Table 2.

Interpretation of sub-themes with sample quotes derived from the semantic analysis

Sub-theme	Quotes	Interpretation
Major theme 1: Self-management
Where to seek care	[How did you know to go to your general practitioner?]. “… Those were the ones we could turn to and we had OK experiences with them previously”. [Was it you or your parents that decided to contact the general practitioner?]. “I think it was a mix. We had a good talk about it.” – Beatrice, 16. [Was it you who decided to go to your general practitioner?]. “I can’t really remember but my initial thought would be that it was my coach that recommended me and my parents to seek care from a general practitioner as it (the pain) had not improved during a full week.” – Amanda, 18.	All adolescents decided to seek care in collaboration with their parents. Most adolescents chose to seek a given health care provider based on guidance from either parents or friends. Among those active in sport, many sought advice from their coach or friends from their sports-environment.
Trigger for seeking care	[When did you know it was the right time to see your general practitioner?]. “Well, I said that I wanted to go to the general practitioner because it (the pain) had gotten so bad and my mom said that going to the general practitioner would be a good idea because she also thought that it (the pain) had gotten bad lately.” – Hellen, 16. [What was your reason for seeking care with a physiotherapist again?]. “That was because I bent down forward to pull my pants up and then I got a violent jab in the right side of my lower back and afterword I could not straighten myself out, I couldn’t move my arms up and I couldn’t walk, I couldn’t do anything.” - Emma, 18.	Despite all adolescents being functionally limited by their LBP, the main trigger for seeking health care was continuous pain or a sudden increase in pain intensity.
Expectations	[What were your expectations beforehand (general practitioner)?]. “Just to get referred on to a physiotherapist” [Why did you decided to go to the doctor?]. “That was actually my mom’s suggestion.” – Kathrine, 18. [What was your expectation beforehand (general practitioner)?]. “I was very optimistic that he would find out what was wrong so I could move on and not have pain anymore. I did not expect it to be a long process because I did not thing it would be this complicated. But he said that he could not figure out what was wrong so he didn’t do much and said that I should just keep taking pills and then he referred me to another doctor.” – Hellen. 16.	The expectations before going to the general practitioner varied among the adolescents. Some had high expectations in terms of examination, diagnostics, and treatment while others only consulted to get referred to another health care provider
Navigating the healthcare system	[Were you ever in doubt about who to contact regarding your back pain?]. “No, my general practitioner has always been our general practitioner even since I was a baby so my mom contacted him. We always contact him when something is up.” – Hellen, 16. “To me it has always been pretty much like, if you have problem then it is your general practitioner (that you go to) and then the general practitioner can often refer you to other places if they themselves can’t help you with it (the problem). I think I will get the most out of going to the general practitioner instead of for instance going to the internet because you do not get much out of that.” Sarah, 17.	Some adolescents displayed sufficient health literacy skill as they knew how to navigate the different aspects of the Danish healthcare system. As such, many adolescents knew to consult their general practitioner initially due to their role as gatekeepers. The were also aware that the general practitioners were able to refer them one if needed.
Pain medicine	[Reflecting on own ability to self-manage]. “Well, when I have to do something about it (the pain) myself then I just take those pills (pain medicine) but they do not really make any difference in terms of me getting better because they only dampen the pain.” Hellen, 16. [Have you taken pain medicine for your back pain?]. “Yes, during periods where it (the pain) was really bad.” [What was your experience with that?]. “It worked during practice or during competition where I had to perform. And then the pain was often worse afterwards because I had used my back too much.” – Beatrice, 16.	For most adolescents, over-the-counter pain medicine was the first attempt to self-manage their LBP. Many used over-the-counter pain medicine repeatedly and for long periods of time despite limited or no effect. Those active in sports frequently used over-the-counter pain medicine to be able to complete training or competition.
Load-management	“… I must remember to say that I did feel a little improvement in my back pain after I went to the physiotherapist. However, it got worse again when I began practicing more.” – Beatrice, 16. “I am on the specialized treatment for 3-months… I began to feel better during that period because I do not train at all… I was able to train full(y) on 6-months after I stopped the specialized treatment…3–4 months after that it started to go downhill again because it (the back) was not really ready”. [How much of your progress do you think is due to the specialized treatment and who much did the break from training influence the pain?]. “I think it was like 50/50” – Diane, 16.	Only a few of the adolescents active in sport seemed to be aware that their pain could be related to their training volume. Further, most of the sports active adolescents were prescribed a load-management/load-reduction strategy however, it was often not described as such by the health professional nor interpreted as such by the adolescents. Even though all the sports active adolescents experienced improvement in pain and function during periods with reduced training volume (load-management) they point to the active components (such as exercise or medicine) as the primary contributors to improvement.
Retention to treatment	[Reflecting on seeking care with a health care provider who previously provided short term pain relief].” I went back because I had seen some physiotherapists and they could not really do anything for me, and the acupuncturist had at least done something. So I went back in hope that she could help me and that it (the pain relief) would be long-term.” – Diane, 16 [What was your reason for discontinuing your course at the chiropractor?]. “Well, that was because I did not feel that it did anything good.” – Tommy, 16.	One of the strongest drivers to retain or revisit treatment modalities and health care providers was if the treatment had proven effective previously. This was true even if the positive effect had only lasted for a few days or even a few minutes the first time. Although not essential for all the adolescents, some were more inclined to discontinue if the purpose of the treatment modality was not clear or if it did not make sense to them.
