Three-dimensional volume and shape of the infrapatellar fat pad during quasi-static knee extension from 30° to 0°: comparisons of patients with osteoarthritic knees and young, healthy individuals.

[Purpose] Previous studies suggest that the infrapatellar-fat-pad is affected by aging or knee osteoarthritis, and that the infrapatellar-fat-pad in knee osteoarthritis cases may be associated with limited mobility during knee movement. This study aimed to determine changes in the shape and volume of the infrapatellar-fat-pad between 30° and 0° of knee extension in knee osteoarthritis cases and in young, healthy individuals, and to characterize differences in patellar mobility, patellar tendon mobility, and length between the groups. [Participants and Methods] We created 3D models of the infrapatellar-fat-pad, the patellar tendon, and bones using sagittal MRI with the knee at 30° and 0°. The following four parameters were determined: (1) movement of the infrapatellar-fat-pad; (2) infrapatellar-fat-pad volume; (3) angle and surface length of the patellar tendon; and (4) patellar movement. [Results] Compared with the knee osteoarthritis group, the healthy group showed (1) reduced anterior movement of the infrapatellar-fat-pad; (2) smaller volume changes only in the infero-postero-lateral portion; and (3) no changes in the angle of the patellar tendon to the tibial plateau between 30° to 0°. [Conclusion] In conclusion, between 30° and 0°, (1) the infrapatellar-fat-pad in patients with knee osteoarthritis exhibited less anterior movement, and (2) the patellar tendon angle was diminished in patients with knee osteoarthritis compared with those of young-healthy knees.

Volume and mobility of the infrapatellar fat pad during quasi-static knee extension after manual therapy in patients with knee osteoarthritis: a randomized control trial study.

[Purpose] This study aimed to determine whether the volume and mobility of the infrapatellar fat pad (IPFP) change as a result of manual release or stretching during quasi-static knee extension in patients with knee osteoarthritis (KOA). [Participants and Methods] Fourteen patients with KOA were allocated to one of two groups: the manual release (R) and stretching (S, control) groups. They all underwent 12 treatment sessions in in a space of four weeks. We created 3D models of the IPFP, tibia, patella, and patellar tendon using sagittal MRI scans with the knee at 30° or 0°. We compared the differences in (1) the distance of anterior movement of the anterior surface of the IPFP (IPFP movement) and (2) the volume of the IPFP, between the R and S groups, using the 3D models. [Results] Neither group showed any anterior movement of the IPFP during quasi-static knee extension at pre-intervention; however, both groups showed significant anterior movement of the IPFP at post-intervention. IPFP movement decreased in the S group, meanwhile it increased in the R group at post-intervention. [Conclusion] Anterior movement of the IPFP was more increased by manual release than by stretching since the latter may have shortened the distance between the patella and tibial tuberosity at 0° and 30° flexion.

Knee kinematics of severe medial knee osteoarthritis showed tibial posterior translation and external rotation: a cross-sectional study.

BACKGROUND: Knee osteoarthritis (OA) gradually reduces knee function and limits activities of daily living with age. However, the progression of abnormal kinematics of the knee in knee OA is unclear. AIMS: This study aimed to clarify the relationship between stage of knee OA and abnormal knee kinematics and to identify a strategy for prevention of knee OA. METHODS: A total of 112 knees of 99 patients (45 men/54 women; 55.9 ± 18.2 years), comprising 28 (27/1) in Kellgren-Lawrence grade 0, 18 (8/10) in grade 1, 27 (2/25) in grade 2, 28 (6/22) in grade 3, and 11 (3/8) in grade 4, were enrolled in this cross-sectional study. In vivo knee kinematics was obtained using a three-dimensional-to-two-dimensional registration technique utilizing CT-based bone models and lateral fluoroscopy during knee extension-flexion in an upright sitting position and squatting. RESULTS: The external rotation angle of the tibia relative to the femur was greater in grade 3/4 knees than in grade 0/1 knees and tibial posterior translation was greater in grade 3/4 knees than in grade 0-2 knees. DISCUSSION: Age-related changes in muscle activity and joint instability are considered to be the cause of these abnormal kinematics. CONCLUSIONS: As the stage of knee OA progresses, there was a tendency toward increasing tibial external rotation and tibial posterior translation during knee extension-flexion in sitting position and squatting. Prevention of the progress of the abnormal knee kinematics may prevent the progression of the knee OA.

