlarged contact area and lower peak pressure, in contrast in the lateral compartment there was a reduced contact area and an increased peak pressure.InterpretationWhile posterior-stabilized design enforces a medio-lateral posterior translation, the medial stabilized arthroplasty system enables a combination of a lateral translation with a medial pivot, which restores the physiological knee kinematics better.     

Reduced step length reduces knee joint contact forces during running following anterior cruciate ligament reconstruction but does not alter inter-limb asymmetry

BackgroundAnterior cruciate ligament reconstruction is associated with early onset knee osteoarthritis. Running is a typical activity following this surgery, but elevated knee joint contact forces are thought to contribute to osteoarthritis degenerative processes. It is therefore clinically relevant to identify interventions to reduce contact forces during running among individuals after anterior cruciate ligament reconstruction. The primary purpose of this study was to evaluate the effect of reducing step length during running on patellofemoral and tibiofemoral joint contact forces among people with a history of anterior cruciate ligament reconstruction. Inter limb knee joint contact force differences during running were also examined.Methods18 individuals at an average of 54.8 months after unilateral anterior cruciate ligament reconstruction ran in 3 step length conditions (preferred, − 5%, − 10%). Bilateral patellofemoral, tibiofemoral, and medial tibiofemoral compartment peak force, loading rate, impulse, and impulse per kilometer were evaluated between step length conditions and limbs using separate 2 factor analyses of variance.FindingsReducing step length 5% decreased patellofemoral, tibiofemoral, and medial tibiofemoral compartment peak force, impulse, and impulse per kilometer bilaterally. A 10% step length reduction further decreased peak forces and force impulses, but did not further reduce force impulses per kilometer. Tibiofemoral joint impulse, impulse per kilometer, and patellofemoral joint loading rate were lower in the previously injured limb compared to the contralateral limb.InterpretationRunning with a shorter step length is a feasible clinical intervention to reduce knee joint contact forces during running among people with a history of anterior cruciate ligament reconstruction.     

Dual-belt treadmill familiarization: Implications for knee function in moderate knee osteoarthritis compared to asymptomatic controls

BackgroundEffect of treadmill familiarization on knee function in osteoarthritis is not clear. Purpose was to determine whether spatiotemporal characteristics, knee joint biomechanics and muscle activation patterns change as individuals with and without medial compartment knee osteoarthritis familiarize to dual-belt treadmill walking over 6 min.Methods20 individuals with knee osteoarthritis and 20 asymptomatic controls walked at a self-selected speed. Spatiotemporal characteristics, sagittal plane joint motions, sagittal and frontal plane moments and knee joint muscle activation patterns, amplitude normalized to maximum isometric contractions were analyzed. Discrete measures were extracted from each biomechanical waveform and principal component analysis was used to determine knee joint muscle activation patterns. Statistical significance was determined using Analysis of Variance models (alpha = 0.05).FindingsSpatiotemporal gait characteristics, knee motion and moment differences were found between groups however no group by time interactions existed and no changes in these variables were found over 6 min of walking. Group differences in muscle activation patterns were found in all muscle activations. Muscle activation amplitude and patterns at minute 5 and 6 were generally lower, less prolonged and more dynamic when compared to minute 1 and 3.InterpretationIndividuals with and without medial compartment knee osteoarthritis familiarized to treadmill walking in a similar manner. Minimal changes to knee biomechanics were found during treadmill familiarization. Five to six minutes of familiarization should be considered for surface electromyography in these populations.     

Patellar taping alters knee kinematics during step descent in individuals with a meniscal injury: An exploratory study

BackgroundMeniscus lesions are common musculoskeletal knee injuries which often lead to pain, limitation and compensations during functional tasks, such as descending stairs. This study investigated the effect of patellar taping with tension and without tension on three-dimensional (3D) kinematics of the knee during a slow step descent task in patients with meniscal lesions.MethodsTen patients diagnosed with a meniscal lesion, confirmed by magnetic resonance imaging, underwent five, step descent movements at slow speed under three different conditions: 1) no taping; 2) tension-free taping; and 3) patellar taping with medial tension. 3D kinematic data were recorded from the injured knee using an eight-camera infrared Vicon motion analysis system. Maximum and minimum angle values and total range of motion (maximum/minimum value) in three movement planes during single-limb stance were compared using a repeated measure ANOVA.FindingsResults showed a significant increase in the maximum and minimum angle value in the sagittal plane (mean differences = 2.4° and 4.2°, respectively) and a decrease in the transverse plane (− 6.3° and − 2.2°, respectively) for the patellar taping condition compared to the no taping condition. A decreased rotational angle range when comparing the patellar taping to the no taping (− 4.1°) and tension-free taping (− 3.1°) conditions was also observed. These changes remained significant when pain was considered as a covariate in the analysis. The tension applied to the patellar tape played a role in controlling the sagittal and transverse plane step-down movement among patients in our study.InterpretationThese results support the use of patellar taping with a medially oriented tension to help to reduce the transversal plane movement of the knee in this population and they bring new light to the taping effect.     

