Hypothesis-Oriented Algorithm for Clinicians II (HOAC II)


The Hypothesis Orientated Algorithm for Clinicians (HOAC) – a method for evaluation and treatment planning - was first published in 1986[1].  In 2003 the algorithm was updated to be compatible with the contemporary physical therapy practice[2]. The update was termed the Hypothesis Orientated Algorithm for Clinicians II (HOAC II). The HOAC II offers a conceptual, patient-centred framework for physical therapists to use in the management of any type of patient[3]. It addresses the five elements of patient management: examination, evaluation, diagnosis, prognosis and intervention. Important for contemporary physical therapy, the HOAC II provides a means to engage in evidence-based practice and to differentiate between the types of evidence and science used[4]

Clinical Reasoning Using the HOAC

Much of the clinical reasoning language utilized below has been modified from the Hypothesis-Oriented Algorithm for Clinicians 2nd Edition (HOAC II)[5]


Pathobiological Mechanisms

  • mechanisms relating to tissues - tissues injured, nature of injury, stage of healingmechanisms relating to pain - input (nociceptive, neurogenic), processing (central, cognitive), output (motor, sympathetic).


Clinical manifestations of the pathobiological processes, these are the patients main problems at that time.

  • dysfunction - general physical dysfunction as described by the patient such as limitations in activity
    restriction in participation
  • impairment - specific impairments in body functions and structures identified on examination.

Patho-Anatomic Hypothesis

The actual anatomical location of the pathobiological mechanisms. What discrete anatomical structure is generating the primary complaint.

Contributing Factors

Any factor relating to the predisposition, development and maintenance of the problem

  • physical - previous injury, nerve root involvement, pain provoked by multiple trunk movemements, reduced muscle control, reduced physical fitness
  • Biomechanical
  • Psychosocial - yellow flags determine a patients potential to proceed to chronicity.
  • Environmental - Ergonomics, Stress, 
  • Emotional
  • Behavioural
  • Nutritional
  • Cultural

Biomechanical Contributions

There are 3 primary forces the human body must dissipate. The biomechanical nature of the condition helps the clinician to determine which of these forces may be the primary contributor to a patient's symptoms. For example: tension overload may be the primary biomechanical nature of a patient who is experiencing patellar tendonitis.

Mechanism of Injury (physical)

Biomechanically mediated injuries should be categorized according to the cause of their symtpoms in the following way:

  1. Microtraumatic
  2. Macrotraumatic
  3. Microtraumatic and Microtraumatic

Centrally Mediated (Central Nervous System) Contributions 

  • Central symptoms or dysfunction is a complex cause of symptoms, impairments, funcitonal limitations and/or disability.

Problem List

Patient Identified Problems (PIP)

These are the patient identified problem(s), either in a symptom AND/OR functional limitation/disability level.

Non Patient Identified Problems (NPIP)

This is essentially a problem list generated by the clinician. This is an ongoing process of evaluation as the subjective examination and physical examination is taking place.

Anticipated Problems

These are problems that if they are not addressed, will lead to PIPs or NPIPs in the future. This is based on the clinicians utilization of best practice as well as there own prognostic skills. For example, research has shown that those wiht a BMI ?25 kg/m2 have an increased likliehood of disc degeneration, notably if this develops at an early age.[6]


  • red flags - need referral on for appropriate medical intervention.
  • yellow flags - highlight the need for a more detailed psychosocial assessment.
  • SIN factor - severity, irritability, nature.

Stage of the Condition

The stage of the condition should closely follow the phases of healing. There is not a consistent language used across physical therapy literature on how to stage a condition. Some refer to symptoms lasting >6 weeks as chronic.

Acute: Early onset of symptoms. This patient is in the inflammatory phase of healing.

Subacute: The inflammatory phase of healing is subsiding and the patient should be in the reparative/proliferative phase of healing.

Chronic:This patient should have completed the maturation stage of healing; however, there may be intrinsic or extrinisc factors limiting the complete recovery of this patient

Acute on Chronic: This patient has reinitiated the inflammatority phase of healing, on a previous chronic condition that may or may not have completed the maturation phase of healing.


The irritiability also helps determine the vigorousness of your examination, the examination sequence and strategy, as well as the dosage of your intervention. The VAS (or audible pain scale of 0-10) is very helpful when determining the irritability. The average 24 hour VAS must be used in context. The presence or absence of pain at rest is helpful and over the course of the day. However, how easily pain is exacerbated and relieved may have just as much relevance.


This helps determine the vigorousness of the examination and the tactics of your intervention, notably the exact positions to avoid and dosage to control. Functional forms are primarily used to will help determine the severity of the condition. Pain scales (such as the VAS) may also be helpful in determining the severity, but these can be misleading at times as pain is a relative experience for each person. Therefore, how the symptoms affect function is a very helpful way to identify how severely this problem is affecting a persons function.

Positive Patient Behaviors

These are behaviors that may improve a patient's prognosis. Example: active participant in plan of care, internal locust of control, trusts therapists judgement/rapport, compliant, respects therapists schedule.

Negative Patient Behaviors

These are behaviors that may negatively affect a patient's prognosis. Example: fear avoider, kinesiophobia, passive participant in POC, non-compliant with recommendations, disrepect for therapists time, external locust of control

Phase of Healing

The phase of tissue healing is closely related to the prognosis of the patient.

