The relationship between knee adduction moment and cartilage and meniscus morphology in women with osteoarthritis

Knowledge mapping and bibliometric analysis of medical knee magnetic resonance imaging for knee osteoarthritis (2004-2023)

Objectives

Magnetic resonance imaging (MRI) is increasingly used to detect knee osteoarthritis (KOA). In this study, we aimed to systematically examine the global research status on the application of medical knee MRI in the treatment of KOA, analyze research hotspots, explore future trends, and present results in the form of a knowledge graph.

Methods

The Web of Science core database was searched for studies on medical knee MRI scans in patients with KOA between 2004 and 2023. CiteSpace, SCImago Graphica, and VOSviewer were used for the country, institution, journal, author, reference, and keyword analyses.

Results

A total of 2,904 articles were included. The United States and Europe are leading countries. Boston University is the main institution. Osteoarthritis and cartilage is the main magazine. The most frequently cocited article was "Radiological assessment of osteoarthrosis". Guermazi A was the author with the highest number of publications and total references. The keywords most closely linked to MRI and KOA were "cartilage", "pain", and "injury".

Conclusions

The application of medical knee MRI in KOA can be divided into the following parts: (1). MRI was used to assess the relationship between the characteristics of local tissue damage and pathological changes and clinical symptoms. (2).The risk factors of KOA were analyzed by MRI to determine the early diagnosis of KOA. (3). MRI was used to evaluate the efficacy of multiple interventions for KOA tissue damage (e.g., cartilage defects, bone marrow edema, bone marrow microfracture, and subchondral bone remodeling). Artificial intelligence, particularly deep learning, has become the focus of research on MRI applications for KOA.

Influence of individual quadriceps and hamstrings muscle architecture and quality on knee adduction and flexion moment in gait

The purpose of this study was to investigate the relationship between muscular parameters of quadriceps/hamstrings and knee joint kinetics in gait. Muscle architecture (thickness, pennation angle, and fascicle length), and quality (echo intensity) of individual quadriceps and hamstrings of 30 healthy participants (16 males and 14 females) was measured using ultrasound. Peak knee flexion moment (KFM), KFM impulse, peak knee adduction moment (KAM), and KAM impulse during walking were obtained at preferred speed. Pearson's correlation coefficient and multiple regression analyses were performed at significance level of 0.05, and Cohen's f2 values were calculated to examine the effect sizes of multiple regression. The hamstring-to-quadriceps muscle thickness ratio (r = 0.373) and semitendinosus echo intensity (r =  - 0.371) were predictors of first peak KFM (R2 = 0.294, P = 0.009, f2 = 0.42), whereas only vastus medialis (VM) echo intensity was a significant predictor of second peak KFM (r = 0.517, R2 = 0.267, P = 0.003, f2 = 0.36). Only the VM thickness was the predictor of first (r = 0.504, R2 = 0.254, P = 0.005, f2 = 0.34) and second peak KAM (r = 0.581, R2 = 0.337, P = 0.001, f2 = 0.51), and KAM impulse (r = 0.693, R2 = 0.480, P < 0.001, f2 = 0.92). In conclusion, the greater hamstring-to-quadriceps muscle thickness ratio and the muscle architecture and quality of medial quadriceps/hamstring play an important role in KFM and KAM, and may have implications in knee osteoarthritis.

Toe-out gait inhibits medial meniscus extrusion associated with the second peak of knee adduction moment during gait in patients with knee osteoarthritis

Background

A medial meniscus extrusion (MME) gradually expands during activities of daily living according to the mechanical stress on the medial compartment of the knee. Increase in MME occurs during the stance phase of the gait cycle, which is key for its expand. The knee adduction moment (KAM) represents the mechanical stress on the medial compartment; however, the relationship between the increase in MME and KAM is still unknown. Therefore, the present study aimed to investigate the relationship between MME during gait and KAM.

Methods

Twenty-one patients with medial knee osteoarthritis and 11 healthy middle-aged adults were recruited. Three-dimensional motion analysis system and ultrasonography were used to measure the KAM and MME in the stance phase. The increase in MME was identified as the difference in MME between the maximum and minimum (ΔMME). Patients with knee osteoarthritis performed two conditions as normal and toe-out gait. The difference in KAM and ΔMME between conditions were evaluated.

Results

ΔMME was correlated with the KAM second peak in normal gait of knee osteoarthritis patients (r = 0.51, p < 0.05). Toe-out gait reduced the KAM second peak and the ΔMME, and these reductions were correlated (r = 0.50, p < 0.05).

Conclusions

Toe-out gait immediately inhibited the expansion of MME associated with the KAM second peak.

Cumulative knee adduction moment during jogging causes temporary medial meniscus extrusion in healthy volunteers

PURPOSE

The cumulative knee adduction moment (KAM) is a key parameter evaluated for the prevention of overload knee injuries on the medial compartment. Medial meniscus extrusion (MME), typical in hoop dysfunctions, is a measure for the cumulative mechanical stress in individual knees; however, its correlation with cumulative KAM is unknown. The aim of this study was to investigate the effect of temporary overload stress on MME and its correlation with cumulative KAM.

METHODS

Thirteen healthy asymptomatic volunteers (13 knees) were recruited for a cohort study (mean age, 23.1 ± 3.3 years; males: n = 8). The cumulative KAM was calculated using a three-dimensional motion analysis system, in addition to the number of steps taken while jogging uphill or downhill. MME was evaluated using ultrasound performed in the standing position. The evaluations were performed four times: at baseline (T0), before and after (T1 and T2, respectively) jogging uphill or downhill, and 1 day after (T3) jogging. Additionally, the Δ-value was calculated using the change of meniscus after efforts as the difference in MME between T1 and T2.

RESULTS

The MME in T2 was significantly greater than those in T0 and T1. Conversely, the MME in T3 was significantly lesser than that in T2. No significant difference was found between those in T0 and T1, and T3. ΔMME exhibited a significant positive correlation with the cumulative KAM (r = 0.68, p = 0.01), but not for peak KAM.

CONCLUSION

The temporary reaction of MME observed in ultrasound correlates with the cumulative stress of KAM.

Knee adduction moment is correlated with the increase in medial meniscus extrusion by dynamic ultrasound in knee osteoarthritis

BACKGROUND

An increase in medial meniscus extrusion (MME) due to abnormal biomechanical stress leads to knee osteoarthritis (OA) progression. MME evaluation during walking is a key method of detecting dynamic changes in the meniscus, and in combination with motion analysis, can provide a deeper understanding of the mechanisms involved in the increase of MME.

OBJECTIVE

To validate the feasibility of MME dynamic evaluation in combination with a motion analysis system based on the correlation between the increase in MME and biomechanical factors.

METHODS

Twenty-three knees from 23 patients with mild to moderate knee OA were analysed in this study. The medial meniscus during walking was evaluated by ultrasound. The increase in MME was calculated as the difference between the minimum and maximum MME during walking. A three-dimensional motion analysis system was synchronised with the ultrasound and then, biomechanical factors such as knee moment and ground reaction force were evaluated.

RESULTS

The wave patterns of the mediolateral and vertical components of ground reaction forces and knee adduction moment were similar to those in the MME based on a high cross-correlation coefficient (>0.8). The increase in MME was significantly correlated with the peak value of the knee adduction moment (r = 0.54, P = 0.0073) but not with the mediolateral and vertical components of the ground reaction force.