The association between sacral morphology and sacroiliac joint conformity demonstrated on CT-based bone models.

INTRODUCTION: Knowledge of the stress distribution on structures around the sacroiliac joint (SIJ) is required to treat or prevent SIJ disorders. The purpose of this study was to reveal the association between sacral morphology and SIJ conformity. MATERIALS AND METHODS: This cross-sectional study included 11 adult patients with unilateral SIJ pain who underwent computed tomography (CT) imaging of the pelvis. Bony coordinate systems for the sacrum and innominates were embedded using anatomical landmarks. Local coordinate systems for the auricular surfaces of the sacrum and innominate were also defined. Conformity of the SIJ was quantified by the offset of the coordinate systems between the auricular surfaces of the sacrum and innominate. Repeated measure ANOVA and multiple regression analysis were used for statistical analyses. RESULTS: There were large variations across subjects in sacral morphology and SIJ conformity. There were no differences in any of the six degrees-of-freedom positions or orientations of the bilateral sacral and innominate auricular surfaces between the symptomatic and asymptomatic sides. The SIJ downward rotation on the asymptomatic and symptomatic sides were 0.0 [-1.0, 1.1]° and 2.1 [1.2, 3.0]°, respectively. Smaller downward rotation of the sacral auricular surface based on the sacral bony coordinate system had significant association with the greater SIJ downward rotation (standard partial regression coefficient: -.44, p = .043). CONCLUSIONS: The results indicate that the morphology of the sacrum is associated with poor SIJ conformity and that separation of the superior portion of the SIJ can be a risk factor for SIJ pain.

Transcultural Reliability and Validity of the Japanese-Language Version of the Pelvic Girdle Questionnaire.

OBJECTIVE: The purpose of this study was to validate a Japanese version of the Pelvic Girdle Questionnaire (PGQ) and to confirm that the Japanese version of the PGQ (PGQ-J) was as valid as the original version. METHODS: This study involves 2 phases: (1) a cross-cultural adaptation study and (2) a cross-sectional study. The English PGQ was translated referring to the cross-cultural adaptation study process. Forty healthy pregnant or postpartum Japanese women participated. Women with pelvic girdle pain (PGP) completed the PGQ-J and 5 other instruments. Internal consistency, construct validity, test-retest reliability, ceiling and floor effects, and discrimination validity of the PGQ-J were analyzed. RESULTS: The PGQ-J showed high internal consistency with a Cronbach α of .968, and an interclass correlation coefficient of .79. The content validity showed a high positive correlation with the Oswestry Disability Index and Disability Rating Scale. CONCLUSION: The PGQ-J was reliable and valid with high internal consistency and content validity for assessing disability owing to PGP in Japanese pregnant and postpartum women. The PGQ-J is expected to facilitate research and clinical practice for PGP in Japan and contribute to the welfare of postpartum women.

Validity and reliability of velocity measurements on ultrasonography using custom software with an optical-flow algorithm.

[Purpose] The purposes of this study were: 1) to validate a commercial software program using an optical-flow algorithm to measure the velocity of muscle movement; and 2) to determine optimal image quality and the size and location of regions of interest. [Materials and Methods] First, a block of pork thigh muscle was pulled at 33 different constant velocities. Subsequently, an accelerometer, a high-velocity camera, and ultrasonography were used to obtain measurements, and an Echolizer software was used to determine ultrasound-based velocities. Finally, the impact of the location and size of the regions of interest and the brightness and contrast of the images was analyzed. [Results] The regression equation was expressed as y=1.150 × -0.071 with a determination coefficient of 0.996. The average absolute error of the software was 0.02 mm/s, and the average relative error was 0.20% of the actual velocity between 2.5 and 16.5 mm/s after the regression equation was applied to the measured data. The accuracy of measurement was reduced owing to the increased size of the regions of interest, which included poor image quality or a deeper zone. [Conclusion] Our method of measuring muscle velocity using a custom program showed high validity and reliability. It is necessary to use the regression equation in the program to improve accuracy. However, the validity of the method could be reduced if the regions of interest involve deep tissues or areas with poor visualization of the muscle bundles, or if the brightness and contrast of the image are set inaccurately.

