Are There Sex Differences in Knee Cartilage Composition and Walking Mechanics in Healthy and Osteoarthritis Populations?

The Mediation Effects of Malalignment on the Relation of Sex to The Risk of Incidence Tibiofemoral Osteoarthritis

OBJECTIVE

To investigate to what extent the higher risk of tibiofemoral radiographic osteoarthritis (TFROA) in females vs. males can be explained by knee malalignment.

DESIGN

Using data from Multicenter Osteoarthritis Study (MOST) and Osteoarthritis Initiative (OAI), we examined the relation of sex to the incident medial and lateral TFROA and performed mediation analyses to assess to what extent varus and valgus malalignments account for sex differences in the incident medial or lateral TFROA.

RESULTS

Of the 3,462 knees without medial and lateral TFROA in MOST, the 7-year risks of medial and lateral TFROA were 16.9% and 10.0% in females, and 15.8% and 4.2% in males, respectively. Females had 2.31-fold (95% CI: 1.73 to 3.08) higher incident lateral TFROA than males, and the relative risk (RR) of the indirect effect of sex on lateral TFROA through valgus malalignment was 1.15 (95% CI:1.09 to 1.20), accounting for 23% of its total effect on lateral TFROA. In OAI (n=3,095 knees), females had 1.54-fold (95% CI:1.15 to 2.04) higher incident lateral TFROA than males, and RR of the indirect effect of sex on lateral TFROA through valgus malalignment was 1.10 (95% CI:1.04 to 1.21), accounting for 26% of its total effect on lateral TFROA. No apparent sex difference in the incident medial TFROA was found in MOST (RR=1.05, 95% CI: 0.89 to 1.25) or OAI (RR=1.02, 95% CI: 0.84 to 1.19).

CONCLUSION

Females had a higher risk of developing lateral TFROA than males; however, valgus malalignment only modestly explained such a difference.

Sexual dimorphism in articular tissue anatomy - Key to understanding sex differences in osteoarthritis

OBJECTIVE

Osteoarthritis (OA) prevalence and incidence varies between women and men, but it is unknown whether this follows sex-specific differences in systemic factors (e.g. hormones) and/or differences in pre-morbid joint anatomy. We recognize that classifications of sex within humans cannot be reduced to female/male, but given the lack of literature on non-binary individuals, this review is limited to the sexual dimorphism of articular tissues.

METHODS

Based on a Pubmed search using relevant terms, and input from experts, we selected articles based on the authors' judgment of their relevance, interest, originality, and scientific quality; no "hard" bibliometric measures were used to evaluate their quality or importance. Focus was on clinical rather than pre-clinical studies, with most (imaging) data being available for the knee joint.

RESULTS

After introducing "sexual dimorphism", the specific literature on articular structures is reviewed, structured by: radiographic joint space width (JSW), meniscus, ligaments, articular cartilage metrics, articular cartilage composition and deformation, and articular tissue response to treatment.

CONCLUSIONS

Sex-specific differences were clearly observed for JSW, meniscus damage, ligament size, and cartilage metrics (volume, thickness, and surface areas) but not for cartilage composition. Ligament and cartilage metrics were smaller in women even after matching for confounders. Taken together, the findings indicate that female (knee) joints may be structurally more vulnerable and at greater risk of OA. The "one size/sex fits all" approach must be abandoned in OA research, and all observational and interventional studies should report their results for sex-specific strata, at least in pre-specified secondary or post-hoc analyses.

Sex differences in osteoarthritis prevalence, pain perception, physical function and therapeutics

OBJECTIVE

Women have a higher prevalence of osteoarthritis (OA) and worse clinical courses than men. However, the underlying factors and therapeutic outcomes of these sex-specific differences are incompletely researched. This review examines the current state of knowledge regarding sex differences in OA prevalence, risk factors, pain severity, functional outcomes, and use and response to therapeutics.

METHODS

PubMed database was used with the title keyword combinations "{gender OR sex} AND osteoarthritis" plus additional manual search of the included papers for pertinent references, yielding 212 references. Additional references were added and 343 that were reviewed for appropriateness.

RESULTS

Globally, women account for 60% of people with osteoarthritis with a greater difference after age 40. The higher risk for women may be due to differences in joint anatomy, alignment, muscle strength, hormonal influences, obesity, and/or genetics. At the same radiographic severity, women have greater pain severity than men, which may be explained by biologically distinct pain pathways, differential activation of central pain pathways, differences in pain sensitivity, perception, reporting, and coping strategies. Women have greater limitations of physical function and performance than men independent of BMI, OA severity, injury history, amount of weekly exercise. Women also have greater use of analgesic medications than men but less use of arthroplasty and poorer prognosis after surgical interventions.

CONCLUSIONS

The recognition of sex differences in OA manifestations and management could guide tailoring of sex-specific treatment protocols, and analysis of sex as a biological variable in future research would enhance development of precision medicine.

Sex does not influence the long-term outcome of matrix-assisted autologous chondrocyte transplantation

PURPOSE

Regenerative techniques for articular cartilage lesions demonstrated heterogeneous clinical results. Several factors may influence the outcome, with sex being one of the most debated. This study aimed at quantifying the long-term influence of sex on the clinical outcome obtained with a regenerative procedure for knee chondral lesions.

