Night pain in hip and knee osteoarthritis: A focus group study

Authors


Abstract

Objective

To explore the experience of night pain in people with hip or knee osteoarthritis (OA).

Methods

Twenty-eight focus groups were conducted in 6 centers in 4 countries, with a total of 130 men and women with hip or knee OA. Two focus groups were excluded from the analysis, leaving 26 groups comprising 123 participants. Sampling was performed to ensure approximately equal representation of individuals with mild, moderate, and severe pain, hip OA, and knee OA. Format and methodology were standardized across centers, and participants described and discussed their experience of night pain. The focus groups were audio-recorded and transcribed. Data were analyzed by identifying emergent codes that were grouped and compared, resulting in the identification of key themes.

Results

The majority of participants (81%) experienced night pain; the remaining 19%, who reported no night pain, were from the moderate or severe pain focus groups. Similar night pain experiences were expressed by the hip and knee OA participants. Night pain was also present regardless of the stage of OA, but severity increased as the disease progressed. Night pain was variable and intermittent. Three key themes were identified: prediction of night pain, sleep disturbance, and adaptations and treatment regimens.

Conclusion

Due to its variability and complexity, the assessment of night pain should take into account the importance of the patient narrative. Also, night pain may not be a distinct marker of disease severity, and this may have implications for its use as a priority indicator for total joint replacement.

INTRODUCTION

Pain is the main symptom of osteoarthritis (OA) (1). Its presence is an obligatory component of the American College of Rheumatology's clinical criteria for the classification of OA (2), and distress caused by pain is the main determinant of help-seeking behavior by patients with this condition (3). Pain severity is also widely used as the primary outcome measure in trials of interventions in OA (4). It is perhaps surprising, therefore, that there is relatively little qualitative research on the pain experience of people with OA (5, 6). The main problem with the assessment of pain is its subjective nature, which makes it hard for people to describe and, therefore, difficult to measure. In orthopedics and rheumatology, pain is usually assessed as current pain severity on a Likert-style scale or visual analog scale (VAS) (5, 7). These scales are said to have many limitations since they do not reflect the complexity of the individual's pain experience (6).

Night pain is a particularly important part of the pain experience in OA, and was highlighted as a key concern by patients in our recent focus group study (8). Night pain is difficult to treat conservatively, and the presence of intrusive night pain is widely used by surgeons as a criterion for recommending total joint replacement (TJR) (9–11). Its presence (or absence) is usually ascertained using simple, dichotomous questions such as, “Do you have pain at night?” or “Does the pain interfere with your sleep?”

Evidence from previous work indicates that pain in OA is intermittent and variable, and associated with activities and modified by the adaptations that patients make (6). Studies on pain and sleep disturbance in other contexts also suggest that night pain is a complex issue, affecting both sleep onset and sleep maintenance (8, 12). Sleep disturbances in people with OA are associated with greater pain and also greater fatigue, disability, and depressed or anxious mood (13, 14). It has been stated that, in people with chronic pain disorders like OA, poor sleep exacerbates pain by decreasing pain tolerance (15, 16).

There have been few previous studies on night pain in OA. Given its importance to patients, as well as doctors when asked to recommend interventions, we thought it important to extend our previous work on patients' overall pain experience to the specific problem of night pain.

PATIENTS AND METHODS

Patients.

Focus groups were conducted in 6 centers in a total of 4 countries: Canada (Toronto and Vancouver), the US (North Carolina and Texas), Australia (Sydney), and the UK (Bristol). Participants were selected from the community using advertisements and fliers, as well as the investigators' clinical practices and existing OA cohorts. Those eligible to participate were English-speaking men and women with hip or knee OA, age ≥40 years, who responded “yes” to a pain question (“Have you experienced aching, discomfort, pain and/or stiffness in or around a hip or knee on most days of at least 1 month during the past year?”), and who had not experienced an injury to the joint area within the last year or a joint replacement of the symptomatic joint.