Altered musculoskeletal mechanics as risk factors for postpartum pelvic girdle pain: a literature review.

[Purpose] The aim of this literature review was to detect the factors associated with pelvic girdle pain persisting for over 3 months in the postpartum period. [Methods] We performed a broad literature search for eligible studies published before May 1, 2018 using electronic databases and processed the data using a review process. [Results] In the initial online search, we identified 12,174 potential studies. Finally, 22 studies met the specified criteria and were included for examination of risk factors for persistent pelvic girdle pain after delivery. Pain intensity and disability during pregnancy were risk factors for pelvic girdle pain persisting for over 6 months after delivery. The active straight leg raising test predicted the risk of persistent pelvic girdle pain after delivery. Dysfunction of the pelvic floor muscles was also a risk factor for persistent pelvic girdle pain. [Conclusion] Pain intensity and disability during pregnancy, positive provocation tests, active straight leg raising test, and musculoskeletal mechanics were positively associated with pelvic girdle pain persisting for over 3 months after delivery.

Reliability and validity in measurement of true humeral retroversion by a three-dimensional cylinder fitting method.

HYPOTHESIS AND BACKGROUND: Humeral retroversion is defined as the orientation of the humeral head relative to the distal humerus. Because none of the previous methods used to measure humeral retroversion strictly follow this definition, values obtained by these techniques vary and may be biased by morphologic variations of the humerus. The purpose of this study was 2-fold: to validate a method to define the axis of the distal humerus with a virtual cylinder and to establish the reliability of 3-dimensional (3D) measurement of humeral retroversion by this cylinder fitting method. METHODS: Humeral retroversion in 14 baseball players (28 humeri) was measured by the 3D cylinder fitting method. The root mean square error was calculated to compare values obtained by a single tester and by 2 different testers using the embedded coordinate system. To establish the reliability, intraclass correlation coefficient (ICC) and precision (standard error of measurement [SEM]) were calculated. RESULTS: The root mean square errors for the humeral coordinate system were <1.0 mm/1.0° for comparison of all translations/rotations obtained by a single tester and <1.0 mm/2.0° for comparison obtained by 2 different testers. Assessment of reliability and precision of the 3D measurement of retroversion yielded an intratester ICC of 0.99 (SEM, 1.0°) and intertester ICC of 0.96 (SEM, 2.8°). DISCUSSION AND CONCLUSION: The error in measurements obtained by a distal humerus cylinder fitting method was small enough not to affect retroversion measurement. The 3D measurement of retroversion by this method provides excellent intratester and intertester reliability.

Scapular Kinematics During Late Cocking of a Simulated Throwing Activity in Baseball Players With Shoulder Injury: A Cross-Sectional Study Using a 3D-to-2D Registration Technique.

CONTEXT: Abnormal scapular kinematics during throwing motion in baseball players with shoulder disorders has not yet been clarified, although altered scapular position has been suggested to be associated with shoulder disorder. OBJECTIVE: To determine if the shoulders of baseball players with throwing disorders demonstrate abnormal scapular kinematics during the simulated arm-cocking phase of throwing activity. DESIGN: Cross-sectional study. SETTING: Laboratory. PARTICIPANTS: Eleven baseball players (age 21.1 ± 1.2 y) with a unilateral shoulder disorder volunteered to participate, including 9 players at the college level and 2 at the adult level. The mean playing experience was 12.1 ± 2.7 y. MAIN OUTCOME MEASURES: Scapular upward/downward rotation, anteroposterior tilting, and external/internal rotation during simulated arm-cocking motion were analyzed using a 3-to-2-dimensional registration technique. RESULTS: Scapular external rotation in the throwing shoulder was significantly smaller by 2.0-6.0° than that of the contralateral shoulder. There were no detectable differences in scapular upward/downward rotation or anteroposterior tilting between the throwing and contralateral shoulders. CONCLUSIONS: Compared with that in the contralateral shoulder, scapular external rotation was smaller in the throwing shoulder, which would increase glenohumeral horizontal abduction during the arm-cocking phase and be related to the throwing-shoulder disorder.

