THE DECLINE STEP-DOWN TEST MEASURING THE MAXIMUM PAIN-FREE FLEXION ANGLE: A RELIABLE AND VALID PERFORMANCE TEST IN PATIENTS WITH PATELLOFEMORAL PAIN

BACKGROUND & OBJECTIVES

Patellofemoral pain (PFP) is a common lower limb complaint that is currently measured and assessed via subjective pain scores and patient-related outcome measures. While these tests tell us about the experiences of the patient, they do not help us understand the underlying cause or contributing factors towards PFP. A classic aggravating factor for PFP is ascending or descending the stairs, along with everyday weight bearing activities like jogging, squatting or jumping. As forces are higher through the patellofemoral joint with descending stairs, this study aimed to validate a decline step test and the inter & intra-rater reliability of performing the test, to provide an objective measure that may also help understand limitations contributing to pain.

The use of this test can be layered upon existing measures for patellofemoral pain, such as pain scales or Patient Reported Outcome Measures, to add an objective measure of pain and function.

METHODS

The authors recruited 34 patients with a minimum 6-week history of “pain around and/or behind the patella” that was aggravated by stairs. Patients were excluded for any existing pathology or trauma to the knee. Using everyday equipment available in most clinics, they constructed a 20-degree decline step (see picture below from the study). Participants were asked to stand at the edge of the step, using fingertip support on the wall to aid balance, then instructed to perform a step down, pausing at the end of pain-free range, just before the onset of pain.

Using a previously validated app called “Dr Goniometer”, two observers independently photographed the position of the knee on an iPad, blinded to the goniometry results. A third, unblinded reviewer then recorded the knee angle. Each participant repeated the test 4 times with 10 minutes rest in between. Alongside this, participants completed a Patient Reported Outcome Measure (PROM) questionnaire, the Anterior Knee Pain Scale (AKPS), a 0-100 scale with 100 being pain-free.

RESULTS

Of the 32 participants, 16 of them had bilateral symptoms, so 48 knees were tested in total. Intra-class correlation demonstrated a near perfect result for reliability of intra-observer assessment. Likewise, inter-observer reliability was also excellent, with a standard error of

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