Welcome back to the Healing Pain Podcast with Deepak Kumar, PT, PhD
In this episode, we are discussing the impact of physical therapy on long-term opioid use for patients undergoing a total knee replacement. My expert guest is Professor Deepak Kumar. He is an Assistant Professor in the Department of Physical Therapy and Athletic Training at Boston University and the Section of Rheumatology at Boston University School of Medicine. He directs the Movement and Applied Imaging Lab at Boston University. The goal of Dr. Kumar’s research is to improve the quality and quantity of movement during everyday life in people with knee osteoarthritis to reduce pain, improve physical function and maintain joint health.
We’re going to review the findings of Professor Kumar’s study called the Association of Physical Therapy Interventions With Long-term Opioid Use After Total Knee Replacement. You can find that article in the October 2021 edition of JAMA Network Open. This show has implications for people with chronic pain. Also, there is important information here for opioid use and the positive impact that physical therapy can have on people’s lives living with chronic pain. Without further ado, let’s begin and let’s meet Professor Deepak Kumar.
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PT Lowers Risk Of Opioid Use After Total Knee Replacement With Deepak Kumar, PT, PhD
Deepak, thanks for joining the show. It’s nice to have you here.
Joe, thank you for having me. I’m happy to be here.
I’m excited to talk with you about this topic. As physical therapists, it is important information for us to talk about opioids and how they can impact certain populations of people living with chronic pain. We’re going to focus on a study that you conducted, an investigation. I want to point everyone toward that so they can read it and look at it. It is in the Journal of the American Medical Association, October 2021.
It’s called the Association of Physical Therapy Interventions With Long-term Opioid Use After Total Knee Replacement. Important study. I read the whole study. It’s full of information for physical therapists, orthopedic surgeons because they’re highly involved in the care process and for people living with pain. Tell us why you chose to study this topic.
Thank you for that question. My research practice, if I can say that, is primarily in people with knee osteoarthritis. If you think about the spectrum of the disease that people who undergo total knee replacement are the people who are at the end stage, as we call the disease process. As we cited in the paper, the number of total knee replacement surgeries is growing rapidly. The numbers are expected to exponentially increase over the next few years, like over $2 million a year by 2030. Despite the fact that it is generally a very successful surgery, depending on which study you cite, 1 in 5 or 1 in 4 individuals continue to have persistent pain after the surgery. Given the large number of surgeries that happened, this number is not revealed.
There is a clear failure of strategies for pain management in these individuals who continue to have pain after surgery. The other aspect is that an insignificant number of individuals who undergo the surgery become long-term opioid users. Depending on whether the person has used opioids before the surgery or hasn’t, they are opioid experienced or naive, as we are calling them here, anywhere from 3% to 50% of these individuals can become long-term opioid users. Again, we note that opioids are not the best way to manage pain in these individuals. In fact, it can even make the pain worse in some individuals.
Again, there’s a clear failure of strategies to manage pain. We know from a lot of prior studies that physical therapy interventions can be very effective at managing pain. They wanted to study whether physical therapy interventions before surgery or after surgery can reduce the likelihood of a person becoming a long-term opioid user. That’s why we did the study.
There are lots of great statistics you have there to open up with. I think there are some great stats that people would be interested in. I want to make sure I understood everything that you said clearly. The first thing that you mentioned is even though people have a knee replacement, so the joint is replaced completely, they still go on to have pain. Can you review that stat with us? It’s an important stat that people should be aware of.
As I was saying, depending on what study you look at but I think the generally accepted number in the field is that 1 in 5 individuals continue to have what is called persistent knee pain, which has been specifically defined as a worsening of previous pain or a presence of a new pain after surgery for at least three or more months after surgery. Again, 1 in 5 individuals is not a small number given a large number of these surgeries.
It might be a little confusing to people who have either had a knee replacement or people who are considering a knee placement. This could be a whole another show in and of itself but maybe give us like one or two points of how if someone had their entire joint replaced. They underwent surgery and had the entire joint placed. How can they continue to have pain?
As you hinted, this might be a whole new can of worms that we can open here but to be honest, our understanding of why people experience pain when they have knee osteoarthritis is not great. The actual damage to the joint is not always the only reason for people to experience pain, as surprising as that might be to people. It’s not uncommon for people to think that. Osteoarthritis means the cartilage is wearing away. That means the bones are touching or coming in contact and that causes some pain.
We know from a lot of studies that’s not always the case. The source of pain in people with knee osteoarthritis can partially be the damage to the joint issues. Cartilage damage itself does not cause pain because there are no pain-sensing fibers in the cartilage but the damage to the bone around the joint. The damage to the covering of the joint is called the synovium. Damage to the muscles can cause pain. In individuals who have chronic pain, like people who have knee osteoarthritis, the pain can mostly be coming from an abnormality and how pain is processed by the brain.