Effect of unpredictable timing on the hip, knee, and ankle kinematics and center of mass during deceleration tasks.

BACKGROUND: Unpredictable stopping or deceleration tasks are crucial to prevent ACL injury. The purpose of this study was to reveal differences and relationships in kinematics during different deceleration tasks with and without anticipation. METHODS: Twenty-four collegiate athletes were recruited. Three commercial video cameras were used to capture frontal and sagittal lower-extremity kinematics. Participants were instructed to perform three deceleration tasks: 1) anticipated stopping and running backward at a point indicated previously (SRB-P); 2) anticipated stopping and running backward in front of a badminton net (SRB-N); and 3) unanticipated stopping and running backward upon random flashing of a light (SRB-U). Differences and relationships between hip, knee, and ankle kinematics at stopping (SS) and deceleration steps (DS) and the height of the great trochanter (HGT) at SS were analyzed. RESULTS: For all tasks, the knee flexion angle was less than 25° at SS. There were no significant differences in hip, knee, and ankle kinematics between tasks. HGT during SRB-U was higher than that in the other tasks at DS. Hip flexion angle at SS and DS was significantly correlated with HGT at SS. During SRB_P and SRB_N, only knee flexion angle at DS was significantly correlated with HGT at SS. CONCLUSIONS: The deceleration task in this study, SRB, causes a low knee-flexion angle at SS. The COM remained higher during unanticipated stopping, which is related only to hip flexion angle during the task. Knee flexion movement does not contribute to lowering COM during an unpredictable deceleration task.

Manual Inter-Structural Release Procedure Can Alter Muscle Shear Modulus.

PURPOSE: Inter-structural release (ISR) procedure to skeletal muscles is believed to attenuate adhesion between neighboring muscles and alleviate subjective symptoms, including perceived stiffness and associated pain. However, objective evidence about the effect of ISR on the mechanical properties of the muscles is limited. The purpose of this study was to test the acute effect of ISR on the shear modulus of adjacent muscles. It was hypothesized that ISR applied to the border between synergistic muscles would acutely reduce the resting shear modulus of the involved muscle. METHODS: To assess the effect of ISR, the shear modulus of the resting peroneus longus (PL) and soleus (SOL) muscles was measured at various ankle joint positions (inversion/eversion) before and after interventions in nine non-symptomatic male individuals (age: 21.9 ± 1.4 years, height: 170 ± 6.6 cm, body mass: 64.3 ± 4.0 kg). Potential muscle activity during the measurement was assessed by recording surface electromyogram from these muscles. The interventions were ISR to the lower leg between the deep fascia of the PL and SOL and sham (massage). RESULTS: As the ankle joint position was passively varied toward inversion, the shear modulus increased substantially in PL and decreased moderately in SOL. Shear modulus of the proximal PL in the most inverted position increased acutely after ISR (by 11.4 ± 5.8%, P < 0.001), but not after the sham, without any change in the amplitude of electromyogram. CONCLUSIONS: These results provide objective evidence that the ISR procedure can acutely alter shear modulus, at least in a specific site in a resting muscle.

In Vivo Kinematics of the Anterior Cruciate Ligament Deficient Knee During Wide-Based Squat Using a 2D/3D Registration Technique.

