Characteristics of Acute Cartilage Response After Mechanical Loading in Patients with Early-Mild Knee Osteoarthritis.

This study determined whether the acute cartilage response, assessed by cartilage thickness and echo intensity, differs between patients with early-mild knee osteoarthritis (OA) and healthy controls. We recruited 56 women aged ≥ 50 years with Kellgren-Lawrence (KL) grade ≤ 2 (age, 70.6 ± 7.4 years; height, 153.7 ± 5.2 cm; weight, 51.9 ± 8.2 kg). Based on KL grades and knee symptoms, the participants were classified into control (KL ≤ 1, asymptomatic, n = 27) and early-mild knee OA groups (KL 1 and symptomatic, KL 2, n = 29). Medial femoral cartilage thickness and echo intensity were assessed using ultrasonographic B-mode images before and after treadmill walking (15 min, 3.3 km/h). To investigate the acute cartilage response, repeated-measures analysis of covariance (groups × time) with adjusted age, external knee moment impulse, steps during treadmill walking, and cartilage thickness at pre-walking was performed. A significant interaction was found at the tibiofemoral joint; after walking, the cartilage thickness was significantly decreased in the early-mild knee OA group compared to the control group (p = 0.002). At the patellofemoral joint, a significant main effect of time was observed, but no interaction was detected (p = 0.802). No changes in cartilage echo intensity at either the tibiofemoral or patellofemoral joints, and no interactions were noted (p = 0.295 and p = 0.063). As acute cartilage response after walking, the thickness of the medial tibiofemoral joint in the early-mild knee OA was significantly reduced than that in the control group. Thus, greater acute deformation after walking might be a feature found in patients with early-mild knee OA.

Understanding muscle coordination during gait based on muscle synergy and its association with symptoms in patients with knee osteoarthritis.

OBJECTIVE: We aimed to investigate the muscle coordination differences between a control group and patients with mild and severe knee osteoarthritis (KOA) using muscle synergy analysis and determine whether muscle coordination was associated with symptoms of KOA. METHOD: Fifty-three women with medial KOA and 19 control patients participated in the study. The gait analyses and muscle activity measurements of seven lower limb muscles were assessed using a motion capture system and electromyography. Gait speed and knee adduction moment impulse were calculated. The spatiotemporal components of muscle synergy were extracted using non-negative matrix factorization, and the dynamic motor control index during walking (walk-DMC) was computed. The number of muscle synergy and their spatiotemporal components were compared among the mild KOA, severe KOA, and control groups. Moreover, the association between KOA symptoms with walk-DMC and other gait parameters was evaluated using multi-linear regression analysis. RESULTS: The number of muscle synergies was lower in mild and severe KOA compared with those in the control group. In synergy 1, the weightings of biceps femoris and gluteus medius in severe KOA were higher than that in the control group. In synergy 3, the weightings of higher tibial anterior and lower gastrocnemius lateralis were confirmed in the mild KOA group. Regression analysis showed that the walk-DMC was independently associated with knee-related symptoms of KOA after adjusting for the covariates. CONCLUSIONS: Muscle coordination was altered in patients with KOA. The correlation between muscle coordination and KOA may be attributed to the knee-related symptoms. Key points • Patients with knee osteoarthritis (OA) experienced a deterioration in muscle coordination when walking. • Loss of muscle coordination was associated with severe knee-related symptoms in knee OA. • Considering muscle coordination as a knee OA symptom-related factor may provide improved treatment.

Ultrasonographic echo intensity in the medial femoral cartilage is enhanced prior to cartilage thinning in women with early mild knee osteoarthritis.

PURPOSE: We aimed to determine whether altered cartilage echo intensity is associated with knee osteoarthritis (OA) severity and whether the alteration occurs before thinning of the femoral cartilage in knee OA. METHODS: The medial femoral cartilage thickness and echo intensity of 118 women aged ≥ 50 years were assessed using an ultrasound imaging device. Based on the Kellgren-Lawrence (KL) grade and knee symptoms, participants were classified into five groups: control (asymptomatic grades 0-1), early OA (symptomatic grade 1), grade 2, grade 3, and grade 4. Analysis of covariance, with adjusted age and height, and the Sidak post hoc test were used to assess the differences in cartilage thickness and echo intensity in knees with varying OA severity. RESULTS: The echo intensity on longitudinal images, equivalent to the tibiofemoral weight-bearing surface, was significantly higher in the grade 2 group than that in the control group (p = 0.049). However, no significant difference was noted in cartilage thickness (n.s.). In the grades 3 and 4 groups, cartilage thickness became thinner as OA progressed (p < 0.001 and p < 0.001, respectively). However, the cartilage echo intensity was not significantly enhanced compared with that of the grade 2 group (n.s.). There were no significant differences in the cartilage thickness and echo intensity between the early OA and control groups on the longitudinal images (n.s.). CONCLUSIONS: The echo intensity of the medial femoral cartilage was high in patients with KL grade 2, without decreased thickness. Our findings suggested that higher echo intensity is a feature of early cartilage degeneration in mild knee OA. Further studies are needed to establish this feature as a useful screening parameter of early cartilage degeneration in knee OA. LEVEL OF EVIDENCE: Level III.

Assessment of fore-, mid-, and rear-foot alignment and their association with knee symptoms and function in patients with knee osteoarthritis.

OBJECTIVE: Hallux valgus, flatfoot, and rearfoot eversion are well-known major complications of knee osteoarthritis (OA). However, there is no consensus on the association between these foot malalignments and knee symptoms or function. Thus, this study aimed to examine the association between foot alignment and knee symptoms or function in patients with knee OA. METHODS: Female patients aged ≥ 50 years with symptomatic knee OA participated in this study. Knee symptoms and function were assessed using the Knee Society Scoring System (KSS). Hallux valgus, navicular/foot ratio, and leg heel alignment were used as the forefoot, midfoot, and rearfoot alignment indices, respectively. The navicular/foot ratio was defined as the ratio of the navicular height to the total foot length. We performed multiple linear regression analysis to examine the associations between foot alignment and knee symptoms or function. RESULTS: Seventy-eight participants participated our study. KSS symptom score was significantly associated with navicular/foot ratio (regression coefficient [ß], -0.30; 95% confidence interval [CI], -109.2 to -20.5; P = 0.005), knee extensor strength (ß, 0.32; 95% CI, 0.02 to 0.09; P = 0.004), and age (ß, 0.24; 95% CI, 0.01 to 0.32; P = 0.036). KSS function score was not associated with foot alignments but with knee extensor strength (ß, 0.40; 95% CI, 0.10 to 0.33; P = 0.001) and body mass index (ß, -0.35; 95% CI, -2.82 to -0.66; P = 0.002). CONCLUSIONS: Knee symptoms were significantly associated with midfoot alignment in patients with medial knee OA. This suggests that lower navicular height in patients with medial knee OA may relate with the alleviation of knee symptoms. Key Points • In patients with medial knee OA, midfoot alignment was significantly associated with knee symptoms in patients with medial knee OA; however, knee function was not associated with foot alignment. • Lower navicular height in patients with medial knee OA may relate with the alleviation of knee symptoms.