CONCLUSION

The findings show that knee adduction moment is correlated with an increase in MME during walking and indicates the validity and feasibility of the dynamic evaluation of MME in combination with a motion analysis system.

Effect of lower limb orthoses on cartilage in patients with knee osteoarthritis: A narrative review

The objective of this review was to infer how the use of an orthosis affects cartilage in patients with knee osteoarthritis. A search was performed in four different databases (Web of Science, Scopus, EMBASE, and PubMed) up to the 21st of November of 2020 to evaluate how the patient's condition was monitored. The parameters chosen for this review were medial tibial cartilage volume, x-ray evaluation, Lequesne Index, pain visual analog scale score, Western Ontario and McMaster Universities Arthritis Index pain score, and Knee Injury and Osteoarthritis Outcome Score pain subscale score. The initial search yielded a total of 12,622 documents. After thoroughly screening them, 38 were selected for analysis. Of the resulting data, only two objectively evaluated the cartilage (medial tibial cartilage volume, n = 1; x-ray evaluation, n = 1), with the remainder evaluating subjective symptoms (Lequesne Index, n = 8; pain visual analog scale score, n = 18; Western Ontario and McMaster Universities Arthritis Index pain score, n = 10; Knee Injury and Osteoarthritis Outcome Score pain subscale score, n = 10). The data did not converge toward any general outcome. The articles read demonstrated a great tendency to evaluate qualitative parameters pertinent to the symptoms of this condition or quantitative parameters related to the biomechanics of the knee. However, these parameters are not ideal because they are ambiguous. As such, a shift toward more objective quantitative parameters that directly assess the cartilage volume of the knee should be considered in future clinical trials.

The relationship between knee loading during gait and cartilage thickness in nontraumatic and posttraumatic knee osteoarthritis

The relationship between knee moments and markers of knee osteoarthritis progression has not been examined in different knee osteoarthritis subtypes. The objective was to examine relationships between external knee moments during gait and tibiofemoral cartilage thickness in patients with nontraumatic and posttraumatic knee osteoarthritis. For this cross-sectional study, participants with knee osteoarthritis were classified into two groups: nontraumatic (n = 22; mean age 60 years) and posttraumatic (n = 19; mean age 56 years, history of anterior cruciate ligament rupture). Gait data were collected with a three-dimensional motion capture system sampled at 100 Hz and force plates sampled at 2000 Hz. External knee moments were calculated using inverse dynamics. Cartilage thickness was determined with magnetic resonance imaging (T1-weighted, 3D sagittal gradient-echo sequence). Linear regression analyses examined relationships between cartilage thickness with knee moments, group, and their interaction. A higher knee adduction moment impulse was negatively associated with medial to lateral cartilage thickness ratio (B = -1.97). This relationship differed between participants in the nontraumatic osteoarthritis group (r = -0.56) and posttraumatic osteoarthritis group (r = -0.30). A higher late stance knee extension moment was associated with greater medial femoral condyle cartilage thickness (B = -0.86) and medial to lateral cartilage thickness (B = -0.73). These relationships also differed between participants in the nontraumatic osteoarthritis group (r = -0.61 and r = -0.51, respectively) and posttraumatic osteoarthritis group (r = 0.10 and r = 0.25, respectively). Clinical Significance: The relationship between knee moments with tibiofemoral cartilage thickness differs between patients with nontraumatic and posttraumatic knee osteoarthritis. The potential influence of mechanical knee loading on articular cartilage may also differ between these subtypes.

Proprioceptive Neuromuscular Facilitation Improves Symptoms Among Older Adults With Knee Osteoarthritis During Stair Ascending: A Randomized Controlled Trial

OBJECTIVE

This study aimed to investigate the effects of a 6-wk proprioceptive neuromuscular facilitation stretching on pain, proprioception, joint range of motion, and joint moments during stair ascending among older adults with knee osteoarthritis.

DESIGN

This study is a randomized, controlled, and assessor-blinded trial. Thirty-six older adults with knee osteoarthritis were randomly assigned to the proprioceptive neuromuscular facilitation and the control groups. They received proprioceptive neuromuscular facilitation stretching and health lecture series, respectively, for 6 wks. Final data analysis included 14 participants of the proprioceptive neuromuscular facilitation group and 13 of the control group. Pain score, joint proprioception, range of motion, and joint moments during stair ascending were measured before and after the stretching. Two-way (group by time) analysis of variance with repeated measures was used to evaluate stretching effects.

RESULTS

Significant interactions were detected in pain score, joint proprioception, external knee adduction moment, and external knee extension moment. Compared with week 0, the pain score, joint proprioception threshold, and external knee adduction moment decreased, whereas the external knee extension moment increased among older adults in the proprioceptive neuromuscular facilitation group at week 7.

CONCLUSIONS

Proprioceptive neuromuscular facilitation could be recommended as one of the clinical treatments for knee osteoarthritis to relieve pain, improve proprioception, and balance load distribution between medial and lateral compartments at the knee.

Dynamic response of medial meniscus extrusion to the lateral wedge insole is correlated with immediate pain reduction in knee osteoarthritis patients: real-time ultrasonographic study

PURPOSE

To investigate the effect of lateral wedge insole (LWI) on medial meniscus extrusion (MME) observed during dynamic evaluation with ultrasound and its correlation with the alteration in knee pain in patients with knee osteoarthritis (OA).

METHODS

This cohort study included 25 participants with knee OA. The medial meniscus was imaged during walking in video mode using ultrasonography. The degree of increase in MME (ΔMME) was calculated as the difference in the value of the maximum and minimum MME. The intensity of knee pain was evaluated immediately after the walking trial using the visual analogue scale (VAS). These measurements were performed with and without the LWI. The participants were categorised into the responder group, which was identified by the constant reduction in the VAS, and the non-responder group.

RESULTS

MME, ΔMME, and knee pain during walking were significantly lower with the LWI than without the LWI (p < 0.01). The reduction in ΔMME with the LWI in the responder group was significantly higher than that in the non-responder group (p < 0.01).

CONCLUSIONS

Our findings showed that MME and knee pain during walking decreased with LWI use, especially in patients whose reduction in knee pain was characterised by inhibition in the increase in MME observed during dynamic evaluation with ultrasound.

Biomechanical Effect of Valgus Knee Braces on the Treatment of Medial Gonarthrosis: A Systematic Review

Background

Valgus braces are prescribed as a common conservative treatment option for patients with medial gonarthrosis to improve their quality of life. Many studies had reviewed the effects of the valgus braces on patients with medial gonarthrosis, while they mainly focused on the knee adduction moment (KAM), with less attention paid to other parameters such as spatiotemporal and morphological parameters.

Objectives

The purpose of this study was to review the effects of valgus braces on the spatiotemporal, kinematic/kinetic, morphological, and muscle parameters.

Methods

Based on the selected keywords, a survey of literatures was performed in Web of Science, PubMed, Scopus, and Google Scholar using the PRISMA methods, and the search period was established from January 2000 to March 2022.

