Clinical and safety outcomes of simultaneous bilateral total knee arthroplasty for Japanese octogenarian patients: a retrospective analysis.

PURPOSE: The demand for simultaneous bilateral total knee arthroplasty (SiBTKA) in older adults is expected to increase with an aging population, thus necessitating evaluating its efficacy and safety. However, there is limited information regarding the clinical outcomes of SiBTKA in older adults, particularly in octogenarians. We aimed to assess the clinical outcomes and safety of SiBTKA in Japanese patients aged ≥ 80 years. METHODS: Of the 176 consecutive knees that underwent SiBTKA between July 2016 and January 2022 at our hospital, 172 were selected. They were divided into two groups according to the patient age as follows: the octogenarian group (≥ 80 years, 74 knees) and the younger control group (< 80 years, 98 knees). In addition, we assessed their preoperative clinical information, clinical outcomes using the Knee Society Score for knee (KSS-K) and function (KSS-F), and the incidence of early (≤ 90 days) and late (> 90 days) postoperative complications. RESULTS: The mean follow-up period was 3.5 years. The KSS-K scores of both groups improved postoperatively than that preoperatively. Both preoperative and postoperative KSS-F scores were lower in the octogenarians; however, their improvement rates were similar to those of the younger controls. We observed no significant intergroup differences in early or late postoperative complications, including infection, systemic complications, periprosthetic fractures, aseptic loosening, and mortality. CONCLUSION: SiBTKA for octogenarians had clinical outcomes and postoperative complication incidence similar to that for younger controls. Therefore, SiBTKA may be a safe and effective treatment option for octogenarians with painful bilateral knee deformities.

A case of subacute combined degeneration of the spinal cord diagnosed with difficulty due to a history of treatment for pyogenic spondylitis.

Early diagnosis of spinal cord subacute combined degeneration (SCD) is difficult, especially in pre-existing lower extremity impairment cases. We report a case of progressive SCD diagnosed after severe anemia. The peripheral symptoms of SCD other than gait disturbance should also be well understood and given close attention.

Preoperative incidence and risk factors of deep vein thrombosis in Japanese patients undergoing total hip arthroplasty.

PURPOSE: Preoperative deep vein thrombosis (DVT) is a risk factor for postoperative venous thromboembolism (VTE), causing severe mortality. Early detection of preoperative DVT is essential to prevent postoperative VTE. However, little is known regarding preoperative DVT in patients undergoing major surgery. The present study aimed to determine the incidence and risk factors of preoperative DVT in patients admitted for total hip arthroplasty (THA). METHODS: From August 2017 to September 2022, 243 patients admitted for THA at our institution were enrolled in this study. Patients medical records and preoperative laboratory data were retrospectively collected. According to the results of lower-limb ultrasonography, patients were divided into either the non-DVT (n = 136) or DVT (n = 43) group. The incidence of DVT and independent risk factors for preoperative DVT were investigated using univariate and multivariate logistic regression analyses. RESULTS: The mean age was 74.0 ± 8.4 years. Preoperative DVT was diagnosed in 43 of the 243 (17.7%) patients. The risk of DVT was significantly high (p < 0.05) in patients with advanced age, increased D-dimer levels, and malnutrition status, as assessed by the Geriatric Nutritional Risk Index (GNRI). Multivariate analysis showed that advanced age, increased D-dimer level, and malnutrition status assessed by the GNRI were independent risk factors for preoperative DVT. CONCLUSION: A high incidence of preoperative DVT was observed in patients undergoing THA. Advanced age, increased D-dimer levels, and malnutrition assessed by the GNRI increased the risk of preoperative DVT. Screening high-risk subgroups for preoperative DVT is necessary to prevent postoperative VTE.

Clinical and radiological outcomes of total hip arthroplasty in octogenarian patients using a three-dimensional porous titanium cup: a retrospective analysis in Japanese patients.

