Knee osteoarthritis (OA) is a common disorder and a major health problem in the general population (Jiang et al., 2012). The prevalence of symptomatic knee OA is increasing worldwide (Nguyen et al., 2011). Overweight, obesity, previous knee injury, and female gender are risk factors for knee OA (Silverwood et al., 2014). The lifetime risk of symptomatic knee OA has been estimated to be approximately 40% in men and 47% in women (Neogi & Zhang, 2013), with pain and physical functional limitation as the primary presenting features (Cubukcu, Sarsan, & Alkan, 2012). Pain-associated reduction in physical function is a strong predictor of future disability and dependency in elderly people (Zakoscielna & Parmelee, 2013). Therefore, knee pain and physical functional limitation might affect the health status of patients with knee OA. However, the relationships between pain and physical function and health status in patients with knee OA remain unclear.
The International Classification of Functioning, Disability, and Health (ICF) is a useful framework for assessing health from biological, personal, and social perspectives (World Health Organization, 2001). Previous studies have demonstrated the effects of knee OA on variables such as pain, anxiety, depression, physical function, work participation, and health-related quality of life (QOL; Bieleman et al., 2011; Hsieh, Lee, Lo, & Liao, 2013). In the ICF scheme, these variables are components of categories of body functions and structures, and activities and participation.
Multidimensional evaluations are required to characterize the health status of a patient with knee OA (Hsieh et al., 2013). In this study, we used the ICF framework to evaluate the health statuses of patients with knee OA and then evaluated the associations between health status and pain and physical functional limitation.
The study participants were patients with knee OA recruited from the Department of Rehabilitation, Shin Kong Wu Ho-Su Memorial Hospital, Taiwan. In all patients, the diagnosis of knee OA fulfilled the clinical and radiographic criteria of the American College of Rheumatology (Singh, Kalaivani, Krishnan, Aggarwal, & Gupta, 2014), and the severity of knee OA was equal to or higher than Kellgren-Lawrence Grade 2 radiographically (Schiphof et al., 2011). This study was approved by the ethics committee of the hospital.
Evaluation of Pain and Physical Function
Pain and physical function were evaluated using the Chinese version of the Western Ontario and McMaster University Osteoarthritis Index (WOMAC; Collins, Misra, Felson, Crossley, & Roos, 2011). This index consists of 24 items in three subscales: pain (five items), physical function (17 items), and stiffness (two items). One-hundred-millimeter visual analog formats were used in each item, and the summated scores of the subscales ranged from 0 to 500 for pain, 0 to 1,700 for physical function, and 0 to 200 for stiffness. A higher score indicates more severe symptoms and greater limitation in function (internal consistency: 0.67–0.98, test–retest reliability: 0.52–0.96, with good construct validity: moderate to strong correlations with Short Form 36; Collins et al., 2011).
Evaluation of Health
The ICF framework, which includes components of body functions and structures, activities and participation, and personal and environmental factors, was used to evaluate health status in patients with knee OA. ICF component-related variables were assessed using instruments such as the Multidimensional Fatigue Inventory (MFI; Hewlett, Dures, & Almeida, 2011), Chronic Pain Grade Questionnaire (Hawker, Mian, Kendzerska, & French, 2011), Knee Injury and Osteoarthritis Outcome Score (KOOS; Collins et al., 2011), Chinese version of the World Health Organization Quality of Life Brief Version (WHOQOL-BREF; Hwang, Liang, Chiu, & Lin, 2003), and Osteoarthritis Quality of Life (OAQoL; Keenan et al., 2008). Physical performance was evaluated in tests of 10-m normal and fast walking times, one-stair climbing and descending time, and five-repetition chair-rising time. Postural stability was evaluated using a Biodex Stability System. Basic information, including age and gender, was collected from each patient, and the body mass index (BMI) was calculated.
The MFI is a 20-item questionnaire that measures five dimensions: general fatigue, physical fatigue, reduced activity, reduced motivation, and mental fatigue (internal consistency: 0.85–0.89, test–retest reliability: 0.57–0.89, with good validity: moderate to strong correlations with Short Form 36; Hewlett et al., 2011). A higher score indicates greater fatigue.
The Chronic Pain Grade Questionnaire comprises seven items and is used to measure pain intensity and disability (internal consistency 0.81–0.89, with good construct validity: strong correlations with Short form 36; Hawker, Mian, et al., 2011). A higher score indicates more severe symptoms and disability.
The KOOS is a self-administered instrument used for evaluating knee-associated problems. It consists of 42 items in five subscales: pain, other symptoms, activities of daily living (ADL), sports and recreation, and knee-related QOL (internal consistency: 0.56–0.98, test–retest reliability: 0.6–0.97, with good construct validity: strong correlation with Short Form 36; Collins et al., 2011). A lower score indicates more severe symptoms.
