The traditional biomedical perspective is problematic for at least three reasons. First, its proponents often inaccurately endorse a linear relationship between noxious stimuli and pain, while it is established that the relationship is highly variable.16,17 Second, it is reductionistic, as it inaccurately assumes that “some underlying pathology is both a necessary and sufficient cause of the symptoms experienced.”18 This minimizes the role of psychological and environmental factors. Third, it is often dualistic: pain is considered either somatic or psychogenic.18,19 When there is no objective evidence that the source of the pain is in the patient's body, the conclusion is that the pain experience must be in the patient's mind.19 The pain experience is then deemed less real, and patients are often stigmatized as a result.20,21 The biomedical view is anchored in an outdated view of pain that does not align with our current understanding that pain is both a sensory and emotional experience,22 and always influenced by biological, psychological, and social factors.

Most persistent and disabling non-traumatic musculoskeletal pain disorders (e.g., chronic low back pain) cannot be explained by pathoanatomical processes alone. This has prompted the development of classifications that appreciate chronic pain as a condition in its own right, rather than a symptom of another underlying condition.23,24 Chronic pain is a multidimensional and multicausal condition5,25–28 and the many potential factors involved are time and context-sensitive, interacting with each other in a nonlinear fashion.29

The biomedical perspective misses the fact that psychosocial factors are important contributors to pain intensity and disability.30–32 Paradoxically, exposure to health care can sometimes have harmful consequences.33–36 Care that is inconsistent with evidence-based recommendations, for example, suggesting to avoid activity to prevent (further) damage to the body, can reinforce beliefs and behaviors which may further contribute to pain and disability.37–42 Communicating that interventions “protect” the damaged body part or “correct” inadequate movement patterns can unintentionally reinforce patients’ fear-avoidance and guarding behaviors.8,40,43 These messages are more likely to come from clinicians who adhere to a biomedical understanding of pain, believing that pain signals the presence of a damaged body part that needs to be investigated, healed, or fixed.37,38,41,44 While tissue damage and pathology can be an important contributor to pain, it is only one piece of the puzzle that we have historically overemphasized in people living with chronic pain.17

Engel proposed his BPS model in 1977 to promote a broader, more humanistic perspective of healthcare by acknowledging psychological and social, in addition to biological, influences on health.45 It later became the conceptual basis for the widely adopted International Classification of Functioning, Disability and Health.46 The BPS model allows for recognition that musculoskeletal pain and disability are entwined with personal and cultural beliefs and inseparable from the social and economic context of people's lives.47 It warrants a multidimensional assessment and management of musculoskeletal pain and is now widely recommended as the best approach for musculoskeletal pain management.47–52 The model was an attempt to avoid the reductionism and dualism of the biomedical view. In principle, there should be no division between its three elements, for it's their combination and interaction, rather than the factors alone, that predict pain-related clinical outcomes.53

In practice, however, the BPS approach is rarely applied in the manner that Engel intended.54,55 The main reason for its misapplication is that the model lacks theoretical depth – it postulates but does not provide a developed account of the dynamic interdependence between the three domains.55 In educational and clinical settings, domains are approached separately, and the approach falls back to a primary focus on the biological factors and “objective” elements such as tissue damage, physical function, or biomarkers.56–58 It often remains unclear for the clinician how different forms of assessment relate to the patient's lived experience, unique concerns, and subjective experience of pain.55,59 In practice, therefore, the BPS approach has had limited theoretical efficacy to educate and influence clinicians about the complexities of pain.60,61

Another source of misapplication is ‘neuromania’.55,62 A recent critical review shows that the BPS approach to low back pain is frequently identified with a biomedical neuro- or brain-centric understanding of pain, with the individual pain experience reduced to a response of the nervous system.58 To this reduction, patients may react by “believing that they are being told ‘the pain is all in your head’, which is a common pitfall of this approach.”63

