Time as an independent variable of outcome for people with musculoskeletal conditions

If you’re still reading this as someone without a background in statistics, science, healthcare, or research I’m glad that the title didn’t put you off.

A typical way to introduce “musculoskeletal (MSK) conditions” would be to say that they are problems or disorders of the muscles, bones, and joints and that they are often associated with symptoms including pain, stiffness, and loss of function. All of that is indeed part of an evolved definition of MSK conditions, but there is undoubtedly so much more.

In my 20 years’ experience of working with people with MSK conditions, every time I ask a question like “what’s your expectations of what I’m going to do today?” and “what’s your main concern?”, apart from the often tongue in cheek response that goes something like “We’ll… you’re going to fix me”, most people respond with a version or some part of “I want to know what’s going on? Is it something serious? How long will it take to get better? What can be done to get it better?”. Of course, there are often many, varied and sometimes complex responses to these questions and as clinicians we are becoming ever more aware of the importance of truly listening to the patient, and the fruits that this brings in terms of helping someone on their own journey.

In broad terms, MSK conditions can be split up into 3 categories: inflammatory conditions (such as rheumatoid arthritis or ankylosing spondylitis), conditions of MSK pain (such as osteoarthritis, back pain, fibromyalgia, and specific injuries) and, osteoporosis and fragility fractures (State of MSK Health 2021). Headline statistics are often useful tools for highlighting the importance of a particular problem or issue and the one that more than 20 million people in the UK have an ongoing MSK condition (accounting for one third of the UK population) speaks volumes. However, it belies what I would propose we might adopt as a maxim, that at some point in our life all of us will have or have had an MSK condition. It’s just a matter of time! I don’t say this to be alarmist. Instead, what I’m trying to allude to is the importance of that arbitrary construct so esteemed by the great Einstein, that we call “Time”.

If the effects of MSK conditions were but fleeting and did not have the potential for reach into time, and moreover we did not worry about this possibility, would MSK conditions hold us to ransom in the way they have done so to date? A question for us to ponder perhaps.

Many MSK conditions take a significantly greater amount of time to get better than we would want. The findings of the SCOPIC trial (Konstantinou et al., 2020) comparing usual care versus stratified care for people attending primary care consultations for sciatica, shows that irrespective of management approach the cumulative proportion of resolved cases is approximately 50% at 12 weeks, and 70-75% at 48 weeks. For patients with frozen shoulder the UK FROST trial (Rangan et al., 2020) demonstrates that, irrespective of treatment type (physiotherapy +/- injection, manipulation under anaesthetic, or arthroscopic release surgery), achieving substantial improvements in patient-reported shoulder pain and function took the best part of 12 months for most people. For tennis elbow, “time” as a specific strategy on the treatment plan appears essential if patients are to avoid invasive, potentially less effective and sometimes potentially harmful interventions such as corticosteroid injections or surgery (Bateman et al., 2019; Bisset et al., 2006; Coombes et al., 2013); especially when a “wait and see” approach appears to, for the most part, lead to better outcomes at 1 year follow up, than for example, corticosteroid injection (Bisset et al., 2006). There are many more examples of MSK conditions where a reasonable amount of time appears to be an essential component of management; plantar heel pain (Babatunde et al., 2019) and subacromial pain (Beard et al., 2018) to name but a few.

Sometimes MSK conditions persist and are not what we might call “self-limiting” (meaning that a condition gets better eventually, albeit with possibly different rates of recovery, irrespective of what we might do). A reasonable question to ask, whether an MSK condition is self-limiting or apparently not self-limiting (I say apparently because I don’t know many instances of patients with for example tennis elbow, that still have the same problem say 5 to 10 years down the line), is whether any intervention will change the fact that time is the thing most strongly associated with improvement or recovery.

Why is this important? Well, one of the little talked about problems with the management of MSK conditions is the burden of unnecessary treatments and wasted resources, some with the possibility of harm; with harm meant in its broadest sense and including direct patient harm, indirect harm, opportunity costs (such as a focus on passive treatments leading to a lack of engagement in active management), or indeed the associated monetary costs.

