Effect of Knee Extensor Strength on Incident Radiographic and Symptomatic Knee Osteoarthritis in Individuals With Meniscal Pathology: Data From the Multicenter Osteoarthritis Study

The control group matters: Pain, physical function and strength improvements relative to the comparator intervention in knee and hip osteoarthritis

BACKGROUND

In knee and hip osteoarthritis (OA), the mechanism for resistance exercise improving clinical outcomes and the dose-response between strength and clinical outcomes are unknown; in part due to inconsistent trial designs across studies.

PURPOSE

To determine whether the effects of resistance exercise interventions on pain and function differ based on comparator group; and whether there is an association between improvements in lower extremity strength with improvements in pain and function in knee and hip OA.

METHODS

We searched 6 databases (inception to January 28 2023,) for randomized controlled trials (RCTs) comparing land-based, resistance exercise-only interventions with no intervention or any other intervention. There were four subgroups for comparator intervention: NONE (none/placebo/sham/usual care), EXE (other exercise interventions alone), NONEXE (non-exercise interventions alone), COMBO (combined exercise + non-exercise interventions). The between-group effect (ES) was calculated for immediate post-intervention pain and function (activities of daily living (ADL) and sports/recreation (SPORT)). Meta-regression analyses were completed to evaluate the association between improvements in lower extremity strength (independent variable) and improvements in pain, ADL and SPORT (dependent variables), irrespective of comparator intervention.

RESULTS

For knee OA (257 studies), there were large benefits for pain [ES (95 % CI) = -0.92 (-1.15, -0.69)], ADL [-0.79 (-1.01, -0.56)] and SPORT [-0.79 (-1.02, -0.56)] favouring resistance exercise interventions compared to NONE. For knee pain, there was also a moderate benefit favouring COMBO interventions compared to resistance exercise interventions [0.44 (0.23, 0.65)]. For hip OA (15 studies), there were moderate benefits for pain [-0.51 (-0.68, -0.33)], ADL [-0.57 (-0.78, -0.36)] and SPORT [-0.52 (-0.70, -0.35)] favouring exercise interventions compared to NONE. For hip pain, there was also a moderate benefit favouring NONEXE interventions compared to resistance exercise interventions [0.57 (0.17, 0.97)]. For knee OA, greater strength gains were associated with larger improvements in pain [β (95 % CI) = -0.24 (-0.38, -0.09)], ADL [-0.43 (-0.73, -0.12)] and SPORT [-0.37 (-0.73, -0.00)].

CONCLUSION

In knee and hip OA, the effects of resistance exercise on pain and function improvements depend on the comparator intervention. For knee OA, a dose-response relationship was observed between lower extremity strength gains with pain and function improvements.

Strength and passive stiffness of the quadriceps are associated with patellar alignment in older adults with knee pain

BACKGROUND

Maintaining normal patellar alignment is important for knee health. Altered activation of individual quadriceps muscles have been found related to patellar alignment. However, the relationships between strength and passive stiffness of the quadriceps and patellar alignment remains unexplored.

METHODS

Participants aged between 60 and 80 years with activity-induced knee pain were recruited. Knee pain was quantified using an 11-point numeric rating scale. Quadriceps strength was assessed using a Cybex dynamometer and passive stiffness of rectus femoris, vastus lateralis, and vastus medialis were measured by shear-wave ultrasound elastography. Patellar alignments were assessed using MR imaging. Linear regression was used to examine relationships between quadriceps properties and patellar alignments with and without controlling for potential covariates.

FINDINGS

Ninety-two eligible participants were assessed (71.7% females, age: 65.6 ± 3.8 years; pain scale: 4.6 ± 2.0), most of whom had knee pain during stair climbing (85.9%). We found that 17% of patellar lateral tilt angle could be explained by lower quadriceps strength (adjusted R2 = 0.117; P < 0.001), especially in females (R2 = 0.281; P < 0.001; adjusted R2 = 0.211; P < 0.001). In addition, a higher stiffness ratio of vastus lateralis/medialis accounted for 12% of patellar lateral displacement (adjusted R2 = 0.112; P = 0.008).