Anterior cruciate ligament (ACL) deficiency increases the risk of early osteoarthritis (OA). Studies of ACL deficient knee kinematics would be important to reveal the disease process and therefore to find mechanisms which would potentially slow OA progression. The purpose of this study was to determine if in vivo kinematics of the anterior cruciate ligament deficient (ACLD) knee during a wide-based squat activity differ from kinematics of the contralateral intact knee. Thirty-three patients with a unilateral ACLD knee consented to participate in this institutional review board approved study with the contralateral intact knee serving as the control. In vivo knee kinematics during the wide-based squat were analyzed using a 2D/3D registration technique utilizing CT-based bone models and lateral fluoroscopy. Comparisons were performed using values between 0 and 100° flexion both in flexion and extension phases of the squat activity. Both the ACLD and intact knees demonstrated increasing tibial internal rotation with knee flexion, and no difference was observed in tibial rotation between the groups. The tibia in the ACLD knee was more anterior than that of the contralateral knees at 0 and 5° flexion in both phases (p < 0.05). Tibiofemoral medial contact points of the ACLD knees were more posterior than that of the contralateral knees at 5, 10 and 15° of knee flexion in the extension phase of the squat activity (p < 0.05). Tibiofemoral lateral contact points of the ACLD knees were more posterior than that of the contralateral knees at 0° flexion in the both phases (p < 0.05). The kinematics of the ACLD and contralateral intact knees were similar during the wide-based squat except at the low flexion angles. Therefore, we conclude the wide-based squat may be recommended for the ACLD knee by avoiding terminal extension.

Dynamic three-dimensional shoulder kinematics in patients with massive rotator cuff tears: a comparison of patients with and without subscapularis tears.

BACKGROUND: Massive rotator cuff tears (MRCTs) with subscapularis (SSC) tears cause severe shoulder dysfunction. In the present study, the influence of SSC tears on three-dimensional (3D) shoulder kinematics during scapular plane abduction in patients with MRCTs was examined. METHODS: This study included 15 patients who were divided into two groups: supraspinatus (SSP) and infraspinatus (ISP) tears with SSC tear (torn SSC group: 10 shoulders) or without SSC tear (intact SSC group: 5 shoulders). Single-plane fluoroscopic images during scapular plane elevation and computed tomography (CT)-derived 3D bone models were matched to the fluoroscopic images using two-dimensional (2D)/3D registration techniques. Changes in 3D kinematic results were compared. RESULTS: The humeral head center at the beginning of arm elevation was significantly higher in the torn SSC group than in the intact SSC group (1.8±3.4 mm vs. -1.1±1.6 mm, p<0.05). In the torn SSC group, the center of the humeral head migrated superiorly, then significantly downward at 60° arm elevation (p<0.05). In the intact SSC group, significant difference was not observed in the superior-inferior translation of the humeral head between the elevation angles. CONCLUSIONS: In cases of MRCTs with a torn SSC, the center of the humeral head showed a superior translation at the initial phase of scapular plane abduction followed by inferior translation. These findings indicate the SSC muscle plays an important role in determining the dynamic stability of the glenohumeral joint in a superior-inferior direction in patients with MRCTs.

Differences in the flexion and extension phases during kneeling investigated by kinematic and contact point analyses: a cross-sectional study.

BACKGROUND: Kneeling is necessary for certain religious and ceremonial occasions, crouching work, and gardening, which many people take part in worldwide. However, there have been few reports about kneeling activities. The purpose of this study was to clarify the kinematics of kneeling. METHODS: The subjects were 15 healthy young males. Kneeling activity was analysed within a knee flexion angle from 100° to maximum flexion (maxflex, mean ± SD = 161.3 ± 3.2°). The kinematic and contact point (CP) analyses were performed using a 2D/3D registration method, in which a 3D bone model created from computed tomography images was matched to knee lateral fluoroscopic images and analysed on a personal computer. RESULTS: In the kinematic analysis, the femur translated 37.5 mm posteriorly and rotated 19.8° externally relative to the tibia during the knee flexion phase. During the knee extension phase, the femur translated 36.4 mm anteriorly, which was almost the same amount as in the knee flexion phase. However, the femur rotated only 7.4° internally during the knee extension phase. In the CP analysis, the amount of anterior translation of the CP in the knee extension phase was greater in the medial CP and smaller in the lateral CP than that of posterior translation in the knee flexion phase. CONCLUSIONS: In kneeling, there was a difference in the rotational kinematics between the flexion phase and the extension phase. The kinematic difference between the flexion and extension phases may have some effect on the meniscus and articular cartilage.

Detection of knee wobbling as a screen to identify athletes who may be at high risk for ACL injury.

