Central Sensitisation in Patients With Haemophilia and Degenerative Arthropathy

The Spanish version of the Central Sensitisation Inventory will be used to assess the presence of central sensitisation in patients. The first part of this inventory consists of 25 items that assess possible healthy symptoms. Each item is assessed using a 5-point Likert scale with a numerical hierarchy: Never (0), Rarely (1), Sometimes (2), Often (3) and Always (4). The second part assesses whether the patient has been diagnosed with any of a list of 10 disorders, including the year of diagnosis. The reliability of this inventory is very high (ICC: 0.82-0.97). The assessment of the first part of this tool ranges from 0 to 100 points, where the higher the score, the greater the clinical severity of the patients.

Fear of movement will be assessed using the Spanish version of the Tampa Scale of Kinesiophobia (TSK-11SV). This scale consists of 11 items, each of which can be scored from 1 to 4. This scale shows high reliability (ICC = 0.87). The score range on the scale is 11 to 44 points, with higher scores indicating greater fear of movement.

The catastrophising of the patients in the study will be measured using the validated Spanish version of the Pain Catastrophising Scale. This scale consists of 13 items, each of which can be scored from 0 to 4. This scale has demonstrated high reliability (ICC = 0.84). The scale ranges from 0 to 52 points, with higher scores indicating greater catastrophising.

The Pain Anxiety Symptoms Scale-20 (PASS-20) will be used to assess levels of anxiety related to pain. This scale has 20 items and measures anxiety and fear responses associated with the experience of chronic or recurrent pain. Each item is rated on a 5-point scale, from 0 (never) to 5 (always). It consists of four domains that measure cognitive anxiety responses, escape and avoidance, fearful thoughts, and physiological anxiety responses. This instrument has shown moderate reliability (CCI= 0.71).

Pressure pain threshold (PPT) at the forearm distal to the painful point will be measured using a handheld algometer with a 1 cm² probe applied perpendicularly to the previously identified site, increasing pressure at a constant rate (≈30 kPa/s or 1 kg/cm²/s) until the participant indicates the transition from pressure to pain; three measurements will be obtained and their mean will be calculated. Unit of measurement: N.

The visual analogue scale will be used to measure perceived joint pain intensity. The score for perceived pain ranges from 0 to 10 points, where 0 is the minimum (no pain) and 10 is the maximum (maximum pain).

Joint damage will be measured using the Haemophilia Joint Health Score (HJHS) tool. This scale is designed to identify joint degeneration in the elbows, knees and ankles in children, adolescents and adults with haemophilia. It consists of eight items: inflammation and its duration, pain, muscle atrophy and strength, crepitus, and loss of flexion and extension. This tool has good reliability (ICC > 70). Scores range from 0 to 20 points (maximum joint damage) per joint. To assess total joint damage, a gait assessment (range 0-4 points) is added, with a maximum score of 124 points.

The sociodemographic variable age will be measured in months completed from the patient's date of birth to the date of the assessment.

The sociodemographic variable marital status will be measured using 4 response options (qualitative variable): single / married / divorced / widowed.

The clinical variable type of haemophilia will be measured using a dichotomous qualitative variable with two response options: haemophilia A / haemophilia B.

The clinical variable severity of haemophilia will be measured using a qualitative variable with three response options: mild/moderate/severe.

The clinical variable development of inhibitors to clotting factor concentrates will be measured using a dichotomous qualitative variable with two response options: yes/no.