The Functional Pain Scale is a Reliable Measure of Pain

Cropped shot of a female doctor showing result of radiography on digital tablet to patient and giving diagnosis. Doctor talking to patient about medical treatment after surgery.
The Functional Pain Scale is a reliable and consistent patient-reported measure of pain.

A prospective, observational, single-center, cohort study found that the Functional Pain Scale (FPS) was a reliable and consistent marker of pain. These findings were published in Cureus.

The FPS, in addition to quantifying self-reported pain, assesses additional components such as loss of function in daily activities, sleep habits, and communication.

Patients (N=49) undergoing hip or knee replacements at the Guthrie Clinic and Robert Packer Hospital in the United States were recruited for participation in this study. After surgery, patients were assessed for pain levels using the FPS (scale 0-10), Numerical Pain Scale (NPS; scale 0-10), and Wong-Baker FACEs (FACEs; 6 pictorial color-coded faces). The FACEs were converted to numerical scores in multiples of 2 in order to compare all pain instruments.

Patients were aged mean 65.8 (standard deviation [SD], 7.47) years, 57.1% were women, and the most common surgical procedures were total knee arthroplasty (32.7%) and total knee MAKOplasty (30.6%).

The median FPS was 4.00 (range, 1.00-9.00), NPS was 4.00 (range, 1.00-8.00), and FACEs was 4.00 (range, 2.00-8.00). The average NPS was significantly higher than FPS (4.53 vs 3.65; P <.05).

Reported scores were all positively correlated, in which FACEs and NPS were most highly correlated (r, 0.906; P <2.2´1016) followed by FPS with FACEs (r, 0.647; P =3.8´107) and FPS with NPS (r, 0.634; P =1.3´106).

Although the FPS evaluated more aspects of pain, it remains limited by not including a component on cognition. In addition, the study authors asserted that some of the language in the assessment may be difficult to understand for some patients, particularly those with cognitive difficulties. It also remains unclear whether the FPS may translate to other clinical areas, such as obstetrics, general surgery, or the inpatient setting.

These data indicated that the FPS was reliable for assessing pain among patients who recently underwent orthopedic surgery.


Adeboye A, Hart R, Senapathi SHV, Ali N, Holman L, Thomas HW. Assessment of Functional Pain Score by Comparing to Traditional Pain Scores. Cureus. 2021;13(8):e16847. doi:10.7759/cureus.16847