The WHOQOL-BREF consists of 28 items in four domains: physical, psychological, social, and environmental. A higher score indicates higher QOL (internal consistency: 0.70–0.77, test–retest reliability 0.76–0.80, with good construct validity to WHOQOL-100; Yao, Chung, Yu, & Wang, 2002).
The OAQoL is a 22-item questionnaire developed specifically to assess the effects of OA on QOL (test–retest reliability: 0.65–0.85, with good construct validity: moderate correlation with WOMAC; Keenan et al., 2008). A higher score indicates poorer QOL.
Tests of 10-m normal and fast walking time, one-stair climbing and descending time, and five-repetition chair-rising time were used to assess physical performance. In all three tests, a longer time indicated poorer physical performance.
A Biodex Stability System was used to measure static and dynamic postural stability (internal consistency for postural stability: 0.78–0.85, for dynamic condition: 0.65–0.77; Arifin, Abu, & Wan, 2013). The device has a movable platform with a sensor and a monitor that displays a patient’s center of gravity to provide visual feedback. Each patient stood on the platform and attempted to maintain his or her center of gravity. The tilt degrees of the platform along the anterior–posterior and medial– lateral axes were recorded, and overall postural stability was determined. A higher score indicated poorer postural stability. The limit of stability was determined by asking a patient to control his or her center of gravity according to the direction displayed randomly by the monitor. A higher score indicates greater dynamic postural control.
A Pearson correlation test was used to determine the associations between health status and pain or physical function in patients with knee OA. A correlation was considered mild when r ≤ .39, moderate when r = .40–.69, and strong when r ≥ .70, and p < .05 was considered statistically significant.
In this study, we evaluated 73 (63 women and 10 men) patients with knee OA. The mean patient age was 60.3 years, and the mean BMI was 26.2 kg/m2. Table 1 lists the patient data.
Table 2 shows the associations between components of body function and pain and between components of body function and physical function in patients with knee OA. The patients’ knee OA-related symptoms exhibited moderate to strong associations with pain (r = .51–.71) and physical functional limitation (r = .41–.65), and their psychological symptoms exhibited mild to moderate associations with pain (r = .26–.37) and physical functional limitation (r = .34–.43). Postural stability was mildly associated with pain (r = .28–.33) and moderately associated with physical functional limitation (r = .57).
Table 3 lists the associations between components of activities and participation and pain and between components of activities and participation and physical functional limitation. The patients’ activities and participation exhibited mild to moderate associations with pain (r = .24–.62) and mild to strong associations with physical functional limitation (r = .39–.88).
Table 4 lists the associations between components of personal and environmental factors and pain and between components of personal and environmental factors and physical functional limitation. The results indicated that, in patients with knee OA, age was mildly to moderately associated with pain and physical functional limitation (r = .24–.55) and QOL was moderately associated with pain and physical functional limitation (r = .40–.62).
According to our research, this study was the first to evaluate the associations between health status and pain and physical function in patients with knee OA. Our results indicated that, in patients with knee OA, pain and physical function are mildly to strongly associated with body functions, activities and participation, and personal and environmental factors components of the ICF.
Pain and physical functional limitation correlated with knee OA-related and psychological symptoms in the study patients. In previous studies, patients with knee OA exhibited substantially higher levels of fatigue than did healthy controls (Hsieh et al., 2013; Snijders et al., 2011). The effects of pain on fatigue and disability can cause patients with knee OA to experience a depressed mood (Hawker Gignac, et al., 2011). In our study patients, fatigue was mildly to moderately associated with pain and physical functional limitation. Snijders et al. (2011) reported that physical therapy, analgesics, and changes in lifestyle can reduce pain and, subsequently, fatigue in patients with knee OA.
Postural stability is defined as control over the body’s position in space to maintain orientation and balance. Patients with knee OA tend to have lower postural stability than do healthy controls (Hsieh et al., 2013). In our patients with knee OA, postural stability was mildly to moderately associated with pain and physical function. Previous studies have indicated that specific physical activities can increase postural stability by increasing muscle strength and coordination (Wooton, 2010). However, fear of falls associated with postural instability can affect physical activity (Delbaere, Crombez, Vanderstraeten, Willems, & Cambier, 2004). Physical activity and postural stability can interact; therefore, interventions are required to limit the impairing effects of physical functional limitation on postural stability in patients with knee OA.
In our patients with knee OA, pain and physical functional limitation were mildly to strongly associated with activities and participation. High levels of pain and physical functional limitation were associated with reduced physical activity, increased disability, reduced function in ADL, and reduced participation in sports and recreation activities as well as social relationships. Therefore, reducing pain and increasing physical function can potentially increase the levels of activity and participation of patients with knee OA.