INTERPRETATION

Quadriceps strength and relative stiffness of lateral to medial heads are associated with patellar alignment in older adults with knee pain. It suggests that quadriceps weakness and relatively stiffer lateral quadriceps may be risk factors related to patellar malalignments in the elderly.

Therapeutic Effect of Acupotomy at Sanheyang for Cartilage Collagen Damage in Moderate Knee Osteoarthritis: A Rabbit Model

Objective

Acupotomy based on the meridian-sinew theory of traditional Chinese medicine has benefits in treating knee osteoarthritis (KOA). The current study aims to prove that acupotomy at the sinew points of Sanheyang protect the knee joint and alleviate the progression of moderate KOA by evaluating KOA symptoms, cartilage structure, and analyzing the changes of cytokines in rabbit cartilage.

Methods

The model used was mono-iodoacetate-induced moderate KOA in the rabbit's right leg. Rabbits were divided into the model group, the acupotomy group, and the control group, with each group receiving two parts of treatment for 2 weeks and 4 weeks. We evaluated pain in the knee joint and range of motion. The articular cartilage sections were stained with Safranin O/Fast Green and Masson. We used immunohistochemistry and real-time PCR to detect the protein and mRNA expressions of collagen prototype II (COL-II), matrix metalloproteinase 13 (MMP13), and integrin-β1 (ITG-β1).

Results

Compared with the model group, the acupotomy group had higher body weight, lower pain score, higher range of motion, lower Mankin score, and significantly lower protein and mRNA expression of MMP13. After 4 weeks of treatment, Col-II expression in the acupotomy group was significantly higher than that in the model group and the expression of ITG-β1 in the model group was abnormally increased.

Conclusion

Acupotomy at Sanheyang improved the pain symptoms and range of joint motion in rabbits with moderate KOA, and could protect Col-II by regulating MMP13, which may be related to ITG-β1-mediated mechanical force transmission, thus reducing the damage to cartilage structure and delaying the progression of moderate KOA.

Passive stiffness of the quadriceps predicts the incidence of clinical knee osteoarthritis in twelve months

BACKGROUND

Quadriceps weakness is a known risk factor for the onset of knee osteoarthritis (OA). In addition to muscle weakness, increased passive stiffness of the quadriceps may affect knee biomechanics and hence contribute to the pathogenesis of knee OA. However, the association between quadriceps stiffness and the risk of knee OA development has not been prospectively investigated.

AIM

The aim of this study was to investigate how baseline quadriceps passive stiffness predicts the incidence of clinical knee OA at the 12-month follow-up.

DESIGN

Prospective cohort study.

SETTING

University laboratory.

POPULATION

Community-dwelling adults aged 60-80 years were recruited. We excluded participants with: 1) knee pain or known arthritis; 2) knee injury; 3) knee or hip joint replacement, 4) cognitive impairment; or 5) neurological conditions.

METHODS

At baseline, passive stiffness of the three superficial quadriceps muscle heads (rectus femoris [RF], vastus lateralis [VL], and vastus medialis oblique [VMO]) was evaluated using shear-wave ultrasound elastography. Knee muscle (quadriceps and hamstrings) strength was tested using a Cybex dynamometer. Knee OA was defined based on clinical criteria 12 months after baseline measurements. Generalized estimating equations were used to examine the associations of quadriceps stiffness and knee muscle strength with the risk of knee OA, controlling for age, sex, Body Mass Index, comorbidities, and activity level.

RESULTS

The analyses included 158 knees (58.2% females, age: 65.6±4.1 years). Twenty-eight knees (17.7%) were classified as having clinical OA at 12 months. Compared with the lowest stiffness tertiles, the highest stiffness tertiles of the RF (relative risk =5.31, 95% CI: 1.34-21.0), VMO (4.15, 1.04-16.6), and total superficial quadriceps (6.35, 1.48-27.3) at baseline were significantly associated with a higher risk of knee OA at the follow-up. The highest strength tertile of quadriceps has a trend of association with a lower risk of knee OA than the lowest tertile (0.18, 0.03-1.25, P=0.083).