PURPOSE: Osteointegration of a three-dimensional (3D) porous titanium material has been experimentally proven, but only a few studies have shown the clinical outcomes of a 3D porous titanium cup in the Japanese elderly population. The purpose of this study was to compare the short-and-medium term clinical and radiographic results of total hip arthroplasty (THA) using a 3D porous titanium cup in patients aged ≥ 80 (octogenarians) versus those aged < 80 (younger controls). METHODS: A total of 104 hips that underwent THA using a 3D porous titanium cup (SQRUM TT, Kyocera Medical) were enrolled in the study and were divided into two groups according to age: the octogenarian group (≥ 80, n = 42) and the younger control group (< 80, n = 62). Furthermore, we evaluated patient characteristics, clinical outcomes determined by the Japanese Orthopedic Association score, cup alignment, and incidence of radiolucent lines around the cup. RESULTS: The mean follow-up period was 4.2 and 4.0 years (p = 0.29) for octogenarians and younger controls, respectively. The clinical outcomes were excellent, and no revision surgery occurred until the last follow-up in both groups. The number of patients with radiolucent lines at the final evaluation was 21 of 62 (33.9%) in younger controls and 16 of 42 (38.1%) in octogenarians. CONCLUSION: THA with 3D porous titanium cup for octogenarians had similar clinical outcomes and incidence of radiolucent lines as those of younger controls, suggesting that the 3D porous titanium cup may be useful in THA for octogenarians. Further investigations will confirm its long-term outcomes.

Effect of Antimicrobial Prophylaxis Duration on Health Care-Associated Infections After Clean Orthopedic Surgery: A Cluster Randomized Trial.

Importance: Postoperative health care-associated infections are associated with a greater deterioration in patients' general health status and social and economic burden, with at least 1 occurring in approximately 4% of acute care hospital patients. Antimicrobial prophylaxis prevents surgical site infections in various orthopedic procedures; however, its relationship with health care-associated infections remains unknown. Objective: To examine whether a shorter antimicrobial prophylaxis duration of less than 24 hours after surgery is not inferior to a longer duration in preventing health care-associated infections after clean orthopedic surgery. Design, Setting, and Participants: This open-label, multicenter, cluster randomized, noninferiority clinical trial was conducted in 5 tertiary referral hospitals in greater Tokyo metropolitan area, Japan, from May to December 2018. Adult patients undergoing clean orthopedic surgery were recruited until the planned number of participants was achieved (500 participants per group). Statistical analysis was conducted from July to December 2019. Interventions: Antimicrobial prophylaxis was discontinued within 24 hours after surgery in group 24 and 24 to 48 hours after surgery in group 48. Group allocation was switched every 2 or 4 months according to the facility-based cluster rule. Study-group assignments were masked from participants. Main Outcomes and Measures: The primary outcome was the incidence of health care-associated infections requiring antibiotic therapies within 30 days after surgery. The noninferiority margin was 4%. Results: Of the 1211 participants who underwent cluster allocation, 633 participants were in group 24 (median [IQR] age, 73 [61-80] years; 250 men [39.5%] and 383 women [60.5%]), 578 participants were in group 48 (median [IQR] age, 74 [62-81] years; 204 men [35.3%] and 374 women [64.7%]), and all were eligible for the intention-to-treat analyses. Health care-associated infections occurred in 29 patients (4.6%) in group 24 and 38 patients (6.6%) in group 48. Intention-to-treat analyses showed a risk difference of -1.99 percentage points (95% CI, -5.05 to 1.06 percentage points; P < .001 for noninferiority) between groups, indicating noninferiority. Results of adjusted intention-to-treat, per-protocol, and per designated procedure population analyses supported this result, without a risk of antibiotic resistance and prolonged hospitalization. Conclusions and Relevance: This cluster randomized trial found noninferiority of a shorter antimicrobial prophylaxis duration in preventing health care-associated infections without an increase in antibiotic resistance risk. These findings lend support to the global movement against antimicrobial resistance and provide additional information on adequate antimicrobial prophylaxis for clean orthopedic surgery. Trial Registration: Identifier: UMIN000030929.

18F-sodium fluoride positron emission tomography may help diagnose nondisplaced peri-prosthetic and peri-implant fracture.

Occult fractures are challenging to diagnose, especially those involving an implant surrounding the suspected fracture site. This is the first case wherein 18F-sodium fluoride positron emission tomography substantially helped to diagnose peri-prosthetic and peri-implant fractures. The application of this imaging modality warrants further study.

Intraosseous epidermal cyst of the great toe that was difficult to distinguish from chronic osteomyelitis: A case report and literature review.