METHODS

Matrix-assisted autologous chondrocyte transplantation (MACT) was used to treat 235 knees which were prospectively evaluated with the International Knee Documentation Committee (IKDC), EuroQol visual analogue scale, and Tegner scores at 14-year mean follow-up. A multilevel analysis was performed with the IKDC subjective scores standardised according to the age/sex category of each patient and/or the selection of a match-paired subgroup to compare homogeneous men and women patients.

RESULTS

At 14 years, men and women showed a failure rate of 10.7% and 28.8%, respectively (p < 0.0005). An overall improvement was observed in both sexes. Women had more patellar lesions and men more condylar lesions (p = 0.001), and the latter also presented a higher preinjury activity level (p < 0.0005). Men had significantly higher IKDC subjective scores at all follow-ups (at 14 years: 77.2 ± 18.9 vs. 62.8 ± 23.1; p < 0.0005). However, the analysis of homogeneous match-paired populations of men and women, with standardised IKDC subjective scores, showed no differences between men and women (at 14 years: -1.6 ± 1.7 vs. -1.9 ± 1.6).

CONCLUSION

Men and women treated with MACT for knee chondral lesions presented a significant improvement and stable long-term results. When both sexes are compared with homogeneous match-paired groups, they have similar results over time. However, women present more often unfavourable lesion patterns, which proved more challenging in terms of long-term outcome after MACT.

LEVEL OF EVIDENCE

Level II.

Sex-related differences in gait characteristics and their associations with symptoms in individuals with patellofemoral osteoarthritis

BACKGROUND

Patellofemoral osteoarthritis (OA) is an important subgroup of knee OA. However, the influence of sex on gait characteristics in patients with patellofemoral OA is unknown.

RESEARCH QUESTION

Compare gait characteristics in females and males with patellofemoral OA and investigate their associations with patellofemoral joint-related symptoms and limitations.

METHODS

Mixed effects polynomial regression models compared knee flexion-extension and adduction moments, knee flexion angles, and vertical ground reaction forces over 100% of stance between 26 females and 22 males with patellofemoral OA, with and without adjustment for walking speed and body mass. Multivariable linear regression models were then used to investigate the associations of gait characteristics with symptoms and limitations measured with the Knee injury and Osteoarthritis Outcome Score Patellofemoral Pain and Osteoarthritis (KOOS-PF) Subscale. Models included a sex-by-gait interaction term, and if significant, separate models were built for females and males.

RESULTS

While controlling for walking speed and body mass, females had lower knee flexion moment (6-19% and 97-100% of stance), knee extension moment (45-86% of stance), knee adduction moment (3-37% and 69-99% of stance), vertical ground reaction force (1-97% of stance) and knee flexion angle (90-100% of stance) compared with males, when fitted over 100% of stance. Lower cadence, lower knee flexion angular impulse, and higher peak knee flexion angle were associated with worse KOOS-PF scores. Associations were not modified by sex.

SIGNIFICANCE

There are distinct sex-based differences in gait characteristics throughout stance with patellofemoral OA when adjusting for body mass and walking speed. Lower cadence and knee flexion angular impulse, and higher peak knee flexion angle were associated with more extreme patellofemoral joint-related symptoms and limitations.

Delayed cartilage oligomeric matrix protein response to loading is associated with femoral cartilage composition post-ACLR

PURPOSE

To determine associations between immediate and delayed response of serum cartilage oligomeric matrix protein (sCOMP) to loading (i.e., 3000 walking steps) and femoral cartilage interlimb T1ρ relaxation times in individual's post-anterior cruciate ligament reconstruction (ACLR).

METHODS

This cross-sectional study included 20 individuals 6-12 months following primary ACLR (65% female, 20.5 ± 4.0 years old, 24.9 ± 3.0 kg/m2, 7.3 ± 1.5 months post-ACLR). Serum samples were collected prior to, immediately following, and 3.5 h following walking 3000 steps on a treadmill at habitual walking speed. sCOMP concentrations were processed using enzyme-linked immunosorbent assays. Immediate and delayed absolute sCOMP responses to loading were evaluated immediately and 3.5 h post-walking, respectively. Participants underwent bilateral magnetic resonance imaging with T1ρ sequences to calculate resting femoral cartilage interlimb T1ρ relaxation time ratios between limbs (i.e., ACLR/Uninjured limb). Linear regression models were fitted to determine associations between sCOMP response to loading and femoral cartilage T1ρ outcomes controlling for pre-loading sCOMP concentrations.

RESULTS

Greater increases in delayed sCOMP response to loading were associated with greater lateral (∆R2 = 0.29, p = 0.02) but not medial (∆R2 < 0.01, p = 0.99) femoral cartilage interlimb T1ρ ratios. Associations between immediate sCOMP response to loading with femoral cartilage interlimb T1ρ ratios were weak and non-significant (∆R2 range = 0.02-0.09, p range = 0.21-0.58).

CONCLUSION

Greater delayed sCOMP response to loading, a biomarker of cartilage breakdown, is associated with worse lateral femoral cartilage composition in the ACLR limb compared to the uninjured limb. Delayed sCOMP response to loading may be a more indicative metabolic indicator linked to deleterious changes in composition than immediate sCOMP response.

Delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Cartilage Values in Hips With Bone Marrow Lesions

OBJECTIVE

Bone marrow lesions (BMLs) are associated with painful and progressive osteoarthritis (OA). Quantitative magnetic resonance imaging (MRI) has been used to study early cartilage degeneration in knees with BML, but similar work has not been done in hips. The purpose of this study was to compare mean delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) relaxation values (T1Gd) in hips with BML to hips without BML in a population-based study. Reduced T1Gd suggests depleted glycosaminoglycan. Our hypothesis was that mean T1Gd is lower in hips with BML compared to hips without BML.

METHODS

Study participants (n = 128) were recruited from a cross-sectional population-based study of people ages 20-49 years with and without hip pain. dGEMRIC and proton density (PD)-weighted MRI scans of 1 hip from each participant were used for this analysis. BMLs were identified from PD-weighted fat-suppressed images. We applied a sampling-weighted linear regression model to determine the association of the presence of BMLs with mean cartilage T1Gd (significance: P < 0.05). The model was adjusted for age, sex, body mass index (BMI), hip pain, cam/pincer deformity, and physical activity.

RESULTS

Thirty-two (25%) of the 128 participants had at least 1 BML. Subjects with at least 1 BML, compared to those without, had similar weighted characteristics of age, BMI, physical activity levels, and frequency of hip pain. Mean T1Gd was 75.25 msec lower (95% confidence interval -149.69, -0.81; P = 0.048) (9%) in the BML compared to the no-BML group.

CONCLUSION

Our results suggest that hips with BMLs are associated with hip cartilage degeneration early in the OA disease process.

Factors affecting pain and physical functions in patients with knee osteoarthritis: An observational study

Knee osteoarthritis (KOA) is more common as people age and have a higher body mass index (BMI). We must know the role of various factors in pain and physical functions in patients with KOA. Therefore, the present study sought to examine the factors associated with pain and physical functions in individuals with KOA. This cross-sectional observational study included patients with KOA (n = 125; 57 men, 68 women; mean age 52.9 years). Using the visual analogue scale and a reduced version of the Western Ontario McMaster Universities Osteoarthritis Index, pain severity and physical functions were assessed. Demographic factors such as age, BMI, sex, and Kellgren-Lawrence (K/L) radiographic grade of KOA were analyzed. Age (R = 0.263, P < .001), BMI (R = 0.379, P < .001), and K/L grade (R = 0.844, P < .001) were significantly associated with knee pain. Similarly, age (R = 0.310, P < .001), BMI (R = 0.374, P < .001), and K/L grade (R = 0.862, P < .001) were associated with physical functions. No significant association of sex with pain (R = 0.071, P = .440) and physical functions (R = 0.055, P = .545) was observed. Age, BMI, and K/L grade explained 71% and 74% of knee pain and physical functions, respectively. Age, BMI, and radiographic (K/L) grades were associated with pain and physical functions in patients with KOA. K/L grade was the most significant predictor of pain and physical functions in KOA.

Preoperative Medial Tightness and Narrow Medial Joint Space Are Predictive Factors for Lower Extremity Alignment Change Toward Varus After Opening-Wedge High Tibial Osteotomy

Background:

Time-dependent changes in lower extremity alignment after an opening-wedge high tibial osteotomy (OWHTO) have been poorly investigated. Moreover, few studies have investigated risk factors of postoperative alignment change.

Purposes:

To investigate time-dependent alignment changes and identify predictive factors for postoperative alignment change after OWHTO.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

This study included patients who underwent OWHTO between March 2010 and September 2018. A total of 142 knees with a mean follow-up of 42 months were included and classified as the change group when the amount of hip-knee-ankle (HKA) angle change was >1°; if otherwise, then as the no-change group. HKA angle was obtained at 6 time points: preoperatively and at 3 months, 6 months, 1 year, 2 years, and final follow-up postoperatively. Multiple regression analysis was performed to identify the factors that were correlated with the changes in the HKA angle from 3 months to the final follow-up.

Results:

Among the 142 knees, 59 (42%) were included in the change group. The overall postoperative HKA angles progressed serially toward varus after OWHTO. The mean angles of the 6 time points were 8.5°, –3.7°, –3.6°, –3.3°, –3.1°, and –2.7°, respectively. The mean HKA angles of the change and no-change groups were 9.1°, –4.3°, –3.4°, –2.8°, –2.0°, and –1.4° and 8.1°, –3.3°, –3.8°, –3.6°, –3.8°, and –3.7°, respectively. Greater change in the HKA angle was predicted by preoperatively greater valgus stress joint line convergence angles and less medial joint space width.

Conclusion:

Of the cases of OWHTO, 42% showed correction loss of >1° at a mean follow-up of 42 months. The overall postoperative HKA angles progressed serially to varus angles after OWHTO. Preoperative greater valgus stress joint line convergence angles and less medial joint space width were predictive factors for greater change in alignment toward varus after OWHTO.

