Musculoskeletal problems are among the most commonly reported complaints in the general population. The knee joint, being a significant weight-bearing joint exposed to considerable stress and use, commonly experiences pain and discomfort.1 Knee pain can affect individuals of all ages, and its prevalence varies widely, ranging from about 10% to 60%, depending on factors such as age, gender, ethnics, and geographical location.2–5 Osteoarthritis (OA), a degenerative joint disease, is one of the most common cause of knee pain and is associated with significant health and economic burden.6

Several factors have been identified as being associated with knee OA and its consequential impairment or disability. These factors include older age, female gender, higher body mass index (BMI), and history of knee injury.7–11 Additionally, higher level of physical activity is also reported as a contributor to knee problems.12 Other risk factors, such as the presence of comorbidities, lower education level, lower social class, and mental distress have also been associated with greater knee problems and disability.12–14 However, community-based studies thoroughly investigating these factors are still lacking.

Knee pain does not just cause physical discomfort; it frequently results in substantial functional limitations and disabilities that profoundly affect one's quality of life. Moreover, recent studies have demonstrated that knee pain is a better predictor of disability and functional status than radiographic severity.15,16 To evaluate patient's perception on symptoms and functioning, patient-reported outcome measures are often employed. The Knee Injury and Osteoarthritis Outcome Score (KOOS) is a knee-specific instrument which has been widely used to assess the patients’ opinions on their knee problems. It evaluates both short-term and long-term symptoms as well as the overall function of the knee in cases of injury and osteoarthritis.17

The World Health Organization and the International League Against Rheumatism (WHO-ILAR) have initiated the Community Oriented Program for Control of Rheumatic Diseases (COPCORD) as a means of screening for rheumatologic symptoms in the population across countries. Utilizing the COPCORD data gathered in Jakarta, Indonesia, this study aims to investigate the factors associated with patient-reported outcome measures – including symptom severity, activity and functional limitations, and quality of life – in the population experiencing knee OA within an urban community setting. Understanding these factors is crucial for identifying populations with knee OA who are at risk of experiencing worse outcomes. This knowledge allows for timely implementation of preventive measures and interventions to halt the progression of disability.

In this study, we investigated the factors associated with patient-reported outcome measures, as assessed by the KOOS questionnaire, in patients experiencing knee OA. Our main results demonstrated that CVD was significantly associated with increased pain and symptoms, greater limitations in daily activities and sports/recreation participation, and a lower quality of life. Furthermore, OA subjects with history of knee injury scored worse specifically in the QoL subscale.

CVD was independently associated with worse KOOS across all subscales in our study, indicating more severe functional impairment and symptoms of knee OA among subjects with CVD. This finding aligns with previous studies demonstrating the close relationship between CVD and OA. Patients with knee OA have been reported to have an increased risk of CVD. A meta-analysis by Wang et al. showed a 24% higher risk of CVD among OA subjects compared to the general population.19 Physical inactivity and the shared risk factors between the two diseases have been postulated to explain the increased risk of CVD among OA patients.19,20 Conversely, we cannot rule out that CVD may also play a role in exacerbating the severity of knee OA symptoms, highlighting the interrelationship between the two conditions. For instance, Goel et al. found that an increasing cardiovascular risk score was positively correlated with greater OA severity.21 There is growing evidence that systemic inflammation and vascular pathology are implicated in the association between CVD and OA. A systematic review by Hussain et al. suggested a link between vascular pathology and knee OA, finding that baseline vascular pathology was associated with the progression of knee OA over subsequent years.22 Additionally, patients with OA were found to have increased arterial stiffness compared to controls.23 These findings suggest that vascular pathology may play a significant role in the development and progression of OA.22 Vascular alterations may hinder blood supply to the subchondral bone region, resulting in ischemia and hypoxia of the bone. This hypothesis aligns with the findings of Chang et al., which demonstrated the presence of hypoxia in the osteoblasts and chondrocytes of OA joints.24

A history of knee injury was significantly associated with the QoL subscale of KOOS. The QoL subscale broadly captures several aspects of knee problems, including self-awareness of knee issues, lifestyle modifications due to knee problems, the feeling of being troubled by knee problems, and the overall consequences.25 Previous studies have shown that the QoL subscale is highly responsive and scores worse in patients undergoing anterior cruciate ligament reconstruction with ongoing symptoms compared to other KOOS subscales, suggesting its high sensitivity in capturing an individual's reported knee problems, especially following an injury.26

Cartilage injury may result in “wear and tear” damage and subsequent OA development. Furthermore, muscle dysfunction associated with injury may result in greater force being transmitted to the bones and joints as impact forces are not being absorbed properly.27 A study assessing knee symptoms among downhill runners found that a self-reported history of knee injuries was associated with worse KOOS scores on all subscales, while our study found a significant association only on the KOOS QoL subscale.9 However, in this study, we did not further explore the details of knee injury, such as the type, severity, and mechanism of injury. It is possible that knee injuries suffered by athletes were more severe, thus affecting the KOOS scores to a greater extent. Exploring the nature of the injury and its effects on symptom severity might help clinicians identify individuals who are at higher risk for OA progression and severity.