The review also indicates that psychological aspects are only narrowly defined and often fused with social aspects, if the latter are not entirely absent from BPS-based approaches. Pain is usually defined as an individual issue attributed to their beliefs, attitudes, behaviors, or mood. It is rarely deemed “social”, that is, contextualized within the broader social environment in which someone is situated.58 In clinical practice, psychological and social domains are often ignored, overly simplified, confused, or ‘referred away’ to other healthcare professionals.64

Because the interrelationship of the domains is not specified and understood, applications of the biopsychosocial model may “chop the patient into three neat packages.”65 Lacking a sufficiently developed theoretical base, the BPS model cannot resist being assimilated into the dominant paradigm and ends up being practiced in a reductionist, fragmented, and linear manner.14 The pain experience is inappropriately considered separable into distinct parts while the involved factors are seen as only linearly connected. We believe that an ecological-enactive framing of musculoskeletal pain and (dys)function can enrich and complement the BPS model toward an approach where biological, psychological, and social factors are considered dynamic and interdependent, as Engel intended.45

Affordances are opportunities for action (good or bad) that the environment offers an organism.67 For example, the sit-ability of a chair or climb-ability of stairs (Fig. 1)68 are typical affordances for adult humans due to their particular body shape (e.g., anatomical leg length), function (e.g., hip and knee flexion/extension), and sociocultural practices (e.g., convention to sit on chairs during meetings and climb stairs to enter buildings). The total set of affordances available to the members of a certain species or social group depends on their abilities and practices and the niche they live in.69–71

Fig. 1.

Affordances are opportunities for action that are specific to an individual's capabilities (from Vaz et al., 2017,68 reproduced with permission).

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Action opportunities available to a particular individual in a particular situation not only depend on species-specific characteristics and sociocultural norms but are further shaped by the individual's abilities, personal history, long-term goals, and present preferences and concerns, including the current physical condition and experience of the body.69–73 The dynamic set of action opportunities constitute what is called a field of affordances that is personally unique. In the field, some action possibilities may seem positive or attractive because of personal needs or desires,72,74 others may be viewed as negative and thus avoided. For example, lying on a bed may appear attractive to someone who is tired as it affords resting. When an individual is weighed down or fatigued, hills appear steeper75,76 and therefore less climbable if one wants to preserve energy. Different situations might call out for different actions, and different people might be responsive to different aspects of a situation, shaping the particular decisions they make.

There are three main implications of these theoretical concepts. First, individuals do not perceive the world from a detached and neutral standpoint; rather, they are related and attuned to the world from a unique and personal point of view. Second, under optimal conditions, the diversity of action opportunities within the field of affordances allows individuals to flexibly adapt to the world in ways that are sensitive to their particular abilities, concerns, and circumstances. Finally, the field of affordances is dynamic and ever-changing as it emerges from the complex interplay of multiple idiosyncratic causal elements.

In an ecological-enactive approach, pain is understood in terms of a person's perceived action possibilities (affordances) in their active engagement with their environment.15 In chronic pain, people tend to experience themselves as trapped in a closed-off or hostile world: their field of affordances fundamentally changes and shrinks in terms of attractive and meaningful action opportunities. For example, the action possibilities of sitting on a chair or climbing stairs may change to be perceived as dangerous or unavailable for a person with severe back pain. Pain can also dilate subjective time77 and distance perception78 and alter subjective space to include “less room” and more restricted bodily motion.79

In chronic pain, the body becomes an obstacle, everyday tasks are harder, and it can become impossible to see how one can engage in certain actions now or in the future.15 People can develop patterns where they stop believing in their bodily abilities, leading to a reduction in activity. They become “stuck” perceiving themselves and their environment in ways that may no longer be adaptive. This can become extremely frustrating to affected individuals as they often feel that others do not fully understand their experience or appreciate why they are acting in the ways they are (e.g., avoiding particular movements or tasks).

Frameworks grounded in ecological and enactive theory often make use of a family of concepts starting with “E”, focusing for present purposes on embodiment, embeddedness, and enaction. Understanding these concepts helps further unpack the affordance-based approach to pain.