Gender-Related Aspects in Osteoarthritis Development and Progression: A Review

Osteoarthritis (OA) is a common degenerative joint disease treated mostly symptomatically before approaching its definitive treatment, joint arthroplasty. The rapidly growing prevalence of OA highlights the urgent need for a more efficient treatment strategy and boosts research into the mechanisms of OA incidence and progression. As a multifactorial disease, many aspects have been investigated as contributors to OA onset and progression. Differences in gender appear to play a role in the natural history of the disease, since female sex is known to increase the susceptibility to its development. The aim of the present review is to investigate the cues associated with gender by analyzing various hormonal, anatomical, molecular, and biomechanical parameters, as well as their differences between sexes. Our findings reveal the possible implications of gender in OA onset and progression and provide evidence for gaps in the current state of art, thus suggesting future research directions.

Tibiofemoral articular cartilage composition differs based on serum biochemical profiles following anterior cruciate ligament reconstruction

OBJECTIVE

Biochemical joint changes contribute to posttraumatic osteoarthritis (PTOA) development following anterior cruciate ligament reconstruction (ACLR). The purpose of this longitudinal cohort study was to compare tibiofemoral cartilage composition between ACLR patients with different serum biochemical profiles. We hypothesized that profiles of increased inflammation (monocyte chemoattractant protein-1 [MCP-1]), type-II collagen turnover (type-II collagen breakdown [C2C]:synthesis [CPII]), matrix degradation (matrix metalloproteinase-3 [MMP-3] and cartilage oligomeric matrix protein [COMP]) preoperatively to 6-months post-ACLR would be associated with greater tibiofemoral cartilage T1ρ relaxation times 12-months post-ACLR.

DESIGN

Serum was collected from 24 patients (46% female, 22.1 ± 4.2 years old, 24.0 ± 2.6 kg/m2 body mass index [BMI]) preoperatively (6.4 ± 3.6 days post injury) and 6-months post-ACLR. T1ρ Magnetic Resonance Imaging (MRI) was collected for medial and lateral tibiofemoral articular cartilage at 12-months post-ACLR. A k-means cluster analysis was used to identify profiles based on biomarker changes over time and T1ρ relaxation times were compared between cluster groups controlling for sex, age, BMI, concomitant injury (either meniscal or chondral pathology), and Marx Score.

RESULTS

One cluster exhibited increases in MCP-1 and COMP while the other demonstrated decreases in MCP-1 and COMP preoperatively to 6-months post-ACLR. The cluster group with increases in MCP-1 and COMP demonstrated greater lateral tibial (adjusted mean difference = 3.88, 95% confidence intervals [1.97-5.78]) and femoral (adjusted mean difference = 12.71, 95% confidence intervals [0.41-23.81]) T1ρ relaxation times.

CONCLUSION

Profiles of increased serum levels of inflammation and matrix degradation markers preoperatively to 6-months post-ACLR are associated with MRI changes consistent with lesser lateral tibiofemoral cartilage proteoglycan density 12-months post-ACLR.

Characterizing the transient response of knee cartilage to running: Decreases in cartilage T2 of female recreational runners

Cartilage transmits and redistributes biomechanical loads in the knee joint during exercise. Exercise-induced loading alters cartilage hydration and is detectable using quantitative magnetic resonance imaging (MRI), where T₂ relaxation time (T₂ ) is influenced by cartilage collagen composition, fiber orientation, and changes in the extracellular matrix. This study characterized short-term transient responses of healthy knee cartilage to running-induced loading using bilateral scans and image registration. Eleven healthy female recreational runners (33.73 ± 4.22 years) and four healthy female controls (27.25 ± 1.38 years) were scanned on a 3T GE MRI scanner with quantitative 3D double-echo in steady-state before running over-ground (runner group) or resting (control group) for 40 min. Subjects were scanned immediately post-activity at 5-min intervals for 60 min. T₂ times were calculated for femoral, tibial, and patellar cartilage at each time point and analyzed using a mixed-effects model and Bonferroni post hoc. There were immediate decreases in T₂ (mean ± SEM) post-run in superficial femoral cartilage of at least 3.3% ± 0.3% (p = .002) between baseline and Time 0 that remained for 25 min, a decrease in superficial tibial cartilage T₂ of 2.9% ± 0.4% (p = .041) between baseline and Time 0, and a decrease in superficial patellar cartilage T₂ of 3.6% ± 0.3% (p = .020) 15 min post-run. There were decreases in the medial posterior region of superficial femoral cartilage T₂ of at least 5.3 ± 0.2% (p = .022) within 5 min post-run that remained at 60 min post-run. These results increase understanding of transient responses of healthy cartilage to repetitive, exercise-induced loading and establish preliminary recommendations for future definitive studies of cartilage response to running.

High-resolution infrared microspectroscopic characterization of cartilage cell microenvironment