Primary phases of healing include:

  1. Inflammatory phase
  2. Fibroblastic (Reparative or Proliferative) phase
  3. Maturation (Remodeling) phase
  4. Degenerative phase

Management and Intervention

Optimal management with a dynamic clinical working diagnosis should follow if all the above categories have been cosidered.

Strategy (of intervention)

There are basic strategies of physical therapy intervention that may be employed.

  1. Stretch
  2. Soft Tissue Mobilization (STM)
  3. Joint Mobilization (JM)
  4. Strengthening/Stabilization
  5. Re-training/Re-education
  6. Education
  7. Offloading
  8. Pain inhibition
  9. Modalities/Physical Agents


  • These are the detailed and specific elements of an intervention. Tactics specify the frequency, duration, and intensity of interventions.
  • In a direct access environment, the therapist decides the stategy and tactic(s) of the treatment, not the physician. In a non-direct access environment, the physician may at times request a specific strategy; however, they rarely dictate the tactics employed. Therefore, it is the therapists responsibility to prescribe and modify the tactics implemented. The strategy may be to strengthen, but the tactics will specificy: quadriceps eccentric load on single leg to maximimum tissue failure for 3 sets, 30 second rest between sets. 3 times per week.
  • The strategy to use ultrasound will need specific tactics to highlight the dosage. Example: 50% pulsed ultrasound, 1.0mhz, .5 w/cm^2, 8minutes, to insertion of extensor carpi radialis brevis, 1.5 ERA (effective radiating area).

Post Test (Testing Criteria)

  • These represent critical values that if attained, would suggest the hypothesis is correct and the associated problem/impairment are improving or has resolved.
  • Establishing valid post-test criteria is an important component of clinical reasoning as it helps to determine if the interventions are moving towards the goals.
  • This is different than goal setting as this is the specific testing employed to prove that your goals have been met, or that your goals are moving in a positive direction.
  • Example: You have a long term goal for a patient to have symmetrical quadriceps strength. Your post-test could look quite different.   EXAMPLE: hand-held maximum isometric strength in the 90 degree position of the knee VS. isokinetic strength throughout the entire range at a specific angular velocity to measure endurance over a 60 second period.

Slope of Recovery

It is key to monitor the patients slope of recovery. Understanding the patients slope of symptoms and functions assists with case management, prognosis, as well as the dosage of interventions. These slopes can be categorized below.

  1. Static
  2. Positive
  3. Negative
  4. Oscillating

Prognosis and Outcomes

To predict potential improvement identify positive and negative prognostic indicators. Consider age, occupation, hobbies, previous treatment response, stage and stability od condition, general health, past medical history, pain mechanisms.

Discharge Criteria

When is the patient ready for discharge? When does optimal care end to address all key NPIP and PIP. You must also consider anticipated problems and the need for re-admittance to physical therapy secondary to inadequate rehabilitation. All patients must of course be discharged. There are some patients that will be discharged prior to the recommended time frame secondary to monetary constraints. Please assume that there are no significant monetary restraints (but be reasonable) and focus on what criteria is in the best interest of the patient as you complete this section. Someone with severe degeneration will be discharged with different criteria than an acute injury. Often, the patient will be ready for discharge because they are back to functioning normally but you are not pleased with their protective mechanisms and HEP intensity. To prevent reinjury, your D/C criteria may be very specific. For instance, normalized core ratios with McGill testing.[7] Tolerating Core IV/V level exercises. Normal cervical ROM for a young neck. 110% of external rotation strength (per hand-held dynamometer) relative to the non-dominant throwing shoulder for a college pitcher. You may officially discharge this college pitcher 6—9 months after surgery. Consider the discharge criteria your absolute last patient encounter before they re-enter the general populace without limitations OR once they have reached their MMI (maximum medical improvement).

Outcomes Measures

Clinical Reasoning Forms

Clinical Reasoning - Post Subjective

Clinical Reasoning - Objective Planning

Clinical Reasoning - Post Objective

Recent Related Research (from Pubmed)


  1. Rothstein JM, Echternach JL. Hypothesis-Oriented Algorithm for Clinicians: a method for evaluation and treatment planning. 1986;66(9):1388-94
  2. Rothstein JM, Echternach JL, Riddle DL. The Hypothesis-Oriented Algorithm for Clinicians II (HOAC II): a guide for patient management. Phys Ther. 2003;83(5):455-70.
  3. Riddle DL, Rothstein JM, Echternach JL. Application of the HOAC II: an episode of care for a patient with low back pain. Phys Ther. 2003;83:471-85.
  4. Thoomes EJ, Schmitt MS. Practical use of the HOAC II for clinical decision making and subsequent therapeutic interventions in an elite athlete with low back pain. J Orthop Sports Phys Ther. 2011;41(2):108-17.
  5. Rothstein JM, Echternach JL, Riddle DL. The Hypothesis-Oriented Algorithm for Clinicians II (HOAC II): a guide for patient management. Physical Therapy. 2003;83(5):455. Available at: http://www.ncbi.nlm.nih.gov/pubmed/12718711
  6. Liuke M, Solovieva S, Lamminen A, et al. Disc degeneration of the lumbar spine in relation to overweight. International Journal of Obesity (2005). 2005;29(8):903-908. Available at: http://www.ncbi.nlm.nih.gov/pubmed/15917859.
  7. McGill SM, Childs a, Liebenson C. Endurance times for low back stabilization exercises: clinical targets for testing and training from a normal database. Archives of physical medicine and rehabilitation. 1999;80(8):941-4. Available at: http://www.ncbi.nlm.nih.gov/pubmed/10453772.