First, experience is embodied. We experience ourselves and our world with, through, and because of our bodies.80,81 The body has a “dual” or “double” status: we (1) experience our body subjectively and (2) objectively have a physical body.82,83 For example, we may experience our back from a private perspective as painful, while we also have a physical back that can be examined by others (e.g., physical therapist) and determined to be injured (or not). These two aspects of the body can become somewhat incongruent. For instance, a clinician's physical assessment of a patient's body may lead to the impression that the patient should be perfectly capable of engaging in a variety of actions. However, the patient's lived experience of their body may frame these actions, from their personal perspective, as impossible or something to be avoided: their field of affordances is restricted. This lived experience cannot be directly seen or observed by other people. However, as we unpack later, others (e.g., clinicians) can influence (intentionally or unintentionally) people's lived experience of their bodies and perceived action opportunities for better or worse.

Second, experience is embedded, that is, we are always situated in a physical and social environment that enables or constrains the types of experiences we have. To paraphrase a remarkable insight about ecological science, to consider embeddedness is to “ask not what's inside the patient's body (or brain), but what the body (and brain) is inside of”.84 How does the patient's environment shape their experience of pain? Embeddedness is a central element of affordance-based frameworks as affordances are essentially relational; the perception and actualization of action opportunities depend on an organism's characteristics in relation to the environment's features.85 Together, embodiment and embeddedness highlight a bi-directional relation between person and environment mediated by the body. Much empirical work substantiates the relational nature of pain and pain-related disability,14,15,86,87 including findings that messages of threat and danger, often conveyed by clinicians,40,88 can amplify pain intensity89 and lead to avoidance of activities (restricting the field of affordances) due to the patient's fear of (re)injury.90,91

Third, experience is enacted. Building on the previous Es, enaction — as the name suggests — focuses on action. Experience is enacted or brought forth through action and perceived action possibilities.81 Enaction is a dynamic process between person and environment. Pain, therefore, cannot be understood in static terms or through an analysis of "root causes" isolated in the individual, let alone just their brain or other body parts.92 Pain is generated and maintained in the dynamic interaction of a person (with a body and brain) and their physical and social context. Chronification of pain is an active multicausal process that evolves as a person actively shapes and is shaped by their environment. In particular, activity and inactivity play a central role.

The ecological-enactive approach to pain complements the BPS model and adds to its theoretical foundation, helping mitigate implementation issues that derive from its frail conceptual basis. Specifically, the relational nature of affordances makes it impossible to only focus on one of the three domains (biological, psychological, or social) or to consider them in isolation from each other, because it is not possible to coherently use the concept of affordances without consideration of both the individual and their environmental context.85,93,94 Centralizing affordances in pain care theory and practice can provide safeguards against the fragmentation and the biomedical dualism and reductionism commonly seen in misapplications and misinterpretations of the BPS model.

Furthermore, embodiment, embeddedness, and enaction emphasize pain as the lived experience of acting in a dynamical relation to the environment. The 3 Es entail taking an ecosystemic view of the person and their physical/social environment (Fig. 2), as they place a fundamental emphasis on the fact that humans are always in a physical and social world, and that context and environment shape experience, meaning, and behavior.4

Fig. 2.

Moving from (a) the biopsychosocial Venn diagram, to (b) a schematic of a dynamic person (the inner circle represents the organism's internal dynamics) coupled (outer circle) to a changing environment (from Stilwell & Harman, 2019,14 reproduced with permission).

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Finally, conceptualizing pain as a multicausal and dynamic process of change of the field of affordances requires innovative ways to reason in face of uncertainty and the absence of “root causes” for chronic musculoskeletal pain. The ecological-enactive perspective calls for clinical reasoning tools to take non-linearity and context-sensitive causation into account.