The lateral resolution of infrared spectroscopy has been inadequate for accurate biochemical characterization of the cell microenvironment, a region regulating biochemical and biomechanical signals to cells. In this study, we demonstrate the capacity of a high-resolution Fourier transform infrared microspectroscopy (HR-FTIR-MS) to characterize the collagen content of this region. Specifically, we focus on the collagen content in the cartilage cell (chondrocyte) microenvironment of healthy and osteoarthritic (OA) cartilage. Human tibial cartilage samples (N = 28) were harvested from 7 cadaveric donors and graded for OA severity (healthy, early OA, advanced OA). HR-FTIR-MS was used to analyze the collagen content of the chondrocyte microenvironment of five distinct zones across the tissue depth. HR-FTIR-MS successfully showed collagen content distribution across chondrocytes and their environment. In zones 2 and 3 (10 - 50% of the tissue thickness), we observed that collagen content was smaller (P < 0.05) in early OA compared to the healthy tissue in the vicinity of cells (pericellular region). The collagen content loss was extended to the extracellular matrix in advanced OA tissue. No significant differences in the collagen content of the chondrocyte microenvironment were observed between the groups in the most superficial (0-10%) and deep zones (50-100%). HR-FTIR-MS revealed collagen loss in the early OA cartilage pericellular region before detectable changes in the extracellular matrix in advanced OA. HR-FTIR-MS-based compositional assessment enables a better understanding of OA-related changes in tissues. This technique can be used to identify new disease mechanisms enabling better intervention strategies. STATEMENT OF SIGNIFICANCE: Osteoarthritis (OA) is the most common degenerative joint disease causing pain and disability. While significant progress has been made in OA research, OA pathogenesis is still poorly understood and current OA treatments are mainly palliative. This study demonstrates that high-resolution FTIR microspectroscopy (HR-FTIR-MS) can characterize OA-induced compositional changes in the cell microenvironment (pericellular matrix) during the early disease stages before tissue changes in the extracellular matrix become apparent. This technique may further enable the identification of new OA mechanisms and improve our current understanding of OA pathogenesis, thus, enabling the development of better treatment methods.

Influence of sex and gender on the management of late-stage knee osteoarthritis

PURPOSE

The exact nature of sex and gender differences in knee osteoarthritis (OA) among patient candidates for total knee arthroplasty (TKA) remains unclear and requires better elucidation to guide clinical practice. The purpose of this investigation was to survey physician practices and perceptions about the influence of sex and gender on knee OA presentation, care, and outcomes after TKA.

METHODS

The survey questions were elaborated by a multidisciplinary scientific board composed of 1 pain specialist, 4 orthopedic specialists, 2 physiatrists, and 1 expert in gender medicine. The survey included 5 demographic questions and 20 topic questions. Eligible physician respondents were those who treat patients during all phases of care (pain specialists, orthopedic specialists, and physiatrists). All survey responses were anonymized and handled via remote dispersed geographic participation.

RESULTS

Fifty-six physicians (71% male) accepted the invitation to complete the survey. In general, healthcare professionals expressed that women presented worse symptomology, higher pain intensity, and lower pain tolerance and necessitated a different pharmacological approach compared to men. Pain and orthopedic specialists were more likely to indicate sex and gender differences in knee OA than physiatrists. Physicians expressed that the absence of sex and gender-specific instruments and indications is an important limitation on available studies.

CONCLUSIONS

Healthcare professionals perceive multiple sex and gender-related differences in patients with knee OA, especially in the pre- and perioperative phases of TKA. Sex and gender bias sensitivity training for physicians can potentially improve the objectivity of care for knee OA among TKA candidates.

The effects of knee pain on knee contact force and external knee adduction moment in patients with knee osteoarthritis

Knee osteoarthritis (OA) is a major cause of knee pain, leading to physical dysfunction. External knee adduction moment (KAM), a surrogate measure of knee contact force (KCF) in the medial compartment, is related to knee pain, but the association between KCF and pain severity remains unclear. This study aimed to reveal the differences in KCF due to pain severity. Twenty-eight patients with knee OA were evaluated knee symptoms including pain severity via the Knee Society Score. Based on the median symptom score, 17 points in this study, subjects were classified as having Mild symptomatic OA (n = 15) and Severe symptomatic OA (n = 13). Subjects walked three times at a comfortable speed along a six-meter walkway, and we calculated KAM during the stance phase. KCF magnitude and distribution were also computed using the subject-specific musculoskeletal model, considering physical characteristics such as the femorotibial angle measured by X-ray. No differences in physical characteristics such as femorotibial angle and gait speed were found by symptom severity, whereas KAM and medial KCF at minimum and second peak in Severe symptomatic OA patients were significantly greater than those in Mild symptomatic OA. A significant medial shift of KCF in Severe symptomatic OA was also seen at first peak and minimum. Severe symptomatic OA had a greater medial KCF and medial shift of KCF. Detailed evaluations of KCF magnitude and distribution in addition to KAM would provide crucial information on knee contact force in relation to symptom severity.

A new technique to evaluate the impact of running on knee cartilage deformation by region

OBJECTIVES

When measuring changes in knee cartilage thickness in vivo after loading, mean values may not reflect local changes. The objectives of this investigation were: (1) use statistical parametric mapping (SPM) to determine regional deformation patterns of tibiofemoral cartilage in response to running; (2) quantify regional differences in cartilage thickness between males and females; and (3) explore the influence of sex on deformation.

MATERIALS AND METHODS

Asymptomatic males (n = 15) and females (n = 15) had MRI imaging of their right knee before and after 15 min of treadmill running. Medial and lateral tibial, and medial and lateral weight-bearing femoral cartilage were segmented. SPM was completed on cartilage thickness maps to test the main effects of Running and Sex, and their interaction. F-statistic maps were thresholded; clusters above this threshold indicated significant differences.

RESULTS

Deformation was observed in all four compartments; the lateral tibia had the largest area of deformation (p < 0.0001). Thickness differences between sexes were observed in all four compartments, showing females have thinner cartilage (p ≤ 0.009). The lateral tibia had small clusters indicating an interaction of sex on deformation (p ≤ 0.012).