Knee joint anatomy predicts high-risk in vivo dynamic landing knee biomechanics

BackgroundWith knee morphology being a non-modifiable anterior cruciate ligament injury risk factor, its consideration within injury prevention models is limited. Knee anatomy, however, directly influences joint mechanics and the potential for injurious loads. With this in mind, we explored associations between key knee anatomical and three-dimensional biomechanical parameters exhibited during landings. We hypothesized that lateral and medial posterior tibial slopes and their ratio, and tibial plateau width, intercondylar distance and their ratio, were proportional to peak stance anterior knee joint reaction force, knee abduction and internal rotation angles.MethodsTwenty recreationally active females (21.2 (1.7) years) had stance phase three-dimensional dominant limb knee biomechanics recorded during ten single leg land-and-cut tasks. Six anatomical indices were quantified for the same limb via a series of two dimensional (sagittal, transverse and coronal) magnetic resonance images. Linear stepwise regression analyses examined which of these anatomical factors were independently associated with each of the three mean subject-based peak knee biomechanical measures.FindingsLateral tibial slope was significantly (P < 0.0001) correlated with peak anterior knee joint reaction force, explaining 60.9% of the variance. Both tibial plateau width:intercondylar distance (P < 0.0001) and medial tibial slope:lateral tibial slope (P < 0.001) ratios were significantly correlated with peak knee abduction angle, explaining 75.4% of the variance. The medial tibial slope:lateral tibial slope ratio was also significantly (P < 0.001) correlated with peak knee internal rotation angle, explaining 49.2% of the variance.InterpretationKnee anatomy is directly associated with high-risk knee biomechanics exhibited during dynamic landings. Continued understanding of multifactorial contributions to the anterior cruciate ligament injury mechanism should dictate future injury screening and prevention efforts in order to successfully cater to individual joint vulnerabilities.     

Differences in lumbar spine and lower extremity kinematics during a step down functional task in people with and people without low back pain

BackgroundWhen functional movements are impaired in people with low back pain, they may be a contributing factor to chronicity and recurrence. The purpose of the current study was to examine lumbar spine, pelvis, and lower extremity kinematics during a step down functional task between people with and without a history of low back pain.MethodsA 3-dimensional motion capture system was used to analyze kinematics during a step down task. Total excursion of the lumbar spine, pelvis, and lower extremity segments in each plane were calculated from the start to end of the task. Separate analysis of variance tests (α = 0.05) were conducted to determine the effect of independent variables of group and plane on lumbar spine, pelvis, and lower extremity kinematics. An exploratory analysis was conducted to examine kinematic differences among movement-based low back pain subgroups.FindingsSubjects with low back pain displayed less lumbar spine movement than controls across all three planes of movement (P-values = 0.001–0.043). This group difference was most pronounced in the sagittal plane. For the lower extremity, subjects with low back pain displayed more frontal and axial plane knee movement than controls (P-values = 0.001). There were no significant differences in kinematics among movement-based low back pain subgroups.InterpretationPeople with low back pain displayed less lumbar region movement in the sagittal plane and more off-plane knee movements than the control group during a step down task. Clinicians can use this information when assessing lumbar spine and lower extremity movement during functional tasks, with the goal of developing movement-based interventions.     

