J.L. Asay

Adaptive patterns of movement during stair climbing in patients with knee osteoarthritis

The purpose of this study was to determine if there is a distinctive characteristic in the pattern of movement (forward trunk lean to reduce demand on the quadriceps muscle) during stair climbing in patients with knee osteoarthritis (OA) that is associated with the severity of the disease. Twenty‐three patients with radiographically diagnosed knee OA and 20 physically active adults performed stair ascending trials without support at their self‐selected speed. Standard gait analysis was used to calculate three‐dimensional lower extremity joint kinematics and kinetics. Forward trunk lean, or trunk flexion, was defined as the sagittal plane projection of the angle between a line connecting the midpoint of the trans‐acromion line and the midpoint of the trans‐iliac crest line and the global vertical axis. Patients with more severe knee OA (KL ≥ 3) had greater forward trunk lean (+6.3°, p = 0.045) and lower knee net quadriceps moments (−35.2%, p = 0.001) than controls. In more severe patients, the forward trunk lean was correlated with a reduction in the net quadriceps moment during stair climbing (R2 = 0.590, p = 0.006). The results of this study identified a distinctive compensatory pattern of movement to reduce the quadriceps demand during stair climbing in patients with more severe knee OA by increasing forward trunk lean. Assessing forward trunk lean during stair climbing may be a useful functional marker for evaluating osteoarthritis status and quadriceps function that appears to be a more sensitive indicator of disease severity than perceived pain.

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/m2), middle‐aged normal‐weight (27 subjects, 47.0 ± 6.5 years, 22.7 ± 1.7 kg/m2), young overweight/obese (27 subjects, 28.4 ± 3.6 years, 33.3 ± 4.6 kg/m2), and middle‐aged overweight/obese (27 subjects, 45.8 ± 7.2 years, 31.9 ± 4.4 kg/m2) individuals. On the lateral condyle, cartilage thickness was positively correlated with weight × height for all groups (R2 = 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 (R2 = 0.19), as was the case for the correlation between adduction moment and medial–lateral thickness ratio (R2 = 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.

A relationship between mechanically-induced changes in serum cartilage oligomeric matrix protein (COMP) and changes in cartilage thickness after 5 years.

OBJECTIVE To evaluate the hypothesis that a mechanical stimulus (30-min walk) will produce a change in serum concentrations of cartilage oligomeric matrix protein (COMP) that is associated with cartilage thickness changes on magnetic resonance imaging (MRI). METHODS Serum COMP concentrations were measured by enzyme-linked immunosorbent assay in 17 patients (11 females, age: 59.0±9.2 years) with medial compartment knee osteoarthritis (OA) at study entry immediately before, immediately after, 3.5 h, and 5.5 h after a 30-min walking activity. Cartilage thickness changes in the medial femur and medial tibia were determined from MR images taken at study entry and at 5-year follow-up. Relationships between changes in cartilage thickness and COMP levels, with post-activity concentrations expressed as a percentage of pre-activity levels, were assessed by the calculation of Pearson correlation coefficients and by multiple linear regression analysis, with adjustments for age, sex, and body mass index (BMI). RESULTS Changes in COMP levels 3.5 h and 5.5 h post-activity were correlated with changes in cartilage thickness in the medial femur and tibia at the 5-year follow-up. The results were strengthened after analyses were adjusted for age, sex, and BMI. Neither baseline pre-activity COMP levels nor changes in COMP levels immediately post-activity were correlated with cartilage thickness changes. CONCLUSIONS The results of this study support the hypothesis that a change in COMP concentration induced by a mechanical stimulus is associated with cartilage thinning at 5 years. Mechanically-induced changes in mechano-sensitive biomarkers should be further explored in the context of stimulus-response models to improve the ability to assess OA progression.