DISCUSSION

SPM identified detailed spatial information on tibiofemoral cartilage thickness differences observed after running, and between sexes and their interaction.

Effects of Increased Step-Width on Knee Biomechanics During Inclined and Declined Walking

The purpose of this study was to investigate effects of preferred step width and increased step width modification on knee biomechanics of obese and healthy-weight participants during incline and decline walking. Seven healthy-weight participants and 6 participants who are obese (body mass index ≥ 30) performed 5 walking trials on level ground and a 10° inclined and declined instrumented ramp system at both preferred and wide step-widths. A 2 × 2 (step-width × group) mixed-model analysis of variance was used to examine selected variables. There were significant increases in step-width between the preferred and wide step-width conditions for all 3 walking conditions (all P < .001). An interaction was found for peak knee extension moment (P = .048) and internal knee abduction moment (KAM) (P = .025) in uphill walking. During downhill walking, there were no interaction effects. As step-width increased, KAM was reduced (P = .007). In level walking, there were no interaction effects for peak medial ground reaction force and KAM (P = .007). There was a step-width main effect for KAM (P = .007). As step-width increased, peak medial ground reaction force and peak knee extension moment increased, while KAM decreased for both healthy weight and individuals who are obese. The results suggest that increasing step-width may be a useful strategy for reducing KAM in healthy and young populations.

The effects of a simulated occupational kneeling exposure on squat mechanics and knee joint load during gait

Occupational kneeling is associated with an increased risk for tibiofemoral knee osteoarthritis. Forces on the knee in the kneeling posture, as well as the greater incidence of meniscus tears among workers, likely contribute to the increased risk. We hypothesise that an additional mechanism may contribute - altered neuromuscular control due to prolonged high knee flexion. Forty participants (20 male, 20 female) completed an evaluation of gait and squatting before, immediately following, and 30 min following a 30 min simulated occupational kneeling exposure. An increase in the peak external knee adduction moment and a delay in vastus medialis activation onset during walking were observed post-kneeling, as well as increased frontal plane knee motion during squatting. This was the first investigation to find changes in high flexion transitions as a result of kneeling. Greater frontal plane knee motion may increase the risk for meniscal tears, and subsequently, knee osteoarthritis. Practitioner Summary: A 30 min simulated occupational kneeling exposure resulted in small but significant gait changes. The greatest effect was on frontal plane knee movement during squatting, which is especially relevant to occupations requiring frequent kneeling/squatting. This increased motion may indicate an increased risk of injury, which supports a link to knee osteoarthritis.

Stem Cells for Cartilage Repair: Preclinical Studies and Insights in Translational Animal Models and Outcome Measures

Due to the restricted intrinsic capacity of resident chondrocytes to regenerate the lost cartilage postinjury, stem cell-based therapies have been proposed as a novel therapeutic approach for cartilage repair. Moreover, stem cell-based therapies using mesenchymal stem cells (MSCs) or induced pluripotent stem cells (iPSCs) have been used successfully in preclinical and clinical settings. Despite these promising reports, the exact mechanisms underlying stem cell-mediated cartilage repair remain uncertain. Stem cells can contribute to cartilage repair via chondrogenic differentiation, via immunomodulation, or by the production of paracrine factors and extracellular vesicles. But before novel cell-based therapies for cartilage repair can be introduced into the clinic, rigorous testing in preclinical animal models is required. Preclinical models used in regenerative cartilage studies include murine, lapine, caprine, ovine, porcine, canine, and equine models, each associated with its specific advantages and limitations. This review presents a summary of recent in vitro data and from in vivo preclinical studies justifying the use of MSCs and iPSCs in cartilage tissue engineering. Moreover, the advantages and disadvantages of utilizing small and large animals will be discussed, while also describing suitable outcome measures for evaluating cartilage repair.

Knee internal contact force in a varus malaligned phenotype in knee osteoarthritis (KOA)

PURPOSE

Multiple phenotypes characterized by different disease mechanisms have been hypothesized to explain the large variability in the knee osteoarthritis (KOA) population. The purpose of this study was: to estimate and compare the medial and lateral knee compression forces (CF) during gait of three subgroups of KOA subjects characterized by different alignment and cartilage disruption patterns.

METHODS

A secondary data analysis was conducted on a sample of 39 KOA subjects and 18 controls (C). The patients were classified in the different groups according to the following criteria: Varus medial disease (VMD) (12): varus alignment and predominant medial cartilage degeneration Varus generalized disease (VGD) (17): varus alignment and cartilage degeneration that extends to the lateral compartment. Neutral alignment (NA) (10): neutral alignment. The total, medial and lateral CF corrected for body weight were estimated using an inverse dynamics model (AnyBody Modeling System, AnyBody Technology) during stance.

RESULTS

The impulse of the medial compressive force (MCF) (overall effect of the CF over the stance) was significantly higher (P < 0.01) in the VMD compared to all the other groups. Peak MCF was higher in the VMD compared to all the other groups, but the difference reached significance only when compared to the VGD group (P < 0.05). The results of the regression analysis showed a significant relationship in the VMD group between alignment and impulse of the MCF (R² = 0.62; P < 0.01). This relationship disappears in the other groups.