I want to be careful of how I say this because nobody likes to be told that the pain is in their brain. Technically, we call this pain sensitization. I’m sure this has come up many times on your show. A large number of people with knee osteoarthritis and other people, other conditions where people have chronic pain like low back pain, fibromyalgia, the way the body processes the pain information goes haywire. People can perceive pain when pain is not helping the body in any way. If you think about acute pain, which is like if you’re walking and you hit your foot against the sidewalk, you stop the dog.
At that time, the pain you feel is the pain that is helpful to you. That you understand that you had an injury, you need to protect that part of your body but in individuals with chronic pain sometimes, they get these pain signals or they perceive pain when there’s not any helpful information carried in these signals if that makes sense. We know that this sensitization can persist after knee replacement surgery, so people can continue to experience sensitization. That can be one reason why they continue to experience pain. We don’t know much more about why people continue to experience pain after total knee replacement, unfortunately.
There are still lots of good take homes in there. The main ones are that you may have osteoarthritis but joint damage is only a part of the equation of what’s contributing to your page or other lifestyle factors and affective or psychosocial factors that impact how pain is processed throughout your body. The nervous system, or the brain, is one place that we talk about the most. Your cohort was quite large in this study. Why don’t you go through some of the details and the findings of what you found in the study?
We used an insurance claims database. If people aren’t familiar with that, it means that we purchased access to insurance information for a large number of people in the country through a third-party service. One thing to know is that in these data, we only have information on insurance claims. That means that we do not have information on how advanced somebody’s osteoarthritis was or how severe their pain was. We don’t have the actual clinical information. You will have information on claims that were filed on their behalf.
Having said that, we looked at people who underwent total knee replacement between 2001 and 2016. We started with over 2.5 million people who underwent surgery in that period time period. Once we applied our study criteria, we ended up with a cohort of about 67,000 individuals who were eligible to be studied in this analysis.
As I was mentioning, whether you have used opioids before or not can be a strong predictor of whether you’ll use opioids in the future. We wanted to separate those two groups out. We took the 67,000 people and we divided them into two groups, people who had used opioids in the twelve months period before surgery and people who had not.
We had about 29,000 people in the opioid-experienced group and about 38,000 people in the opioid-naive group. We looked at our main question, which is, do physical therapy interventions before surgery or after surgery are associated with a reduced likelihood of long-term opioid use? Long-term opioid use was defined as 90 or more days of opioid prescriptions that were filled by the patients.
For our physical therapy before surgery, we looked at it 90 days before surgery. For physical therapy after surgery, we looked at 90 days after surgery. One difference was that before surgery and we looked at physical therapy interventions provided in outpatient settings or inpatient settings. For after surgery, we only looked at physical therapy interventions provided in outpatient settings because almost everybody gets at least one or two days of physical therapy immediately after surgery. We wanted to focus on the outpatient physical therapy care after surgery to be clear over there.
We also wanted to see whether they’re specific attributes of physical therapy interventions after surgery that might be more associated with a reduced likelihood of chronic opioid use. For example, if we looked at how quickly after surgery did somebody see an outpatient physical therapist. We also looked at a number of outpatient physical therapy sessions and we also looked at the type of physical therapy interventions. We classified them into active, which we consider as interventions where the patient is participating in the intervention. These are exercises, teaching them how to walk differently and teaching them how to self-manage their symptoms, etc.
Passive interventions, where if you think about it, the patient is not participating in the interventions of the things like pants or a hot pack or cold pack, things like that modalities. We wanted to see if those two types of interventions have differing effects on the likelihood of long-term opioid use. That’s how the study was set up. We looked at the outcome over a one-year period starting 90-days after surgery. We found that both physical therapy interventions before surgery and physical therapy interventions after surgery were both associated with a reduced likelihood of people using opioids long-term.
This was consistent in people who had used opioids before and who hadn’t used opioids before. We also found strong effects for starting physical therapy care early after the surgery. If you start outpatient physical therapy within 30 days of the surgery, your likelihood of using opioids long-term was much lower compared to people who start outpatient physical therapy more than 30 days after surgery.
We also form some signal for almost like a dose-response, which means that the greater number of physical therapy sessions was associated with a reduced likelihood of long-term opioid use. This was a bit inconsistent across the two groups. The one surprising finding we had was that we did not find an association between active physical therapy interventions and opioid use in this cohort.
I know it can say for all of our colleagues that there’s a lot of good information in here for the physical therapy profession. I think there’ll be excited to hear the impact of physical therapy both before pre and post a total knee replacement. Did anything surprise you from the study once you started to analyze the data?