Results

Thirty-four articles were included. According to the conclusion of these articles, the valgus brace can be used to relieve the symptoms of patients with medial gonarthrosis by decreasing the varus angle, decreasing the KAM, and redistributing the knee compartment loads. However, the effects of valgus braces on other biomechanical parameters (e.g., walking speed, cadence, joint angle, and joint space) had not reached a consensus.

Conclusions

The valgus knee brace can effectively relieve the symptoms of medial gonarthrosis through multiple mechanisms, while there is still some confusion about the effectiveness of the valgus brace on the other biomechanical parameters.

Relationships between tibial articular cartilage, in vivo external joint moments and static alignment in end-stage knee osteoarthritis: A micro-CT study

Biomechanical factors (e.g., joint loading) have a significant role in the progression of osteoarthritis (OA). However, some relationships between in vivo joint loading indices and tibial cartilage thickness are conflicting. This study investigated relationships between pre-operative in vivo external knee joint moments, joint alignment and regional tibial cartilage thickness using micro-CT in subjects with end-stage knee OA. Tibial plateaus from 25 patients that underwent knee replacement for OA were micro-CT scanned (17 µm/voxel). Prior to surgery, subjects underwent gait analysis to calculate external knee moments. The mechanical axis deviation (MAD) was obtained from pre-operative radiographs. Cartilage thickness (Cart.Th) was analyzed from micro-CT images, in anteromedial, anterolateral, posteromedial and posterolateral subregions of interest. Medial-to-lateral Cart.Th ratios were also explored. Relationships between Cart.Th and joint loading indices were examined using Pearson's correlations. Significant correlations were found between Cart.Th and joint loading indices, positive anteromedially with the first peak knee adduction moment (r = 0.55, p < 0.01) and external rotation moment (ERM; r = 0.52, p < 0.01), and negative with MAD (r = -0.76, p < 0.001). In the lateral regions, these correlations had opposite signs. The medial-to-lateral Cart.Th ratio correlated strongly with ERM (r = 0.63, p = 0.001) and MAD (r = -0.75, p < 0.001). Joint loading indices correlated with regional cartilage thickness values and their medial-to-lateral ratios in end-stage knee OA subjects, with higher regional loads corresponding to thinner cartilage. These relationships have the opposite sign compared to the subchondral bone microarchitecture found in our previous study on the same specimens, which may suggest a complementary bone-cartilage interplay in response to loading.

Investigating acute changes in osteoarthritic cartilage by integrating biomechanics and statistical shape models of bone: data from the osteoarthritis initiative

Objective

Methods

Results

Discussion

Supplementary Information

Individual and cumulative measures of knee joint load associate with T2 relaxation times of knee cartilage in young, uninjured individuals: A pilot study

BACKGROUND

Articular cartilage structure and chondrocyte health are sensitive and reliant on dynamic joint loading during activities. The purpose of this pilot study was to determine the association between measures of individual and cumulative knee joint loading with T2 relaxation times in the knee cartilage of young individuals without knee injury.

METHODS

Twelve participants (17-30 years old) without history of knee injury or surgery completed MRI, physical activity (PA), and biomechanical gait testing. T2 relaxation times were calculated in the cartilage within the patella and lateral and medial compartments. Accelerometry was used to measure mean daily step counts, minutes of PA, and % sedentary time over 7 days. Vertical ground reaction force, external knee joint moments and peak knee flexion angle were measured during stance phase of gait using three-dimensional motion capture. Cumulative knee joint loading was calculated as daily step count by external knee joint moment impulse. The relationship between measures of knee joint loading and T2 relaxation times was assessed using Pearson correlations.

RESULTS

Higher T2 relaxation times in the femoral and tibial cartilage were consistently correlated to greater body mass, daily step counts, moderate and vigorous PA, and peak knee joint moments (r = 0.10-0.84). Greater cumulative knee flexion and adduction loading was associated with higher T2 relaxation times in the femoral and tibial cartilage (r = 0.16-0.65).

CONCLUSION

Preliminary findings suggest that individual loading factors and cumulative knee joint loading are associated with higher T2 relaxation times in the articular cartilage of young, healthy knees.

A half marathon shifts the mediolateral force distribution at the tibiofemoral joint

Runners' gait patterns vary during a half marathon and influence the knee joint mechanics. Joint contact force is a better estimate of the net joint loadings than external joint moments and closely correlates to injury risks. This study explored the changes of lower limb joint kinematics, muscle activities, and knee joint loading in runners across the running mileages of a half marathon. Fourteen runners completed a half marathon on an instrumented treadmill where motion capture was conducted every 2 km (from 2 to 20 km). A musculoskeletal model incorporating medial/lateral tibiofemoral compartments was used to process the movement data and report outcome variables at the selected distance checkpoints. Statistics showed no changes in joint angles, muscle co-contraction index, ground reaction force variables, and medial tibiofemoral contact force (p > 0.05). Knee adduction moment at 18 km was significantly lower than those at 2 km (p = 0.002, γ = 0.813) and 6 km (p = 0.001, γ = 0.663). Compared to that at 2 km, lateral tibiofemoral contact force was reduced at 18 km (p = 0.030, Hedges' g = 0.690), 16 km (p < 0.001, Hedges' g = 0.782), 14 km (p = 0.045, Hedges' g = 0.859), and 10 km (p < 0.001, Hedges' g = 0.771) respectively. Mechanical realignment of the lower limb may be the cause of the altered knee loadings and possibly led to reduced running economy in response to a prolonged run. The injury potential of the redistributed tibiofemoral forces warranted further studies.

The correlation between osteoarthritis stage and the effect of the lateral wedge insole for 3 months on medial meniscus extrusion in the knee joint

BACKGROUND

Medial meniscus extrusion (MME) leads to symptomatic knee osteoarthritis (OA) due to increased mechanical stress. MME increases with weight-bearing, and the difference in MME between non-weight-bearing and weight-bearing status (ΔMME) is a factor that causes greater MME. The lateral wedge insole (LWI) is an ideal approach for decreasing the amount of ΔMME associated with the reduction of medial loading stress in the early stage of knee OA. However, the effect of the LWI for 3 months on the ΔMME and its response to OA stage have not been elucidated.

OBJECTIVE

To investigate the effects of the LWI for 3 months on MME and the ΔMME in each stage of OA.

METHODS

Participants were divided into three groups: no intervention with the LWI (control group; n = 9) and intervention with the LWI in early OA (early OA group: Kellgren-Lawrence (K/L) stage = 2, n = 17) and late OA (late OA group: K/L stage > 2, n = 13). MME was evaluated using ultrasound, and the ΔMME was obtained as the difference in MME from non-weight-bearing and weight-bearing conditions. These measurements were performed at two time points: the initial office visit as a baseline and post-3 months.

RESULTS

The weight-bearing MME and ΔMME values post-3 months were significantly decreased compared with those at baseline in the early OA group but not in the control or late OA groups.

CONCLUSIONS

The use of the LWI for 3 months decreased weight-bearing MME and ΔMME values, and its effectiveness was more pronounced in the early stage of knee OA.