Obtaining a correct intraosseous epidermal cyst diagnosis is difficult due to the extreme rarity of this cyst. Further, the clinical manifestations and radiographic findings are very similar to those of a malignancy or infection. Early histopathological analysis is required for accurate diagnosis and for avoiding unnecessary antibiotic administration and amputation.

18F-sodium fluoride positron emission tomography may help determine better treatment for thigh pain after hip arthroplasty-A case report.

Thigh pain after hip arthroplasty is multifactorial; uncovering its etiology is paramount for optimal treatment. This is the first case where 18F-sodium fluoride positron emission tomography substantially helped in diagnosing the post-hip arthroplasty persistent thigh pain and appropriate treatment selection. This imaging modality warrants further study and more widespread application.

A sliding scale to predict postoperative complications undergoing posterior spine surgery.

BACKGROUND: There is a lack of consensus of operative time (OT) and estimated blood loss (EBL) for elderly patients based on the predicted risk of complications after posterior spine surgery. The purpose of this study was to evaluate the effect of age, OT, and EBL on the postoperative complication risk and to develop a simple sliding scale. METHODS: We explored prospectively collected data of consecutive patients who underwent posterior spine surgery in seven tertiary referral hospitals from November 2013 to May 2016. Age (<70, 70-74, 75-79, 80-84, ≥85 years), OT (<2, 2-<3, 3-<4, 4-<5, ≥5 h), and EBL (<500, 500-<1000, 1000-<1500, 1500-<2000, ≥2000 ml) were categorized ranging from 1 (lowest) to 5 (highest). The association between the crude cumulative categories' number and the incidence of complications was analyzed. We further evaluated the association by re-categorizing the cumulative number into three groups (3-4, 5-10, ≥11). RESULTS: Total of 2416 patients (median age: 70 years old) were enrolled and major complications were observed in 75 (3.1%) patients. Age, OT, and EBL showed similar odds ratio (1.18-1.19) as each category increased. The cumulative categories' number fitted the estimate complication risk (Hosmer-Lemeshow P = 0.87), and statistically significant trend was observed between predicted and actual complication rates (Cochran-Armitage test, P < 0.001). When cumulative categories' numbers were stratified into three groups, significant increasing trend of risk were observed (Mantel-Haenszel P < 0.001). Based on the categorical numbers, we proposed a simple sliding scale. CONCLUSION: Our data indicated that the risk of postoperative complication was associated with cumulative score based on increased age, OT, and EBL. A simple sliding scale was developed based on these factors, which may be useful to predict complication risk after posterior spine surgery.

Association Between Normothermia at the End of Surgery and Postoperative Complications Following Orthopedic Surgery.

BACKGROUND: Maintaining perioperative normothermia is recommended by recent guidelines for the prevention of surgical site infections (SSIs). However, the majority of supporting data originates outside the field of orthopaedic surgery. METHODS: The effect of normothermia was explored using the prospectively collected data of consecutive patients who underwent single-site surgery in 7 tertiary referral hospitals between November 2013 and July 2016. SSIs, urinary tract infections (UTIs), respiratory tract infections (RTIs), cardiac and cerebral events (CCE), and all-cause mortality rates within 30 days after surgery were compared between patients with normothermia (body temperature ≥36°C) and those with hypothermia (<36°C) at the end of surgery, after closure. Multivariable adjusted and inverse-probability weighted regression analyses were performed. RESULTS: The final cohort included 8841 patients. Of these, 11.4% (n = 1008) were hypothermic. More than 96% were evaluated in person by the physicians. After adjusting for multiple covariates, normothermia was not significantly associated with SSIs (adjusted odds ratio [aOR] 1.18, 95% confidence interval [CI] 0.59-2.33), UTIs (aOR 1.14, 95% CI 0.66-1.95), RTIs (aOR 0.60, 95% CI 0.31-1.19), or CCE (aOR 0.53, 95% CI 0.26-1.09). In contrast, normothermia was associated with a lower risk of 30-day mortality (aOR 0.26, 95% CI 0.11-0.64; P < .01; weighted hazard ratio 0.21, 95% CI 0.07-0.68; P = .002). In a subgroup analysis, normothermia was associated with reduced mortality in all types of surgical procedures. CONCLUSIONS: Whereas our findings suggest no clear association with SSI risks following orthopedic surgery, our study supports maintaining perioperative normothermia, as it is associated with reduced 30-day mortality.