Sampling was performed to ensure approximately equal representation of individuals with mild, moderate, and severe pain with hip or knee OA, across 3 age groups (40–54 years, 55–64 years, and >75 years), and for men and women. Subjects were allocated to groups based on their response to a 10-point Likert-style rating scale (where 1 = no pain and 10 = extreme pain) for usual pain experienced in the most painful joint over the past 3 months. Participants were categorized as mild (scores of ≤4), moderate (scores 5–7), or severe (scores 8–10). Complete details of the participants have been described previously (6–8, 17). Ethics approval was obtained from each of the participating centers, and participants provided their written consent to take part in the study.

Focus group format and methodology was standardized across centers. During the focus group sessions, initial questions were aimed at obtaining detailed descriptions of hip and knee pain, as well as exploring changes in these characteristics over time. Later questions, such as “Do you experience different kinds of pain depending on whether it is night or day?” and “How do you manage your pain at night?” focused on the impact of the night pain on the participants' lives.

Focus groups were audio-recorded and fully transcribed. Transcripts from the 6 centers were read and the sections relating to night pain were selected. Using methods of constant comparison (18), data were analyzed by detailed scrutiny of the transcripts and inductive coding. Samples of transcripts were independently coded by 2 experienced qualitative researchers (GW and RG-H), who then met and reached a consensus on appropriate coding. A coding frame was developed, discussed, and refined within the research team. The data were then examined for similarities and differences, thereby retaining the context of the discussion and the characteristics of the participants. The coding frame was refined as new transcripts were analyzed and the codes were grouped into broader themes. The descriptive accounts produced from the analyses were also circulated to coauthors (PD and GH) to check the credibility (internal validity), plausibility (reliability), and clinical relevance of the findings (19). The themes and quotations that emerged from the data relating to night pain are presented below.

RESULTS

A total of 28 focus groups were conducted in 6 centers, with a total of 130 participants with hip or knee OA (50 men and 80 women, ages 47–92 years), all of whom reported either hip or knee pain. However, 2 of the focus groups were not audio-recorded and so were excluded from this analysis. This left 26 focus groups comprising 123 participants. Eleven groups comprised people with hip pain (n = 47), and 15 comprised people with knee pain (n = 76). Focus groups ranged in size from 3 to 7 participants.

Night pain was discussed in all 26 focus groups, and only 24 (19%) of the 123 participants stated that they did not experience night pain (n = 7 hip OA participants, n = 17 knee OA participants). These participants were from either the moderate or severe hip or knee pain group, which implies that it is possible to experience intense and debilitating symptoms of OA without necessarily experiencing pain at night; conversely, night pain clearly can be a relatively early feature of the disorder.

Similar experiences of night pain were expressed by both the hip pain and knee pain groups. This was consistent between the different centers. Three key themes regarding the experience of night pain were identified: prediction of night pain, sleep disturbance, and adaptations and treatment.

Prediction of night pain.

Daytime activity.

Both hip and knee pain participants stated that they could predict the occurrence or severity of night pain, since it was dependent on the level of activity they did throughout the day. Therefore, the more active they were during the day, the more pain they would experience at night. This forecast of night pain was consistent for mild, moderate, and severe hip and knee pain groups. Participants stated that night pain was “an overuse thing,” and that if they “overdid it” during the day, they would “pay for it” at night-time. The activities that exacerbated night pain were everyday activities (e.g., standing, cooking, shopping, and walking), as well as recreation, sport, and occupational activities.

R5: “I have more pain at night than I do in the daytime. And I found that if I've been doing a lot of standing, cooking, and shopping and things like that…when I go to bed I have a lot of pain, and I wake up a lot” (mild knee pain group).

In addition, carrying relatively heavy objects caused a “delayed reaction” resulting in pain at night:

AM: “My five-year-old, occasionally I'll carry him, and I find that I have serious problems usually during the night. The knee will seize up a lot more; it's kind of like a delayed reaction” (severe knee pain group).

