This study aimed to analyze the stratification of pain levels through a mathematical model built using the diffuse joint theory and to investigate the relationship between range of motion and pain related aspects.

The incidence of pain is due to traumatic actions, surgical interventions, new habits of life, increased longevity of the individuals and the reduction of the tolerance of the suffering by the man. Musculoskeletal pain is more evident in adult individuals, being the main cause of chronic pain throughout society, generating an impact on the quality of life, interfering in the daily activity of 30 to 50% of the patients. Pain measurement can be divided into four levels, which include the nominal, the ordinal, the interval and the ratio, with both one-dimensional and multidimensional versions. In the health area, diagnosis and treatment of diseases involve various levels of imprecision and uncertainties. A single disease or symptom may manifest totally differently in different patients and with varying degrees of severity. These effects usually generate many uncertainties and inaccuracies affecting the interpretations of the exams and the diagnosis, as well as the treatment. Fuzzy Systems Theory, also known as nebulous logic, is used to interpret the approximate mode of human reasoning, to take it to a numerical format and to obtain answers in an environment of uncertainties that serve as a subsidy to decision-making . A Fuzzy system based on Fuzzy logic. It can also be considered as a kind of expert, knowledge-based system. The development of the proposed Fuzzy Scale for Skeletal Muscle Pain Evaluation used the Mamdani method that allowed the representation of specialist knowledge (s) to construct the rule base. The construction of this system was based on the numerical scale of pain adopted and spread worldwide, and on the range of motion represented by the action of the muscles and articular components of the human body. The diffuse model proposed by the Fuzzy Scale for Muscle Skeletal Pain Evaluation uses 25 rules using binary XOR logic. For the volunteer tests, the proposed model was a non-randomized single intervention transverse study to analyze and compare the model of diffuse pain evaluation with the numerical pain scale performed with 535 volunteers.

Inclusion Criteria:

• Included in this study were male and female subjects
• Age between 18 and 90 years
• With complaint of skeletal muscle pain
• Do not present cognitive deficit that makes the study impossible

Exclusion Criteria:

• Individuals who did not agree to participate in the study
• Volunteers with decreased range of motion
• Volunteers without complaint of skeletal muscle pain

535 individuals with complaint of skeletal muscle pain