Articular cartilage is sensitive to mechanical loading, so increased risk of osteoarthritis in older or obese individuals may be linked to changes in the relationship between cartilage properties and extrinsic joint loads. A positive relationship has been reported between ambulatory loads and cartilage thickness in young individuals, but whether this relationship exists in individuals who are older or obese is unknown. This study examined the relationship between femoral cartilage thickness and load, measured by weight  height and the peak adduction moment, in young normal-weight (28 subjects, age: 28.0 AE 3.8 years, BMI: 21.9 AE 1.9 kg/m 2 ), middle-aged normal-weight (27 subjects, 47.0 AE 6.5 years, 22.7 AE 1.7 kg/m 2 ), young overweight/obese (27 subjects, 28.4 AE 3.6 years, 33.3 AE 4.6 kg/m 2 ), and middle-aged overweight/obese (27 subjects, 45.8 AE 7.2 years, 31.9 AE 4.4 kg/m 2 ) individuals. On the lateral condyle, cartilage thickness was positively correlated with weight  height for all groups (R 2 ¼ 0.26-0.20) except the middle-aged overweight/ obese. On the medial condyle, weight  height was significantly correlated only in young normal-weight subjects (R 2 ¼ 0.19), as was the case for the correlation between adduction moment and medial-lateral thickness ratio (R 2 ¼ 0.20). These results suggest that aging and obesity are both associated with a loss of the positive relationship between cartilage thickness and ambulatory loads, and that the relationship is dependent on the compartment and whether the load is generated by body size or subject-specific gait mechanics. ß

Measures of mean cartilage thickness over predefined regions in the femoral plate using magnetic resonance imaging have provided important insights into the characteristics of knee osteoarthritis (OA), however, this quantification method suffers from the limited ability to detect OA-related differences between knees and loses potentially important information regarding spatial variations in cartilage thickness. The objectives of this study were to develop a new method for analyzing patterns of femoral cartilage thickness and to test the following hypotheses: (1) asymptomatic knees have similar thickness patterns, (2) thickness patterns differ with knee OA, and (3) thickness patterns are more sensitive than mean thicknesses to differences between OA conditions. Bi-orthogonal thickness patterns were extracted from thickness maps of segmented magnetic resonance images in the medial, lateral, and trochlea compartments. Fifty asymptomatic knees were used to develop the method and establish reference asymptomatic patterns. Another subgroup of 20 asymptomatic knees and three subgroups of 20 OA knees each with a Kellgren/Lawrence grade (KLG) of 1, 2, and 3, respectively, were selected for hypotheses testing. The thickness patterns were similar between asymptomatic knees (coefficient of multiple determination between 0.8 and 0.9). The thickness pattern alterations, i.e., the differences between the thickness patterns of an individual knee and reference asymptomatic thickness patterns, increased with increasing OA severity (Kendall correlation between 0.23 and 0.47) and KLG 2 and 3 knees had significantly larger thickness pattern alterations than asymptomatic knees in the three compartments. On average, the number of significant differences detected between the four subgroups was 4.5 times greater with thickness pattern alterations than mean thicknesses. The increase was particularly marked in the medial compartment, where the number of significant differences between subgroups was 10 times greater with thickness pattern alterations than mean thickness measurements. Asymptomatic knees had characteristic regional thickness patterns and these patterns were different in medial OA knees. Assessing the thickness patterns, which account for the spatial variations in cartilage thickness and capture both cartilage thinning and swelling, could enhance the capacity to detect OA-related differences between knees.

While cartilage thickness alterations are a central element of knee osteoarthritis (OA), differences among disease stages are still incompletely understood. This study aimed to quantify the spatial-variations in cartilage thickness using anatomically standardized thickness maps and test if there are characteristic patterns in patients with different stages of medial compartment knee OA. Magnetic resonance images were acquired for 75 non-OA and 100 OA knees of varying severities (Kellgren and Lawrence (KL) scores 1-4). Three-dimensional cartilage models were reconstructed and a shape matching technique was applied to convert the models into two-dimensional anatomically standardized thickness maps. Difference thickness maps and statistical parametric mapping were used to compare the four OA and the non-OA subgroups. This analysis showed distinct thickness patterns for each clinical stage that formed a coherent succession from the non-OA to the KL 4 subgroups. Interestingly, the only significant difference for early stage (KL 1) was thicker femoral cartilage. With increase in disease severity, typical patterns developed, including thinner cartilage in the anterior area of the medial condyle (significant for KL 3 and 4) and thicker cartilage in the posterior area of the medial and lateral condyles (significant for all OA subgroups). The tibial patterns mainly consisted of thinner cartilage for both medial and lateral compartments (significant for KL 2-4). Comparing anatomically standardized maps allowed identifying patterns of thickening and thinning over the entire cartilage surface, consequently improving the characterization of thickness differences associated with OA. The results also highlighted the value of anatomically standardized maps to analyze spatial variations in cartilage thickness. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2442-2451, 2017.

