Patients will be questioned about their nighttime pain intensity using a visual analog scale (VAS). A 10-cm-long horizontal straight line is used for the VAS assessment. 0 is considered no pain, and 10 is considered the most severe pain. Nighttime pain intensity is measured as the average of the pain intensity experienced over the last 48 hours at each assessment. Nighttime pain is questioned as pain upon awakening from sleep or shoulder pain that awakens the patient from sleep.

Patients' shoulder-area pressure pain thresholds will be assessed using a manual pressure algometer (Baseline Dolorimeter®). Patients' pain perception thresholds will be measured at the midpoint of the bilateral trapezius muscle, the midpoint of the supraspinatus muscle, the midpoint of the deltoid muscle, and the midpoint of the volar aspect of both forearms. During measurement, the 1.52 cm2 flat circular probe of the algometer will be placed on the affected area, and the pressure will be increased at a rate of 1 kg/second. Patients will be asked to report the first time they experience pain. The value for each reference area will be obtained by calculating the arithmetic mean of the paired measurements.

Shoulder-related disability and activities of daily living will be assessed using the The Shoulder Pain and Disability Index (SPADI). The SPADI is a 13-item patient completed instrument. Its categories include "pain" (5 items) and "disability" (8 items), with the total score often described as a percentage, resulting from the summation of each component. Overall total scores range from 0 to 130 with a percentage score of 0 indicating less shoulder disability and 100 indicating more shoulder dysfunction.