Creating a meaningful connection with people suffering with pain is essential for the exploration of their narrative. Connection requires careful, considerate, and curious forms of communication to establish trust and acknowledge the person within their unique circumstances.95 It is widely recognized that people suffering with persistent pain are often stigmatized and marginalized20 and as such, the creation of safe spaces to establish a therapeutic relationship is of the utmost importance. It is particularly important to not be dismissive or judgmental of “unhelpful” beliefs that the person may express and instead explicitly validate their lived experience. Well-established methods such as motivational interviewing can help establish a partnership, allow a space for acceptance of the other, facilitate compassion, and evoke a rich narrative96,97 that brings into the open causally relevant information for their pain.29

Clinical reasoning strategies have historically favored a “third-person perspective”: the interpretation of the patient's situation is external to them, made by the clinician. For example, in hypothetico-deductive reasoning, clinicians generate hypotheses based upon signs, symptoms, and indices in an attempt to interpret the clinical presentation and formulate a diagnosis.98 Alternatively, in inductive reasoning the clinician evaluating patterns of presentations matches them onto their previous experiences and diagnostic categories built over time.98,99 In other approaches such as narrative, collaborative, and ethical reasoning98 an interactive perspective is used to interpret the person's lived experience: the clinician involves the patients as an active agent in the reasoning process. Taking an ecological-enactive approach to pain encourages a shift from the historically favored third-person perspectives to an interactive perspective. Reasoning together, clinician and patient can get a co-constructed picture of how action/inaction and perceived action (im)possibilities shape the experience of pain, its personal meaning and related behavior, with a shared understanding of the situation that would not be available to each (clinician and patient) on their own. New tools that allow both patient and clinician to get more comfortable with causal complexity and uncertainty can add significant support to this process.

One practical tool for interactive reasoning is the mind-map (Fig. 3). It brings together the results of the physical examination, the clinician's expertise, and the patient's context, history, needs, desires, and fears in a shared space.29 The contents of the mind map should be discussed openly with permission given to patients to adjust and change their elements. The shared mind-map can illuminate complex and circular causal connections between biological, psychological, and social factors that may be perpetuating the pain experience. It can clarify how action possibilities are being blocked and indicate potential points of entrance to open up the field of affordances. This interpretative map is adapted and modified as the experience of expanding action possibilities evolves over time.

Fig. 3.

Mind Map that brings together the results of the clinician's and patient's interactive reasoning, illuminating multiple causal loops among contributing factors. Asterisks indicate most easily changeable factors identified by therapist and patient; they are entry points to intervene in the loop. For simplicity, protective factors are not represented (please see them in the vector model in Fig. 4).

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Another practical tool useful to reconceptualize causes of pain and identify factors amenable to change is the vector model29 (Fig. 4). It can help both clinicians and patients overcome biomedical causal beliefs that have been found to be a barrier to recovery.100 For example, when patients believe in a linear causal relationship between activity and pain and therefore choose to restrict their activities, but continue to experience pain, frustration ensues. This often feeds a self-fulfilling cycle of negative emotion, despondency, frustration, and anger that adds to the pain experience.101 The vector model, derived collaboratively with the patient from the mind-map, helps clinicians and patients move away from the assumption of necessary and sufficient causes for pain as it promotes a dispositional perspective of causation.

Fig. 4.

Vector Model showing a set of potential causal influences that dispose toward or away from the generation of pain, summarizing the Mind Map and adding protective factors. The resultant vector conveys the concept of tendency instead of necessary and sufficient causes. The effect (pain and disability) is reached when a single or combination of dispositions exceeds a threshold as different causal powers may interrupt, counteract, or intervene. Asterisks indicate most easily changeable factors identified by therapist and patient.

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In dispositional theories, causes are interpreted as a cluster of powers, or dispositions, orientated toward an effect.102 For example, a glass has the disposition to shatter when struck. This disposition has to do with its possible shattering in certain conditions. Thus, the fact that the glass has been struck does not necessarily mean that it will break, because other causal powers may interrupt, counteract, or intervene. The effect (shattering) is only reached when a single or a combination of dispositions exceeds a threshold.

