Is outcome observed in performance of clinical tests associated with patient-reported outcome measures after patellofemoral pain treatment? Secondary analysis of data from a randomized clinical trial

BACKGROUND: Clinical functional tests for patellofemoral pain (PFP), such as step-up, step-down and squat, are commonly used in clinic practice, although the extent to which changes in these tests reflect changes in patient-reported outcome measures (PROMs) remains unclear. OBJECTIVE: Investigate how changes in step-up, step-down, and squat tests are associated with changes in PROMs in individuals with PFP. METHODS: This secondary analysis used data from a randomized controlled trial (N = 218) comparing 12-week outcomes following either foot orthoses or 4-week hip exercise program. The number of pain-free repetitions in the functional tests of step-up, step-down and squat was assessed. PROMs included the Kujala, the Knee Injury and Osteoarthritis Outcome Scale (KOOS) subscales (Symptoms, Pain, Activities of Daily Living, Sporting and Recreation and Quality of Life (QoL), and the Global Rating of Change (GROC). Associations between change scores (differences between follow-up and baseline) in pain-free repetitions in the clinical functional tests and PROMs were analyzed using multivariate regression and binary logistic regression for dichotomized GROC (p < 0.05). RESULTS: Data was available for 157 participants. There was a positive association between change scores in functional tests and PROMs, with explained variances ranging from 11 to 30%. The step-up test was weakly to moderately associated with KOOS Symptoms, Pain, QoL and Sport/Recreation. Step-down was associated with Kujala and KOOS Sport/Recreation. The squat test was not associated with any PROM. CONCLUSIONS: Improvement in step-up test is associated with better PROMs. Clinicians might use the step-up test to monitor progress in individuals with PFP.