Interrelations between factors related to physical activity in inactive adults with knee pain

Abstract

Purpose:

The purpose was to explore interrelations between factors related to engagement in physical activity in inactive adults with knee pain.

Method:

Inactive adults with knee pain (n=35) participated in six focus groups designed to inquire about barriers and facilitators related with engagement in physical activity. Directed content analysis and inductive thematic analysis were used to identify factors related to physical activity and associated interrelations respectively. As an exploratory analysis, sex differences in barriers and facilitators to physical activity were assessed.

Results:

In this cohort (age=60.9±8.6 years; 22 females), self-reported physical activity was 26.3±46.8 min/week. Factors related to physical activity grouped into domains of physical status, psychological status, environment, knowledge, and resources. It was seen that the interrelations between a person and their environment, as well as, between impairments and everyday responsibilities influenced engagement in physical activity. Females were more likely to identify physical and psychological status, social expectations, and lack of knowledge as barriers. Males indicated a preference for using mobile technologies to overcome barriers.

Conclusion:

Interplay of various barriers and facilitators is related to engagement in physical activity in inactive older adults with knee pain. Interventions to promote physical activity should address these interrelations and sex differences.

INTRODUCTION

Exercise is the most effective intervention for knee osteoarthritis (OA) outside of total knee replacement surgery[1,2]. Even small amounts of physical activity can reduce knee pain, physical disabilities, and associated risk of mortality in adults with knee OA[3,4]. Despite benefits and interventions especially geared towards increasing physical activity[1,2], only 13% of adults with knee OA meet the recommended amounts of physical activity (i.e.) 2018 Center of Disease Control (CDC) physical activity guidelines[5]. Hence, it is important to study why adults with knee pain due to OA do not engage in adequate amounts of physical activity.

Prior studies have identified some factors influencing physical activity in adults with knee pain[6–11]. The findings align with the biopsychosocial model and identify several biological factors (pain), psychological factors (beliefs and psychological well-being), and social factors (environment, relationships) that influence physical activity[6–11]. However, these studies include all adults with knee pain due to OA irrespective of their physical activity levels. Since interventions to increase physical activity are most needed for inactive adults with knee pain, factors underlying physical activity behavior in inactive adults need further study.

It is likely that physical activity is influenced by a complex interplay between individual factors, for instance, association between physical and psychosocial factors[10], and between OA-related experiences and beliefs regarding physical activity[9]. A better understanding of these associations could help researchers and clinicians develop more effective behavioral interventions to promote greater participation in physical activity for adults with knee pain. Furthermore, objective physical activity measurements show that females with knee OA engage in less physical activity than males[12,13]. These differences may also translate to factors that influence physical activity in both sexes. For instance, males with knee OA considered physical activity as a way of life and had a direct relationship between disease-related impairments and physical activity[8,14], while females were more influenced by society’s view of them which in turn affected their physical activity[8]. If factors related to physical activity differ by sex, physical activity interventions may need to be tailored differently for males and females.

The purpose of this qualitative study was to identify factors related to physical activity and their interrelations in inactive adults with knee pain who do not meet 2008 CDC physical activity guidelines. An exploratory purpose was to assess sex differences in factors related to physical activity in this population.

METHODS

Participants

Participants were purposively recruited using advertising in the local metropolitan area and an existing database from previous studies. Interested participants were screened over phone from February 2018 to January 2019. Eligibility criteria included age 45–80 years, body mass index less than 40 kg/m², knee pain at least 4 on a 0–10 numeric scale, pain on most days of past 3 months for at least 2 years, able to ambulate for a minimum of 20 minutes without assistive devices, own a smartphone, and able to speak and understand English. Exclusion criteria included engagement in 150 minutes or more of moderate-intensity physical activity per week[5], inflammatory arthritis (rheumatoid arthritis), neurological conditions (stroke, Parkinson’s disease, etc.), muscular diseases (muscular dystrophy), or total knee replacement in one or both knees. All participants provided written informed consent and the study was approved by an Institutional Review Board.

Study Design

As perspectives of inactive people experiencing knee pain are integral to developing a physical activity intervention, this qualitative study is based on a descriptive approach to identify factors related to physical activity based on the participant’s lived experiences. This qualitative study will be reported in line with Consolidated Criteria for Reporting of Qualitative Studies[15].

