“Oh,… but I heard from someone else with the same diagnosis that she was helped the most with mobilisation exercises and deep massage techniques? Couldn’t you treat me the same?”

Do you feel where it is going to? At least, I do. This is something you hear working in a clinical practice as a physiotherapist on a frequent basis. Most patients think and feel there is one optimal treatment to fix their symptoms if a biomedical diagnosis is confirmed. However, in most cases, there isn’t.

Clinical practice

Fortunately, to date, we’re already many steps forward. We can explain to the patient that their problem is much broader than pure the biomedical diagnosis. Therefore, a clear physical therapy diagnosis does exist and various forms can help the physiotherapist to ensure that all domains of the biopsychosocial model are stipulated. Because that is what we need to do: we need to analyse the whole patient, and not forget to focus on their thoughts, feelings and environment; and adapt patients’ treatment to these findings (1).


Evidence-based medicine or practice is the starting point for optimal treatment and rehabilitation in physical therapy. To ensure clear evidence-based practice guidelines, high quality research including the highest ranked study designs is necessary. For example, a systematic review or meta-analysis of randomized controlled trials of substantial quality is the perfect basis to provide some clinical practice guidelines (2). However, conducting high quality research taking into account the complete individual patient and their environment isn’t that simple.

Problem in research

In randomized controlled trials, standardisation is extremely important. A large and homogenous sample is therefore necessary to make firm conclusions. However, in reality and as mentioned in the first paragraph, not a single patient is exactly the same. As such, a unique treatment is necessary for a unique patient.

In many cases, conflicting evidence is found, just because the intervention is given to a heterogenous group of patients with the same biomedical diagnosis (for example knee osteoarthritis patients), without considering other individual features/symptoms. Some therapies, techniques or exercises are proven not effective , or only low to moderate evidence exists in evidence-based research (3).

Starting point in research

Therefore, research about revealing subgroups in patients with the same diagnosis has increased substantially during last years (4,5). This is a huge step forward in research, as previous research mainly focused on a ‘one-size-fits-all’ approach and this could have attenuated treatment effects of rehabilitation and physical therapy interventions in the past (6).  

For example, knee osteoarthritis represents as a heterogenous disease (3) and therefore five different clinical subgroups (also called ‘phenotypes’) are suggested (4). Identifying the right phenotype and thus identifying which patients are the most suitable for a certain therapy is postulated crucial to provide the most efficacious treatment in clinical research. To date, it is already known that in knee osteoarthritis, but also in other heterogenous disorders, such as chronic dizziness or cerebral palsy, patients need to be approached with an individual diagnosis and treatment. But even then, more research is necessary to define all sub-groups (4). The next step is to use this information for inclusion in high quality research, because the results found in clinical research papers will form the basis for the guidelines used in clinical practice.

But… What if the subgrouping patients results in a too small sample size?

If you are not able to collect a sufficient sample size for a randomized controlled trial, or subgroups do not yet exist in a certain pathology, other options for high quality research are available. An upcoming research design created for compensating the weaknesses of a randomized controlled trial is a single-case experimental design. This is also high-quality research, which is ranked as a Level 1 evidence for making decisions of treatment modality/focus in the individual patient. This method is typically used in patient groups who are too heterogenous or too small to implement in a randomized controlled trial or before testing these patients in a time-consuming and costly randomized controlled trial. More details of this study design can be found in the study of Krasny-Pacini et al. (7).

Main message

Clinical subgroups or more specific patient characteristics need to be addressed in clinical diagnosis and practice, but also in clinical research it is extremely important to identify them and thereby to avoid attenuating the effect of the optimal treatment (8). Therefore, the first step is to identify the specific patients’ characteristics and/or phenotype of a patient. The second step is then to adapt the treatment to these characteristics and finally to test the real treatment effect.

Sophie Vervullens

Physiotherapist and PhD student at the University of Antwerp (MOVANT) and University of Maastricht (CAPHRI).

2021 MOVANT research

References and further reading:

1.           Jiandani MP, Mhatre BS. Physical therapy diagnosis: How is it different? J Postgrad Med. juni 2018;64(2):69–72.

2.           Snell K, Hassan A, Sutherland L, Chau L, Senior T, Janaudis-Ferreira T, e.a. Types and Quality of Physical Therapy Research Publications: Has There Been a Change in the Past Decade? Physiother Can. 2014;66(4):382–91.

3.           Bierma-Zeinstra SMA, Verhagen AP. Osteoarthritis subpopulations and implications for clinical trial design. Arthritis Res Ther. 5 april 2011;13(2):213.

4.           Dell’Isola A, Allan R, Smith SL, Marreiros SS, Steultjens M. Identification of clinical phenotypes in knee osteoarthritis: a systematic review of the literature. BMC Musculoskelet Disord. 2016/10/14 dr. 12 oktober 2016;17(1):425.

5.           Deveza LA, Nelson AE, Loeser RF. Phenotypes of osteoarthritis - current state and future implications. Clin Exp Rheumatol. 2019;37(Suppl 120):64–72.

6.           Bennell KL, Hall M, Hinman RS. Osteoarthritis year in review 2015: rehabilitation and outcomes. Osteoarthritis Cartilage. januari 2016;24(1):58–70.

7.           Krasny-Pacini A, Evans J. Single-case experimental designs to assess intervention effectiveness in rehabilitation: A practical guide. Ann Phys Rehabil Med. 2017/12/19 dr. mei 2018;61(3):164–79.

8.           Foster NE, Hill JC, O’Sullivan P, Hancock M. Stratified models of care. Best Pract Res Clin Rheumatol. 1 oktober 2013;27(5):649–61.