Pathogenesis and clinical management of obesity-related knee osteoarthritis: Impact of mechanical loading

Obesity-related osteoarthritis (OA) is a complex, multifactorial condition that can cause significant impact on patients' quality of life. Whilst chronic inflammation, adipocytokines and metabolic factors are considered to be important pathogenic factors in obesity related OA, there has been limited investigation into the biomechanical impact of obesity on OA development. This review aims to demonstrate that mechanical factors are the major pathological cause of obesity-related OA. The effect of obesity on pathological changes to the osteochondral unit and surrounding connective tissues in OA is summarized, as well as the impact of obesity-related excessive and abnormal joint loading, concomitant joint malalignment and muscle weakness. An integrated therapeutic strategy based on this multi-factorial presentation is presented, to assist in the management of obesity related OA.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

Despite the high prevalence of obesity-related OA, there is no specific guideline available for obesity-related OA management. In this review, we demonstrated the pathological changes of obesity-related OA and summarized the impact of biomechanical factors by proposing a hypothetical model of obesity-related OA change. Therapeutic strategies based on adjusting abnormal mechanical effects are presented to assist in the management of obesity-related OA.

Foot strike alters ground reaction force and knee load when stepping down during ongoing walking

BACKGROUND

When stepping down from a raised surface, either a toe or heel contact strategy is performed. Increased vertical momentum is likely to be experienced during a step descent, yet the extent to which these descent strategies influence the development of load at the ground and knee has not been examined.

RESEARCH QUESTION

Does descent strategy influence ground and knee joint loading? Does the contribution from leading and trailing limb joint mechanics differ between descent strategies?

METHODS

Twenty-two healthy male participants (age: 34.0 ± 6.5 years, height: 179 ± 6.3 cm, mass: 83.5 ± 13 kg) walked along a raised platform, stepped down from a 14 cm height utilising either a toe (n = 10) or heel (n = 12) initial contact, and continued walking. Vertical ground reaction forces and knee external adduction and flexor moments were extracted for the duration of the braking phase. Joint work was calculated for the ankle, knee, and hip in both the leading and trailing limbs.

RESULTS

Waveform analysis of the loading features indicated that a toe-contact strategy resulted in significantly reduced loading rates during early braking (1-32% of the braking phase) and significantly increased magnitude in late braking (55-96% of the braking phase). Individuals performing toe landings completed 33% greater overall work (p = 0.091) in the lead limb and utilised the lead limb ankle joint as the main shock absorber (79% of total lead limb work). Concurrently, the trailing limb performed 29% and 21% less work when lowering the centre of mass and propulsion, respectively, compared to a heel landing.

SIGNIFICANCE

A toe-contact strategy results in reduced limb and knee joint loading rates through greater utilisation of the lead limb ankle joint. A heel-contact strategy, however, can reduce loading during late braking by utilising the functionality of the trailing limb.

Mechanisms to Attenuate Load in the Intact Limb of Transtibial Amputees When Performing a Unilateral Drop Landing

Individuals with unilateral transtibial amputations experience greater work demand and loading on the intact limb compared with the prosthetic limb, placing this limb at a greater risk of knee joint degenerative conditions. It is possible that increased loading on the intact side may occur due to strength deficits and joint absorption mechanics. This study investigated the intact limb mechanics utilized to attenuate load, independent of prosthetic limb contributions and requirements for forward progression, which could provide an indication of deficiencies in the intact limb. Amputee and healthy control participants completed 3 unilateral drop landings from a 30-cm drop height. Joint angles at touchdown; range of motion; coupling angles; peak powers; and negative work of the ankle, knee, and hip were extracted together with isometric quadriceps strength measures. No significant differences were found in the load or movement mechanics (P ≥ .31, g ≤ 0.42), despite deficits in isometric maximum (20%) and explosive (25%) strength (P ≤ .13, g ≥ 0.61) in the intact limb. These results demonstrate that, when the influence from the prosthetic limb and task demand are absent, and despite deficits in strength, the intact limb adopts joint mechanics similar to able-bodied controls to attenuate limb loading.

Effect of physical therapy on early knee osteoarthritis with medial meniscal posterior tear assessed by MRI T2 mapping and 3D-to-2D registration technique: A prospective intervention study

Objectives: The purpose of this study was to verify that exercise aimed at improving knee kinematics in early-stage knee osteoarthritis (OA) patients with medial meniscus posterior root tears (MMPRTs) reduces knee adduction angle during gait and prevents rapid cartilage degeneration in the medial compartment of the knee.Methods: Subjects were randomly assigned to an adapting alignment exercise (AAE) group, with the goal of improving knee kinematics, and a muscle training and exercise (MTE) group. Before the start of the six-month intervention and following its completion, we performed an analysis of knee kinematics during gait using a 3D-to-2D registration technique and identified the area of cartilage degeneration using MRI T2 mapping.Results: The amount of change between pre- and post-intervention measurements of the maximum angle of adduction was 0.48° (95% CI: -0.14, 1.09) in the MTE group and -0.40° (-0.84, 0.04) in the AAE group (p = .039). The amount of change in the area of cartilage degeneration according to MRI T2 mapping expressed as MTE/AAE group was 7.7 mm² (-0.4, 15.8)/-2.7 mm² (-10.8, 5.3) at the posterior knee (p = .043).Conclusion: AAE could be a potential treatment method that improves the natural course of knee OA with MMRPTs.

Modeling knee osteoarthritis pathophysiology using an integrated joint system (IJS): a systematic review of relationships among cartilage thickness, gait mechanics, and subchondral bone mineral density

OBJECTIVE

To introduce an integrated joint system (IJS) model of joint health and osteoarthritis (OA) pathophysiology through a systematic review of the cross-sectional relationships among three knee properties (cartilage thickness, gait mechanics, and subchondral bone mineral density).

METHODS

Searches using keywords associated with the three knee properties of interest were performed in PubMed, Scopus, and Ovid databases. English-language articles reporting cross-sectional correlations between at least two knee properties in healthy or tibiofemoral OA human knees were included. A narrative synthesis of the data was conducted.

RESULTS

Of the 5600 retrieved articles, 13 were included, eight of which reported relationships between cartilage thickness and gait mechanics. The 744 tested knees were separated into three categories based on knee health: 199 healthy, 340 at-risk/early OA, and 205 late OA knees. Correlations between knee adduction moment and medial-to-lateral cartilage thickness ratios were generally positive in healthy, inconclusive in at-risk/early OA, and negative in late OA knees. Knee adduction moment was positively correlated with medial-to-lateral tibial subchondral bone mineral density ratios in knees of all health categories. One study reported a positive correlation between lateral tibial subchondral bone mineral density and femoral cartilage thickness in at-risk/early OA knees.

CONCLUSIONS

The correlations identified between knee properties in this review agreed with the proposed relationship-based IJS model of OA pathophysiology. Accordingly, the IJS model could provide insights into overcoming current barriers to developing disease-modifying treatments by considering multiple aspects of OA disease, aspects that could be assessed simultaneously at an in vivo system level.

Relationships between in vivo dynamic knee joint loading, static alignment and tibial subchondral bone microarchitecture in end-stage knee osteoarthritis

OBJECTIVE

To study, in end-stage knee osteoarthritis (OA) patients, relationships between indices of in vivo dynamic knee joint loads obtained pre-operatively using gait analysis, static knee alignment, and the subchondral trabecular bone (STB) microarchitecture of their excised tibial plateau quantified with 3D micro-CT.