CONCLUSIONS

Greater passive stiffness of the quadriceps at baseline was associated with a higher risk of clinical knee OA incidence at the 12-month follow-up.

CLINICAL REHABILITATION IMPACT

Interventions for reducing the passive stiffness of the quadriceps should be included in preventative training programs for older adults.

Quadriceps strength is negatively associated with knee joint structural abnormalities-data from osteoarthritis initiative

OBJECTIVE

The aim of this study was to explore the longitudinal associations between baseline quadriceps strength and knee joint structural abnormalities in knee osteoarthritis (KOA).

METHODS

This study is a longitudinally observational study based on Osteoarthritis Initiative (OAI) cohort, including men and women aged 45-79. Quadriceps strength was measured by isometric knee extension testing at baseline. Knee joint structural abnormalities, including cartilage damage, bone marrow lesions (BMLs), effusion-synovitis and Hoffa-synovitis, were evaluated by Magnetic Resonance Imaging Osteoarthritis Knee Score (MOAKS) at baseline and 1-year follow-up. Generalized estimating equations were employed to examine the associations between quadriceps strength and knee structural abnormalities. All analyses were stratified by sex.

RESULTS

One thousand three hundred thirty-eight participants (523 men and 815 women) with a mean age of 61.8 years and a mean BMI of 29.4 kg/m² were included in this study. For men, no significantly longitudinal association of quadriceps strength with structural abnormalities was detected. In contrast, quadriceps strength was significantly and negatively associated with changes in cartilage damage and BMLs in lateral patellofemoral joint (PFJ) (cartilage damage: OR: 0.91, 95% CI 0.84 to 0.99, P = 0.023; BMLs: OR: 0.85, 95% CI 0.74 to 0.96, P = 0.011) and effusion-synovitis (OR = 0.88, 95% CI 0.78 to 0.99, P = 0.045) among females longitudinally. Higher quadriceps strength was significantly associated with less progression of lateral PFJ cartilage damage, BMLs and effusion-synovitis in females.

CONCLUSIONS

Higher quadriceps strength was associated with changes in cartilage damage and BMLs within the lateral PFJ and effusion-synovitis among females, suggesting the potential protective role of quadriceps strength on joint structures in women.

Knee extensor muscle weakness is a risk factor for the development of knee osteoarthritis: an updated systematic review and meta-analysis including 46 819 men and women

OBJECTIVE

To update a systematic review on the association between knee extensor muscle weakness and the risk of incident knee osteoarthritis in women and men.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Systematic searches in PubMed, EMBASE, SPORTDiscus, CINAHL, AMED and CENTRAL in May 2021.

ELIGIBLE CRITERIA FOR SELECTING STUDIES

Longitudinal studies with at least 2 years follow-up including baseline measure of knee extensor muscle strength, and follow-up measure of symptomatic or radiographic knee osteoarthritis. Studies including participants with known knee osteoarthritis at baseline were excluded. Risk of bias assessment was conducted using six criteria for study validity and bias. Grading of Recommendations Assessments, Development and Evaluation assessed overall quality of evidence. Meta-analysis estimated the OR for the association between knee extensor muscle weakness and incident knee osteoarthritis.

RESULTS

We included 11 studies with 46 819 participants. Low quality evidence indicated that knee extensor muscle weakness increased the odds of symptomatic knee osteoarthritis in women (OR 1.85, 95% CI 1.29 to 2.64) and in adult men (OR 1.43, 95% CI 1.14 to 1.78), and for radiographic knee osteoarthritis in women: OR 1.43 (95% CI 1.19 to 1.71) and in men: OR 1.39 (95% CI 1.07 to 1.82). No associations were identified for knee injured populations except for radiographic osteoarthritis in men.