Although participants were able to predict night pain, it often did not stop them from being active during the day and showing a degree of stoicism and acceptance:

G: “You know if you over-exert yourself you're going to pay the price [at night] and sometimes you do because you gotta live, right?” (moderate/severe hip pain group).

The weather.

Another way that participants were able to predict the onset of night pain was the weather. Participants in the mild hip and moderate knee groups stated that cold, damp, and windy “low-pressure” weather caused more night pain:

CR: “It's that pain that is like a vice. Can you imagine somebody putting a vice on your knee?” Moderator: “Yeah. And that's just at night?” CR: “Mostly just at night because of the dampness. I don't know what it is, I don't question it, walking the ground, the dampness comes from the ground” (moderate knee pain group).

Sleep disturbance.

Pain.

Four subthemes are discussed below: pain, movement and position, greater awareness of pain at night, and fatigue. All focus groups (apart from the mild hip pain groups) stated that the actual pain from the hip or knee awakened them from their sleep. To describe their night pain, participants used a wide range of terms for their hip or knee pain. These ranged from the mild (“a dull ache,” “throbbing,” “irritating,” “hurting,” “toothache,” and “burning”) to the extreme (“sharp,” “excruciating,” “strong,” “vice-like,” and “stabbing”). The regularity and duration of night pain was discussed, with participants stating that “pain is not consistent”:

M2: “I get pain at night from time to time, it's not constant” (moderate knee pain group).

R1: “And I really don't have that every night, but perhaps half the time, maybe 50 percent of the time” (moderate knee pain group).

Participants described the duration of night pain. For many of the moderate knee group, changing position would ease the pain:

AM: “When I'm actually in bed, and it will awaken me because I'll get a sharp pain, literally. But I have to kind of get into what I call the recovery position, and then I bend slightly and put that one leg up a little bit, and then it's okay” (severe knee pain group).

The majority of the moderate and severe hip and knee groups stated that the onset of the night pain came as their OA progressively worsened. The frequency and intensity of the night pain was discussed:

G: “I find the disease progresses, then you have more constant pain. That's when you get that radiating pain when you're sleeping at night early in the stage of the disease. But I find as the disease progressed there's a shift, it's not that it's shifted to night pain, it's just you're having pain all the time but that includes the night, whereas at the early stages you're not having pain all the time” (moderate/severe hip pain group).

The onset of night pain and its increased frequency and intensity led to fears about the future:

R: “It's scaring me, I don't know, to look forward to, I don't know what's going to happen then, later on“ (moderate knee pain group).

Movement and position.

All focus groups described how their position or any movement in bed instigated their pain and disrupted their sleep. Many had only a limited number of sleeping positions that would allow them to be comfortable and pain free.

S: “There are days when it goes on all day and you don't even really sleep much at night because every time you go to turn, it takes an hour to find a comfortable position, and you sleep for an hour and then your body tells you it's time to get up” (moderate/severe knee pain group).

Conversely, the lack of movement was also given as a reason for night pain. As a result of the knee or hip being inactive while asleep, the joint would stiffen up and cause night pain:

K3: “I think it's just lying in bed that sort of stiffens the leg up, and as I say, seconds or so after I'm up and moving it's alright then” (moderate knee pain group).

Getting off to sleep was problematic, resulting in restless, nonrefreshing sleep:

R: “But really, when it bothered me the most is to try and sleep. I mean if you try one way, you try the other way, you try every which way and you just get up and forget it” (moderate hip pain group).

Greater awareness of night pain.

Both the hip and knee participants stated that during the night, they became more aware and anxious of their night pain and discomfort, due to the lack of stimulation and mental distraction: “It's more basically at rest I think I'm more conscious of it” (moderate hip pain group), and “Well I think at night, I think you're quiet and there's not noises about, and I think sometimes … it used to be more painful” (severe knee pain group). This lack of mental distraction increased anxiety and therefore heightened their experience of night pain:

AP: “I can cope during the day because I've got things to do, I'm moving all the time, but it's at night, all of a sudden all you have to think about is how bad your knee hurts” (moderate knee pain group).