Participants were screened for eligibility over the phone. Self-reported physical activity data in terms of duration and frequency of physical activity in a week was obtained during the phone screening process. Participants whose physical activity met the CDC physical activity guidelines were excluded. Of the 104 participants screened, 51 were eligible. Of the 51 eligible participants, 15 participants withdrew or did not show up. In total, 36 participants participated in six in-person, semi-structured focus group interviews at Boston University. The research team present during these interviews included the male principal investigator of the study with expertise in knee osteoarthritis (DK), female co-investigator with expertise in qualitative research (JK), male lab-manager (AG) who organized the interviews, and first-year female doctoral student (NS) who was an observer during the interviews. The interviews were primarily facilitated by JK. Although no specific relationship was established prior to the interviews, JK introduced the members of the research team, the purpose of the study, and clarified that the research team will have a neutral stance in the ongoing discussion. JK emphasized that it was a safe space for the participants to share their personal views and experiences, and encouraged discussion with an inquisitive tone whenever needed. During the interviews, open-ended questions regarding understanding of the term “physical activity”, barriers to and facilitators of physical activity, and perceptions of physical activity guidelines (Table 1).

Table 1.

Focus Group Guide

Physical activity	When you think about being “physically active”, what comes to mind?
	“The CDC i.e. the Center for Disease Control and Prevention published the physical activity guidelines for Americans in 2008. They defined “physical activity” to very broadly refer to any bodily movement that enhances health. A lot of what you described falls within this definition. We will use this definition as a guide for our discussion today. This definition is on the piece of paper in front of you on the first page.”
Barriers and facilitators to physical activity	When you think about being “physically active”, what comes to mind?
	What prevents you from being more active?  PROMPT: We are interested in things that are within you and those that are outside of you.
	What helps you be more active?  PROMPT: We are interested in things that are within you and those that are outside of you.
Perceptions towards public health guidelines regarding physical activity in adults with knee osteoarthritis	Please take a couple of minutes to review these public health guidelines for physical activity for people with knee osteoarthritis. How do you feel about these guidelines?“ Recommended minimum physical activity for people with knee osteoarthritis Walking at least 6000 steps/day At least 150 minutes of moderate intensity physical activity in a week OR at least 75 minutes of vigorous intensity physical activity in a week”  PROBE: If a doctor or another healthcare professional told you that you should meet these guidelines, how would you do it? What would you need to do? Do you think you meet these guidelines now, why or why not? What do you do already that you think meets the guidelines? What strategies do you try and use to meet the guidelines?
For additional focus groups
Interrelations between barriers and facilitators to physical activity	Take a look at the thoughts and feelings on this list. You already told us how your thoughts and feelings can impact your ability to do physical activity. But what other things impact your thoughts and feelings? How or when might other things on this list influence your thoughts and feelings?
	How do your everyday responsibilities, like work, housework, errands, or taking care of others, impact your ability to be physically active?  PROBE: What do you to stay physically active even with all your responsibilities?
	How do you think changes related to age have impacted your physical activity?  PROBE: How do those changes make you feel?  PROBE: What strategies do you use to deal with those changes?  PROBE: How do other’s attitudes about aging and physical activity impact you/ your physical activity?

At first, four focus groups (23 participants) were conducted. Each focus group included about 5–7 participants and were about 1.5 hours long. Participants in these four focus groups were given handouts that included the CDC definition of physical activity and general recommendations for physical activity in adults with knee osteoarthritis. Participants also completed surveys including the Knee Injury and Osteoarthritis Outcome Score (KOOS) and Center for Epidemiological Studies Depression Scale (CES-D). Two additional focus groups (12 participants) were conducted later in the study to achieve data saturation and understanding of emerging themes during data analysis of the previous four focus groups. The handouts in the additional focus groups included a list of factors identified by the previous four focus groups to aid discussion. All focus groups were audio-recorded, transcribed verbatim using transcription services (GMR Transcription Services, Boston, USA), and de-identified for analysis. The transcripts or findings were not returned to participants for comments, correction, or feedback.