DISCUSSION

There is low quality evidence that knee extensor muscle weakness is associated with incident symptomatic and radiographic knee osteoarthritis in women and men. Optimising knee extensor muscle strength may help to prevent knee osteoarthritis.

PROSPERO REGISTRATION NUMBER

CRD42020214976.

Appendicular Lean Mass, Grip Strength, and the Development of Knee Osteoarthritis and Knee Pain Among Older Adults

Objective

The association of sarcopenia with development of knee osteoarthritis (OA) or knee pain in older adults is uncertain. We examined the relationship of grip strength and appendicular lean mass (ALM) with the likelihood of developing knee OA and knee pain in older adults in the Health ABC (Health, Aging, and Body Composition) Study.

Methods

ALM and grip strength were assessed at baseline by dual‐energy x‐ray absorptiometry and handheld dynamometry, respectively. Incident clinically diagnosed, symptomatic knee OA, defined as new participant report of physician‐diagnosed knee OA and concurrent frequent knee pain, and incident frequent knee pain over 5 years of follow‐up were examined. Separate regression analyses, stratified by sex, modeled associations of baseline ALM and grip strength with the likelihood of incident clinically diagnosed, symptomatic knee OA and incident knee pain over follow‐up, adjusting for covariates.

Results

Among the 2779 subjects without OA at baseline, 95 men (6.9%) and 158 women (11.3%) developed clinically diagnosed, symptomatic knee OA, and, among the 2182 subjects without knee pain at baseline, 315 men (28.3%) and 385 women (36.1%) developed knee pain over follow‐up. Among men only, each SD decrement of ALM was associated with decreasing likelihood of incident knee OA (odds ratio [OR] per SD decrement: 0.68; 95% confidence interval [CI]: 0.47‐0.97), and each SD decrement of grip strength was associated with increasing likelihood of incident knee pain (OR per SD decrement: 1.20; 95% CI: 1.01‐1.42).

Conclusion

In older men, ALM and grip strength may be associated with the development of knee OA and knee pain, respectively.

Muscle strength and osteoarthritis progression after surgery or exercise for degenerative meniscal tears: Secondary analyses of a randomized trial

OBJECTIVE

To evaluate muscle strength changes following partial meniscectomy or exercise therapy for degenerative meniscal tears and the relationship between baseline muscle strength and osteoarthritis progression.

METHODS

Secondary analysis of a randomized trial (n=140 participants). Isokinetic quadriceps and hamstrings strength (peak torque [N·m/kg] and total work [J/kg]) were assessed at baseline, three-, 12-month, and five-year follow-up. Between-group differences were analyzed using intention-to-treat linear mixed models. The relationship between baseline muscle strength and osteoarthritis progression (Kellgren and Lawrence, ≥1 grade increase) were assessed using logistic regression models.

RESULTS

We found statistically significant between-group differences favoring exercise therapy at three months (quadriceps: -0.30 N·m/kg, 95% CI -0.40, -0.20; hamstrings: -0.10 N·m/kg, 95% CI -0.15, -0.04) and 12 months (quadriceps: -0.13 N·m/kg, 95% CI -0.23, -0.03; hamstrings: -0.08 N·m/kg, 95% CI -0.14, -0.03). At five years, between-group differences were -0.10 N·m/kg (95% CI -0.21 to 0.01) for quadriceps and -0.07 N·m/kg (95% CI -0.13 to -0.01) for hamstrings. Quadriceps muscle weakness at baseline was associated with knee osteoarthritis progression over five years: adjusted odds ratio of 1.40 for every 0.2 N·m/kg decrease (95% CI 1.15 to 1.71). The adjusted odds ratio for hamstrings was 1.14 (95% CI 0.97-1.35) for every 0.1 N·m/kg decrease.

CONCLUSION

Exercise therapy was effective in improving muscle strength at three and 12-month follow-up compared to partial meniscectomy, but the effect was attenuated at five years. Quadriceps muscle weakness at baseline was associated with higher odds of osteoarthritis progression over five years.

