The goal of this study is to determine the validity and reliability of the Turkish version of the Functional Disability Inventory (FDI), which assesses functional disability in daily life, school, and home activities of children aged 8 to 18, as well as to ensure cultural adaptation of this measurement. Chronic pain is the most frequent type of pain in children and adolescents, affecting one-quarter of the population. Children and adolescents with chronic pain have difficulty completing activities such as walking, jogging, and participating in sports, as well as daily activities. There is no valid and reliable measurement that measures pain-related disability in everyday life, at home, or at school from the perspective of a child in the literature. This study hypothesizes that the Functional Disability Inventory is a valid and reliable measurement for measuring functional disability in the Turkish population of children with chronic pain.

Chronic pain in children and adolescents is defined as pain that lasts longer than three months and is unabsorbable. Approximately 5% of the children said they were suffering from moderate to severe chronic pain, as well as impairments in their physical and psychosocial functions. Children and adolescents with chronic pain have difficulty completing activities such as walking, jogging, and participating in sports, as well as daily activities. Schoolchildren with chronic pain, for example, were shown to be five times more likely than their classmates without pain to miss school (13.9 percent vs. 2.4 percent), and it has been observed that absenteeism from school increases the likelihood of grade repeat in children with chronic pain.

Headaches affect between 57 and 82 percent of children and adolescents aged 7 to 15. It is wrong to believe that a headache with this frequency and associated concomitant conditions does not result in functional disability and limitations in everyday activities. When compared to their peers without headaches, 62 percent of children and adolescents with headaches reported more functional disability due to moderate to severe headache, limitation in daily activities, and absenteeism from school. Pain and functional incapacity caused by pain cannot be assumed to have no impact on a person's ability to participate in activities. The term "participation" refers to a person's involvement in the circumstances of his or her life. Participation in daily activities is critical for all children's healthy development, regardless of their age.

The fundamental goal of functional evaluation is to demonstrate a person's ability to function in society independently. This skill is employed in everyday activities such as personal care, social contact, housework, and recreational activities. The importance of these functions in daily life in pediatric patients, on the other hand, receives less emphasis (5). Walker and Greene (1991) developed the Functional Disability Inventory (FDI) to assess impairments in children and adolescents caused by a variety of pediatric health conditions (6). There are fifteen items in the FDI category. These tasks are used to assess how difficult it is for the youngster to walk, climb stairs, eat, do household chores, go to school, participate in sports, read and write, and watch television.

On a four-point Likert scale, (0=no issue, 4=impossible), each item is rated. With the child's own report, FDI assesses the difficulty in physical and psychological functions caused by the child's physical health. It is determined by taking into account the child's activity restrictions throughout the previous two weeks. The scale runs from 0 to 60. The total score is calculated by summing the individual item scores. A higher score indicates a higher level of disability. The purpose of this study is to see if the Turkish version of the Functional Disability Inventory (FDI) is valid and reliable in a Turkish sample of children with chronic pain.

Inclusion Criteria:

• Clinical diagnosis of chronic pain
• Age between 8-18 years
• Native language is Turkish

Exclusion Criteria:

- Diagnosis of autism spectrum disorder and attention deficit and hyperactivity disorder, psychotic symptoms, depression, etc.

Inclusion Criteria for control group:

• Not diagnosed of chronic pain and psychiatric and neurological disease
• Aged at 8-18 years old
• Native language is Turkish

Exclusion Criteria for control group:

• Children whose parents or themselves refused to participate
• Native language is not Turkish

children are diagnosed with chronic headache and their health peers

the results will be published in the journal