Previous studies have determined that health-related QOL is lower in patients with knee OA than in normal controls (Hsieh et al., 2013) and that reducing pain and physical functional limitation can improve the health-related QOL of patients with knee OA (Vincent et al., 2013). Our study results indicated that aging is positively associated with pain and physical functional limitation. Elderly people with knee OA typically experience greater levels of pain and physical functional limitation than do younger patients with knee OA. The prevalence of knee OA increases with age. There is an annual increase in the number of elderly people in developed countries worldwide (Lu, 2012). Therefore, reducing pain and physical functional limitation and, thus, improving health-related QOL in patients with knee OA, particularly aged patients, has become a priority.
In this study, we used multiple assessment tools to evaluate the health statuses of our patients with knee OA. The ICF core set is commonly used in health status evaluations. Although it is a highly comprehensive scheme consisting of 55 items (Schwarzkopf, Ewert, Dreinhofer, Cieza, & Stucki, 2008), the ICF core set can be inconvenient and impractical to use in clinical practice.
First, the cross-sectional design of our study limited our capacity to draw causal inferences from our results. Second, the study had a convenience sample and the sample size was small. It might limit the generalization of the result. Third, we provided no intervention to the patients with knee OA. Therefore, we obtained no evidence to support that reducing pain and physical functional limitation can improve the health status in patients with knee OA.
Conclusion and Clinical Implications
Knee OA is the major cause of pain, and the physical functional limitation resulted in locomotion disability. It is a common and major health problem worldwide. The ICF is a useful framework for assessing the health status of patients with knee OA from biopsychosocial perspectives. Our evaluations of the health of patients with knee OA by using the ICF framework indicate that health status is mildly to strongly associated with pain and physical functional limitation in patients with knee OA. Therefore, reducing pain and physical functional limitation might improve the health status of patients with knee OA. Our findings emphasize the need for comprehensive assessment of patients with knee OA in clinical practice to reduce pain, improve physical function, and improve health status.
Pain and physical functional limitation are the primary presenting features in patients with knee OA. Pain-associated reduction in physical function further aggravates disability and dependency in patients with knee OA, especially for aged people. Most patients with knee OA who require oral nonsteroidal anti-inflammatory drugs for pain relief are likely to be older and at relatively high risk for adverse gastrointestinal, cardiovascular, and renal effects. Therefore, nonpharmaceutical treatments are highly recommended in patients with knee OA. Conservative treatments, such as topical nonsteroidal anti-inflammatory drugs, physical therapy, exercise, weight reduction, insoles or orthotics, and intra-articular corticosteroid, hyaluronic acid, and platelet-rich plasma injections are commonly prescribed in patients with knee OA in rehabilitation clinics. It is commonly recommended to refer for consideration of orthopedic surgical intervention, after all conservative treatment options have failed.
How can rehabilitation nurses specifically help with reducing pain, improving physical function, and ultimately improving health status for patients with knee OA? First, rehabilitation nurses can assist patients with knee OA to participate in self-management programs for measurements of pain, functional and physical limitation, and disability in their daily activities. Second, rehabilitation nurses can teach the benefits of exercise and encourage patients with knee OA to participate in low-impact aerobic exercise, such as bicycling or swimming, particularly incorporate resistance-based lower limb and quadriceps strengthening exercise, either land-based or water-based. Third, as overweight/obesity is one of the major modifiable risk factors for knee OA, weight reduction for symptomatic knee OA and BMI ≥ 25 is recommended to avoid overload over the knee joints (Jevsevar, 2013). Therefore, rehabilitation nurses can help overweight or obese individuals with knee OA to perform weight loss programs (McAlindon et al., 2014). Finally, rehabilitation nurses can actively provide the information related to OA knee treatment recommendations to patients with knee OA and their families. Rehabilitation nurses can play an active role as advocates for providing appropriate education for the importance of self-management programs, regular physical exercise, weight reduction, and knowledge for treatment recommendations to patients with knee OA to further improve their pain, physical function, and health status.
Key Practice Points
- Knee osteoarthritis (OA) has effects on pain, anxiety, depression, physical function, work participation, and health-related quality of life.
- The International Classification of Functioning, Disability, and Health is a useful framework for assessing health from biological, personal, and social perspectives.
- Health status is mildly to strongly associated with pain and physical functional limitation in patients with knee OA.
- Reducing pain and physical functional limitation in knee OA patients might improve their health status.
This study was supported by research grants from the Shin Kong Wu Ho-Su Memorial Hospital (SKH-8302-102-DR-32), Taipei, Taiwan, and the Taiwan Ministry of Science and Technology (NSC 102-2628-B-002-036-MY3; NSC 102-2314-B-341-001; MOST 103-2314-B-341-002). This study was approved by the Institutional Review Board for the Protection of Human Subjects of Shin Kong Wu Ho-Su Memorial Hospital (20101203R), Taipei, Taiwan.
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