Distinctions of introarticular force distribution between genesis-II posterior stabilized and cruciate retaining total knee arthroplasty: An intraoperative comparative study of 45 patients

BackgroundAlthough both the posterior stabilized and cruciate retaining total knee arthroplasty have been proven to effectively relieve pain and restore basic functions, the joint gap width during flexion was reported to be different due to the presence or absence of posterior cruciate ligament, which may lead to different intra-articular force distribution. In this study, we investigated the distinctions in intra-articular force distribution between the two types of TKA designs in patients with varus knee osteoarthritis.MethodsForty five patients (50 knees) with varus knee osteoarthritis were prospectively included, with each 25 knees receiving cruciate retaining and posterior stabilized total knee arthroplasty, respectively. With an intra-articular force measurement system, the intra-articular force distribution with knee flexion at 0°, 30°, 45°, 60°, 90°, and 120° were recorded in all patients.FindingsThe total force was similar for posterior stabilized and cruciate retaining knees at all flexion degrees. However, force in the medial compartment accounted for 59.8% –84.0% of total force in posterior stabilized knees, while 27.4% –65.7% in cruciate retaining knees. In cruciate retaining knees, no significant difference was found between forces in the two compartments at 30° flexion (P = 0.444), but force was significantly concentrated in the lateral side during 45° –120° flexion (P = 0.000– 0.028).InterpretationAlthough the entire intra-articular forces were similar between CR and PS knees at different flexion angles, medial part had higher force than lateral part when PS knee was used. The posterior cruciate ligament do a role in soft balance, and make the force more evenly distributed.     

The immediate effects of foot orthoses on hip and knee kinematics and muscle activity during a functional step-up task in individuals with patellofemoral pain

BackgroundEvidence shows that anti-pronating foot orthoses improve patellofemoral pain, but there is a paucity of evidence concerning mechanisms. We investigated the immediate effects of prefabricated foot orthoses on (i) hip and knee kinematics; (ii) electromyography variables of vastus medialis oblique, vastus lateralis and gluteus medius during a functional step-up task, and (iii) associated clinical measures.MethodsHip muscle activity and kinematics were measured during a step-up task with and without an anti-pronating foot orthoses, in people (n = 20, 9 M, 11 F) with patellofemoral pain. Additionally, we measured knee function, foot posture index, isometric hip abductor and knee extensor strength and weight-bearing ankle dorsiflexion.FindingsReduced hip adduction (0.82°, P = 0.01), knee internal rotation (0.46°, P = 0.03), and decreased gluteus medius peak amplitude (0.9 mV, P = 0.043) were observed after ground contact in the ‘with orthoses’ condition. With the addition of orthoses, a more pronated foot posture correlated with earlier vastus medialis oblique onset (r = − 0.51, P = 0.02) whilst higher Kujala scores correlated with earlier gluteus medius onset (r = 0.52, P = 0.02).InterpretationAlthough small in magnitude, reductions in hip adduction, knee internal rotation and gluteus medius amplitude observed immediately following orthoses application during a task that commonly aggravates symptoms, offer a potential mechanism for their effectiveness in patellofemoral pain management. Given the potential for cumulative effects of weight bearing repetitions completed with a foot orthoses, for example during repeated stair ascent, the differences are likely to be clinically meaningful.     

Lower limb kinematics and hip extensors strengths are associated with performance of runners at high risk of injury during the modified Star Excursion Balance Test

BackgroundReduced trunk and lower limb movement and hip and trunk muscles weakness may compromise the athletes’ performance on the modified Star Excursion Balance Test (mSEBT).ObjectiveTo investigate the relationship of trunk and lower limb kinematics and strength with the performance on the mSEBT of runners at high risk of injury.MethodsThirty-nine runners performed the mSEBT with the dominant limb as the support limb. An Inertial System was used to capture the trunk, hip, knee and ankle movement during the mSEBT. A handheld dynamometer was used to measure the strength of trunk extensors and lateral flexors muscles, and hip extensors, lateral rotators and abductors of the support limb. Multiple regressions were used to investigate if trunk and lower limbs kinematics and trunk and hip muscles strength are associated with performance during the mSEBT.ResultsReduced hip flexion and greater knee flexion range of motion (ROM) were associated with anterior reach in the mSEBT (r² = 0.45; p < .001), greater hip flexion ROM was associated with posteromedial reach (r² = 0.15; p = .012) and greater knee flexion ROM was associated with posterolateral reach (r² = 0.23; p < .001). Hip extensor strength was associated with posteromedial (r² = 0.14; p = .017), posterolateral (r² = 0.10; p = .038) and composite reaches (r² = 0.16; p = .009).ConclusionHip and knee kinematics in the sagittal plane explained 15–45% of the runners’ performance on the mSEBT and hip extensor strength explained 10–16% of the mSEBT performance. These findings provide useful information on the contribution of joints kinematics and strength when evaluating dynamic postural control in runners at high risk of injury.     