Analysis

The first step in data analysis consisted of reading the transcripts repeatedly in order to get a sense of factors that influence physical activity in this cohort. Researchers (JK, NS) performed directed content analysis[16] using a qualitative data management software (NVIVO v11.0, Boston, USA) to investigate biopsychosocial influences on physical activity. Based on the systematic review by Kanavaki et al.[9], researcher JK created an initial code list to identify factors that affect engagement in physical activity in the cohort. Researcher NS listened to the audio recordings of the interviews, read the transcripts, took notes while reading, and used a line-by-line coding approach to categorize factors related to physical activity into respective codes in the code-list. The authors did not provide a code-tree but presented the code-list in a word document which was then mapped on NVIVO data management software. The transcripts and the codes in NVIVO were reviewed by researcher JK who combined codes, created sub-categories, or created additional codes if the concept was not adequately represented in existing codes. Both researchers then organized the codes into factors that encouraged or discouraged physical activity. As analysis continued, codes were further examined for similarities and differences, and collapsed into categories and subcategories of factors influencing physical activities. The categories and subcategories, with subordinate codes, were then reviewed by another member of the research team (DK) to ensure credibility of the codes.

The interrelationships between independent factors were identified by an inductive thematic analysis approach by researcher JK. The thematic analysis was done on a semantic and latent level to identify ideas, thoughts, and concepts that were missed during content analysis. Themes that emerged during this process were discussed by all members of the research team (JK, NS, DK) until a consensus was achieved. At this stage, it was observed that some sub-categories like “comparison to past physical-activity” (Psychological Factors) and “social perception” (Social Environment) were mentioned repeatedly. In order to explore this pattern, focus group 5 and 6 were conducted. Directed content analysis and thematic analysis of data was repeated for the two additional focus groups. The additional focus groups were coded by one member of the team (NS), reviewed by a second (JK), and as needed, the codebook, emerging categories, and themes were further refined.

During these analyses, sex differences in the factors were added as an exploratory analysis by researcher NS. For this, each code in the updated code list was reviewed and the number of times each factor was mentioned by a sex was noted in a Microsoft Excel spreadsheet. In the second step, the factors mentioned by males and females in each code were kept side-to-side to look for patterns and number of mentions in the data. This was repeated for all the codes in the code-list. The segregated data based on sex were then reviewed by another member (DK) and consensus on results were achieved.

RESULTS

Participant Characteristics

Of the thirty-six individuals who participated in the focus-group interviews, data from one participant was excluded during analysis due to suspected drug use during interviews. Therefore, data from thirty-five participants is included in the study. As shown in table 2, individuals in this urban and racially diverse cohort of adults with knee pain were overweight with females being slightly older than males. Importantly, this cohort reported moderate levels of knee pain and reported presence of depressive symptoms, with somewhat worse scores in females. Overall, the physical activity was low with females reporting slightly greater levels of activity than males.

Table 2:

Participant Characteristics

Characteristics	Total (n=35)	Males (n=13)	Females (n=22)
Age (years)	60.9 ± 8.6*	58.0 ± 6.5*	62.7 ± 9.3*
BMI (kg/m2)	28.4 ± 4.7*	28.1 ± 5.5*	28.6 ± 4.4*
Race n (%)	African Americans = 11 (31.4%) Asians = 2 (25.7%) Caucasians = 18 (51.4%) Do not wish to report = 4 (11.4%)	African Americans = 7 (53.8%) Asians = 0 Caucasians = 5 (38.5%) Do not wish to report = 1 (7.7%)	African Americans = 4 (18.1%) Asians = 2 (9.1%) Caucasians = 13 (59.1%) Do not wish to report = 3 (13.6%)
Education level n (% without an undergraduate degree)	7 (20%)	3 (23.1%)	4 (18.2%)
Annual Income n (% < $50,000 per year)	15 (42.9%)	8 (61.5%)	7 (31.8%)
Physical Activity* (min/week)	26.3 ± 46.8	10.8 ± 33.3	35.5 ± 51.8
KOOS Pain*	50.3 ± 17.3	45.4 ± 14.5	53.4 ± 18.4
CES-D*	18.2 ± 11.9	16.6 ± 14.2	17.8 ± 10.4

^*Values are in Mean ± Standard Deviation; BMI = Body Mass Index; KOOS = Knee Injury and Osteoarthritis, Outcome Scores; CES-D = Center of Epidemiological Studies Depression Scale

Factors related to physical activity participation

The barriers and facilitators to physical activity identified by the cohort were categorized into domains of physical status, psychological status, physical environment, social environment, knowledge, and resources (table 3).

