The majority of literature on decision processes within physiotherapy relates to what can be referred to as "reasoning that results in action"-cognitive processes that determine initial treatment and its modification after reassessment. Particularly expert clinicians also use "reasoning in interaction" including ongoing, interactive processes that occur during the application of treatments. The theory behind the approach discussed in this article can be stated as: If the extent of a deficit (pain or limitation of passive movement) is related to the extent of a patient's limitations (impairments or functional limitations), then 1) a change in the deficit would be expected to be accompanied by a change in the patient's limitations and 2) the relative magnitude of a change in the deficit would be expected to correspond with the relative magnitude of change in the patient's limitations. When applied to manual therapy interventions, the theory suggests that rather than all parameters of a treatment technique being predetermined , therapists continually adjust their treatment in real time. Adjustments are made in real-time to maximise improvement and are informed by patient response (typically changes in pain or range or stiffness of (passive) movement). Implications for other areas of practice and teaching are discussed.