DESIGN

Twenty-five knee OA patients scheduled for total knee arthroplasty underwent pre-operative gait analysis. Mechanical axis deviation (MAD) was determined radiographically. Following surgery, excised tibial plateaus were micro-CT-scanned and STB microarchitecture analysed in four subregions (anteromedial, posteromedial, anterolateral, posterolateral). Regional differences in STB microarchitecture and relationships between joint loading and microarchitecture were examined.

RESULTS

STB microarchitecture differed among subregions (P < 0.001), anteromedially exhibiting highest bone volume fraction (BV/TV) and lowest structure model index (SMI). Anteromedial BV/TV and SMI correlated strongest with the peak external rotation moment (ERM; r = -0.74, r = 0.67, P < 0.01), despite ERM being the lowest (by factor of 10) of the moments considered, with majority of ERM measures below accuracy thresholds; medial-to-lateral BV/TV ratios correlated with ERM, MAD, knee adduction moment (KAM) and internal rotation moment (|r|-range: 0.54-0.74). When controlling for walking speed, KAM and MAD, the ERM explained additional 11-30% of the variations in anteromedial BV/TV and medial-to-lateral BV/TV ratio (R² = 0.59, R² = 0.69, P < 0.01).

CONCLUSIONS

This preliminary study suggests significant associations between tibial plateau STB microarchitecture and knee joint loading indices in end-stage knee OA patients. Particularly, anteromedial BV/TV correlates strongest with ERM, whereas medial-to-lateral BV/TV ratio correlates strongest with indicators of medial-to-lateral joint loading (MAD, KAM) and rotational moments. However, associations with ERM should be interpreted with caution.

Tibial Osteotomy as a Mechanical Model of Primary Osteoarthritis in Rats

This study has presented the first purely biomechanical surgical model of osteoarthritis (OA) in rats, which could be more representative of the human primary disease than intra-articular techniques published previously. A surgical tibial osteotomy (TO) was used to induce degenerative cartilage changes in the medial knee of Sprague-Dawley rats. The presence of osteoarthritic changes in the medial knee compartment of the operated animals was evaluated histologically and through analysis of serum carboxy-terminal telepeptides of type II collagen (CTX-II). In-vivo biomechanical analyses were carried out using a musculoskeletal model of the rat hindlimb to evaluate the loading conditions in the knee pre and post-surgically. Qualitative and quantitative medial cartilage degeneration consistent with OA was found in the knees of the operated animals alongside elevated CTX-II levels and increased tibial compressive loading. The potential avoidance of joint inflammation post-surgically, the maintenance of internal joint biomechanics and the ability to quantify the alterations in joint loading should make this model of OA a better candidate for modeling primary forms of the disease in humans.

Effect of Asymmetrical Load Carrying on Joint Kinetics of the Lower Extremity During Walking in High-Heeled Shoes in Young Women

BACKGROUND

Carrying a load asymmetrically and walking in high-heeled shoes are common in women. Knowledge of the effects of the two combined conditions on lower-limb kinetics is lacking. We sought to examine the effects of walking in high-heeled shoes and carrying an asymmetrical load on the joint kinetics of the lower extremity in young women.

METHODS

Fifteen participants were asked to walk in flat-heeled and 9-cm high-heeled shoes and to asymmetrically carry loads of 0% body weight (BW), 5% BW, and 10% BW. The three-dimensional joint moments of the hip, knee, and ankle in each of the walking conditions were studied through ground reaction force measurements and motion analysis.

RESULTS

Walking in high-heeled shoes and asymmetrically carrying a load of 5% or 10% BW resulted in significant differences in ankle joint moments of the loaded and unloaded lower limbs. Compared with walking in flat-heeled shoes, walking in high-heeled shoes and carrying a load asymmetrically significantly increased hip extension, hip abduction, knee extension, and knee adduction moments and decreased ankle plantar moment of the loaded leg. Walking in high-heeled shoes carrying a load of 10% BW resulted in greater significant changes in hip abduction, knee extension, and ankle dorsiflexion moments in the loaded leg than did carrying a load of 5% BW.

CONCLUSIONS

These findings indicate that walking in high-heeled shoes and asymmetrical load carrying create significant differences in joint loading between the two limbs and alter lower-extremity kinetics.

Wolff's law in action: a mechanism for early knee osteoarthritis

There is growing interest in the role of bone in knee osteoarthritis. Bone is a dynamic organ, tightly regulated by a multitude of homeostatic controls, including genetic and environmental factors. One such key environmental regulator of periarticular bone is mechanical stimulation, which, according to Wolff’s law, is a key determinant of bone properties. Wolff’s law theorizes that repetitive loading of bone will cause adaptive responses enabling the bone to better cope with these loads. Despite being an adaptive response of bone, the remodeling process may inadvertently trigger maladaptive responses in other articular structures. Accumulating evidence at the knee suggests that expanding articular bone surface area is driven by mechanical stimulation and is a strong predictor of articular cartilage loss. Similarly, fractal analysis of bone architecture provides further clues that bone adaptation may have untoward consequences for joint health. This review hypothesizes that adaptations of periarticular bone in response to mechanical stimulation cause maladaptive responses in other articular structures that mediate the development of knee osteoarthritis. A potential disease paradigm to account for such a hypothesis is also proposed, and novel therapeutic targets that may have a bone-modifying effect, and therefore potentially a disease-modifying effect, are also explored.

Real-time visual feedback for gait retraining: toward application in knee osteoarthritis

Real-time visual feedback might be effective for gait retraining in patients with knee osteoarthritis, to potentially relieve symptoms and postpone knee replacement. In this study, we investigated the effect of various types of real-time visual feedback on a kinetic and a kinematic gait parameter and the different kinematic strategies adopted to reduce knee load. Seventeen healthy subjects walked on an instrumented treadmill while receiving real-time visual kinetic feedback aimed at minimizing the external knee adduction moment (KAdM, reflecting the knee load) or kinematic feedback on the hip internal rotation angle (HIR, a gait modification to reduce the KAdM). Four types of visual feedback (bar, polar plot, color change, graph) were provided. The KAdM decreased by 50 % with kinetic feedback, while kinematic feedback resulted in an HIR increase of 8° but no decrease in KAdM. The degree of change was not influenced by the type of visual feedback. The kinematic changes that reduced KAdM were increased toe-in, increased step width, and decreased hip adduction. Real-time visual feedback can effectively modify gait parameters. Feedback of the KAdM may be more effective in reducing the KAdM than controlling a kinematic parameter that is assumed to unload the knee.

Frontal plane knee mechanics and medial cartilage MR relaxation times in individuals with ACL reconstruction: A pilot study

BACKGROUND

The objective of this pilot study was to evaluate cartilage T1ρ and T2 relaxation times and knee mechanics during walking and drop-landing for individuals with anterior cruciate ligament reconstruction (ACL-R).

METHODS

Nine patients (6 men and 3 women, age 35.8 ± 5.4 years, BMI 23.5 ± 2.5 kg/m(2)) participated 1.5 ± 0.8 years after single-bundle two-tunnel ACL reconstruction. Peak knee adduction moment (KAM), flexion moment (KFM), extension moment (KEM), and peak varus were calculated from kinematic and kinetic data obtained during walking and drop-landing tasks. T1ρ and T2 times were calculated for medial femur (MF), and medial tibia (MT) cartilage and compared between subjects with low KAM and high KAM. Biomechanical variables were compared between limbs.