The vector model, therefore, provides a visualization of a whole set of potential causal influences that dispose towards or away from the generation of pain. It helps show that no single causal factor necessitates an effect on pain for all patients, rather, effects are context-dependent, dynamically interacting, and unique to each person (please see Fig. 4 captions for further details). Confidence and optimism can be increased by using the concept of tendency rather than the concept of necessity or inevitability (e.g., avoiding the idea of inevitable pain due to processes of ‘wear and tear’ in osteoarthritis).101Uncertainty can be reframed in a positive light: multicausality implies that there are multiple options to reduce apprehension and pain. This is an innovative tool to reason in face of uncertainty and the absence of single ‘root causes’ for chronic musculoskeletal pain.29

With a comprehensive viewpoint of a person's unique situation, an opportunity to facilitate a shared decision-making process can develop.103,104 Seeing the bigger picture, a (mind)map alongside the causal terrain for pain (vector model), the patient and clinician together evaluate not only the most relevant factors that appear to be significant drivers of the situation but also which may be felt to be modifiable or open to change.29 Interactive clinical reasoning aided by the mind map and the vector model allows for consideration of complex and dynamical causality while retaining and valuing the patient's narrative and lived experience, as originally intended by Engel's BPS model.

Based on this interactive investigation of the field of affordances and its causes, interventions will be chosen to create opportunities for patients to view and experience their body and world in positive ways, better adapting to their environments to reach their goals and aspirations.14,15,55 Adaptability and autonomy are key components to achieve pain self-management.105,106

First, embodiment is the means by which people interact with environments to perceive and enact possibilities to act. The lived experience of one's body and abilities are therefore determinants of the field of affordances. A very significant route for change is the active engagement of the body, affecting both actual and perceived abilities (self-efficacy) to function in life situations. Trust in the body's strength and adaptability can be enhanced with graded exercise. Exercise is a complex intervention with multiple potential biological and psychosocial benefits for chronic pain.108–111 Because evidence showing that one form of exercise is clearly better than another is not available for common musculoskeletal conditions, such as low back pain, patient preferences should be taken into account in deciding the type of exercise.47,110,112 However, because skill acquisition science disavows assuming that gains from traditional tissue-focused exercise generalize to functional activities,113 the addition of person-specific graded skill building (focused on patient-chosen challenging activities) is likely needed to help improve functional ability.68,114 Skill training can produce superior effects not only on function but also on pain when compared to strength and flexibility exercise.114

Another aspect of embodiment that should guide intervention choices is that behavioral flexibility and versatility should be fostered. Optimal variability of body movements and postures is linked to flexible, adaptive, healthy functional behavior,115,116 that is, to enacting a rich set of action opportunities. Therefore, a priori defined, idealized (biomechanically ‘correct’) or prototypical movement patterns or postures are not a reasonable expectation. ‘Incorrect’ spine posture during sitting, standing, and lifting can neither predict nor prevent low back pain and disability.117,118 ‘Correction’ or ‘normalization’ of movement patterns or postures, therefore, should not be a primary goal of intervention.68 Instead, ‘naturalization’– the adoption of varied and relaxed postures and ample, agile, and less protective movements – seems to be a better approach.117–119 Therapy should aim for individual- and context-dependent fluid movement solutions, enhanced by creative practice variability built into skill acquisition programs, allowing for personalized optimal solutions.68 ‘One-size-fits-all’ solutions cannot work; routes to improvement are highly individualized.117,119,120