This study developed a method to detect knee wobbling (KW) at low knee flexion. KW consists of quick uncontrollable medio-lateral knee movements without knee flexion, which may indicate a risk of ACL injury. Ten female athletes were recorded while performing slow, single-leg squats. Using motion capture data, the ratio of the frontal angular velocity to sagittal angular velocity (F/S) was calculated. An 'F/S spike' was defined when the F/S ratio exceeded 100%. The number of F/S spikes was counted before and after low-pass filtering at different cut-off frequencies. Intraclass correlation coefficients for KW and filtered F/S spike were analysed. KWs per squat cycle showed a median (range) of 3 (2-8) times. F/S spikes before and after low-pass filtering at 3-, 6-, 10-, and 15-Hz were 51 (12-108), 2 (0-6), 3 (1-12), 5 (2-21), and 9 (3-33) times, respectively. KWs and F/S spikes on motion capture with 6-Hz, low-pass filtering were well correlated (r = 0 .76). Median percentages of valgus and varus F/S spikes were 71% and 29%, respectively. After 6Hz, low-pass filtering, the number of F/S spikes was strongly correlated with observed KWs. An F/S spike assessment may be used to objectively detect KW, including flexion and varus/valgus angular velocity.

Consistent femoral external rotation during weight-bearing knee flexion is associated with better patient-reported pain and mediolateral balance after total knee arthroplasty.

BACKGROUND: Normal knees generally show consistent femoral external rotation during knee flexion, although knees that have had total knee arthroplasty exhibit various rotational patterns with less rotational angle. This study aimed to determine whether consistent femoral external rotation during weight-bearing knee flexion after total knee arthroplasty is associated with better patient-reported outcomes and mediolateral joint balance. METHODS: A total of 40 total knee arthroplasty knees with a high-flexion posterior-stabilized prosthesis were divided into two groups based on their axial rotational kinematic pattern during squatting activity, and the clinical results including patient-reported outcomes and joint laxity were compared between the consistent external rotation group (20 knees) and the inconsistent external rotation group (20 knees). The unpaired Student's t-test or Welch's test were used for group comparison, and Fisher's exact test was applied for categorical data. FINDINGS: "Pain at rest" and "Pain at first gait in the morning" measured using a numerical rating scale (/10) were significantly lower in the consistent external rotation group compared with those in the inconsistent external rotation group. "Pain during gait on flat surface" tended to be lower in the consistent external rotation group. Medial stability was obtained in both groups with significantly greater lateral laxity in extension in the inconsistent external rotation group. INTERPRETATION: Total knee arthroplasty knees with consistent femoral external rotation during weight-bearing knee flexion exhibited better patient-reported pain and mediolateral soft tissue balance. Surgical procedures that control the mediolateral balance with medial stability would induce consistent femoral external rotation and improve patient-reported pain.

Changes in pelvic alignment in a woman before and after childbirth, using three-dimensional pelvic models based on magnetic resonance imaging: A longitudinal observation case report.

3-dimensional pelvic models based on magnetic resonance images (MRI) can be used to investigate accuracy and specifics of changing pelvic alignment during pregnancy and after childbirth. Few studies have investigated changes of pelvic alignment during pregnancy and after childbirth using three-dimensional pelvic models. This case report documents the changes of pelvic alignment during late pregnancy and after childbirth using MRI-based three-dimensional (3D) pelvic models. This was a longitudinal observation case report. A woman was imaged with MRI at 28 and 39 gestational weeks, as well as 4 and 72 weeks after childbirth. Greater internal, anterior, and downward rotation of both innominates at week 39 was observed from that at gestation week 28. Decreased internal, anterior, and downward rotation of both innominates at week 4 after child birth was observed compared with that at gestation week 39. We report the first case in Japan of changes of pelvic alignment measured using an MRI-based 3D pelvic alignment model during pregnancy and after child birth. This case suggests that the small changes of pubic area and greater separation of anterior portions of sacroiliac joints. Internal, anterior, and downward rotation of both innominates was observed in a Japanese primipara woman having no pelvic pain.

Characteristic kinematics of floor-sitting activities after posterior-stabilized total knee arthroplasty determined using model-based shape-matching techniques.