Sensitivity of gait parameters to the effects of anti‐inflammatory and opioid treatments in knee osteoarthritis patients

The study aim was to address the need for objective markers of pain‐modifying interventions by testing the hypothesis that selective gait measures of knee joint loading can distinguish differences between non‐steroidal anti‐inflammatory (NSAID), analgesic treatment (opioid‐receptor agonist), and placebo in patients medial knee osteoarthritis (OA). A randomized, single‐blind washout, double‐blind treatment, double‐dummy cross‐over trial using three treatment arms placebo, opioid (Oxycodone), and NSAID (Celecoxib) in medial compartment knee OA patients. Six patients with Kellgren–Lawrence radiographic severity grades of 2 or 3 completed six testing sessions (gait and pain assessment) at 2‐week intervals. A significant increase was found in the knee total reaction moment and vertical ground reaction force (GRF) for Celecoxib compared to placebo (p = 0.005, p = 0.003), but not for Oxycodone compared to placebo (p = 0.20, p = 0.27) treatments. Walking speed was significantly higher for the Celecoxib and Oxycodone compared to placebo treatment (p = 0.041 and p = 0.031, respectively). Self‐reported function (WOMAC scores) was not different among treatments (p > 0.05). The changes in total reaction moments and GRFs for only the NSAID suggest that greater increases in joint loading occurs when joint inflammation is treated in addition to pain. The total knee reaction moment, representing the magnitude of the extrinsic moment, appears to be a sensitive marker, more so than self‐reported metrics, for evaluating knee OA treatment effects.

Adduction moment increases with age in healthy obese individuals

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 (R2 = 0.19), but not in normal‐weight individuals (R2 = 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 (R2 = 0.19 and 0.51), but only limb position changed with age (R2 = 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.

Effects of high heel wear and increased weight on the knee during walking

Knee osteoarthritis (OA), a leading cause of disability, is more prevalent in women than men. Wearing high heeled shoes has been implicated as a potential contributing factor for the higher lifetime risk of osteoarthritis in women. This study tests the hypotheses that changes to knee kinematics and kinetics observed during high heeled walking increase in magnitude with increasing heel height and are accentuated by a 20% increase in weight. Fourteen healthy females were tested using marker‐based gait analysis in combinations of footwear (flat athletic shoe, 3.8 cm and 8.3 cm heeled shoes) and weight (with and without 20% bodyweight vest). At preferred walking speed, knee flexion angle at heel‐strike and midstance increased with increasing heel height and weight. Maximum knee extension moment during loading response decreased with added weight; maximum knee extension moment during terminal stance decreased with heel height; maximum adduction moments increased with heel height. Many of the changes observed with increasing heel height and weight were similar to those seen with aging and OA progression. This suggests that high heel use, especially in combination with additional weight, may contribute to increased OA risk in women.

Repeatability of Gait Analysis for Measuring Knee Osteoarthritis Pain in Patients with Severe Chronic Pain

Gait measures are receiving increased attention in the evaluation of patients with knee osteoarthritis (OA). Yet, there remains a need to assess variability of gait analysis in patients with knee osteoarthritis over time and how pain affects variation in these gait parameters. The purpose of this study was to determine if important gait parameters, such as the knee adduction moment, knee flexion moment, peak vertical ground reaction force, and speed, were repeatable in patients with mild‐to‐moderate knee OA over a trial period of 12 weeks. Six patients were enrolled in this cross‐over study design after meeting strict inclusion criteria. Gait tests were conducted three times at 4 week intervals and once after the placebo arm of a randomized treatment sequence; each gait test followed a 2‐week period of receiving a placebo for a pain modifying drug. Repeatability for each gait variable was found using intraclass correlation coefficients (ICC) with a two‐way random model. This study found that the knee adduction moment was repeatable throughout the four gait tests. However, normalized peak vertical ground reaction force and knee flexion moment were not as repeatable, varying with pain. This suggests that these gait outcomes could offer a more objective way to measure a patients level of pain.

Gait mechanics 2 years after anterior cruciate ligament reconstruction are associated with longer-term changes in patient-reported outcomes.