As I started to mention in the response to the last question, the last part, the finding that active physical therapy associations were not any more likely to reduce reliance on long-term opioids was surprising to us. This is coming from the literature on people who have knee osteoarthritis in general and not specifically people who have knee replacement surgeries. There are decades of information that exercise interventions are more effective than passive interventions for people who have knee osteoarthritis and we know that it’s an accepted fact at this point.
We were quite surprised that wasn’t the case in this particular analysis that we did. There are a couple of reasons why that’s what we found. One reason could be that the may be defined active interventions might not be the best. We defined active interventions as 50% or more of the interventions being in the active category. Perhaps, what matters is if they received any active interventions versus a certain proportion of the intervention being active because they’re 50% number. Although it came from prior studies, it’s still arbitrary. Perhaps future studies can look at any active interventions versus completely passive interventions.
Another reason could be that, again, this is not well-studied in people with a knee replacement. Given what we know about why these people continue to experience pain, it might be sensitization or psychosocial factors, it’s possible that exercise interventions by themselves might not be sufficient to deal with these biological processes. Something else might be needed for these individuals that are not currently provided in physical therapy interventions, for example, cognitive behavioral therapy or mindfulness, etc.
You bring in the psychosocial aspects. You probably have received some feedback from colleagues. How are you recommending that professionals, whether it’s a physical therapist or another licensed health professional? How can they take this information and use it either for public health promotion or potentially in their own clinic or their own practice or maybe even talk with a payer who may be interested in ways to manage pain more effectively?
I think before I respond. I want to put a caveat out there that this was not a clinical trial. The caveat that comes from the fact that this was an observational study applies here but given that our effects were very consistent, strong and large, I’m comfortable saying that if payers and providers can ensure that people who undergo knee replacement can get to an outpatient physical therapist within 30 days of surgery.
If they can receive some physical therapy before surgery, that might help with reducing the likelihood of having long-term opioid use in the future, if that makes sense. Anything more than that probably would need like other studies. These findings are to be replicated in other studies or clinical trials but I’m fairly comfortable making that statement here. Is that what you were looking for, Joe?
It is. It starts to take me down another path as I’ve read your study and we’re talking here. To play devil’s advocate, Deepak, as you know with evidence-based medicine, people are always looking for, “Who is this person? Why did they do this study? Is there a conflict of interest?” People might say, “This guy is a physical therapist. He’s going to find good results for physical therapy. He’s biased toward physical therapy, helping people with regard to opioid misuse and opioid misuse disorder.” What feedback might you have for someone who is thinking those things?
It’s a fair question to ask. I want to disclose that the people who conducted this study, including myself, were supported by funding from the National Institutes of Health. A couple of the authors had funding from pharmaceutical companies for work not related to the study. The motivation for this study came about from a rheumatologist colleague of mine, Dr. Tuhina Neogi, who was a co-author, and myself. We came up with this idea and the findings are what they are. The data have not been manipulated in any way. We’re happy to make the data freely available to individuals. There’s no conflict of interest for any of the authors and for this study.
Even though it’s a different patient population, there have been similar studies with regard to low-back pain and the impact of physical therapy on opioid use and misuse disorder.
That’s correct. There has been work in people with low back pain where early physical therapy after an acute or emergency room visit to look for low back pain condition has been shown to reduce the use of opioids term. We also have found similar findings in people who have knee osteoarthritis but are not yet ready for surgery. We’re seeing a consistent pattern there. These findings do seem to be valid in many different populations with chronic musculoskeletal pain and not only people who undergo a knee replacement.
We’re seeing this pattern consistent with people with chronic low back pain. We’re seeing the pattern consistent with people who are undergoing a total knee replacement and people who are seeking conservative care for knee osteoarthritis. There are three key groups there. If there’s a researcher who’s reading or maybe a physical therapist who’s interested in researching this topic more, I always think of like, in the center of the circle, we have opioids in knee osteoarthritis but there are overlapping circles with this topic. What areas do you start to think of, “We should start to investigate?” It’s similar to this but another population or another topic.
Let me first say that within this population even, there are unanswered questions that need to be looked at. For example, one very important area to further look at is, “Are these findings consistent across different racial and ethnic groups?” As you might know, Joe and as the audience might know already, there are inequities in access to physical therapy care for inpatient minorities, especially in Black and Hispanic adults.
They are referred to physical therapy less often than non-Hispanic Whites. There are some inequity issues here that need further study in terms of whether these findings hold true for different racial or ethnic subgroups. In terms of other populations, it would be interesting to see whether these findings are similar and other groups of individuals who undergo surgeries. For example, people who undergo total hip replacement, which is another big of people who get surgery and that number is also going up all the time. That’s another group to look at in terms of seeing whether physical therapy dimensions there are similarly associated with reduced likelihood of opioid use.