Non-inferior comparative study comparing one or two day antimicrobial prophylaxis after clean orthopaedic surgery (NOCOTA study): a study protocol for a cluster pseudo-randomized controlled trial comparing duration of antibiotic prophylaxis.

BACKGROUND: Antimicrobial prophylaxis (AMP) is one of the most important measures for preventing surgical site infections (SSIs); however, controversies remain regarding its adequate duration. Although the World Health Organization and the Center for Disease Control and Prevention do not recommend additional AMP after closure, the American Society of Health-System Pharmacists and the Musculoskeletal Infection Society permit the use of postoperative AMP, but recommend discontinuation within 24 h. Similarly, the Japanese Society of Chemotherapy and the Japan Society for Surgical Infection also permit AMP within 24-48 h after various orthopaedic procedures. In these guidelines, recommendations regarding AMP duration were weak due to a relative lack of evidence, and currently, there is no high-quality evidence comparing AMP use within 24 h versus 24-48 h regarding orthopaedic procedures. Urinary tract infection (UTI) and respiratory tract infection (RTI) are also important health care-associated infections (HAIs) faced after surgery. Although AMP duration may affect these HAIs, its effects have not been well evaluated. METHODS: We have organized a multicenter, prospective, cluster pseudo-randomized controlled trial to examine the non-inferiority of shorter AMP duration (within 24 h) against longer duration (24-48 h) in preventing postoperative HAIs. Participating facilities will be divided into two groups. In Group 24, AMP will be discontinued within 24 h after surgery. In Group 48, AMP will be discontinued within 24-48 h after surgery. The group allocation will be switched every 2 months until the targeted recruitment (500 participants per group) is met. The primary outcome will be the cumulative incidence of all HAIs (SSI, UTI, RTI, and other infectious diseases), which require antibiotic therapies within 30 days after surgery. In addition to mortality and cardiovascular events, prolonged hospitalization (> 30 days) and the rate of antibiotic resistance rate of SSI pathogens will also be evaluated. Outcomes will be evaluated within 30-180 days after surgery in person by the surgeon, by mail, or by telephone survey. Data will be analyzed by a statistician not engaged in data collection. DISCUSSION: This study may provide valuable information for developing future recommendations for adequate AMP duration after clean orthopaedic surgery. TRIAL REGISTRATION: UMIN000030929, registered January 22, 2018.

NaF PET assessment of bone metabolic changes around the femoral canal by intramedullary femoral alignment technique in total knee arthroplasty.

We used the NaF PET scan to assess osteometabolic changes around the distal half of the femoral canal by intramedullary (IM) drill for femoral IM guiding rod insertion in total knee arthroplasty. Gentle IM rod insertion and focused attention can minimize surgical stress-induced biological reaction of the femoral IM canal.

Quadriceps muscle strength, radiographic knee osteoarthritis and knee pain: the ROAD study.

BACKGROUND: The objective of this study was to clarify the association of quadriceps muscle strength with knee pain using a large-scale, population-based cohort of the Research on Osteoarthritis/osteoporosis Against Disability (ROAD) study. METHODS: From the 2566 subjects at the third visit of the ROAD study, the present study analyzed 2152 subjects who completed radiographic examinations and measurements of muscle strength and mass (690 men and 1462 women; mean age, 71.6 ± 12.2 years). Knee pain was assessed by an experienced orthopedist. Knee osteoarthritis (OA) was defined according to Kellgren-Lawrence (KL) grade. Quadriceps muscle strength and muscle mass at the lower limbs were measured by the Quadriceps Training Machine (QTM-05F, Alcare Co., Ltd. Tokyo, Japan) and the Body Composition Analyzer MC-190 (Tanita Corp., Tokyo, Japan), respectively. RESULTS: Quadriceps muscle strength and weight bearing index (WBI: quadriceps muscle strength by weight) were significantly associated with knee pain after adjustment for age and body mass index, whereas grip strength and muscle mass at the lower limbs were not. The significant association of quadriceps muscle strength with knee pain was independent of radiographic knee OA. CONCLUSION: The present cross-sectional study showed an independent association of quadriceps muscle strength with knee pain.

Does osteophytosis at the knee predict health-related quality of life decline? A 3-year follow-up of the ROAD study.