Table 3.

Barriers and Facilitators of physical activity categorized into domains

Domains	Barriers/Discouraging Factors	Facilitators/Encouraging Factors
Physical Factors	Aging, comorbidities and trauma Fatigue and sleep Pain	Body image and weight Improved health
Psychological Factors	Comparison to past levels of physical activity Negative moods and worries Self-regulation	Positive frame of mind Push myself Fear
Physical Environment	Built environment Natural environment	Natural environment
Social Environment	Social perceptions	Relationships Kids
Knowledge	Misunderstanding contraindications Unclear understanding of public health physical activity recommendations	Everyday physical activity Meeting physical activity goals Exercise as prescription
Resources	Money	Ambulation or aids for activity of daily living ADLs Special Programs Medicine and alternative medicine

Physical Status:

This domain included aging, pain, comorbidities, difficulty sleeping, and fatigue as barriers to physical activity. Many participants believed that physical changes were inevitable, and expressed frustration with worsening of life long comorbidities or past injuries. Pain was another influential barrier, which included actual physical discomfort in the moment of exercise, anticipations of pain that could result from exercise, and the unpredictability of pain. A female participant below the average physical activity levels in the group anticipated pain, and explained, “ID039: and sometimes the fear that my knee may lock or whatever prevents me from doing something.” Another female participant below the average physical activity levels in the group was discouraged by the unpredictability of pain, for instance, “ID007: I’ve had trouble with stairs. going up and down, so it’s random. Sometimes I’m fine and others days I’m just oh it really hits.. so that’s where it limits me.”

Facilitators were body image and weight (subjective mental image of one’s own body/ physical activity facilitated by using weight loss as an incentive), and desire for generalized improved health.

Psychological Factors:

Psychological barriers were poor self-regulation (difficulty initiating or maintaining exercise behaviors and habits), negative moods, and tendency of adults to hold their previous physical activity abilities as a self-expectation for current physical activity abilities. A female participant below the average physical activity levels in the group experienced negative moods, worries, and fear of falling, and explained,

“ID101: I see this worries, feelings and thoughts. I don’t know if it relates to my knee, but when I had a back injury—because it’s kinda related because I think the back injury and the knee are related—I was a lot of times very inactive out the fear of really hurting my back again, and not being able to walk again at all. So, that was – I can – I can relate to that one. I was definitely even afraid of falling, literally.”

More commonly, individuals had the tendency to compare their current physical activity levels to their previous physical activity levels. While males were discouraged because they couldn’t keep up with their previous sports activity, females were discouraged for not being able to keep up with a variety of activities including walking, dancing, biking, etc. A male participant below the average physical activity levels in the group shared,

“ID099: I just know I can’t play anymore. it’s aggravating. I’ve tried, and you just – like you said, you know, a game. I – I can’t even get to two games, and this was in my 20s! You know, so at this age I know I can’t play no more but, um, it’s just hard dealing with it, it’s just hard accepting it for me; it really is. You know, I wish I could, and I know I can’t, but I’m still fighting it in my head, you know?”

Some adults were encouraged by a positive frame of mind (emotional state that is optimistic and future thinking like acceptance, gratitude and hope) and fear of negative outcomes (apprehension of potentially negative outcomes such as surgery, poor health outcomes like being dependent on family or having no caregivers that encourage physical activity). Adults who had tendency to push themselves (discipline to adhere to exercise either by motivation or making it a routine) participated in greater amounts of physical activity.

Physical Environment:

Barriers identified were both built (infrastructure and buildings) and natural environment (weather, incline, and other natural resources). Adults frequently mentioned stairs, ice, weather, and hills as problematic. A female participant above the average physical activity levels in the group said, “ID084: And, um, I – I miss walking outside as much as I used to because sometimes when the terrain isn’t good, like I’ll often go to like a supermarket or something. Or, you know – or like a mall or someplace where I know I’m not gonna be tripping over things. Um, because around here the sidewalks are so uneven.”

The facilitators in this domain was natural environment (weather, location, and other natural resources). Good weather, especially springtime, encouraged adults to be more physically active.