Steep medial tibial slope and prolonged delay to surgery are associated with bilateral medial meniscus posterior root tear

PURPOSE

Contralateral medial meniscus posterior root tear (MMPRT) can sometimes occur after primary surgeries for MMPRT and lead to unsatisfactory outcomes. The incidence rate and risk factors for contralateral MMPRT have not been well investigated, despite their clinical importance. Therefore, the incidence and predictors of bilateral MMPRT were aimed to be evaluated.

METHODS

Fourteen patients with bilateral MMPRT (group B) and 169 patients with unilateral MMPRT (group U) were enrolled in this study. Sex, age, body mass index, time between injury and surgery, and medial tibial slope angle (MTSA) were compared between the groups. MTSA was measured using lateral radiographs.

RESULTS

The incidence rate of bilateral MMPRT was 6.2% among all patients with MMPRTs. Multivariate logistic regression analysis showed that a prolonged time between injury and surgery (odds ratio [OR], 1.0; 95% confidence interval [CI] 1.00-1.01; P < 0.05) and steeper MTSA (OR, 1.85; 95% CI 1.21-2.64; P < 0.01) were significantly associated with the development of bilateral MMPRT. Receiver operating characteristic curve analysis showed that MTSA > 10.0° was associated with bilateral MMPRT, with a sensitivity of 93% and specificity of 69%.

CONCLUSION

A longer time between injury and surgery and steeper MTSA were risk factors for the development of bilateral MMPRT. Surgeons need to pay close attention to the contralateral knee in addition to the primary injured knees when treating knees with steep MTSA. Besides, early meniscal repair of primary MMPRT would be important to prevent the events of contralateral MMPRT.

LEVEL OF EVIDENCE

III.

Total Serum Testosterone and Western Ontario and McMaster Universities Osteoarthritis Index Pain and Function Among Older Men and Women With Severe Knee Osteoarthritis

OBJECTIVE

To investigate whether serum total testosterone level is associated with knee pain and function in men and women with severe knee osteoarthritis (OA).

METHODS

We enrolled 272 adults age ≥60 years (mean ± SD age 70.4 ± 4.4 years, 53% women) who underwent unilateral total knee replacement (TKR) due to severe knee OA. Serum testosterone levels and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain and function of the operated and contralateral knee were measured at 6-8 weeks after surgery. At the nonoperated knee, 56% of participants had radiographic knee OA with a Kellgren/Lawrence grade ≥2. Cross-sectional analyses were performed by sex and body mass index (BMI) subgroups, using multivariable regression adjusted for age, physical activity, and BMI.

RESULTS

At the operated knee, higher testosterone levels were associated with less WOMAC pain in men (B = -0.62, P = 0.046) and women (B = -3.79, P = 0.02), and less WOMAC disability scores in women (B = -3.62, P = 0.02) and obese men (B = -1.99, P = 0.02). At the nonoperated knee, testosterone levels were not associated with WOMAC pain in men or women, but higher testosterone levels were associated with less disability in women (B = -0.95, P = 0.02). Testosterone levels were inconsistently associated with pain and disability in BMI subgroups among men. Only among obese women, testosterone levels were inversely associated with radiographic knee OA (odds ratio = 0.10, P = 0.003).

CONCLUSION

Higher total testosterone levels were associated with less pain in the operated knee in men and women undergoing TKR and less disability in women. At the nonoperated knee, higher testosterone levels were inconsistently associated with less pain and disability.

Early knee osteoarthritis prevalence is highest among middle-aged adult females with obesity based on new set of diagnostic criteria from a large sample cohort study in the Japanese general population

PURPOSE

A few new criteria for early detection and prevention of early knee osteoarthritis (EKOA) have been proposed. However, its prevalence, risk factors, relationship with function and prognosis have not been clarified. The purpose of this study was to investigate the prevalence of EKOA and its risk factors in the Japanese general population.