CONCLUSIONS

These findings suggest the existence of a phenotype characterized by increased MCF.

The influence of sex and obesity on gait biomechanics in people with severe knee osteoarthritis scheduled for arthroplasty

BACKGROUND

Sex and body mass may influence knee biomechanics associated with poor total knee arthroplasty (TKA) outcomes for knee osteoarthritis (OA). This study aimed to determine if gait differed between men and women, and overweight and class I obese patients with severe knee OA awaiting TKA.

METHODS

34 patients with severe knee OA (average age 70.0 (SD 7.2) years, body mass index 30.3 (4.1kg/m²)) were recruited from a TKA waiting list. Three-dimensional gait analysis was performed at self-selected walking speed. Comparisons were made between men and women, and overweight (body mass index (BMI) 25.0-29.9kg/m²) and class I obese (BMI 30.0-34.9kg/m²) participants. Biomechanical outcomes included absolute and body size-adjusted peak knee adduction moment (KAM), KAM impulse, peak knee flexion moment, as well as peak knee flexion and varus-valgus angles, peak varus-valgus thrust, and peak vertical ground reaction force (GRF).

FINDINGS

Men had a higher absolute peak KAM, KAM impulse and peak GRF compared to women, and this sex-difference in frontal plane moments remained after adjusting for body size. However, when additionally adjusting for static knee alignment, differences disappeared. Knee biomechanics were similar between obesity groups after adjusting for the greater body weight of those with class I obesity.

INTERPRETATION

Men had greater KAM and KAM impulse even after adjustment for body size; however adjustment for their more varus knees removed this difference. Obesity group did not influence knee joint kinematics or moments. This suggests sex- and obesity-differences in these variables may not be associated with TKA outcomes.

Sex-specific hip osteoarthritis-associated gait abnormalities: Alterations in dynamic hip abductor function differ in men and women

BACKGROUND

Hip osteoarthritis results in abnormal gait mechanics, but it is not known whether abnormalities are the same in men and women. The hypothesis tested was that gait abnormalities are different in men and women with hip osteoarthritis vs. sex-specific asymptomatic groups.

METHODS

150 subjects with mild through severe radiographic hip osteoarthritis and 159 asymptomatic subjects were identified from an Institutional Review Board-approved motion analysis data repository. Sagittal plane hip range of motion and peak external moments about the hip, in all three planes, averaged from normal speed walking trials, were compared for men and women, with and without hip osteoarthritis using analysis of variance.

FINDINGS

There were significant sex by group interactions for the external peak hip adduction and external rotation moments (P=0.009-0.045). Although asymptomatic women had peak adduction and external rotation moments that were respectively 12% higher and 23% lower than asymptomatic men (P=0.026-0.037), these variables did not differ between men and women with hip osteoarthritis (P≥0.684). The osteoarthritis vs. asymptomatic group difference in the peak hip adduction moment was 45% larger in women than in men. The osteoarthritis vs. asymptomatic group difference in the peak hip external rotation moment was 55% larger for men than for women (P<0.001). Sex did not influence the association between radiographic severity and gait variables.

INTERPRETATION

Normal sex differences in gait were not seen in hip osteoarthritis. Sex-specific adaptations may reflect different aspects of hip abductor function. Men and women with hip osteoarthritis may require different interventions to improve function.

Gender-specific differential expression of exosomal miRNA in synovial fluid of patients with osteoarthritis

The pathogenesis of osteoarthritis (OA) is poorly understood, and therapeutic approaches are limited to preventing progression of the disease. Recent studies have shown that exosomes play a vital role in cell-to-cell communication, and pathogenesis of many age-related diseases. Molecular profiling of synovial fluid derived exosomal miRNAs may increase our understanding of OA progression and may lead to the discovery of novel biomarkers and therapeutic targets. In this article we report the first characterization of exosomes miRNAs from human synovial fluid. The synovial fluid exosomes share similar characteristics (size, surface marker, miRNA content) with previously described exosomes in other body fluids. MiRNA microarray analysis showed OA specific exosomal miRNA of male and female OA. Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis identified gender-specific target genes/signaling pathways. These pathway analyses showed that female OA specific miRNAs are estrogen responsive and target TLR (toll-like receptor) signaling pathways. Furthermore, articular chondrocytes treated with OA derived extracellular vesicles had decreased expression of anabolic genes and elevated expression of catabolic and inflammatory genes. In conclusion, synovial fluid exosomal miRNA content is altered in patients with OA and these changes are gender specific.

T1ρ/T2 mapping and histopathology of degenerative cartilage in advanced knee osteoarthritis

AIM

To investigate whether normal thickness cartilage in osteoarthritic knees demonstrate depletion of proteoglycan or collagen content compared to healthy knees.

METHODS

Magnetic resonance (MR) images were acquired from 5 subjects scheduled for total knee arthroplasty (TKA) (mean age 70 years) and 20 young healthy control subjects without knee pain (mean age 28.9 years). MR images of T1ρ mapping, T2 mapping, and fat suppressed proton-density weighted sequences were obtained. Following TKA each condyle was divided into 4 parts (distal medial, posterior medial, distal lateral, posterior lateral) for cartilage analysis. Twenty specimens (bone and cartilage blocks) were examined. For each joint, the degree and extent of cartilage destruction was determined using the Osteoarthritis Research Society International cartilage histopathology assessment system. In magnetic resonance imaging (MRI) analysis, 2 readers performed cartilage segmentation for T1ρ/T2 values and cartilage thickness measurement.