The objective of the present longitudinal study was to clarify whether osteophytosis and joint space narrowing predict quality of life (QOL) decline using a longitudinal population-based cohort of the Research on Osteoarthritis/osteoporosis Against Disability (ROAD) study. The present study analyzed 1,525 participants who completed the radiographic examination at baseline and questionnaires regarding QOL at a 3-year follow-up (546 men and 979 women; mean age, 67.0 ± 11.0 years). This study examined the associations of osteophyte area (OPA) and minimum joint space width (mJSW) in the medial compartment of the knee at baseline with pain and physical functional disability measured by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). OPA and mJSW in the medial compartment of the knee were measured using a knee osteoarthritis (OA) computer-aided diagnosis system. Overall, OPA independently predicted physical functional disability after 3 years of follow-up. When analyzed in men and women separately, OPA, rather than mJSW, was an independent predictor for pain and physical functional disability after 3 years of follow-up in men. OPA, rather than mJSW, also predicted worsening of pain in men during the 3-year follow-up, whereas in women, mJSW, rather than OPA, predicted worsening of pain. In conclusion, the present longitudinal study using a large-scale population from the ROAD study found gender differences in the association of osteophytosis and joint space narrowing with pain and physical functional disability.

A review of denosumab for the treatment of osteoporosis.

Osteoporosis is an age-related systemic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue, with a consequent increase in bone fragility. Bone remodeling involves two types of cells: osteoblasts and osteoclasts. Receptor activator of nuclear factor-κB ligand (RANKL) is a key regulator of the formation and function of bone-resorbing osteoclasts, and its cell surface receptor, receptor activator of nuclear factor-κB (RANK), is expressed by both osteoclast precursors and mature osteoclasts. Denosumab is a fully human monoclonal anti-RANKL antibody that inhibits the binding of RANKL to RANK, thereby decreasing osteoclastogenesis and bone-resorbing activity of mature osteoclasts. Although there are many medications available for the treatment of osteoporosis, inhibition of RANKL by denosumab has been shown to significantly affect bone metabolism. Denosumab appears to be a promising, highly effective, and safe parenteral therapy with good adherence for osteoporosis. Moreover, denosumab may be cost-effective therapy compared with existing alternatives. Therefore, in this review, we focus on studies of denosumab and the risks and benefits identified for this type of treatment for osteoporosis.

Association of knee osteoarthritis with onset and resolution of pain and physical functional disability: the ROAD study.

OBJECTIVES: To examine the onset and resolution of pain and physical functional disability using Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and their association with knee osteoarthritis (OA) in the longitudinal large-scale population of the nationwide cohort study, Research on Osteoarthritis/osteoporosis Against Disability (ROAD). METHODS: Subjects from the ROAD study who had been recruited during 2005-2007 were followed up 3 years later. A total of 1,578 subjects completed the WOMAC questionnaire at baseline and follow up, and the onset and resolution rate of pain and physical functional disability were examined. We also examined the association of onset of pain and physical functional disability and their resolution with severity of knee OA as well as age, body-mass index and grip strength. RESULTS: After a 3.3-year follow-up, the onset rate of pain was 35.0% and 35.3% in men and women, respectively, and the onset rate of physical functional disability was 38% and 40%, respectively. Resolution rate of pain was 20.3% and 26.2% in men and women, respectively, and resolution rate of physical functional disability was 16% and 14% in men and women, respectively. Knee OA was significantly associated with onset and resolution of pain and physical functional disability in women, but there was no significant association of knee OA with onset of pain and resolution of physical functional disability in men. CONCLUSIONS: The present longitudinal study revealed the onset rate of pain and physical functional disability as well as their resolution, and their association with knee OA.

Association of physical activities of daily living with the incidence of certified need of care in the long-term care insurance system of Japan: the ROAD study.