Reducing anterior tibial translation by applying functional electrical stimulation in dynamic knee extension exercises: Quantitative results acquired via marker tracking

BackgroundPain that accompanies anterior cruciate ligament deficiency during dynamic knee extension exercises is usually caused by excessive anterior tibial translation, which can be restricted if the anterior cruciate ligament was intact.MethodsA functional electrical stimulator is incorporated with a training device to induce hamstring contractions during certain degrees of knee extension to replicate effects similar to those generated by an intact anterior cruciate ligament and to reduce anterior tibial translation. By using a camera that tracks markers placed on bony prominences of the femur and tibia, the anterior tibial translations corresponding to various settings were determined by customized image processing procedures.FindingsIn the electrical stimulation sessions, the knee extensions with electrical stimulation feedback induced significantly (n = 6, P < .05) less anterior tibial translation over the range of 20 to 50° when compared to those using the standard isokinetic shank restraint. Likewise, the knee extensions with an anti-shear device that blocks tibia displacement mechanically also induced significantly (n = 6, P < .05) less anterior tibial translation, but over a different range of knee extension (30 to 70°).InterpretationDespite the fact that both the electrical stimulator and the anti-shear device assisted in reducing anterior tibial translation, the tendency of the curves generated with the functional electrical stimulation was generally more similar to those generated when using the standard isokinetic shank restraint.     

Effects of hip and trunk muscle strengthening on hip function and lower limb kinematics during step-down task

BackgroundStrengthening of the hip and trunk muscles has the potential to change lower limb kinematic patterns, such as excessive hip medial rotation and adduction during weight-bearing tasks. This study aimed to investigate the effect of hip and trunk muscles strengthening on hip muscle performance, hip passive properties, and lower limb kinematics during step-down task in women.MethodsThirty-four young women who demonstrated dynamic knee valgus during step-down were divided into two groups. The experimental group underwent three weekly sessions of strengthening exercises for eight weeks, and the control group continued their usual activities. The following evaluations were carried out: (a) isokinetic maximum concentric and eccentric work of hip lateral rotators, (b) isokinetic hip passive torque of lateral rotation and resting transverse plane position, and (c) three-dimensional kinematics of the lower limb during step-down.FindingsThe strengthening program increased concentric (P < 0.001) and eccentric (P < 0.001) work of hip lateral rotators, and changed hip resting position toward lateral rotation (P < 0.001). The intervention did not significantly change hip passive torque (P = 0.089, main effect). The program reduced hip (P = 0.002), thigh (P = 0.024) and shank (P = 0.005) adduction during step-down task. Hip, thigh and knee kinematics in transverse plane and foot kinematics in frontal plane did not significantly modify after intervention (P ≥ 0.069, main effect).InterpretationHip and trunk strengthening reduced lower limb adduction during step-down. The changes in hip maximum work and resting position may have contributed to the observed kinematic effects.     

Effects of hip joint transverse plane range of motion with a modeled effusion and capsular tear: A cadaveric study

BackgroundMultiple factors contribute to range of motion of the hip joint in the transverse plane: bony anatomy, hip capsule, corresponding ligaments, articular labrum, ligamentum teres, and negative intra-articular pressure. We hypothesized that violation of the negative pressure of the hip and simulation of an effusion would increase range of motion in the transverse plane in a cadaver model.MethodsTen hip specimens were obtained and dissected with the femur and iliac wing mounted in a custom joint-testing rig in neutral position. Specimens were tested at 0 and at 90° of flexion with 1.5 Nm internal and external rotational torque. Three conditions were assessed: (1) intact specimen, (2) an effusion modeled by a 10 ml saline infusion, and (3) a capsular tear.FindingsThe modeled effusion decreased rotational range of motion limits in both 0 and 90° of flexion, with a greater effect on the specimens at 0° flexion in external rotation with 4.1° less external rotation (p = 0.009). A modeled capsular tear increased rotational motion limits in 0° of flexion in both internal and external rotation and in 90° flexion in internal rotation only (p < 0.025).InterpretationAn effusion may decrease the rotation of the hip, and a capsular tear may increase its rotation. This should be considered in hips with traumatic capsular tears or arthroscopic portals.     