METHODS

A total of 1104 volunteers (443 males, 661 females) who participated in the Iwaki cohort study in Japan were enrolled in this cross-sectional study. Their bilateral weight-bearing anterior-posterior knee radiographs were classified by Kellgren-Lawrence (KL) grade. EKOA (KL grade 0/1) was defined according to the following criteria: knee injury and osteoarthritis outcome score < 85%, joint line tenderness, and crepitus and its prevalence among age-sex groups was calculated. Logistic regression analyses were performed to determine the risk factors for EKOA.

RESULTS

Eight hundred and twenty-two participants had KL grade 0/1, and the EKOA prevalence was 9.5% in males and 15.0% in females (p = 0.011). The prevalence of EKOA increased with age. The highest prevalence was noted in females aged 50-59 years. Logistic regression analysis showed that the risk factors for EKOA were age (p < 0.001, odds ratio (OR) 1.1), female sex (p = 0.002, OR 2.5), high body mass index (p < 0.001, OR 1.2), and history of knee injury (p < 0.001, OR 21.7).

CONCLUSIONS

The highest EKOA prevalence was observed in middle adult females (50-59 years old). The risk factors for EKOA were female sex, ageing, obesity and knee injury history, which were extremely similar to those of definitive knee osteoarthritis.

LEVEL OF EVIDENCE

Level I in diagnostic studies-investigating a diagnostic test.

Association between thigh muscle strength four years after partial meniscectomy and radiographic features of osteoarthritis 11 years later

Background

Meniscus injury and meniscectomy both entail increased risk of knee osteoarthritis (OA). Thigh muscle weakness is a suggested mediator of OA but there is little evidence of its importance for knee OA development after meniscectomy. This study aimed to examine the association between thigh muscle strength after partial meniscectomy in middle-aged subjects with a non-traumatic meniscal tear and later radiographic knee OA changes.

Methods

Thirty-four out of 45 participants in an exercise-trial underwent testing for isokinetic thigh muscle strength 4 years after arthroscopic partial meniscectomy and had radiographic examination 11 years later (15 years post-surgery, mean age at follow-up of 57 years (range 50–61)). Outcomes were grade of joint space narrowing and osteophyte score in the medial tibiofemoral compartment of the operated knee and the contralateral knee. We tested the association between muscle strength at baseline and the radiographic outcomes at follow-up using logistic regression analyses adjusted for sex and overweight.

Results

At follow-up, 33/34 subjects had joint space narrowing and 27/34 subjects had osteophytes in the operated knee, in the contralateral knee joint space narrowing was found in 23 subjects. In the operated knee baseline knee extensor and flexor strength were negatively associated with grade of joint space narrowing at follow-up (OR 0.972 and 0.956, p = 0.028 and 0.026, respectively) and also with osteophyte score (OR 0.968 and 0.931, p = 0.017 and 0.011, respectively). In the contralateral knee longitudinal associations between strength and radiographic OA features were similar, OR 0.949–0.972, p < 0.05.

Conclusion

The finding that stronger thigh muscles 4 years after meniscectomy were associated with less severe osteoarthritic changes in the medial tibiofemoral compartment of both the operated and contralateral knee 11 years later, may suggest that strong thigh muscles can help to preserve joint integrity in middle-aged subjects at risk of knee OA.

Recovery after unilateral knee replacement due to severe osteoarthritis and progression in the contralateral knee: a randomised clinical trial comparing daily 2000 IU versus 800 IU vitamin D

Objective

To test whether daily high-dose vitamin D improves recovery after unilateral total knee replacement.

Methods

Data come from a 24-month randomised, double-blind clinical trial. Adults aged 60 and older undergoing unilateral joint replacement due to severe knee osteoarthritis were 6-8 weeks after surgery randomly assigned to receive daily high-dose (2000 IU) or standard-dose (800 IU) vitamin D₃. The primary endpoints were symptoms (Western Ontario and McMaster Universities Arthritis Index pain and function scores) assessed at baseline, 6, 12, 18 and 24 months in both knees, and the rate of falls over 24 months. The secondary outcomes were sit-to-stand performance, gait speed, physical activity and radiographic progression in the contralateral knee.