Social Environment:

Barrier in this domain was social perception (changing behaviors and choices regarding physical activity to manage how others perceive one’s abilities and limitations, or negative behavior based on comparison to others). Some adults provided examples of how they changed their behaviors and activity choices to ensure that others didn’t see them as limited. For instance, a female participant below the average physical activity levels in the group mentioned “ID039: not being able to keep up. if you take a class you’re worried about you’re not gonna be able to keep up, all doing yourself just to impress the next person..then hurting the next day because you tried so hard to impress someone.”

The facilitators in this domain were relationships (associations and interactions with other individuals that encourage physical activity), and kids (motivation to play with kids and grandkids that facilitates physical activity). This was explained by a female participant below the average physical activity levels in the group “ID007: well things that motivate me are going on outings with friends but we always have to do what we call a step count. how far is it to from the car to the museum and if its within kind of a range that I can manage, then I go and I’d like to go.”

Knowledge:

The barriers in this domain were unclear understanding of physical activity recommendations (difficulty interpreting physical activity guidelines) and misunderstanding contraindications to exercise (insufficient knowledge on what physical activity one can and cannot do given one’s current physical health and/or knee pain). Many participants had an unclear understanding of public health physical activity guidelines and had difficulty interpreting the recommended suggestions for weekly physical activity. One female participant below the average physical activity levels in the group shared, “ID101: I did have a question about this [physical activity guidelines]. Is it “and” or “either/or” walking at least 6,000 steps a day? And you should also be trying to get 150 minutes of another?” Additionally, a few adults reported that they avoided physical activity due to insufficient knowledge on what physical activity was appropriate given their current physical health and/or knee pain; they were concerned that physical activity could worsen their condition, as explained by a male participant below the average physical activity levels in the group, “ID022: I like kind of always cautious with the pain I can deal with but the only thing is you don’t want to extend or damage or make you know make it serious, the condition of your knee that’s why I tell you I cannot know the extent of what kind of exercise I know the body can endure.”

The facilitators in this domain were everyday physical activity (understanding how to incorporate routines and activity into everyday life that contributes to physical activity), and meeting physical activity goals (having the knowledge and strategies to know how to achieve physical activity and recommendations). Adults who knew how to incorporate physical activity into their everyday routines and break down physical activity in terms of activity pacing were more likely to engage in physical activity. One male participant explained how he incorporated physical activity into his everyday life by, “ID108: I’ll walk down to like, the Star Market or whatever, and walk back. And, you know, just try to uh, um, keep myself moving, ‘cause you know, as you get older, when you stop, forget about it. It’s hard to get started again.” Finally, adults felt more confident and safe engaging in physical activity when they received an exercise protocol from a healthcare professional.

Resources:

Barriers in this domain were lack of financial resources. Some adults expressed that money or cost restricted their activity. However, adults more frequently mentioned how the availability of resources increased their ability to engage in physical activity. These included use of ambulation or assistive aids (any equipment used to promote functional capabilities), involvement in special programs (programs or events designed to support physical activity), and access to medicines and alternative medicine (availability/access to traditional medication and/or alternative medicine). Additionally, specialized programming in the community or through health care systems was frequently mentioned as supportive of physical activity. Examples included exercise classes, special support offered through clinics or research studies that encourage physical activity, volunteering and charity organizations that include physical activity, and community walkathons

Interrelations between factors related to physical activity:

The following themes identified the relationships between factors that influence physical activity

1. Person and their environment influence each other and impact physical activity

   Physical and social environments have a dynamic influence on a person’s physical health and psychological factors that consequently influences physical activity behavior. A male participant who had physical activity levels below the average in the group described how his physical environment influences his decision to go for a walk,

   ID084: But I – like, if I have to run an errand, like it’s, it’s so convenient, like where I live. Everything is local and walking distance. So, I take advantage of that walk, just to get out, to breathe some fresh air, to get my daily exercise if I don’t go to the gym.

   One participant described how social perceptions of others contributed to a negative mood and, as a result, her ability to self-regulate her physical activity. This was explained by a female participant with physical activity levels lower than the average in the group,

   ID019: other people that don’t understand your limitations. I used to take the dog down to the park and then um people miss you and they wonder where you are. He’s a puller and they all know that and I can’t handle him, which I can’t, he’s too big… so I had to come up with excuses I guess because then they would be constantly asking me, ‘how do you feel? How do you feel? how do you feel?’ and once you let the cat out of the bag then you have to keep reporting back and I don’t I don’t like to tell people too much ‘cuz then I don’t wanna have to explain good or bad so. … it’s just easier not to go there.

