Objective People with knee osteoarthritis (OA) are thought to walk with high loads at the knee which are yet to be quantfied using modeling techniques that account for subject specific EMG patterns, kinematics and kinetics. The objective was to estimate medial and lateral loading for people with knee OA and controls using an approach that is sensitive to subject specific muscle activation patterns. Methods 16 OA and 12 control (C) subjects walked while kinematic, kinetic and EMG data were collected. Muscle forces were calculated using an EMG-Driven model and loading was calculated by balancing the external moments with internal muscle and contact forces Results OA subjects walked slower and had greater laxity, static and dynamic varus alignment, less flexion and greater knee adduction moment (KAM). Loading (normalized to body weight) was no different between the groups but OA subjects had greater absolute medial load than controls and maintained a greater %total load on the medial compartment. These patterns were associated with body mass, sagittal and frontal plane moments, static alignment and close to signficance for dynamic alignment. Lateral compartment unloading during mid-late stance was observed in 50% of OA subjects. Conclusions Loading for control subjects was similar to data from instrumented prostheses. Knee OA subjects had high medial contact loads in early stance and half of the OA cohort demonstared lateral compartment lift-off. Results suggest that interventions aimed at reducing body weight and dynamic malalignment might be effective in reducing medial compartment loading and establishing normal medio-lateral load sharing patterns.

Purpose To develop a semi-quantitative MR-based hip osteoarthritis (OA) evaluation system (Scoring hip osteoarthritis with MRI, SHOMRI), and to test its reproducibility and face validity. Material and Methods The study involved 98 subjects with informed consent. Three-Tesla MR imaging of hip was performed in three planes with intermediate-weighted fat saturated FSE sequences. Two radiologists assessed cartilage loss, bone marrow edema pattern, subchondral cyst in 10 subregions, and assessed labrum in 4 subregions. In addition, presence or absence of ligamentum teres integrity, paralabral cysts, intraarticular body, and effusion in the hip joint were analyzed using the SHOMRI system. The reproducibility was assessed with intra-class correlation coefficient (ICC), Cohen’s Kappa values and percent agreement. SHOMRI scores were correlated with radiographic Kellgren-Lawrence (KL) and OARSI atlas gradings, and clinical parameters, the hip osteoarthritis outcome score (HOOS) and hip range of motion (ROM), using Spearman’s rank correlation and ordinal logistic regression. Results ICC values were in excellent ranging from 0.91 to 0.97. Cohen’s Kappa values and percent agreement ranged from 0.55 to 0.79 and 66 to 99 %, respectively. SHOMRI demonstrated significant correlations with KL and OARSI gradings as well as with clinical parameters, HOOS and ROM (P < 0 .05). Among the SHOMRI features, subchondral cyst and bone marrow edema pattern showed the highest correlation with HOOS and ROM. Conclusion SHOMRI demonstrated moderate to excellent reproducibility and significant correlation with radiographic gradings and clinical parameters.

Background Understanding the acute response of healthy knee cartilage to running may provide valuable insight into functional properties. In recent years, quantitative magnetic resonance (MR) imaging techniques (T1ρ and T2 relaxation measurement) have shown tremendous potential and unique ability to noninvasively and quantitatively determine cartilage response to physiologic levels of loading occurring with physiologic levels of exercise. Purpose To measure the short-term changes in MR T1ρ and T2 relaxation times of knee articular cartilage and meniscus in healthy individuals immediately after 30 minutes of running. Study Design Descriptive laboratory study. Methods Twenty young healthy volunteers, aged 22 to 35 years, underwent 3T MR imaging of the knee before and immediately after 30 minutes of running. Quantitative assessment of the cartilage and menisci was performed using MR images with a T1ρ and T2 mapping technique. After adjusting for age, sex, and body mass index, repeated-measures analysis of variance was used to determine the effects of running on MR relaxation times. Results The post-run T1ρ and T2 measurement showed significant reduction in all regions of cartilage except the lateral tibia when compared with the pre-run condition. The medial tibiofemoral (T1ρ: 9.4%, P < .0001; T2: 5.4%, P = .0049) and patellofemoral (T1ρ: 12.5%, P < .0001; T2: 5.7%, P = .0007) compartments experienced the greatest reduction after running. The superficial layer of the articular cartilage showed significantly higher change in relaxation times than the deep layer (ΔT1ρ: 9.6% vs 8.2%, P = .050; ΔT2: 6.0% vs 3.5%, P = .069). The anterior and posterior horns of the medial meniscus (9.7%, P = .016 and 11.4%, P = .001) were the only meniscal subregions with significant changes in T1ρ after running. Conclusion Shorter T1ρ and T2 values after running suggest alteration in the water content and collagen fiber orientation of the articular cartilage. Greater changes in relaxation times of the medial compartment and patellofemoral joint cartilage indicate greater load sharing by these areas during running.