How exactly can computer simulation predict the kinematics and contact status after TKA? Examination in individualized models

BackgroundIt is unknown whether a computer simulation with simple models can estimate individual in vivo knee kinematics, although some complex models have predicted the knee kinematics. The purposes of this study are first, to validate the accuracy of the computer simulation with our developed model during a squatting activity in a weight-bearing deep knee bend and then, to analyze the contact area and the contact stress of the tri-condylar implants for individual patients.MethodsWe compared the anteroposterior (AP) contact positions of medial and lateral condyles calculated by the computer simulation program with the positions measured from the fluoroscopic analysis for three implanted knees. Then the contact area and the stress including the third condyle were calculated individually using finite element (FE) analysis.FindingsThe motion patterns were similar in the simulation program and the fluoroscopic surveillance. Our developed model could nearly estimate the individual in vivo knee kinematics. The mean and maximum differences of the AP contact positions were 1.0 mm and 2.5 mm, respectively. At 120° of knee flexion, the contact area at the third condyle was wider than the both condyles. The mean maximum contact stress at the third condyle was lower than the both condyles at 90° and 120° of knee flexion.InterpretationIndividual bone models are required to estimate in vivo knee kinematics in our simple model. The tri-condylar implant seems to be safe for deep flexion activities due to the wide contact area and low contact stress.     

Individuals with chronic ankle instability exhibit altered landing knee kinematics: Potential link with the mechanism of loading for the anterior cruciate ligament

BackgroundAlterations in sagittal plane landing biomechanics in the lower extremity have been observed within the chronic ankle instability (CAI) population. Interestingly, a potential link between the risk of anterior cruciate ligament (ACL) injury and ankle sprain history has been proposed. However, it is not known if the observed biomechanical changes associated with CAI could mimic factors related to the mechanism of ACL injury. We investigated the influence of CAI on anterior tibial shear force (ATSF), lower extremity sagittal plane kinematics, and posterior ground reaction force (GRF) in a jump landing task.MethodsNineteen participants with CAI and 19 healthy control participants performed a vertical stop jump. Peak ATSF was calculated during the first landing of the stop jump, with sagittal-plane kinematics and posterior GRF measured at peak ATSF. Independent t-tests, multiple linear regression, and Pearson bivariate correlation were used for statistical analysis.FindingsParticipants with CAI demonstrated less knee flexion at peak ATSF compared to the controls (P = .026). No group-differences were found for peak ATSF or the other biomechanical variables. Knee flexion was moderately correlated with peak ATSF (r = −0.544, P = .008); however, the contributing factor that most explained the variance in ATSF was posterior GRF (R2 = 0.449; P = .002) in the CAI group.InterpretationOur findings indicate that the CAI group may be exhibiting altered knee function during functional movement. Screening knee movement patterns in individuals with CAI may help develop preventative measures for future joint injury throughout the kinetic chain.     

Large medial proximal tibial angles cause excessively medial tibiofemoral contact forces and abnormal knee kinematics following open-wedge high tibial osteotomy

BackgroundRecurrent varus deformity and poor outcome sometimes occur following open-wedge high tibial osteotomy, but the mechanism remains unclear. The hypothesis of this study was that an excessively large medial proximal tibial angle with lateral joint surface inclination can worsen postoperative knee biomechanics.MethodsA computer-simulated knee model was validated based on a volunteer knee. Osteotomy models with medial proximal tibial angles ranging from 90° to 97° in 1° increments were developed. Varus alignment correction of the distal femur was performed in each model to maintain identical coronal alignment passing through a point 62.5% lateral to the tibial plateau. The peak tibiofemoral contact forces and knee kinematics were compared in each model during walking and squatting.FindingsAll the osteotomy models demonstrated higher peak contact forces on the lateral tibiofemoral joints than on the medial tibiofemoral joints during walking. However, larger medial proximal tibial angles caused excessive increases in medial tibiofemoral contact forces, and the dominant tibiofemoral contact forces shifted to the medial side. Increased medial proximal tibial angles also caused progressive medial collateral ligament tension in knee flexion, but partial medial collateral ligament release effectively reduced medial tibiofemoral contact forces. Models with large medial proximal tibial angles showed nonphysiological roll-forward of the lateral femoral condyle during squatting and no screw-home movement around knee extension.InterpretationExcessively large medial proximal tibial angles following open-wedge high tibial osteotomy resulted in increased medial tibiofemoral contact forces and abnormal knee kinematics during knee flexion due to medial joint line elevation and ligament imbalance.     

