Rehabilitation theory; what and why?

What is a General Theory of Rehabilitation, and why is it needed? Some might say we have managed well without one for a century, so why waste time and effort developing a theory? In reply, we might have done much better with one, and this post will consider the challenges and questions a theory might address. I will explore generally what a theory is and its influence before considering the outstanding issues we must solve in rehabilitation and why a theory might help. One of rehabilitation’s early and astounding successes was its transformation for people with spinal cord injury without achieving any significant change in the lost motor control and sensory loss associated with complete spinal cord injury. When I trained, rehabilitation was considered only appropriate for people with a recent loss and expecting a significant recovery, especially those with stroke and traumatic brain injury.

Table of Contents

Mind-Map of this page's content


Newton’s theory of gravity explained many previously unexplained observations and centuries later was used to land man on the moon. Theories affect us all. We generate theories regularly when faced with observations we do not understand. When our car stops suddenly, we look at the fuel gauge because our theory (explanation) is that we have run out of petrol. Many significant theories that many people use lack evidence; this is obvious for conspiracy theories, such as that the moon landings were fabricated. Other theories, such as the miasma illness theory, were widely accepted without evidence.

Priscilla Alderson stressed “The importance of theories in healthcare.” in 1998. She pointed out that “All thinking involves theories …” and that “ …  theories powerfully influence how evidence is collected, analysed, understood, and used, …”. More presciently for rehabilitation, she said, “… when theories are implicit, their power to clarify or to confuse, and to reveal or obscure new insights, can work unnoticed.” The implicit biomedical theory of healthcare and its associated biomedical model of illness are both unnoticed, although Peter Halligan and I drew attention to its influence and the related harm in 2004.

In a discussion on ‘Theory development and a science of rehabilitation’, Richard Siegert and colleagues concluded, “More time spent on rehabilitation theory building may enhance the fruits of empirical theory testing.” They also said, “ … we treat the terms theory and model as essentially synonymous while noting that in some discussions of philosophy of science, this is not so.” I will briefly discuss theories and how a model might differ as I consider the nature and need for a rehabilitation theory.

What is a theory?

The Oxford English Dictionary [OED]describes a theory as “a supposition or a system of ideas intended to explain something, especially one based on general principles independent of the thing to be explained.” This highlights that it sets out general principles that help in understanding something. In the article, Theories and Models: What They Are, What They Are for, and What They Are About, Eiko Fried discusses theories and models, suggesting that a theory is a logically consistent conceptual framework that integrates various ideas, whereas a model is a specific representation of the theory.

In other words, theory should not simply describe something; it should explain existing observations and, ideally, make predictions that can be tested and helpful. When there are several theories, one can compare how succinctly and accurately they explain observations and whether their predictions are accurate.

Another explanation suggests theories are broad, general principles explaining a wide range of phenomena. Ideally, they are “concise, without exceptions, coherent, systematic, predictive and broadly predictive.

The features of a good and less good theory can be illustrated by comparing the biomedical and biopsychosocial models (theories) of illness. How well do they explain illness, the broader personal and societal aspects of ill health?

Comparing theories

Biomedical and biopsychosocial theories

The biomedical theory explains and predicts disease, the underlying pathology affecting structure or function. It is concise, generally applicable, and has allowed many diseases to be identified and treated. However, it cannot describe, explain, or predict illness. This is mainly because illness relates to the person and is influenced significantly by culture and society. Illness without disease cannot be explained, but it occurs in 25% of people attending healthcare.

The biopsychosocial theory explains and predicts illness without an identifiable underlying disease. It is also much better at explaining sickness and disability. This is because it encompasses physical, personal, and social factors. It is helpful when analysing an illness. It is less concise because it covers a much broader scope than the biomedical theory. The biomedical theory fits within the biopsychosocial theory.

A worthwhile theory should:

  1. Be testable, suggesting a hypothesis that can be examined. If the data do not support the theory, it is invalid.
  2. Be coherent, with internal logical consistency and no contradictions. It should also be comprehensible.
  3. Economical, concise and with as few relevant variables as possible, fewer than any competing theories.
  4. Broadly applicable, covering all relevant phenomena and instances. For healthcare, it should cover all branches of rehabilitation.
  5. Explanatory, being compatible with all known observations, and no observations should contradict the theory.

Existing rehabilitation theory.

The one theory strongly associated with rehabilitation is the biopsychosocial model of illness, which I discuss extensively on this site. This is a theoretical framework that rehabilitation works within. It provides a structured approach when considering assessment or interventions. It is used to classify aspects of a patient’s state. It has many other uses.

Rehabilitation is a process. The biopsychosocial model (theory) is about a structure and inter-relationships, not about a process. One cannot deduce anything about rehabilitation from a descriptive theory. Therefore, although the biopsychosocial model of illness is powerful and rehabilitation works within its structure, it is not a rehabilitation theory.

The theoretical foundations of rehabilitation were reviewed by John Whyte in 2008. He did not find “A Grand Unified Theory of Rehabilitation.” None has been published since. However, he pointed out that rehabilitation practice used theories when appropriate.

In 2014, he published another article about the “Contributions of Treatment Theory and Enablement Theory to Rehabilitation Research and Practice.” Enablement theory hypothesises about the inter-relationships between different components of the biopsychosocial model, for example, between leg strength, gait speed and endurance, and community mobility. They draw on ideas about the disablement process.  Treatment theories relate to how interventions targeted at changing a factor have their effects.

For example, motor learning theories guide therapists in the methods available to help patients learn or relearn how to perform motor tasks like walking.  Enablement theories allow a prediction of how much community mobility would be increased by a change in walking speed or endurance.