Objectives To compare thigh muscle intramuscular fat (intraMF) fractions and area between people with and without knee radiographic osteoarthritis (ROA); and to evaluate the relationships of quadriceps adiposity and area with strength, function and knee MRI lesions. Methods Ninety six subjects (ROA: KL >1; n = 30, control: KL = 0,1; n = 66) underwent 3-Tesla MRI of the thigh muscles using chemical shift-based water/fat MR imaging (fat fractions) and the knee (clinical grading). Subjects were assessed for isometric/isokinetic quadriceps/hamstrings strength, function (KOOS, stair climbing test [SCT], and 6-minute walk test [(6MWT]. Thigh muscle intraMF fractions, muscle area and strength, and function were compared between controls and ROA subjects, adjusting for age. Relationships between measures of muscle fat/area with strength, function, KL and lesion scores were assessed using regression and correlational analyses. Results The ROA group had worse KOOS scores but SCT and 6MWT were not different. The ROA group had greater quadriceps intraMF fraction but not for other muscles. Quadriceps strength was lower in ROA group but the area was not different. Quadriceps intraMF fraction but not area predicted self-reported disability. Aging, worse KL, and cartilage and meniscus lesions were associated with higher quadriceps intraMF fraction. Conclusion Quadriceps intraMF is higher in people with knee OA and is related to symptomatic and structural severity of knee OA, where as the quadriceps area is not. Quadriceps fat fraction from chemical shift-based water/fat MR imaging may have utility as a marker of structural and symptomatic severity of knee OA disease process.

Objective The objective of this study was to evaluate the effects of mechanical loading on knee articular cartilage T1ρ and T2 relaxation times in patients with and without OA. Design MR images were acquired from 137 subjects with and without knee OA under two conditions: unloaded and loaded at 50% body weight. Three sequences were acquired: a high-resolution 3D-CUBE, a T1ρ relaxation time, and a T2 relaxation time sequences. Cartilage regions of interest included: medial and lateral femur (MF, LF); medial and lateral tibia (MT, LT), laminar analysis (superficial and deep layers), and subcompartments. Changes in relaxation times in response to loading were evaluated using generalized estimating equations adjusting for age, gender, and BMI. Results In response to loading, we observed significant reductions in T1ρ relaxation times in the MT and LT. In both the MF and LF, loading resulted in significant decreases in the superficial layer and significant increases in the deep layer of the cartilage for T1ρ and T2. All subcompartment of MT and LT showed significant reduction in T1ρ relaxation times. Reductions were larger for subjects with OA (range: 13–19% change) when compared to healthy controls (range: 3–13% change). Conclusions Loading of the cartilage resulted in significant changes in relaxation times in the femur and tibia, with novel findings regarding laminar and subcompartmental variations. In general, changes in relaxation times with loading were larger in the OA group suggesting that the collagen-proteoglycan matrix of subjects with OA is less capable of retaining water, and may reflect a reduced ability to dissipate loads.