Participants described the impact of personal circumstances on their perception of night pain. For instance, one woman identified her situation as a widow as intensifying her pain:

K10: “I've been a widow for 27 years now, so I'm on my own. So I think, you know, when you're on your own as well, then and at night, then I think, you know, it sort of, it seems worse” (severe knee pain group).

Fatigue.

Fatigue was not discussed in great detail and it was noticeably absent for the more moderate and severe groups. However, participants in the mild hip and knee pain groups described how lack of sleep led to tiredness, which affected their quality of life:

E: “You need your sleep. I don't enjoy food that much because if you don't sleep properly, food is not the first thing in my head. You're not getting the exercise because the … for sure is that when I exercise, I eat much better. I have much greater appetite and my sleep is like undisturbed. Then if I get up at night, that's it, forget it” (mild knee pain group).

Adaptations and treatment regimens.

In addition to describing the triggers and characteristics of night pain, participants also discussed their night pain in terms of adaptations and treatment regimens. Nighttime adaptations included purchasing new beds, walking around, or temperature control of the affected joint. Some participants preferred warmth while others preferred coolness. A common adaptation was the use of a pillow behind the hip or in between the knees, especially by participants who reported moderate to severe OA pain:

RP: “I sleep with the pillow between, but if it slips away or something and there's pressure on the knee, that will, it will hurt enough to wake me.” Moderator: [to RN] “You're nodding.” RN: “I have the same problem. I sleep with a pillow between my knees and if that pillow wasn't there, in no time at all I'll wake up with that knee hurting” (moderate knee pain group).

Although the use of pillows was an essential adaptation for many participants, some found pillows awkward when trying to change position in bed, and therefore more of a hindrance than help:

R1: “I get woken by my pain, and it's because I've got into a position of … where I get the body pillow down one side and another pillow between my knees. If I'm lying on my hip side, I can't lie on my back because I have a pillow between my knees and ankles. And when I find myself rolled over, I need to somehow use the body pillow to do the same on the other side” (moderate hip pain group).

The most common treatment for pain at night was pain medication. For many, pain medication conferred pain relief, although some took medication primarily for its sedative effect:

AP: “Because I find I take painkillers more to sedate myself in the hopes of getting to sleep rather than, because it doesn't really take away the pain” (moderate knee pain group).

However, fear of dependency and negative side effects associated with taking medication prevented many from continuing this regimen:

K6: “I'm trying to condition myself not to take any more pills because again, over a long period of time, I think they do affect probably your digestion” (moderate knee pain group).

Participants in the moderate to severe hip and knee groups tried to limit the amount of pain medication that they took during the day, either to remain alert or in an attempt to gain greater benefit from the medicine at night:

C: “I have to be competent, I have to be alert, I have to think, so I absolutely refuse to take anything in the daytime. But I take it at night because if I didn't, my body would never relax for me to actually fall asleep” (moderate/severe hip pain group).

DISCUSSION

Despite night pain being a common symptom of OA, and also a key indication for TJR, the characteristics, determinants, and significance of OA night pain have not been extensively researched (20–22). This study has provided descriptions of night pain, participants' beliefs about what triggers and exacerbates it, and the adaptations and treatments that individuals employ to relieve night pain symptoms.

In this study, 81% of participants experienced night pain. The remaining 19% who reported no night pain were from the moderate or severe pain focus groups. This demonstrates that night pain can occur among people with varying levels of current pain severity and may not solely be a phenomenon of “end-stage OA.” Therefore, night pain may not be a distinct marker of disease severity, and may have implications for its use as a priority indicator for TJR. However, the results do suggest that night pain is related to progression of the disease, since participants stated that their night pain became more intense as their disease progressed. Due to a limitation in the inclusion criteria of this study, there were few participants with “very early” onset of OA symptoms, and therefore we cannot comment on the exact stage in the OA trajectory when night pain initially arises. Nevertheless, our results do illustrate that night pain at any stage comprises part of the “unacceptable pain level” that clinicians should consider when assessing need for treatment or surgery.

