Overview[edit | edit source]
The S.I.N.S.S. model is an adaptation by Evidence In Motion of the original S.I.N.S. model described in Geoffrey Maitland's Vertebral Manipulation. There have also been numerous proposed adaptations to this evaluation model. SINSS is an abbreviation for Severity, Irritability, Nature, Stage, and Stability.
Model[edit | edit source]
The SINSS model is used by physical therapists to help reduce clinical reasoning errors. The SINSS model is used to assist the practitioner in understanding the patient’s symptoms. It aids in determining “the appropriate vigour and extent of a physical examination as well as treatment and intervention”. The use of the model begins at the subjective portion of the exam which established that the patient is receiving the appropriate extent of the objective examination for optimal diagnosis and optimal recovery, making sure not to over or under examine and/or treat. Utilizing SINSS maximizes the likelihood of better clinical outcomes. This benefits therapists by giving them an outline to help them keep their clinical assessments and ensuring that nothing is omitted.
Using the SINSS model as a method to improve examination and treatment is essential to the evaluation process. This model ensures that subjective data is identified and collected effectively using clinical reasoning skills to appropriately determine subjective questions and objective examinations. Once the data collection has occurred, the practitioner can then use that information as an outline for their examination, relying heavily on the beginning portion of the model to determine which tests should be used and when, in order not to aggravate the symptoms of the patient, which can later affect the exam findings.
Severity[edit | edit source]
Severity relates to the intensity of the condition including one’s subjective pain level. A crucial determinant in the way severity is measured is the extent to which the patient’s daily life is affected. The more severe one’s pain is the more their ADLs are affected. A patient’s perception of their pain can have a great impact on their recovery. To decipher the limitations that may come with one’s pain, it is best to have the patient measure their experience. This pain can be measured in a multitude of ways such as through the visual analogue scale. Using tools to help gauge the patient’s pain will help assist the clinician in objectively categorizing the patient’s symptoms. Assessing one’s severity further lends itself to assessing the patient’s prognosis and outcome which supports the therapist in their overall treatment of the patient.
Considering the patient’s severity includes determining the suitable vigor and extent used for the examination process. “Vigor refers to the amount of force or pressure applied during a test or measure or the intensity and complexity of an intervention. Extent refers to the depth of movement into resistance, the number of movements tested, and the magnitude of an examination or intervention technique.” 
Irritability[edit | edit source]
Irritability is the amount of vigorous activity it takes to aggravate the patient's symptoms. When the clinician is planning the evaluation and subsequent interventions, they should consider the amount of activity required to aggravate symptoms. This understanding helps the clinician provide the most effective treatment. The clinician should also consider the extent to which they challenge the patient. An important factor of irritability is tissue and functional reactivity. "Tissue reactivity" refers to the level of irritable response provoked by the clinician through a passive range of motion.
Tissue reactivity can be categorized in three ways:
1. Minimal tissue reactivity: The end range of motion is achieved with no pain; the patient may experience discomfort upon completion of the examination.
2. Moderate tissue reactivity: End range of motion is achieved with pain.
3. High tissue reactivity: End range of motion is not achieved due to pain; muscle guarding produces the end feel. 
Functional reactivity is gathered in the subjective information and is patient-determined. Functional reactivity is also categorized in three ways:
1. Minimal functional reactivity: the patient can perform a functional activity without experiencing any pain or limitations.
2. Moderate functional reactivity: the patient can perform a functional activity, but experiences pain and/or limitations.
3. High functional reactivity: the patient is unable to perform a functional activity due to pain and/or limitations.
Nature[edit | edit source]
Nature relates to the diagnosis of the patient and the symptoms of the diagnosis. Nature also includes the psychosocial aspect of the patient and how the symptoms of the diagnosis affect them mentally.
Stage[edit | edit source]
Stage refers to the stage of healing that the patient is in at the time of the evaluation. The values for the stage are acute, subacute, chronic, or overlap multiple stages. For example, a patient could be experiencing an acute phase of a chronic condition.
Symptom timelines: [edit | edit source]
- Acute: typically days-weeks (<3 weeks)
- Subacute: typically weeks (3-6 weeks)
- Chronic: typically weeks-months (>6 weeks)
- Acute stage of a chronic condition: recent exacerbation of symptoms of a condition that the patient has been experiencing for >6 weeks
- Subacute stage of a chronic condition: later stage of exacerbation of symptoms of a condition that the patient has been experiencing for >6 weeks.
Every patient does not necessarily experience every stage of healing. The clinician may need to take into consideration a settled phase that occurs after the subacute phase and before the chronic stage is reached. 
Stability[edit | edit source]
In the gathering of subjective information from the patient, the clinician can begin to determine the progression of the condition and if it has been improving, staying the same, or worsening.
Understanding the fragility of the tissues through other parts of the SINSS model helps the clinician determine where the intervention starts. For example, the consideration of the stages of healing when deciding to use palliative versus more corrective interventions.
Conclusion[edit | edit source]
There are multiple models of clinical reasoning. This presents a methodical approach that requires research to further understand its relativity to patient outcomes.
References[edit | edit source]
- Petersen EJ, Thurmond SM, Jensen GM. Severity, Irritability, Nature, Stage, and Stability (SINSS): A clinical perspective. Journal of Manual & Manipulative Therapy 2021;29:297-309.
- Paris SV, Loubert PV. Foundations of Clinical Orthopaedics. St Augustine: Institute of Physical Therapy 1999.
- Baker SE, Painter EE, Morgan BC, Kaus AL, Petersen EJ, Allen CS et al. Systematic Clinical Reasoning in Physical Therapy (SCRIPT): Tool for the Purposeful Practice of Clinical Reasoning in Orthopedic Manual Physical Therapy. Physical Therapy 2016;97.
- Koury MJ, Scarpelli E. A Manual Therapy Approach to Evaluation and Treatment of a Patient With a Chronic Lumbar Nerve Root Irritation. Physical Therapy 1994;74:548-560.