RESULTS

The high KAM group had higher T1ρ for MT (p=0.01), central MT (p=0.05), posterior MF (p=0.04), posterior MT (p=0.01); and higher T2 for MT (p=0.02), MF (p=0.05), posterior MF (p=0.002) and posterior MT (p=0.01). During walking, ACL-R knees had greater flexion at initial contact (p=0.04), and lower KEM (p=0.02). During drop-landing, the ACL-R knees had lower KAM (p=0.03) and KFM (p=0.002).

CONCLUSION

Patients with ACL-R who have higher KAM during walking had elevated MR relaxation times in the medial knee compartments. These data suggest that those individuals who have undergone ACL-R and have higher frontal plane loading, may be at a greater risk of knee osteoarthritis.

Age and obesity alter the relationship between femoral articular cartilage thickness and ambulatory loads in individuals without osteoarthritis

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 ± 3.8 years, BMI: 21.9 ± 1.9 kg/m(2)), middle-aged normal-weight (27 subjects, 47.0 ± 6.5 years, 22.7 ± 1.7 kg/m(2)), young overweight/obese (27 subjects, 28.4 ± 3.6 years, 33.3 ± 4.6 kg/m(2)), and middle-aged overweight/obese (27 subjects, 45.8 ± 7.2 years, 31.9 ± 4.4 kg/m(2)) individuals. On the lateral condyle, cartilage thickness was positively correlated with weight × height for all groups (R(2)  = 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)  = 0.19), as was the case for the correlation between adduction moment and medial-lateral thickness ratio (R(2)  = 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.

Quadriceps and hamstrings morphology is related to walking mechanics and knee cartilage MRI relaxation times in young adults

STUDY DESIGN

Controlled laboratory study using a cross-sectional design.

OBJECTIVES

To analyze the relationship of quadriceps-hamstrings and medial-lateral quadriceps anatomical cross-sectional area (ACSA) ratios with knee loads during walking and articular and meniscal cartilage composition in young, healthy subjects.

BACKGROUND

Muscle forces affect knee loading during walking, but it is not known if muscle morphology is associated with walking mechanics and cartilage composition in young subjects.

METHODS

Forty-two knees from 27 young, healthy, active volunteers (age, 20-35 years; body mass index, <28 kg/m(2)) underwent 3-T magnetic resonance imaging (MRI) and 3-D motion capture. Standard MRI sequences were used for articular and meniscal cartilage T1rho and T2 relaxation times and for quadriceps and hamstrings muscle ACSA. Frontal plane kinetics during the stance phase of walking was calculated. Generalized estimating equation models were used to identify muscle variables that predicted MRI and gait parameters.

RESULTS

Quadriceps-hamstrings and medial-lateral quadriceps ACSA ratios were positively related to frontal plane loading (β = .21-.54, P≤.006), global articular cartilage relaxation times (β = .22-.28, P≤.041), and the medial-lateral ratio of meniscus T1rho relaxation time (β = .26-.36, P≤.049). The medial-lateral quadriceps ACSA ratio was positively related to global meniscus T1rho relaxation times (β = .30, P = .046).

CONCLUSION

Higher quadriceps-hamstrings and medial-lateral quadriceps ACSA ratios were associated with higher frontal plane loading during walking and with articular and meniscal cartilage T1rho and T2 relaxation times. These findings highlight the relationships between different knee tissues and knee mechanics in young, healthy individuals.

Is increased joint loading detrimental to obese patients with knee osteoarthritis? A secondary data analysis from a randomized trial

OBJECTIVE

To investigate whether increased knee joint loading due to improved ambulatory function and walking speed following weight loss achieved over 16 weeks accelerates symptomatic and structural disease progression over a subsequent 1 year weight maintenance period in an obese population with knee osteoarthritis (OA).

METHODS

Data from a prospective study of weight loss in obese patients with knee OA (the CARtilage in obese knee OsteoarThritis (CAROT) study) were used to determine changes in knee joint compressive loadings (model estimated) during walking after a successful 16 week weight loss intervention. The participants were divided into 'Unloaders' (participants that reduced joint loads) and 'Loaders' (participants that increased joint loads). The primary symptomatic outcome was changes in knee symptoms, measured with the Knee injury and Osteoarthritis Outcome Score (KOOS) questionnaire, during a subsequent 52 weeks weight maintenance period. The primary structural outcome was changes in tibiofemoral cartilage loss assessed semi-quantitatively (Boston Leeds Knee Osteoarthritis Score (BLOKS) from MRI after the 52 weight maintenance period.

RESULTS

157 participants (82% of the CAROT cohort) with medial and/or lateral knee OA were classified as Unloaders (n = 100) or Loaders (n = 57). The groups showed similar significant changes in symptoms (group difference: -2.4 KOOS points [95% CI -6.8:1.9]) and cartilage loss (group difference: -0.06 BLOKS points [95% CI -0.22:0.11) after 1 year, with no statistically significant differences between Loaders and Unloaders.

CONCLUSION

For obese patients undergoing a significant weight loss, increased knee joint loading for 1 year was not associated with accelerated symptomatic and structural disease progression compared to a similar weight loss group that had reduced ambulatory compressive knee joint loads.

CLINICALTRIALSGOV

NCT00655941.

Investigation of the biomechanical effect of variable stiffness shoe on external knee adduction moment in various dynamic exercises

Background

The growing ageing population and high prevalence of knee osteoarthritis (OA) in athletes across nations have created a strong demand for improved non-invasive therapeutic alternatives for knee OA. The aim of this study is to investigate the effect of the variable stiffness shoe (VSS), a new non-invasive therapeutic approach, on external knee adduction moment (EKAM) in various dynamic exercises. EKAM is believed to have positive correlation with the progression and development of knee OA.

Methods

Thirty young participants (16 male and 14 female; age 22.6 ± 1.9 years) from National University of Singapore were enrolled in this study. The tested activities were walking, running, drop-landing, and lateral hopping. All the dynamic exercises were recorded simultaneously by the 8-camera VICON Motion Systems (Oxford Metric, UK) with a sampling rate of 100 Hz.

Results

The results showed that the EKAM was reduced in all the dynamic exercises with the use of VSS. The VSS produced significant reductions in the peak EKAM during walking (4.97%, p = 0.039), running (11.15%, p = 0.011), drop-landing (11.18%, p = 0.038) and lateral hopping (17.34%, p = 0.023) as compared to the control shoe.

Conclusions

The reduction of EKAM with the use of VSS in various dynamic exercises demonstrates its potential in delaying the onset and the progression of knee OA in early stage of knee OA patients.

Tibial coverage, meniscus position, size and damage in knees discordant for joint space narrowing - data from the Osteoarthritis Initiative

INTRODUCTION

Meniscal extrusion is thought to be associated with less meniscus coverage of the tibial surface, but the association of radiographic disease stage with quantitative measures of tibial plateau coverage is unknown. We therefore compared quantitative and semi-quantitative measures of meniscus position and morphology in individuals with bilateral painful knees discordant on medial joint space narrowing (mJSN).