This study tested the hypothesis that side‐to‐side differences in knee gait mechanics 2 years after anterior cruciate ligament (ACL) reconstruction are associated with long‐term (∼8 years post‐reconstruction) changes in patient‐reported outcome scores. Sixteen subjects (5 males; age: 29.1 ± 7.1 years) with primary unilateral ACL reconstruction were gait tested at baseline (2.2 ± 0.3 years post‐ACL reconstruction) and filled out KOOS and Lysholm surveys. At long‐term follow‐up (7.7 ± 0.7 years post‐ACL reconstruction), the same subjects completed KOOS and Lysholm surveys. Pearson correlation coefficients assessed relationships between side‐to‐side differences in kinematics and kinetics at baseline and changes in Lysholm and KOOS Pain/QOL scores from 2 to 8 years post‐ACL reconstruction. Significant associations were seen between greater average varus rotation (Lysholm: R = −0.654, p = 0.006) and less anterior femoral displacement (Lysholm: R = 0.578, p = 0.019) during stance of the ACL reconstructed knee versus the contralateral knee at baseline and worse follow‐up outcome scores. Significant associations were seen between greater peak knee flexion moment (KOOS Pain: R = −0.572, p = 0.026; KOOS QOL: R = −0.636, p = 0.011), peak knee adduction moment (Lysholm: R = −0.582, p = 0.018; KOOS Pain: R = −0.742, p = 0.002; KOOS QOL: R = −0.551, p = 0.033), and peak internal rotation moment (Lysholm: R = 0.525, p = 0.037; KOOS Pain: R = 0.815, p < 0.001; KOOS QOL: R = 0.777, p = 0.001) in the ACL reconstructed knee at baseline with worse follow‐up outcomes. The results of this study support the hypotheses that early changes in gait mechanics following ACL reconstruction are associated with longer‐term clinical changes in patient‐reported outcomes, suggesting that biomechanical markers obtained as early as 2 years after ACL reconstruction may be useful to understand clinical outcomes in this population.

The effects of active feedback gait retraining to produce a medial weight transfer at the foot in subjects with symptomatic medial knee osteoarthritis

This study aimed to determine if active feedback gait retraining to produce a medial weight transfer at the foot significantly reduces the knee adduction moment in subjects with medial compartment knee osteoarthritis. Secondarily, changes in peak knee flexion moment, frontal plane knee and ankle kinematics, and center of pressure were investigated. Ten individuals with medial compartment knee osteoarthritis (9 males; age: 65.3 ± 9.8 years; BMI: 27.8 ± 3.0 kg/m2) were tested at self‐selected normal and fast speeds in two conditions: Intervention, with an active feedback device attached to the shoe of their more affected leg, and control, with the device de‐activated. Kinematics and kinetics were assessed using a motion capture system and force plate. The first peak, second peak, and impulse of the knee adduction moment were significantly reduced by 6.0%, 13.9%, and 9.2%, respectively, at normal speed, with reductions of 10.7% and 8.6% in first peak and impulse at fast speed, respectively, with the active feedback system, with no significant effect on the peak knee flexion moment. Significant reductions in peak varus knee angle and medialized center of pressure in the first half of stance were observed, with reductions in peak varus knee angle associated with reductions in the knee adduction moment. This study demonstrated that active feedback to produce a medial weight‐bearing shift at the foot reduces the peaks and impulse of the knee adduction moment in patients with medial compartment knee osteoarthritis. Future research should determine the long‐term effect of the active feedback intervention on joint loading, pain, and function.

Changes in the total knee joint moment in patients with medial compartment knee osteoarthritis over 5 years: OA TOTAL KNEE JOINT MOMENT

Progression of medial compartment knee osteoarthritis (OA) has been associated with repetitive mechanical loading during walking, often characterized by the peak knee adduction (KAM) and knee flexion moments (KFM). However, the relative contributions of these components to the knee total joint moment (TJM) can change as the disease progresses since KAM and KFM are influenced by different factors that change over time. This study tested the hypothesis that the relative contributions of KAM, KFM, and the rotational moment (KRM) to the TJM change over time in subjects with medial compartment knee OA. Patients with medial compartment knee OA (n = 19) were tested walking at their self‐selected speed at baseline and a 5‐year follow‐up. For each frame during stance, the TJM was calculated using the KAM, KFM, and KRM. The peaks of the TJM and the relative contributions of the moment components at the time of the peaks of the TJM were tested for changes between baseline and follow‐up. The percent contribution of KFM to the first peak of the TJM (TJM1) significantly decreased (p < 0.001) and the percent contribution of KAM to TJM1 significantly increased (p < 0.001), while the magnitude of the TJM1 did not significantly change over the 5‐year follow‐up. These gait changes with disease progression appear to maintain a constant TJM1, but the transition from a KFM to a KAM dominance appears to reflect gait changes associated with progressing OA and pain. Thus, the TJM and its component analysis captures a comprehensive metric for total loading on the knee over time. Published 2018. This article is a U.S. Government work and is in the public domain in the USA. 36:2373–2379, 2018.