Age, weight, and duration of symptoms have been associated with an unfavourable response to treatment for plantar heel pain (PHP), but no studies were found that examined predictors of response to physical therapy intervention. The purpose of this investigation was to investigate the influence of age, body mass index (BMI), and symptom duration on treatment response to physical therapy intervention. Sixty participants received 6 visits over 4 weeks of physical therapy intervention that included manual therapy and exercise or electrophysiological agents and exercise. Outcomes were assessed using the Foot and Ankle Ability Measure (FAAM), Numeric Pain Rating Scale (NPRS), and Global Rating of Change Scale (GRC). Logistic regression (P < .05) was used to analyze age, BMI, and symptom duration as potential predictors of a successful response based on the minimal clinically important difference of the outcome measures. Sensitivity analysis was used to assess the influence of success based on minimal clinically important changes in the FAAM, NPRS, and GRC or only the FAAM and NPRS. Receiver operating curves were used to determine the cut point for the significant predictor. At the 6-month follow-up to physical therapy intervention, NPRS was improved by 3 points (95% CI, 2.4-3.6) and FAAM improved by 22.5 points (95% CI, 16.8-28.2). Individuals with symptoms less than 7.2 months were 4.2 (95% CI, 1.3-13.8; P = .016) and 8.5 (95% CI, 2.5-28.9; P = .001) times more likely to respond to treatment based on the NPRS/FAAM/GRC and NPRS/FAAM success criteria, respectively. Age and BMI were not significant predictors (P ≥ .455 and P ≥ .450, respectively).
Age and BMI were not found to be related to outcomes and obese individuals did achieve a successful outcome with the physical therapy intervention used in the clinical trial. Individuals with PHP symptoms longer than 7 months need additional consideration and further investigation of effective strategies to improve treatment response.