RESULTS

Eleven areas in MRI including normal or near normal cartilage thickness were selected. The corresponding histopathological sections demonstrated mild to moderate osteoarthritis (OA). There was no significant difference in cartilage thickness in MRI between control and advanced OA samples [medial distal condyle, P = 0.461; medial posterior condyle (MPC), P = 0.352; lateral distal condyle, P = 0.654; lateral posterior condyle, P = 0.550], suggesting arthritic specimens were morphologically similar to normal or early staged degenerative cartilage. Cartilage T2 and T1ρ values from the MPC were significantly higher among the patients with advanced OA (P = 0.043). For remaining condylar samples there was no statistical difference in T2 and T1ρ values between cases and controls but there was a trend towards higher values in advanced OA patients.

CONCLUSION

Though cartilage is morphologically normal or near normal, degenerative changes exist in advanced OA patients. These changes can be detected with T2 and T1ρ MRI techniques.

Osteoarthritis year in review 2016: imaging

PURPOSE

The current narrative review covers original research related to imaging in osteoarthritis (OA) in humans published in English between April 1st 2015 and March 31st 2016, in peer reviewed journals available in Medline via PubMed (http://www.ncbi.nlm.nih.gov/pubmed/).

METHODS

Relevant studies in humans, subjectively decided by the authors, contributing significantly to the OA imaging field, were selected from an extensive Medline search using the terms "Osteoarthritis" in combination with "MRI", "Imaging", "Radiography", "X-rays", "Ultrasound", "Computed tomography", "Nuclear medicine", "PET-CT", "PET-MRI", "Scintigraphy", "SPECT". Publications were sorted according to relevance for the OA imaging research community with an emphasis on high impact special interest journals using the software for systematic reviews www.covidence.org.

RESULTS

An overview of newly published studies compared to studies reported previous years is presented, followed by a review of selected imaging studies of primarily knee, hip and hand OA focussing on (1) results for detection of OA and OA-related pathology (2) studies dealing with treatments and (3) studies focussing on prognosis of disease progression or joint replacement. A record high number of 1420 articles were published, among others, of new technologies and tools for improved morphological and pathophysiological understanding of OA-related changes in joints. Also, imaging data were presented of monitoring treatment effect and prognosis of OA progression, primarily using established radiographic, magnetic resonance imaging (MRI), and ultrasound (US) methods.

CONCLUSION

Imaging continues to play an important role in OA research, where several exciting new technologies and computer aided analysis methods are emerging to complement the conventional imaging approaches.

Baseline Cartilage Thickness and Meniscus Extrusion Predict Longitudinal Cartilage Loss by Quantitative Magnetic Resonance Imaging: Data From the Osteoarthritis Initiative

OBJECTIVE

This study aimed to assess how meniscus damage and baseline cartilage thickness influence the rate of cartilage loss and knee pain.

METHODS

Of 4796 participants in the Osteoarthritis Initiative, 86 had baseline and 48-month follow-up quantitative magnetic resonance imaging data for medial compartment cartilage thickness. Baseline meniscus pathology was scored by a musculoskeletal radiologist using Whole-Organ Magnetic Resonance Imaging Score. Findings were correlated with 72-month Knee injury and Osteoarthritis Outcome Score.

RESULTS

Univariate analysis showed cartilage change was not influenced by demographic variables. Multivariable regression revealed that initial cartilage thickness (-1.07 mm at 48 months for every 1 mm decrease at baseline, P < 0.001) and meniscus extrusion (-0.33 mm if present at baseline, P < 0.001) were the strongest predictors of medial compartment cartilage thickness at 48 months. Knee injury and Osteoarthritis Outcome Score pain scores did not correlate with cartilage loss.

CONCLUSIONS

Baseline cartilage thickness and meniscus extrusion are important and independent predictors for accelerated cartilage loss. However, the degree of cartilage loss did not correlate with midterm change in clinical outcome scores.

T1ρ magnetic resonance: basic physics principles and applications in knee and intervertebral disc imaging

T1ρ relaxation time provides a new contrast mechanism that differs from T1- and T2-weighted contrast, and is useful to study low-frequency motional processes and chemical exchange in biological tissues. T1ρ imaging can be performed in the forms of T1ρ-weighted image, T1ρ mapping and T1ρ dispersion. T1ρ imaging, particularly at low spin-lock frequency, is sensitive to B0 and B1 inhomogeneity. Various composite spin-lock pulses have been proposed to alleviate the influence of field inhomogeneity so as to reduce the banding-like spin-lock artifacts. T1ρ imaging could be specific absorption rate (SAR) intensive and time consuming. Efforts to address these issues and speed-up data acquisition are being explored to facilitate wider clinical applications. This paper reviews the T1ρ imaging's basic physic principles, as well as its application for cartilage imaging and intervertebral disc imaging. Compared to more established T2 relaxation time, it has been shown that T1ρ provides more sensitive detection of proteoglycan (PG) loss at early stages of cartilage degeneration. T1ρ has also been shown to provide more sensitive evaluation of annulus fibrosis (AF) degeneration of the discs.