   Participants also described how personal factors interacted with each other, providing a dynamic picture of the influences on physical activity. For example, poor physical health also contributed to negative moods and emotions, which subsequently led to difficulty regulating physical activity. Adults frequently explained how pain or changes in their physical health related to aging had negative ramifications on their psychological states.

2. People manage everyday routines and responsibilities, even when they experience pain

   The time, energy, and physical requirements to fulfill everyday responsibilities like errands, cleaning, laundry, and lawn maintenance was overwhelming for many adult participants, especially in the presence of pain and fatigue. Participants felt obligated to fulfill these responsibilities, and therefore were unable to reduce the time or physical demands to accommodate engagement in physical activity. This was explained by a male participant below the average physical activity levels, “I had tremendous spasms when I did many things, like maybe I’ll do my laundry, and my Walgreen’s, and CVS”. Participants described how they modified these activities in several ways order to better match the physical demands of the activities to their capacity. Strategies like changing the task (carrying 1 bag of groceries instead of multiple while climbing stairs), using equipment (foldable shopping carts), asking for help (help from neighbors or walking buddy), and changing the pace or timing of the task were used. Moreover, physical and emotional demands associated with caregiving or work responsibilities placed further restrictions on participants’ capacity to engage in additional physical activity. A male participant below the average physical activity levels mentioned, “… And I think if you work all day, then you could get out of work and it’s raining or whatever, it’s like really frigid out, you’re not gonna have the motivation or desire to go work out.”

Sex Differences

Females were more likely to mention difficulty sleeping, fatigue, body-image related to weight gain, anxiety and fear (related to injuries, falls, and worsening pain), depression, boredom, and a lack of motivation. A female participant above the average physical activity levels discussed her fatigue, “ID107: …I can’t do it (exercise) so much ‘cause I’ve been taking care of the kids, they get (me) so exhausted mind-wise that it feels like the body (is fatigued) too.” More females than men admitted that they had difficulty initiating exercise behaviors. About half of the females in the group (11 of 22) admitted to having lack of motivation, need for instant gratification, found exercise boring or they “didn’t feel like it”. Females more frequently mentioned changing their physical activity behavior in order to manage how others perceive them and being discouraged by family/friends not doing well. A female participant below the average physical activity levels explained “ID039: so you may be having a pretty good week maybe or pretty good day and then you talk to your friend on the phone and she’s telling you all about whether it’s arthritis or any other issue that’s going on…by the time you get off the phone it’s like oh my god. I’m gonna shoot myself you know.” Females more often described having a poor understanding of exercise including insufficient knowledge about correct exercise techniques and when to push through pain and when to stop. A female participant below the average physical activity levels explained, “ID059: …and that right there gets you to think and worry too. how much (exercise) should I do? how much can I do? do I need to do that?” Particularly females in this group found that when an exercise program was given by a healthcare professional, they were more likely to follow the exercise routine. Finally, only females discussed using alternative medicine or making dietary changes to manage their symptoms.

Males suggested using mobile health technologies like pedometer and mobile phone apps to set goals, document goals, and to track their progress, as explained by, “ID108: what I would like to do is document it (exercise). Get a piece of paper, put the date or whatever, all this stuff. Uh, first a small goal, you know, for about, uh, maybe a week-and-a-half. Then maybe a, another – a medium goal, you know? Then maybe that medium goal for like two weeks, and then, you know, see what I can get from that, or – and that way there, you can tell if you’re progressing.

DISCUSSION

Our purpose was to investigate factors related to engagement in physical activity in inactive adults with knee OA who do not meet the 2018 CDC Physical Activity Guidelines[5]. Our findings agree with previous literature[7,9,10] that the decision to engage in physical activity results from the influences of physical health, psychological factors, environment (physical and social), knowledge, and resources. In this cohort of urban, racially diverse adults with moderate knee pain and depressive symptoms, we observed interrelations between the person and their environment and between disease-related impairments and everyday responsibilities that influence their engagement in physical activity. These findings align with the biopsychosocial model and provide guidance for clinicians and future studies on interventions to increase physical activity in inactive adults with knee pain.