Second, embeddedness directs attention to an often-neglected focus: psychological and social contextual factors can enable or constrain experiences.121 For physical therapists, the context of exercise prescription is of special importance because, on the one hand, for many musculoskeletal conditions no form of exercise seems to be superior to another47,110,112 and positive effects of exercise on pain and disability often do not seem to be attributable to any improvement in musculoskeletal impairments, muscle activity, or kinematic parameters.122–125 Rather, successful outcomes after exercise may relate to building a sense of mastery or control over challenges, renewed expectations and attributions, and increased self-efficacy,110 which can expand the field of affordances. On the other hand, the way exercise is prescribed can indeed constrain a patient's perceptions of action possibilities. When anatomical explanations, expressions like ‘degeneration’ and ‘wear and tear’, diagnostic labels such as spinal ‘muscle imbalance’, ‘weakness’, ‘instability’, ‘incorrect’ movement patterns or postures are used to explain the presence of pain and exercise recommendation, they may increase fear-avoidance.126 Note that this is not to say that impairments should not be addressed in therapy but to say that the contextual effects of impairment-targeted interventions should be considered.

More generally, embeddedness is antithetical to narrow, unidimensional tissue-based approaches, that are exclusively or primarily focused on musculoskeletal or brain tissue. Again, this is not to say that unidimensional or linear causal reasoning is never useful; it is certainly accurate and necessary to diagnose and treat acute injuries, for instance. However, given the complexity of chronic musculoskeletal pain, problematic neurocentric pain explanations such as ‘pain is in the brain’ and ‘retrain your brain’ may result in patient frustration, confusion, or perceived stigmatization as they believe they are being told ‘the pain is all in your head’.14,55,58 Reductive approaches that ignore embeddedness can trivialize non-reducible factors beyond the body such as social context and culture,127 neglecting the fact that situations can create a sense of threat or safety, worsening or dampening pain. Some therapeutic approaches may start from the question “what is inside this body/brain?” to define a treatment for pain, but ecological-enactive inspired therapy must also ask “what is this body/brain inside of?”.84 Therapy must therefore also aim to modify sources of threat and to create an environment where patients can freely express their concerns, be validated, and feel confident that they can move safely.55 Clinical messages and interventions need to move away from an impairment focus that perpetuates ‘body-as-(broken)-machine’ views toward an empowering participatory discourse and practice to promote richer involvement in life situations,128 enlarging the field of affordances.

Lastly, enaction puts strong emphasis on conceiving pain as an experiential process that depends on our active engagement with the world.14,15 Our primary perception (and understanding) of the world is and changes in terms of what we can do.67,85,107 One powerful route for patients to change their understanding of pain and perception of action possibilities is by means of experiential learning. Traditional educational approaches assume knowledge can be ‘transmitted’ from the knowledgeable (therapist) to the unknowledgeable (patient) with prescription and explication (lecturing) to ‘correct unhelpful beliefs’; ‘filling’ the patient with content to receive and memorize.129 In this model, learners are spectators, not (re)creators of knowledge.130,131 Experiential (learning by doing) approaches,132,133 however, assume that knowledge and skills cannot be isolated from active, first-hand experience.131To learn is to change what one can do, is to inhabit a richer field of affordances.134 Thus, guided active learning can be an effective means for patients to reduce the sense of threat and improve pain and activity limitation.120,122,124,125,135 Ultimately, through experiential learning, autonomy and self-management105,106 should be sought as an empowering culmination of an enactive-ecological approach to musculoskeletal pain care.55

Some current approaches like Cognitive Functional Therapy,8,136,137 or Cognition-Targeted Functional Exercise135 although not originally based on enactive-ecological theory, are multidimensional, person-centered interventions based on experiential learning. They foster positive experiences of safe completion of movement tasks that are functionally meaningful for the person but were previously perceived as dangerous or damaging. In consonance with favoring a functional focus for therapy,68 patients are encouraged to focus on achieving personally relevant lifestyle goals.7,136,138 Rather than being prescriptive, intervention is reflective: each individual is encouraged to find their unique strategies to respond to pain and perform valued activities with confidence and without hypervigilance. The new strategies are integrated into activities of daily living to generalize the learning and build self-efficacy, autonomy, and self-management.136,138 As action-oriented approaches that promote (re)learning of (new) action possibilities, these therapeutic interventions may work by enlarging the field of affordances. These conceptual tools may guide future research on the mechanisms and effects of different interventions and guide their refinement.