This study demonstrates that night pain, like daytime pain (6), is variable and intermittent. Participants described their night pain as inconsistent and dependent on the position they slept in or the various adaptations they used. In addition, descriptions of night pain ranged from mild to extreme, and varied according to the amount of activities done in the preceding days. Due to the variability of night pain, these findings highlight the complexity of assessing it. The findings suggest that night pain in OA cannot be adequately assessed with the use of a simple dichotomous question at a single time point or with relatively simple measures of pain severity, such as Likert-style scales and a VAS. In response to the findings from this focus group, a new pain measure for hip and knee OA, the Measure of Intermittent and Constant Osteoarthritis Pain (ICOAP), has been developed and tested psychometrically for validity and reliability (7). This measure incorporates an item in the scale about the impact of the respondent's pain on sleep. A further way of understanding the variability of joint pain is to elicit patients' complex narratives by using existing quantitative measures as trigger questions. In this approach, participants are encouraged to talk around their answers, thereby reflecting the whole personal experience (23).

Participants were able to identify the factors that affected their night pain. Daytime activity patterns and weather conditions were reported as associated with subsequent night pain. Participants believed that they could predict the likely occurrence of night pain based on the pain and daily activities in the preceding days. However, they regularly reported that this often did not deter them from carrying out those activities, despite the likely consequences. Pain being inextricable from function has also been highlighted in participants describing day pain from OA (6).

Participants described how their sleep disturbance took different forms, including sleep onset and sleep maintenance, which is consistent with previous studies (8, 12). The primary reason for sleep disturbance reported in this study was pain itself. In some individuals pain was exacerbated by lying still, while in others moving during sleep caused or made pain worse. The experience of pain during the night was reported as being different from day pain; night pain was often described as more severe and associated with more anxiety and distress than daytime pain, primarily due to the heightened awareness associated with the lack of activity and distractions during the night. This is also consistent with previous studies that focus generally on fatigue (13, 14). Participants employed a variety of methods to attempt to relieve the night pain, including the use of pain relief medicine and adaptive sleeping positions. In some cases there was a reluctance to regularly take pain relief drugs for fear of dependency, side effects, and a decline in efficacy, as reflected in previous studies on adherence to pain medication (24, 25).

A strength of this study was the scope for communication between research participants in the focus groups. Individuals were able to discuss, explore, and compare their experiences, allowing for clarifications of their views. A further strength was the inclusion of men and women with a range of ages and from different geographic sites. However, focus group dynamics may mean that group norms and public accounts may be articulated at the expense of individual voices of dissent or private accounts (26). For instance, some of the more private or intimate aspects of living with night pain might not be stated in a group context.

This study illustrates that there is a range of issues and strategies for people living with OA-related night pain. This wider understanding would be valuable for all health care professionals who help people to manage their arthritis, including orthopedic surgeons who ask patients about night pain when assessing priority for surgical intervention. In addition to the development of the ICOAP and the importance of eliciting patients' narratives, this study indicates that a specific measurement tool related to night pain, which focuses on the 3 key themes from this study, is required. This measurement tool would improve on current methods for using night pain as an indication for surgical intervention. Future research might also include one-to-one in-depth interviews about night pain experience in order to explore the more private aspects of night pain, as well as large-scale longitudinal research to examine the onset, development, and risk factors for night pain.

AUTHOR CONTRIBUTIONS

All authors were involved in drafting the article or revising it critically for important intellectual content, and all authors approved the final version to be submitted for publication. Dr. Woolhead had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Study conception and design. Woolhead, Gooberman-Hill, Dieppe, Hawker.

Acquisition of data. Woolhead, Gooberman-Hill, Dieppe, Hawker.

Analysis and interpretation of data. Woolhead, Gooberman-Hill, Dieppe, Hawker.

Acknowledgements

The authors thank all the people with OA who took part in the study, as well as the funders and collaborators of the primary research.

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