The thematic analyses found relationships between environmental and personal domains (physical health and psychological factors); this has been recognized in literature in terms of how natural and built physical environment and social support affects pain, motivation, and behavioral regulation[9,17,18] . Our results suggest that social perception (changing physical activity behavior based on others view of themselves) affects an individual’s moods, beliefs about capabilities, and eventually physical activity engagement. Additionally, environment (built and natural) also affects an individual’s mental frame of mind, health, and physical activity engagement just as much as social environment can. These findings align with the Socioecological theory which suggests that environment influences participation and adherence to exercise[19]. We also noted that some adults were engaged in activities they felt obligated to despite their pain and discomfort. This suggests that OA-related symptoms alone cannot explain physical activity behavior. Although, the physical and emotional demands associated with such responsibilities placed restrictions on additional physical activity, this relationship shows that with appropriate incentive and motivation, adults engaged in physical activities despite physical symptoms. This is shown by Maly et al in their study where adults with knee OA who had higher self-efficacy were able to better regulate negative influences on performance from impairments like pain and stiffness than adults with lower self-efficacy[20]. Our analyses also highlighted that engagement in physical activity is shaped by personal and social perceptions of abilities and challenges. These results suggest that the decision to engage in physical activity is influenced not only by one’s beliefs regarding the importance of exercise but also by how one’s abilities are perceived in the society. Prior studies have noted the influence of one’s beliefs[6] and other’s perception[7] on physical activity participation. These findings reinforce the Socioecological Theory. Thus, self-efficacy, social programs, and self-management programs are important to incorporate in treatment interventions, as is recognized by the updated American College of Rheumatology guidelines[21].

Females in this study more frequently discussed concerns regarding sleep, mood, fatigue, body-image, and knowledge on how to exercise while males in this study discussed physical activity related to sports and use of mobile health technologies. Although obesity, quality of diet, knee OA symptoms have been traditionally associated with physical inactivity[22], Stubbs et al found that increasing age and sex might also be determinants of physical inactivity in adults with knee OA[11]. Considering that fewer females (7.7%) than males (12.9%) meet the CDC physical activity guidelines[13], sex difference might be an important consideration to make while assessing individuals with knee pain. Interestingly, females in this cohort reported slightly greater physical activity than the men (35.5 min/week versus 10.8 min/week). Gay et al found that males were driven by performance while females were driven by other’s perception of them[8]. The findings from this study align with previous studies[8], and add to literature that psychological and social factors might affect a female’s decision to engage in physical activity more than males. This finding can guide interventions to include treatments specifically addressing motivation, fear of falls, social perception, and guidance related to incorporating physical activity in daily life for females while including mobile-health technologies more in treatment for males with knee pain.

Although the data presented were largely consistent with the findings, this study has several limitations that should be considered while interpreting the results. Sex differences were exploratory in nature. The sample included more females than males (22 females, 13 males) which could have affected the results, however, the sex differences seen were limited to some of the factors and aligned with prior research raising confidence in our findings. The cohort included urban racially diverse adults and results may not be generalizable to other populations with knee OA who may differ in key characteristics. Moreover, description of the minor themes based on these differences in key characteristics are not presented in the findings. Adults were considered inactive based on self-reported physical activity measures and not objective measures like accelerometry. However, given that adults with knee pain tend to over-estimate their physical activity levels, it is unlikely that the cohort was more active than reported. Finally, although the participants in the study had chronic knee pain indicative of OA, they did not require radiographic or clinical diagnosis of knee OA for participation in the study.

CONCLUSION

Interrelations between a person and their environment, as well as, between impairments and responsibilities influenced engagement in physical activity in inactive adults with knee pain. Females were more likely to identify physical and psychological status, social expectations, lack of knowledge as barriers. Males indicated a preference for using mobile technologies to overcome barriers.

Implications for Rehabilitation.

• Interrelations between individual factors related to engagement in physical activity and sex differences in these factors are present in inactive adults with knee pain

• Interventions to improve physical activity should be implemented by addressing factors and interrelations between factors related to physical activity in inactive adults with knee pain

• Interventions to address low levels of physical activity in adults with knee pain should take into account sex differences