Results

We recruited 273 participants, 137 were randomised to receive 2000 IU and 136 were randomised to receive 800 IU vitamin D per day. 2000 IU vitamin D increased 25-hydroxyvitamin D levels to 45.6 ng/mL and 800 IU vitamin D to 37.1 ng/mL at month 24 (p<0.0001). While symptoms improved significantly in the operated knee and remained stable in the contralateral knee over time, none of the primary or secondary endpoints differed by treatment group over time. The rate of falls over 24 months was 1.05 with 2000 IU and 1.07 with 800 IU (p=0.84). 30.5% of participants in the 2000 IU and 31.3% of participants in the 800 IU group had radiographic progression in the contralateral knee over 24 months (p=0.88).

Conclusions

Our findings suggest that a 24-month treatment with daily 2000 IU vitamin D did not show greater benefits or harm than a daily standard dose of 800 IU among older adults undergoing unilateral total knee replacement.

Knee extensor strength and body weight in adolescent men and the risk of knee osteoarthritis by middle age

OBJECTIVES

To assess the extent to which knee extensor strength and weight in adolescence are associated with knee osteoarthritis (OA) by middle age.

METHODS

We studied a cohort of 40 121 men who at age 18 years in 1969/1970 underwent mandatory conscription in Sweden. We retrieved data on isometric knee extensor strength, weight, height, smoking, alcohol consumption, parental education and adult occupation from Swedish registries. We identified participants diagnosed with knee OA or knee injury from 1987 to 2010 through the National Patient Register. We estimated the HR of knee OA using multivariable-adjusted Cox proportional regression model. To assess the influence of adult knee injury and occupation, we performed a formal mediation analysis.

RESULTS

The mean (SD) knee extensor strength was 234 (47) Nm, the mean (SD) weight was 66 (9.3) kg. During 24 years (median) of follow-up starting at the age of 35 years, 2049 persons were diagnosed with knee OA. The adjusted HR (95% CI) of incident knee OA was 1.12 (1.06 to 1.18) for each SD of knee extensor strength and 1.18 (1.15 to 1.21) per 5 kg of body weight. Fifteen per cent of the increase in OA risk due to higher knee extensor strength could be attributed to knee injury and adult occupation.

CONCLUSION

Higher knee extensor strength in adolescent men was associated with increased risk of knee OA by middle age, challenging the current tenet of low muscle strength being a risk factor for OA. We confirmed higher weight to be a strong risk factor for knee OA.

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.

Osteoarthritis year in review 2016: mechanics

Inappropriate biomechanics, namely wear-and-tear, has been long believed to be a main cause of osteoarthritis (OA). However, this view is now being re-evaluated, especially when examined alongside mechanobiology and new biomechanical studies. These are multiscale experimental and computational studies focussing on cell- and tissue-level mechanobiology through to organ- and whole-body-level biomechanics, which focuses on the biomechanical and biochemical environment of the joint tissues. This review examined papers from April 2015 to April 2016, with a focus on multiscale experimental and computational biomechanical studies of OA. Assessing the onset or progression of OA at organ- and whole-body-levels, gait analysis, medical imaging and neuromusculoskeletal modelling revealed the extent to which tissue damage changes the view of inappropriate biomechanics. Traditional gait analyses studies reported that conservative treatments can alter joint biomechanics, thereby improving pain and function experienced by those with OA. Results of animal models of OA were consistent with these human studies, showing interactions among bone, cartilage and meniscus biomechanics and the onset and/or progression OA. Going down size scales, experimental and computational studies probed the nanosize biomechanics of molecules, cells and extracellular matrix, and demonstrated how the interactions between biomechanics and morphology affect cartilage dynamic poroelastic behaviour and pathways to OA. Finally, integration of multiscale experimental data and computational models were proposed to predict cartilage extracellular matrix remodelling and the development of OA. Summarising, experimental and computational methods provided a nuanced biomechanical understanding of the sub-cellular, cellular, tissue, organ and whole-body mechanisms involved in OA.