METHODS

A sample of 60 participants from the first half (2,678 cases) of the Osteoarthritis Initiative cohort fulfilled the inclusion criteria: bilateral frequent pain, Osteoarthritis Research Society International (OARSI) mJSN grades 1-3 in one, no-JSN in the contra-lateral (CL), and no lateral JSN in either knee (43 unilateral mJSN1; 17 mJSN2/3; 22 men, 38 women, body mass index (BMI) 31.3 ± 3.9 kg/m(2)). Segmentation and three-dimensional quantitative analysis of the tibial plateau and meniscus, and semi-quantitative evaluation of meniscus damage (magnetic resonance imaging (MRI) osteoarthritis knee score = MOAKS) was performed using coronal 3T MR images (MPR DESSwe and intermediate-weighted turbo spin echo (IW-TSE) images). CL knees were compared using paired t-tests (between-knee, within-person design).

RESULTS

Medial tibial plateau coverage was 36 ± 9% in mJSN1 vs 45 ± 8% in CL no-JSN knees, and was 31 ± 9% in mJSN2/3 vs 46 ± 6% in no-JSN knees (both P < 0.001). mJSN knees showed greater meniscus extrusion and damage (MOAKS), but no significant difference in meniscus volume. No significant differences in lateral tibial coverage, lateral meniscus morphology or position were observed.

CONCLUSIONS

Knees with medial JSN showed substantially less medial tibial plateau coverage by the meniscus. We suggest that the less meniscal coverage, i.e., less mechanical protection may be a reason for greater rates of cartilage loss observed in JSN knees.

The biomechanical demands of standing yoga poses in seniors: The Yoga empowers seniors study (YESS)

Background

The number of older adults participating in yoga has increased dramatically in recent years; yet, the physical demands associated with yoga performance have not been reported. The primary aim of the Yoga Empowers Seniors Study (YESS) was to use biomechanical methods to quantify the physical demands associated with the performance of 7 commonly-practiced standing yoga poses in older adults.

Methods

20 ambulatory older adults (70.7 + − 3.8 yrs) attended 2 weekly 60-minute Hatha yoga classes for 32 weeks. The lower-extremity net joint moments of force (JMOFs), were obtained during the performance of the following poses: Chair, Wall Plank, Tree, Warrior II, Side Stretch, Crescent, and One-Legged Balance. Repeated-measure ANOVA and Tukey’s post-hoc tests were used to identify differences in JMOFs among the poses. Electromyographic analysis was used to support the JMOF findings.

Results

There was a significant main effect for pose, at the ankle, knee and hip, in the frontal and sagittal planes (p = 0.00 – 0.03). The Crescent, Chair, Warrior II, and One-legged Balance poses generated the greatest average support moments. Side Stretch generated the greatest average hip extensor and knee flexor JMOFs. Crescent placed the highest demands on the hip flexors and knee extensors. All of the poses produced ankle plantar-flexor JMOFs. In the frontal plane, the Tree generated the greatest average hip and knee abductor JMOFs; whereas Warrior II generated the greatest average hip and knee adductor JMOFs. Warrior II and One-legged Balance induced the largest average ankle evertor and invertor JMOFs, respectively. The electromyographic findings were consistent with the JMOF results.

Conclusions

Musculoskeletal demand varied significantly across the different poses. These findings may be used to guide the design of evidence-based yoga interventions that address individual-specific training and rehabilitation goals in seniors.

Clinical trial registration

This study is registered with NIH Clinicaltrials.gov #NCT 01411059

Gait characteristics and lower limb muscle strength in women with early and established knee osteoarthritis

BACKGROUND

Based on novel classification criteria using magnetic resonance imaging, a subpopulation of "early knee osteoarthritis patients" was clearly defined recently. This study assessed whether these early osteoarthritis patients already exhibit gait adaptations (knee joint loading in particular) and changes in muscle strength compared to control subjects and established knee osteoarthritis patients.

METHODS

Fourteen female patients with early knee joint degeneration, defined by magnetic resonance imaging (early osteoarthritis), 12 female patients with established osteoarthritis and 14 female control subjects participated. Specific gait parameters and lower limb muscle strength were analyzed and compared between groups. Within the osteoarthritis groups, association between muscle strength and dynamic knee joint loading was also evaluated.

FINDINGS

Early osteoarthritis patients presented no altered gait pattern, no significant increase in knee joint loading and no significant decrease in hamstring muscle strength compared to controls, while established osteoarthritis patients did. In contrast, early osteoarthritis patients experienced significant quadriceps weakness, comparable to established osteoarthritis patients. Within the osteoarthritis groups, muscle strength was not correlated with knee joint loading during gait.

INTERPRETATION

The results suggest that gait changes reflect mechanical overload and are most likely the consequence of structural degeneration in knee osteoarthritis. Quadriceps weakness might however contribute to the onset and progression of the disease. This study supports the relevance of classification of early osteoarthritis patients and assists in identifying their functional characteristics. This helps to understand the trajectory of disease onset and progression and further develop more targeted strategies for prevention and treatment of knee osteoarthritis.

Trabecular bone structure and spatial differences in articular cartilage MR relaxation times in individuals with posterior horn medial meniscal tears

OBJECTIVE

To analyze knee trabecular bone structure and spatial cartilage T(1ρ) and T(2) relaxation times using 3-T magnetic resonance imaging (MRI) in subjects with and without tears of posterior horn of the medial meniscus (PHMM).

DESIGN

3-T MRI from 59 subjects (>18 years), were used to evaluate PHMM tears based on modified Whole-Organ Magnetic Resonance Imaging Score (WORMS) scoring; and to calculate apparent trabecular bone-volume over total bone volume fraction (app. BV/TV), apparent trabecular number (app. Tb.N), apparent trabecular separation (app. Tb.Sp) and apparent trabecular thickness (app. Tb.Th) for overall femur/tibia and medial/lateral femur/tibia; and relaxation times for deep and superficial layers of articular cartilage. A repeated measures analysis using Generalized Estimating Equation (GEE) was performed to compare trabecular bone and cartilage relaxation time parameters between people with (n = 35) and without (n = 24) PHMM tears, while adjusting for age and knee OA presence.

RESULTS

Subjects with PHMM tears had lower app. BV/TV and app. Tb.N, and greater app. Tb.Th, and app. Tb.Sp. They also had higher T(1ρ) times in the deep cartilage layer for lateral tibia and medial femur and higher T(2) relaxation times for the deep cartilage layer across all compartments.

CONCLUSIONS

PHMM tears are associated with differences in underlying trabecular bone and deep layer of cartilage. Over-load of subchondral bone can lead to its sclerosis and stress shielding of trabecular bone leading to the resorptive changes observed in this study. The results underline the importance of interactions of trabecular bone and cartilage in the pathogenesis of knee OA in people with PHMM tears.