There are other parts of rehabilitation with theories. For example, Lesley Scobbie and colleagues identified five theories underlying goal setting in adult rehabilitation.


No published general rehabilitation theory applies to all types of rehabilitation in all settings.

Rehabilitation puzzles.

Presently, rehabilitation is understood in the implicit biomedical healthcare model. This considers rehabilitation treatment or therapy given to a patient to improve the target condition, and, in this model, there should be a dose-response relationship; more rehabilitation should be associated with a more significant benefit. Various rehabilitation phenomena are not easily understood within this theory.

The most striking is the success of spinal cord rehabilitation, which I have emphasised on another page. There is no recovery from complete spinal cord injury; losses remain unchanged. Without rehabilitation, patients face early death and minimal social participation, but with it, life expectancy is near-normal, and many people have full involvement in society. Most implicit rehabilitation models cannot explain or predict this success when there is no change in the person’s losses.

Another puzzle concerns the effectiveness of rehabilitation under virtually all circumstances. Rehabilitation can be effective:

  • In conditions with any prognosis – recovery, static, fluctuant, or progressive,
  • Delivered to patients in hospital or at home
  • At any age (there was limited evidence available for children)
  • At any stage after the onset of the condition
  • With disease affecting any structure or organ, including psychiatric conditions and functional disorders.

Most of the evidence can be found in my review of effective rehabilitation.

No existing theories explain or predict that rehabilitation can be effective for almost all patients.

A third difficulty concerns research, where one usually compares the effect of an intervention against its absence; sometimes, one compares different quantities. Defining the state of no rehabilitation is the first difficulty. Taking someone who has had a stroke, is no rehabilitation the same as receiving no input once the diagnosis is made and any acute disease-modifying treatment has been given? This process rarely extends beyond one day. This would be unethical and impossible. One would provide care.

But carers will give advice, offer emotional support, and help someone to move and undertake activities. So, is it receiving nursing and medical care but no therapist input? The nurses, doctors, and other care staff will have some experience in helping people with disabilities, and friends may well have experience, too, giving advice and help in learning to do things. Equipment will be provided.

Ultimately, the only definition of ‘no rehabilitation’ possible is no input from a person or team identified as an expert in rehabilitation. However, people in the no-rehabilitation group will have received much support, advice, and help of variable quality.

A similar difficulty extends to describing the natural history of change in function; the environment will influence it.

These difficulties highlight a difficulty in defining rehabilitation, a challenge that follows from lacking a theory.

The challenge extends to quantifying rehabilitation input. The recent NICE guideline on stroke rehabilitation recommends three hours daily, five days a week. But what is one to measure? Is the measure of face-to-face direct teaching and practice of activities? It is undoubtedly true that increasing the time someone practices an activity is vital, but rehabilitation includes many other patient-centred crucial activities, such as:

  • Regular meetings with members of the team to discuss patient goals, progress, and plans
  • Liaising with other professionals and teams, especially as the time of transfer back to the community approaches,
  • Teaching self-management skills
  • Supporting, educating, and training family members
  • Organising care and training carers
  • Assessing for equipment and adaptations and negotiating the many complex systems involved in funding and obtaining them
  • Undertaking home visits

Which of these many activities should be quantified? If a team member spends two hours contacting Social Services to arrange a home visit, does this count as two hours or zero if the attempt fails?

A theory might help untangle some of these puzzles.

Rehabilitation services and research.

The UK Medical Research Council recently updated its excellent guidance and gave a new framework for developing and evaluating complex interventions. The second step in any project is to describe the theory underpinning the intervention, the programme theory. This can be done for some specific part of rehabilitation, such as setting goals, training motor skills, or providing cognitive behavioural therapy. No programme theory for rehabilitation exists to “… describe how an intervention is expected to lead to its effects and under what conditions.”

The absence of any general rehabilitation theory has caused significant problems with service design and delivery.

Rehabilitation is generally misunderstood, with people making different assumptions about it. Consequently, patients are often not referred to rehabilitation services, the patients may be given unrealistic expectations about forthcoming rehabilitation, the referring agency, such as Social Services, may have unrealistic expectations of the rehabilitation service, etc.

Rehabilitation has a low priority. This is especially evident in the UK. Services are grossly under-resourced compared to the situation in most comparable countries. They also do not have any theory but have attracted more attention.

Rehabilitation services are chaotic. There is no systematic approach to the organisation and funding of rehabilitation services. This leads to much waste, patchy and uneven services with a few excellent services and many locations with few, if any, services.

A general theory of rehabilitation could identify some crucial areas where research might improve rehabilitation. It would then facilitate the design and planning of suitable research programmes. Rehabilitation research is currently piecemeal, without any coherent framework which would enable better generalisation of findings; at present, much research is only considered within a narrow field of rehabilitation practice.


A general rehabilitation theory is crucial, and until now, it has not existed until now. The lack of a theory has been associated with the marginalisation of rehabilitation within the UK health services, receiving much less resources and attention than other services. Worldwide, it is associated with less theory-driven research, which has led to less funding, and it has been challenging to know how much findings in one area of practice (e.g. cardiac rehabilitation) can generalise to other areas (e.g. musculoskeletal). A good theory will apply broadly, covering all types of rehabilitation and will give general principles so that the framework is universal. It should explain all existing observations, predict testable observations, and suggest new research avenues.

Scroll to Top

Subscribe to Blog

Enter your email address to receive an email each time a new blog post is published. 
Then press the black ‘Subscribe’ button.