BACKGROUND: Detailed kinematics of floor-sitting activities after total knee arthroplasty (TKA) have not been well explored. Knee kinematics of cross-legged sitting, seiza-sitting, and side-sitting after TKA were examined to clarify the differences in tibiofemoral kinematics of each activity. METHODS: Subjects were 40 knees in 20 osteoarthritic patients who underwent bilateral TKA with a high-flexion fixed-bearing posterior-stabilized prosthesis. Dynamic radiographs of floor-sitting activities were taken, and the knee kinematics were compared among the three activities. The patients were also divided into two groups (possible/easy group and impossible/no-try group) for each activity, and group comparisons were conducted. RESULTS: The maximum implant flexion angle was significantly greater in seiza-sitting. In valgus/varus rotation, seiza-sitting demonstrated neutral rotation, while cross-legged sitting showed varus of about 10°, and side-sitting exhibited valgus. In tibial internal/external rotation, seiza-sitting demonstrated a constant rotational angle, while cross-legged sitting showed tibial internal rotation with flexion, and side-sitting exhibited tibial external rotation with flexion. The kinematic pathway during deep flexion illustrated the medial pivot pattern in cross-legged sitting, a small amount of bicondylar rollback in seiza-sitting, and the weak lateral pivot pattern in side-sitting. A greater flexion angle was the important factor for the performance of each floor-sitting activity followed by varus laxity at 10° knee flexion. CONCLUSIONS: This study successfully revealed characteristic kinematic patterns of TKA knees in three floor-sitting activities. Obtaining a greater knee flexion with adequate lateral laxity is the key to enhancing postoperative floor-sitting activities.

In vivo comparison of knee kinematics before and after high-flexion posterior cruciate-retaining total knee arthroplasty.

The objectives of this study were to compare preoperative and postoperative knee kinematics for subjects implanted with flexion-enhanced posterior cruciate-retaining total knee arthroplasty during deep flexion and to examine flexion performance of the prosthesis design. Three-dimensional kinematics was analyzed by fluoroscopic examinations of subjects using a single-plane model-image registration technique. Preoperatively, knee kinematics demonstrated small posterior femoral translation and limited axial rotation. These motions differed significantly from patterns previously reported for normal knees. Postoperatively, flexion performance was maintained, averaging 130 degrees , and kinematic patterns were similar to preoperative patterns. Although total knee arthroplasty can reduce pain and maintain functional performance, it appears that the characteristics of varus arthritic knee mechanics persist after arthroplasty.

High validity of measuring the width and volume of medial meniscal extrusion three-dimensionally using an MRI-derived tibial model.

BACKGROUND: Medial meniscal extrusion (MME) is an important marker of knee osteoarthritis (KOA) progression. The purposes of this study were: 1) to determine whether there are morphological differences between CT- and MRI-derived tibial plateau models; and 2) to determine whether measurement of MME volume and width using an MRI-derived tibial model is as accurate as measurements on a CT-derived tibial model. METHODS: This was a cross-sectional study that enrolled ten participants with medial KOA (Kellgren-Lawrence grade 1 to 3). Primary outcome was surface difference of the medial tibial plateau between CT- and MRI-derived models. Furthermore, volume and cross-sectional area of the medial tibial plateau were compared between CT- and MRI-derived models. Measurements of MME volume and width were compared between CT- and MRI-derived tibial models. RESULTS: Minimal and maximal surface differences of the medial tibial plateau between the CT- and MRI-derived models were - 0.15 [- 0.44, 0.14] mm (mean [95% confidence interval]) and 0.24 [- 0.09, 0.57] mm, respectively. There were no significant differences in volume and cross-sectional area of the medial tibial plateau between CT- and MRI-derived tibial models. The MME volumes measured on CT- and MRI-derived models were 942.6 [597.7, 1287.6] mm3 and 916.2 [557.9, 1274.6] mm3, respectively (p = 0.938). The MME widths measured on CT- and MRI-derived models were 4.2 [1.9, 6.5] mm and 4.5 [2.2, 6.9] mm, respectively (p = 0.967). CONCLUSIONS: CT- and MRI-derived models of the medial tibial plateau did not show significant morphological differences. Both CT- and MRI-derived tibia can be used as a reference to measure MME in early-to-moderate medial KOA.