Have any payers reached out to you with regards to your data asking to access the data or to discuss the data with them?
That’s interesting because the data is from the payers. It’s all insurance data. It’s their own data, so they can look at it anytime they want. We had to buy the data if they have it.
That’s interesting to think about. They have the data, but the question is, are they analyzing the data the way you did?
To answer your original question, none of the payers have reached out to us but our methods are in the paper, to be honest. The methods are not super innovative or groundbreaking. It’s something that has been done in many of the studies. It’s fairly straightforward. It’s about defining your cohort well. Again, the payers have the ability to try and replicate these findings for their client population base and see if that holds true and that can inform their policies and what they want to reimburse and when they want to reimburse.
How many visits they’d like to reimburse for physical therapy status post total knee replacement. Your study looks at probably around the number six visit, so to speak. Is it where people show the strongest benefit or show a significant benefit?
We categorized visits into 5 or less and 6 to 12 or 13 or more. We found that compared to five or less, the other two groups had a progressively larger protective effect. At least six would be a starting point for people to think about what’s the minimum number but going up to 10 or 12 is probably more helpful because the effect keeps getting stronger. We also know from other studies that, generally, physical therapy interventions can be cost-effective when compared to say intra-articular injections or other amazing procedures.
That’s another reason to think about using physical therapy interventions to manage pain versus some of these more invasive procedures. Also, given the fact that physical therapy interventions, generally speaking, are very available. They’re available to most individuals. Those are some of the reasons to think about them.
Physical therapy interventions are available but wouldn’t it be nice if payers took this information and said, “This looks like most patients with a total knee replacement needs six visits. Let’s make a rule that every patient who receives a total knee replacement can receive six visits of outpatient physical therapy. No questions asked. No pre-authorization. No fighting with the insurance company. No back and forth.” We take down some of the barriers that exist for patients. These are barriers for us as well as providers but the biggest barriers are for the patient.
How do we help people overcome what they’re experiencing? That jumped out to me on the page, like, “Here’s a real-life clinical application of how this information can weave its way through the payer’s networks.” Oftentimes, they were third parties that will administer care, so to speak or authorized care than us as the professional and the patient trying to provide care.
For us as professionals or as providers, we probably want to think about how we can do a better job of getting the patients into the clinic as quickly as we can because that 30-day period seems important. I know sometimes our practices are busy and patients have to wait. Whatever we can do to get them in and that’s not my area of research. You probably know about it more than I do.
Six visits within 30 days. That’s important for people. If you have a total knee replacement, what the data starting to show is you’ll benefit from receiving physical therapy within 30 days and probably for an average of about six visits, at least, it looks like. I appreciate that. Deepak, this is great work. I’d love for you to come back. My platform is yours. If you have any other information on the impact of PT on people with pain and opioids, please come back and join us. In the meantime, tell everyone how they can learn more about you and follow your work.
Thanks, Joe. I want to say that I want to thank you for all that you do to disseminate what we do as scientists to the public because sometimes, we as scientists, don’t do a good job of it. Thank you for helping us out. To learn more about what we do, I would invite people to visit our lab website. We are at Boston University in Boston University School of Medicine. We have a large group of researchers, interdisciplinary rheumatologists, physical therapists and engineers who work together to solve problems around managing pain and people with knee osteoarthritis, check us out.
You can also tweet out to Deepak on social media. It’s @ProfDeepakKumar on Twitter and you can reach out to him. At the end of every episode, I ask you to share this information with your friends and colleagues. If you’re a physical therapist, I would love for you to hop on Instagram or Facebook and Twitter and tweet this out so we can educate the public about the impact of physical therapy and opioids for people with total knee replacements. It’s been a pleasure spending this time and we’ll see you on the next episode.
- Department of Physical Therapy and Athletic Training
- Boston University School of Medicine
- Association of Physical Therapy Interventions With Long-term Opioid Use After Total Knee Replacement
- @ProfDeepakKumar – Twitter
- @BU_MoveLab – Twitter
- @BU_MoveLab – Instagram
About Deepak Kumar, PT, PhD
Deepak Kumar, PT, PhD is an Assistant Professor in the Department of Physical Therapy & Athletic Training at Boston University and Section of Rheumatology at Boston University School of Medicine. He directs the Movement & Applied Imaging Lab at Boston University. The goal of Dr. Kumar’s research is to improve quality and quantity of movement during everyday life in people with knee osteoarthritis to reduce pain, improve physical function, and maintain joint health.
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