The physical demands of the tree (vriksasana) and one-leg balance (utthita hasta padangusthasana) poses performed by seniors: a biomechanical examination

Yoga is considered especially suitable for seniors because poses can be modified to accommodate practitioners' capabilities and limitations. In this study, biomechanical assessments on healthy seniors (n = 20; 70.1 ± 3.8 yr) were used to quantify the physical demands, (net joint moments of force [JMOFs] and muscular activation in the lower extremities) associated with the performance of 3 variations (introductory, intermediate, advanced) of 2 classical Hatha yoga poses - Tree and One-Leg Balance (OLB). ANOVA and Cohen's-d were used to contrast the postural variations statistically. The advanced (single-limb, without additional support) versions were hypothesized to generate the greatest demands, followed by the intermediate (single-limb [Tree] and bilateral-limb [OLB] with support) and introductory (bilateral-limb) versions. Our findings, however, suggest that common, long-held conceptions about pose modifications can be counter-intuitive. There was no difference between the intermediate and advanced Tree variations regarding hip and knee JMOFs in both the sagittal and frontal planes (P = 0.13-0.98). Similarly, OLB introductory and intermediate variations induced sagittal JMOFs that were in the opposite direction of the classic advanced pose version at the hip and knee (P < .001; d = 0.98-2.36). These biomechanical insights provide evidence that may be used by instructors, clinicians and therapists when selecting pose modifications for their yoga participants.

The relationship between pain and dynamic knee joint loading in knee osteoarthritis varies with radiographic disease severity. A cross sectional study

OBJECTIVE

In a cross sectional study, we investigated the relationships between knee pain and mechanical loading across the knee, as indicated by the external knee adduction moment (KAM) during walking in patients with symptomatic knee OA who were distinguished by different radiographic disease severities.

METHODS

Data from 137 symptomatic medial knee OA patients were used. Based on Kellgren/Lawrence (K/L) grading, the patients were divided into radiographically less severe (K/L ≤ 2, n=68) or severe (K/L>2, n=69) medial knee OA. Overall knee pain was rated on a 10 cm visual analog scale, and peak KAM and KAM impulses were obtained from gait analyses. Mixed linear regression analyses were performed with KAM variables as the outcome, and pain and disease severity as independent variables, adjusting for age, gender, and walking speed.

RESULTS

In adjusted analyses, less severe patients demonstrated negative relationships between pain intensities and dynamic loading. The severe patient group showed no relationship between pain intensity and peak KAM, and a positive relationship between pain intensity and KAM impulse.

CONCLUSION

In radiographically less severe knee OA, the negative relationships between pain intensity and dynamic knee joint loading indicate a natural reaction to pain, which will limit the stress on the joint. In contrast, either absent or positive relationships between pain and dynamic loading in severe OA may lead to overuse and accelerated disease progression. These findings may have a large potential interest for strategies of treatment in knee OA.

Relationship between knee kinetics during jumping tasks and knee articular cartilage MRI T1rho and T2 relaxation times

BACKGROUND

Articular cartilage of young healthy individuals is dynamic and responsive to loading behaviors. The purpose of this study was to evaluate the relationship of cartilage T(1ρ) and T(2) relaxation times with loading kinetics during jumping tasks in healthy young individuals.

METHODS

Fourteen healthy subjects underwent: 1) motion analysis while performing a unilateral hopping task and bilateral drop jumping task; and 2) quantitative imaging using a 3 Tesla MRI for T(1ρ) and T(2) relaxation time analysis. Three dimensional net joint moments and angular impulse was calculated using standard inverse dynamics equations. Average T(1ρ) and T(2) relaxation times and medial-lateral ratios for each were calculated. Multiple regression was used to identify predictors of cartilage relaxation times.

FINDINGS

Average knee flexion moment during hopping was observed to best predict overall T(1ρ) (R(2)=.185) and T(2) (R(2)=.154) values. Peak knee adduction moment during a drop jump was the best predictor of the T(1ρ) medial-lateral ratio (R(2)=.220). The T(2) medial-lateral ratio was best predicted by average internal rotation moment during the drop jump (R(2)=.174).

INTERPRETATION

These data suggest that loads across the knee may affect the biochemistry of the cartilage. In young healthy individuals, higher flexion moments were associated with decreased T(1ρ) and T(2) values, suggesting a potentially beneficial effect. The medial-to-lateral ratio of T(1ρ) and T(2) times appears to be related to the frontal and transverse plane joint mechanics. These data offer promising findings of potentially modifiable parameters associated with cartilage composition.

Sex-specific gait patterns of older adults with knee osteoarthritis: results from the Baltimore longitudinal study of aging

Men and women exhibit different gait patterns during customary walking and may respond differently to joint diseases. The present paper aims to identify gait patterns associated with knee-OA separately in men and women. Participants included 144 men and 124 women aged 60 years and older enrolled in the Baltimore Longitudinal Study of Aging (BLSA) who underwent gait testing at a self-selected speed. Both men and women with knee-OA had lower ankle propulsion mechanical work expenditure (MWE; P < .001 for both) and higher hip generative MWE (P < .001) compared to non-OA controls. Women with knee-OA had a higher BMI (P = .008), slower gait speed (P = .049), and higher knee frontal-plane absorbing MWE (P = .007) than women without knee-OA. These differences were not observed in men. Understanding sex-specific differences in gait adaptation to knee-OA may inform the development of appropriate strategies for early detection and intervention for knee-OA in men and women.

The Influence of Radiographic Severity on the Relationship between Muscle Strength and Joint Loading in Obese Knee Osteoarthritis Patients

Objective. To investigate the relationship between knee muscle strength and the external knee adduction moment during walking in obese knee osteoarthritis patients and whether disease severity influences this relationship. Methods. This cross-sectional study included 136 elderly obese (BMI > 30) adults with predominant medial knee osteoarthritis. Muscle strength, standing radiographic severity as measured by the Kellgren and Lawrence scale, and the peak external knee adduction moment were measured at self-selected walking speed. Results. According to radiographic severity, patients were classified as “less severe” (KL 1-2, N = 73) or “severe” (KL 3-4, N = 63). A significant positive association was demonstrated between the peak knee adduction moment and hamstring muscle strength in the whole cohort (P = .047). However, disease severity did not influence the relationship between muscle strength and dynamic medial knee joint loading. Severe patients had higher peak knee adduction moment and more varus malalignment (P < .001). Conclusion. Higher hamstring muscle strength relates to higher estimates of dynamic knee joint loading in the medial compartment. No such relationship existed for quadriceps muscle strength. Although cross sectional, the results suggest that hamstrings function should receive increased attention in future studies and treatments that aim at halting disease progression.

Quantitative cartilage imaging in knee osteoarthritis

Quantitative measures of cartilage morphology (i.e., thickness) represent potentially powerful surrogate endpoints in osteoarthritis (OA). These can be used to identify risk factors of structural disease progression and can facilitate the clinical efficacy testing of structure modifying drugs in OA. This paper focuses on quantitative imaging of articular cartilage morphology in the knee, and will specifically deal with different cartilage morphology outcome variables and regions of interest, the relative performance and relationship between cartilage morphology measures, reference values for MRI-based knee cartilage morphometry, imaging protocols for measurement of cartilage morphology (including those used in the Osteoarthritis Initiative), sensitivity to change observed in knee OA, spatial patterns of cartilage loss as derived by subregional analysis, comparison of MRI changes with radiographic changes, risk factors of MRI-based cartilage loss in knee OA, the correlation of MRI-based cartilage loss with clinical outcomes, treatment response in knee OA, and future directions of the field.