Patellofemoral Pain Syndrome (PFPS) is a common knee condition causing pain on, around or behind the knee cap. The causes of PFPS are multiple and although there is no agreed consensus on best management, treatment usually involves conservative interventions such as muscle strengthening, stretching and taping.

Evaluating the effect of interventions is important and several disease specific patient reported outcome measures (PROMs) have been developed for this task. The question is – which are the most suitable? The aim of this paper was to investigate the measurement properties of these PROMS.

Here’s what they did

Following PRISMA guidelines the authors conducted a systematic review of studies evaluating at least one PROM measurement property such as reliability, validity, responsiveness or interpretability. To be included studies must have involved mainly participants with PFPS with symptoms provoked by at least two of the following: prolonged sitting or kneeling, stair walking, running, squatting, hopping, a positive Clarke’s sign or grind test, a positive patella compression test and recognisable painful symptoms on palpation of the patella facets.

Using the COSMIN tool the authors evaluated the methodological quality of the studies themselves to determine their trustworthiness. Then, the reported findings on measurement properties were synthesised across studies to determine the level of evidence for each PROM (“strong”, “moderate”, “limited” or “conflicting”) using the Cochrane Back Review groups criteria (van Tulder et al. 2003).

Here’s what they found

Only 7 out of 2177 publications identified were eligible for inclusion. The mean age of participants ranged from 23-32 years, only three studies reported average duration of symptoms and this ranged between 12 to 38.6 months. Twelve PROMS were evaluated: Activity of Daily Living Scale (ADLS); the Eng and Pierrynowski Questionnaire (EPQ), also known as the Visual Analogue Pain Scale during Activity; Flandry Questionnaire; Kujala/Anterior Knee Pain Scale (AKPS); Modified Functional Index Questionnaire (MFIQ); Persian Version Kujala/AKPS; Patellofemoral Function Scale (PFS); PFPS Severity Scale Syndrome (PSS); Visual Analogue Pain Scale (VAS), also referred to as the Numerical Pain Rating Score (NPRS); and the Visual Analogue Pain Scales for least pain (VAS-L), usual pain (VAS-U) and worst pain (VAS-W).

Using COSMIN, the authors found common methodological shortcomings within the studies such as: small sample sizes, absent a priori hypotheses, missing details/references for comparator instruments during the evaluation of responsiveness and a failure to check the uni-dimensionality of a scale prior to the evaluation of internal consistency.

On synthesis of the reported measurement properties they found ‘moderate’ level of evidence to support the construct validity (structural validity) of six PROMs:

• Flandry Questionnaire,
• AKPS,
• MFIQ,
• EPQ,
• VAS-U and
• VAS-W.

And ‘limited’ level of evidence supporting the reliability (test-retest) and validity (cross-cultural and hypothesis testing) of the Persian version of the AKPS. The authors reported that many other important PROM measurement properties were either evaluated with poor methodological quality (e.g. measurement error), or were not evaluated at all (e.g. interpretability).

The authors concluded

Unfortunately, no measure was able to satisfy all of the recently agreed minimum standards for PROMs advocated by the International society for Quality of Life research.

Current disease-specific outcome measures for Patellofemoral Pain Syndrome require further investigation.

The Musculoskeletal Elf’s view

The findings of this review echo an earlier blog on a study investigating the measurement properties of outcome measures for osteoarthritis of the knee.

There is increasing awareness of the need for good quality studies testing the measurement properties of existing PROMS.

What do you think?

• Have you used any of these outcome measures in your management of PFPS?

Send us your views on this blog and become part of the ever expanding Musculoskeletal Elf community. Post your comment below, or get in touch via social media (Facebook, Twitter, LinkedIn, Google+).

Links

• Green A, Liles C, Rushton A, Kyte DG, 2014, “Measurement properties of patient-reported outcome measures (PROMS) in Patellofemoral Pain Syndrome: A systematic review”, Manual Therapy, Vol.19, no.6, pp.517-526,
• Terwee CB, Mokkink LB, Knol DL, Ostelo RW, Bouter LM, de Vet HC. 2012, “Rating the methodological quality in systematic reviews of studies on measurement properties: a scoring system for the COSMIN checklist”, Quality of Life Research, Vol. 21, no.4, pp.651-7,
• van Tulder M, Furlan A, Bombardier C, Bouter L, 2003, “Updated method guidelines for systematic reviews in the Cochrane Collaboration back review group.” Spine, Vol.28, no.12, pp.1290-9