This finding supports the hypothesis that graft placement plays a critical role in the restoration of normal ambulatory mechanics after anterior cruciate ligament reconstruction and thus could provide a partial explanation for the increased incidence of premature osteoarthritis at long-term follow-up in patients with anterior cruciate ligament reconstruction.

There is a need to understand how obesity and aging interact to cause an increased risk of medial knee osteoarthritis (OA). This study tested whether the knee adduction and flexion moments increase with age in healthy normal-weight and obese adults, as well as the mechanism of this increase. We analyzed whether ground reaction force magnitude, knee alignment, step width, toe-out angle, body volume distribution, and limb position (knee position relative to the pelvis center) are associated with the adduction moment and whether these variables also change with age. Ninety-six healthy volunteers (60 normal-weight and 36 obese) were tested using marker-based gait analysis; knee alignment was based on marker positions during quiet standing. Adduction moment increased with age in obese (R 2 ¼ 0.19), but not in normal-weight individuals (R 2 ¼ 0.01); knee flexion moment did not change with age in either group. In the obese, only knee alignment and limb position were related to the adduction moment (R 2 ¼ 0.19 and 0.51), but only limb position changed with age (R 2 ¼ 0.26). The resulting increase in adduction moment suggests greater medial compartment loads, which may combine with elevated levels of inflammation to contribute to the increased risk of medial OA in this population. Keywords: osteoarthritis; aging; obesity; knee; gait Obesity and aging are among the strongest risk factors for the incidence of knee osteoarthritis (OA), 1,2 yet the interaction between these factors in the development of knee OA is not well understood. While increased joint loads due to excess weight are an obvious consideration in understanding the causes of OA in obese individuals, more subtle changes in gait mechanics may provide insight into the pathway to OA in this population and open other avenues for interventions to reduce OA risk in the elderly obese. There is therefore a need to investigate the changes in the gait mechanics of older obese individuals in order to understand how obesity and aging combine to create increased OA risk in this population.Aging leads to an increase in knee OA in all compartments, but since the medial compartment is the region most frequently involved, 3 this study focuses on the mechanical loads in the medial compartment. Previous work 4 has shown that the contact force in the medial compartment is explained by a combination of the peak knee flexion and first peak knee adduction moments; the medial-lateral distribution of the contact force was associated with the adduction moment and the magnitude of the total force was associated with the flexion moment. While differences in knee moments between obese and normal-weight individuals have been reported, 5-8 there remain unanswered questions about the effect of age, 5 walking speed, 6 OA status, 7 and normalizing joint moments, 8 making the results difficult to interpret.Given the increased risk of OA in the older obese population, the high frequency of medial compartment involvement, and the fact that the adduction moment is a surrogate measure of...

The purpose of this study was to determine the presence and prevalence of asymmetry in lower extremity joint moments within and across healthy populations during overground walking. Bilateral gait data from several studies performed at two institutions were pooled from 182 healthy, pain-free subjects. Four distinct populations were identified based on age, activity level and body mass index. Mean peak external joint moments were calculated from three to six trials of level overground walking at self-selected speed for each subject. Right and left limb moments were reclassified as “greater” or “lesser” moment for each subject to prevent obscuring absolute asymmetry due to averaging over positive and negative asymmetries across subjects. A clinically relevant asymmetry measure was calculated from the peak joint moments with an initial chosen cutoff value of 10%. Confidence intervals for the proportion of subjects with greater than 10% asymmetry between limbs were estimated based on the binomial distribution. We found a high amount of asymmetry between the limbs in healthy populations. More than half of our overall population exceeded 10% asymmetry in peak hip and knee flexion and adduction moments. Group medians exceeded 10% asymmetry for all variables in all populations. This may have important implications on gait evaluations, particularly clinical evaluations or research studies where asymmetry is used as an outcome. Additional research is necessary to determine acceptable levels of joint moment asymmetry during gait and to determine whether asymmetrical joint moments influence the development of symptomatic pathology or success of lower extremity rehabilitation.

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The finding that asymptomatic subjects with cartilage loss had gait and inflammatory characteristics similar to those previously reported in symptomatic OA patients supports the idea that there are specific mechanical and biological factors that precede the onset of knee pain in the pathogenesis of OA.