And so, to the nub of this post. Time as an independent variable for outcome for people with MSK conditions. An independent variable is something you can vary to produce a change in a dependent variable. So, what does that mean? Let’s use an example. To do that we need a hypothesis, something like “tennis elbow gets better the longer it is left alone”.

To test this hypothesis, we’re going to need to imagine an alternate universe where it’s acceptable to create identical human beings (a scary thought) and identical context; same person, same composition, same experiences, same activity levels, same onset, same mechanism, same loading history (I think you catch my drift). We then see how much tennis elbow gets better (the dependent variable) over different periods of time (the independent variable). If my hypothesis is incorrect then there should be no relationship between the amount of time that passes and the likelihood of recovery of tennis elbow (the null hypothesis). If, however, there is a relationship between the amount of time that passes and the likelihood of recovery of tennis elbow, then we would accept our hypothesis that “tennis elbow gets better the longer it is left alone”.

I would say that the empirical evidence through observation alone would suggest that we could substitute “tennis elbow” in the above example, for many a MSK condition, stating that “x gets better the longer it is left alone”. However, although the idea of doing nothing aside from observing the passage of time (the so called “wait and see” approach) seems unappealing, and raises a plethora of ethical questions regarding “the right thing to do”, it doesn’t change the fact that, in some instances, although possibly more difficult to do, allowing time to do that thing it keeps doing … “ticking away” … might just be a better option, than turning to more invasive interventions that may cause more harm than good in the medium to long term.

I want to draw this blog to a close by saying that in no way is the line of thinking presented above comprehensive when exploring the question posed in the blog title. It’s just one way of looking at things, and a way to make the point that time is an important independent variable when it comes to the management of MSK conditions. Furthermore, that when discussing a treatment plan with a patient, we should feel confident to include “time” as a key component of that treatment plan. If not, there is a risk that we fill that time void with any number of unnecessary and possibly harmful interventions. It was Leo Tolstoy in War & Peace who wrote that “the two most powerful warriors are patience and time”, alongside the possibly more prophetic quote by the father of tragedy himself, Aeschylus, that “Time brings all things to pass”.

Babatunde, O.O., Legha, A., Littlewood, C., Chesterton, L.S., Thomas, M.J., Menz, H.B., Windt, D. van der, Roddy, E., 2019. Comparative effectiveness of treatment options for plantar heel pain: a systematic review with network meta-analysis. Br. J. Sports Med. 53, 182–194. https://doi.org/10.1136/bjsports-2017-098998

Bateman, M., Littlewood, C., Rawson, B., Tambe, A.A., 2019. Surgery for tennis elbow: a systematic review. Shoulder Elb. 11, 35–44. https://doi.org/10.1177/1758573217745041

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Bisset, L., Beller, E., Jull, G., Brooks, P., Darnell, R., Vicenzino, B., 2006. Mobilisation with movement and exercise, corticosteroid injection, or wait and see for tennis elbow: randomised trial. BMJ 333, 939. https://doi.org/10.1136/bmj.38961.584653.AE

Coombes, B.K., Bisset, L., Brooks, P., Khan, A., Vicenzino, B., 2013. Effect of Corticosteroid Injection, Physiotherapy, or Both on Clinical Outcomes in Patients With Unilateral Lateral Epicondylalgia: A Randomized Controlled Trial. JAMA 309, 461–469. https://doi.org/10.1001/jama.2013.129

Konstantinou, K., Lewis, M., Dunn, K.M., Ogollah, R., Artus, M., Hill, J.C., Hughes, G., Robinson, M., Saunders, B., Bartlam, B., Kigozi, J., Jowett, S., Mallen, C.D., Hay, E.M., Windt, D.A. van der, Foster, N.E., 2020. Stratified care versus usual care for management of patients presenting with sciatica in primary care (SCOPiC): a randomised controlled trial. Lancet Rheumatol. 2, e401–e411. https://doi.org/10.1016/S2665-9913(20)30099-0

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