BACKGROUND: The present study aimed to investigate association of physical activities of daily living with the incidence of certified need of care in the national long-term care insurance (LTCI) system in elderly Japanese population-based cohorts. METHODS: Of the 3,040 participants in the baseline examination, we enrolled 1,773 (699 men, 1,074 women) aged 65 years or older who were not certified as in need of care-level elderly at baseline. Participants were followed during an average of 4.0 years for incident certification of need of care in the LTCI system. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) was used assess function. Associated factors in the baseline examination with the occurrence were determined by multivariate Cox proportional hazards regression analysis. Receiver operating characteristic curve analysis was performed to evaluate cut-off values for discriminating between the occurrence and the non-occurrence group. RESULTS: All 17 items in the WOMAC function domain were significantly associated with the occurrence of certified need of care in the overall population. Cut-off values of the WOMAC function score that maximized the sum of sensitivity and specificity were around 4-6 in the overall population, in men, and in women. Multivariate Cox hazards regression analysis revealed that a WOMAC function score ≥4 was significantly associated with occurrence with the highest hazard ratio (HR) for occurrence after adjusting for confounders in the overall population (HR [95 % confidence interval (CI)] 2.54 [1.76-3.67]) and in women [HR (95 % CI) 3.13 (1.95-5.02)]. A WOMAC function score ≥5 was significantly associated with the highest HR for occurrence in men [HR (95 % CI) 1.88 (1.03-3.43)]. CONCLUSIONS: Physical dysfunction in daily living is a predictor of the occurrence of certified need of care. Elderly men with a WOMAC function score ≥5 and women with a score ≥4 should undergo early intervention programs to prevent subsequent deterioration.

Incidence of certified need of care in the long-term care insurance system and its risk factors in the elderly of Japanese population-based cohorts: the ROAD study.

AIM: To examine the incidence of certified need of care in the national long-term care insurance (LTCI) system, and to determine its risk factors in the elderly of Japanese population-based cohorts of the Research on Osteoarthritis/Osteoporosis Against Disability (ROAD) study. METHODS: Of the 3040 participants in the baseline examination of the ROAD study, we enrolled 1773 (699 men, 1074 women) aged 65 years or older who were not certified as in need of care level elderly at baseline. Participants were followed for incident certification of need of care in the LTCI system. Associated factors in the baseline examination with occurrence were determined by multivariate Cox proportional hazards regression analysis. Muscle dysfunction was defined in accordance with the European Working Group on Sarcopenia in Older People algorithm for screening sarcopenia. RESULTS: A total of 54 men and 115 women were certified as in need of care level elderly during the average 4.0-year follow up. The incidence was 2.0 and 2.5 per 100 person-years in men and women, respectively. Identified risk factors were region, age, body mass index <18.5 or ≥ 27.5 kg/m(2), grip strength, knee extension torque, usual gait speed, chair stand time and muscle dysfunction. CONCLUSIONS: Both underweight and obesity, as well as low muscle strength and physical ability, are risk factors for certification of need of care. Considering muscle dysfunction is a risk factor for occurrence, screened individuals are recommended to receive early intervention programs regardless of muscle volume.

Incidence and risk factors for radiographic knee osteoarthritis and knee pain in Japanese men and women: a longitudinal population-based cohort study.

OBJECTIVE: To examine the incidence and progression of radiographic knee osteoarthritis (OA) and the incidence of knee pain, and their risk factors in Japan, using the large-scale population of the nationwide cohort study ROAD (Research on Osteoarthritis/osteoporosis Against Disability). METHODS: Subjects from the ROAD study who had been recruited in 2005-2007 were followed up with knee radiography 3 years later. A total of 2,262 paired radiographs (74.4% of the original sample) were scored using the Kellgren/Lawrence (K/L) grading system, and the incidence and progression rate of knee OA was examined. The incidence rate of knee pain was also examined. In addition, risk factors were tested for their association with incident and progressive radiographic knee OA and incident knee pain. RESULTS: Given the ∼3.3-year followup, the rate of incident K/L grade ≥2 radiographic knee OA was 6.9% and 11.9% in men and women, respectively, while that of K/L grade ≥3 knee OA was 8.4% and 13.9% in men and women, respectively. The rate of progressive knee OA was 17.8% and 22.3% in men and women, respectively. The incident rate of knee pain was 21.2% and 27.3% in men and women, respectively. Female sex was a risk factor for incident K/L grade ≥2 knee OA, but was not associated with incident K/L grade ≥3 knee OA or progressive knee OA. Knee pain was a risk factor for incident and progressive knee OA. Previous knee injury was a risk factor for knee pain but not for radiographic knee OA. CONCLUSION: The present longitudinal study revealed a high incidence of radiographic knee OA in Japan.