Help to self-manage	[Did you miss anything during the course of your treatment for back pain?]. “I actually think that could be something like having a health professional that you were connected to and whom you had the possibility of calling or emailing and say, I am actually a little worried because it (the pain) is moving down in my legs, and then there would actually be someone who replied. To just know that you had a health professional that could answer your questions or help when you were insecure.” – Amanda, 18. [What do you think is the best treatment for your back pain?]. “To get across the finish line with these exercises. Also, I think it would be good to build up some muscles and activate them. However, if it (the pain) continues I might get a hold on a physiotherapist who can check if these are the right exercises.” – Sarah, 17.	Most adolescents expressed a desire to self-manage their LBP however, many had a need for guidance and validation from a health care provider in order to be confident in self-managing.
Major theme 2: Pain and function
Pain as a limiting factor	[What does it mean to you to experience pain?]. “It has been irritating me for some time because I can’t do anything and that can get frustrating… For instance, I have trouble bending forward and I feel like an old woman. I feel it is a little bit early to feel old when you are only 16”. [Do you feel hampered by you back pain in other activities that you like to do?]. “Train. I feel limited all the time when I train. I can’t train like I did before, not even close.” – Diane, 16. [What does it mean to you to experience pain?]. “It is very substantial in my opinion… I am almost limited in everything I do. You can say that I can do everything, but everything also hurts… for instance, this Monday I had to write (to) my teacher to get a home assignment because I am not able to stay seated for so long during class. It is like, we have 45 min (of class) and then a 10-minute break, but I am not able to sit for 45 min. It is the same when I am at work… So, I am very limited during both school and work.” – Amanda, 18.	All adolescents were functionally limited by their LBP. They often report pain to be problematic and hampering in relation to school, work, sports, and social activities.
Explanation for pain	[In your own words, what do you think is wrong with your back?]. “I really don’t know what the problem is. I think maybe my back isn’t strong enough or that was what I thought in the beginning. But now when I have trained so much, and it still haven’t got better I don’t know what is wrong… It can also be a tense nerve. I have also been wondering if that could be the reason.” Hellen, 16. [You talked to two physiotherapists and one of them said that your back needed to be straightened out?]. “Yes, he thought that I was crocked so he moved my hips around and cracked and straightened (me) out and all sorts of stuff.” – Diane, 16.	Many adolescents had a purely biomechanical explanation for their back pain. This explanation was either deduced by themselves, or more commonly based on the explanation given by a health care provider.
Diagnostic uncertainty	[Reflecting on underlying reason for back pain]. “Some believe that as I have pain in my body, my muscles get tense in the back. So that means I am going around and being tense all the time. Some believe that anyway (underlying mistrust).” – Kathrine, 18. [What treatment do you think would be the best for your back pain]. “I think it would be to figure out why I have to go around and have so much pain because it can’t be because I got an injury so many years ago… So, I really just want to know what is wrong with me so I can take my precautions in order to get better.” – Emma, 18.	Many adolescents expressed continuous frustration regrading not knowing the cause of their LBP. Although some were provided with an explanation for their pain, some adolescents questioned this or even dismissed it entirely.
Major theme 3: Communication
Difficulties understanding and being understood.	“I went to the physiotherapist with my mom. I have always liked to have her come along because physiotherapists and medical doctors in general they can say things where you fall a bit behind because you don’t understand it.” – Amanda, 18. “The help I need, it needs to be very through because it can be completely unmanageable to call other grown people and not be completely sure what to say. So very thorough help otherwise I think young people may just forfeit.” – Sarah, 17.	Many adolescents were explicit about not being able to understand what health care providers told them about their LBP. Also, some adolescents expressed a concern of not being understood by the health care provider during consultation.
Not being taken seriously.	“… (at the consultation waiting room) at some point I overheard that the older people are taken much more serious and even though their pain threshold may even be lower, and we (the younger once) have more pain, we don’t get taken serious in the same way (as the older). We are just children and should be in good health even though we are not.” – Tommy, 16 [Did you miss anything during the course of your treatment for back pain?]. “Communication and to be taken 100% seriously so that they believe in you” [What should not be a part of the treatment for adolescent back pain?]. “I think that would be people that give up easily and thinkWell, young people don’t know what real pain is and it is probably not as bad as she thinks.” – Emma, 18.	Many adolescents felt they were not taken seriously in relation to their back pain. They especially felt that health care providers did not believe that they experience as much pain as they say they do.
Help to take the next step.	[What is the most important when treating young patients with back pain?]. “From my point of view is being understood very important. To have someone understand that, at least for me, that you get a little bit desperate. You want people to help you and to understand you. So, I think it is very important to try to explain to young people who it is all connected instead of saying, I can’t help you, because what can we use that for? We cannot do anything with that. I would much rather that health professionals took a little extra time to explain why can’t help or what they think could help you.” – Amanda, 18. “I have had a physiotherapist who gave up on me… I got a bunch of exercises, 10 I think, and I come back one day and I say that it doesn’t work and that the pain keeps getting worse and that I can’t stand doing them (the exercises) where the physiotherapist replies that, he think it is best that we stop because he can’t do anything more for me as all he try to do makes it (the pain) worse…” – Emma, 18.	Many adolescents felt that they at some point in their course with LBP reached a standstill because their current health care provider stated that they could not aid them further. Furthermore, many subsequently experienced that the health care provider did not help them initiate “the next step” or provide them with knowledge of what to do from that point forward in terms of managing their pain.