The disablement model is distinctly different from the classic medical model, where the emphasis is on treating the specific diagnosis with pharmacology or surgery. The disablement model emphasizes the functional and health status of individuals, with intervention based on improving these aspects of the patient’s condition. The model has four elements to it:

Pathology ↔ Impairment ↔ Functional limitation ↔ Disability

Pathology is the interruption of the normal cellular processes from a biomechanical, physiologic, or anatomic perspective. The body will often go on the defensive to restore the normal state. Examples of this include hemarthrosis, tumor, fracture, connective tissue damage (tear/stretch), diabetes, and rheumatoid arthritis. Intervention at this level is generally handled by physicians and is often pharmacologic and/or surgical in nature.

Impairment is any loss or abnormality of physiologic, psychological, or anatomic structure or function at the level of organs and body systems. Physical therapists typically measure the signs and symptoms and try to correct impairments. Examples of physiologic impairments would be muscle weakness, range-of-motion loss, pain, and abnormal joint play. Anatomic impairments would include genu recurvatum, scoliosis, femoral anteversion, and pes planus.

Functional limitation is a deviation from the normal behavior in performing tasks and activities that would be traditional or expected for the individual. These are tasks or activities that are not done in the usual efficient or proficient fashion. Problems with transfers, standing, walking, running, and climbing stairs are all examples of functional limitations.

Disability is the incapacity in performing a broad range of tasks and activities that are usually expected in specific social roles. Inability to function as a spouse, student, parent, or worker (in the home or outside of the home) constitutes a disability.

The disablement process represents a two-way continuum and is affected by intra-individual and extra-individual risk factors. Intra-individual factors include habits, lifestyle, behavior, psychosocial characteristics, age and sex, educational level and income, weight, and family history. Extra-individual factors are things like the medical care received, the pharmacologic and other therapies available, the physical environment, and any external supports. The relationship between these aspects will vary between individuals and will ultimately determine the impact of the disease or injury. We have all treated patients who suffered from significant impairments but were still extremely functional. We have also treated patients who were disabled by what seemed to be minor limitations. Unfortunately, there are few studies in the literature to show a direct cause-and-effect relationship between impairments and functional limitations/disabilities.

Physical therapists traditionally examine and intervene at the impairment and functional limitation levels. The patient who has weakness in the quadriceps and an inability to climb stairs will be managed with a strengthening program and activities that include stair climbing. This organization is the basis for the preferred practice patterns.

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