Kinematic predictors of star excursion balance test performance in individuals with chronic ankle instability

BackgroundThe Star Excursion Balance Test has identified dynamic postural control deficits in individuals with chronic ankle instability. While kinematic predictors of Star Excursion Balance Test performance have been evaluated in healthy individuals, this has not been thoroughly examined in individuals with chronic ankle instability.MethodsFifteen individuals with chronic ankle instability completed the anterior reach direction of the Star Excursion Balance Test and weight-bearing dorsiflexion assessments. Maximum reach distances on the Star Excursion Balance Test were measured in cm and normalized to leg length. Three-dimensional trunk, hip, knee, and ankle motion of the stance limb were recorded during each anterior reach trial using a motion capture system. Sagittal, frontal, and transverse plane displacement observed from trial initiation to the point of maximum reach was calculated for each joint or segment and averaged for analysis. Pearson product–moment correlations were performed to examine the relationships between kinematic variables, maximal reach, and weight-bearing dorsiflexion. A backward multiple linear regression model was developed with maximal reach as the criterion variable and kinematic variables as predictors.FindingsFrontal plane displacement of the trunk, hip, and ankle and sagittal plane knee displacement were entered into the analysis. The final model (p = 0.004) included all three frontal plane variables and explained 81% of the variance in maximal reach. Maximal reach distance and several kinematic variables were significantly related to weight-bearing dorsiflexion.InterpretationIndividuals with chronic ankle instability who demonstrated greater lateral trunk displacement toward the stance limb, hip adduction, and ankle eversion achieved greater maximal reach.     

Is latero-medial patellar mobility related to the range of motion of the knee joint after total knee arthroplasty?

Diminished range of motion (ROM) of the knee joint after total knee arthroplasty (TKA) is thought to be related to reduced patellar mobility. This has not been confirmed clinically due to a lack of quantitative methods adequate for measuring patellar mobility. We investigated the relationship between patellar mobility by a reported quantitative method and knee joint ROM after TKA. Forty-nine patients [osteoarthritis – OA: 29 knees; rheumatoid arthritis – RA: 20 knees] were examined after TKA. Respective medial and lateral patellar mobility was measured 1 and 6 months postoperatively using a patellofemoral arthrometer (PFA). Knee joint ROM was also measured in each of those 2 sessions. Although the flexion and extension of the knee joints improved significantly from 1 to 6 months after TKA, the medial and lateral patellar displacements (LPDs) failed to improve during that same period. Moreover, only the changes in knee flexion and medial patellar displacement (MPD) between the two sessions were positively correlated (r = 0.31, p < 0.05). However, our findings demonstrated that medial and lateral patellar mobility had no sufficient longitudinal relationship with knee ROM after TKA.     

Increased internal femoral torsion can be regarded as a risk factor for patellar instability — A biomechanical study

BackgroundIncreased internal femoral torsion is regarded as a risk factor for patellar instability. Biomechanical investigations confirming this hypothesis are missing.MethodsEight fresh-frozen cadaver knees were tested on a specially designed simulator. Patellar motion and patellofemoral pressure were evaluated for 0°, 10°, and 20° of increased internal and external femoral torsion with native and with transected medial patellofemoral ligaments used to simulate patellar instability. A regression analysis was used for statistical analysis.FindingsIn native medial patellofemoral ligaments, there were no significant changes in mean or peak pressures for any torsional states (P ≥ 0.07). At 20° increased internal femoral torsion, there was a significant center of force shift towards the lateral side (P = 0.01). Patellar shift was directed laterally at low knee flexion angles up to 30°. Lateral patellar tilt increased significantly at 10° and 20° of increased internal femoral torsion (P ≤ 0.004). In transected medial patellofemoral ligaments, mean pressure (P ≤ 0.005) and peak pressure (P ≤ 0.02) decreased significantly for all torsional states. There was a significantly greater lateral center of force shift with increased internal femoral torsion (P ≤ 0.04). Lateral patellar tilt increased significantly (P < 0.001). Patellar shift did not change significantly with increased internal femoral torsion (P ≥ 0.30).InterpretationIn a native medial patellofemoral ligament, 20° of increased internal femoral torsion can be regarded as a significant risk factor for patellar instability. With an insufficient medial patellofemoral ligament, 10° of increased internal femoral torsion already represents a significant risk factor.