Age was found to be significantly negatively correlated with the overall KOOS, Symptoms, ADL, and Sport/Rec subscales; however, this association was not significant upon multivariate analysis. This finding aligns with a previous study by Oishi et al. in a Japanese population, which showed that overall KOOS scores and all its subscales decreased with age, with an approximately 20-point decrease per decade.28 Although age is known to be one of the main risk factors for OA development, the current multifactorial concept of OA emphasizes that aging alone does not directly cause OA. Other OA risk factors, in addition to musculoskeletal aging, contribute to OA development.29 This highlights the importance of controlling other known OA risk factors, especially in the elderly population, to prevent further OA development and progression.

BMI was not found to be correlated with symptom severity in our OA subjects, in contrast to findings from previous studies. Higher BMI has been identified as a risk factor for knee OA.30 Studies on the influence of BMI on KOOS scores have demonstrated variable results. For example, a study by Larsen et al. in Denmark involving obese and superobese patients who were planning bariatric surgery demonstrated significantly worse KOOS subscales compared to values from the general population.31 However, this study included patients with a BMI of 35kg/m2 and higher, with a mean BMI of 48.3, which is significantly higher than that of our subject population (mean BMI 23.87). Marot et al. studied KOOS score variations in a healthy population and found that individuals with a BMI over 25kg/m2 scored worse specifically on the ADL subscale, yet no clinically significant differences (defined as a difference of more than 8 points) were observed across all subscales.32

Although knee OA subjects often present with overweight or obesity, it is interesting to note that the mean BMI in our knee OA population is relatively lower compared to other studies, especially those conducted in Western populations, which tend to have a higher obesity prevalence. For instance, a study by Fosdahl et al. in Norway involving 4265 individuals with knee or hip OA had a mean BMI of 28.1±4.9kg/m2.33 Values tend to be lower in Asian populations; for example, Park et al. reported a mean BMI of 24.2±2.9kg/m2 among OA subjects in a Korean population.34 Traditionally, obesity has been associated with increased mechanical load on the joints. However, recent studies have indicated that obesity-induced adipokine production also contributes to the inflammatory component in OA development and progression.35 This is supported by evidence showing that central obesity is associated with OA, even without general obesity (as indicated by BMI), confirming the role of adipose tissue in OA inflammation. Therefore, exploring other obesity-related parameters aside from BMI, such as waist circumference, may further explain the link between obesity and OA, especially in Asian populations, which are more likely to be centrally obese than their Caucasian counterparts with the same BMI.34,36

There are several limitations to this study. First, we cannot establish causality between the factors and patient-reported knee outcomes due to the cross-sectional design. Second, the OA diagnosis was made solely based on clinical criteria without radiological evidence. Combining clinical and radiological criteria would provide a more accurate diagnosis. Furthermore, the information obtained from subjects was self-reported, including comorbidities and history of injury, without confirmation from medical records, which may introduce recall bias. Finally, our community-based study was conducted in only one city with a relatively small number of OA subjects. Including a greater number of cities, representing both urban and rural areas, would make the findings more representative of the Indonesian population and yield more generalizable results.

In conclusion, cardiovascular disease and a history of knee injury were significantly associated with worse patient-reported knee outcomes among knee OA subjects as assessed by KOOS. Future studies involving more cities are recommended to confirm these findings and provide more robust results for the Indonesian population.

This research is funded by Directorate of Research and Development, Universitas Indonesia under Hibah PUTI 2023 (grant no. NKB-148/UN2.RST/HKP.05.00/2023).

R.H. and F.P. conceived and designed the study. F.P. coordinated the sampling process. S., S.A.K.W., A.A., J.D., and A.P.A. contributed to data acquisition and analysis. R.H., F.P., J.A., and M.A. performed data interpretation. All authors contributed equally to drafting the manuscript and reviewing the manuscript substantively. All authors have read and approved of the final manuscript.

The authors declared no conflict of interests.