A Word of Caution for Future Studies in Patellofemoral Pain: A Systematic Review With Meta-analysis

Abstract

Background: Patellar maltracking is widely accepted as an underlying mechanism of patellofemoral pain. However, methodological differences in the literature hinder our ability to generate a universal quantitative definition of pathological patellofemoral kinematics (patellar maltracking) in patellofemoral pain, leaving us unable to determine the cause of patellofemoral pain. Purpose: To systematically review the literature to provide evidence regarding the influence of confounding variables on patellofemoral kinematics. Study Design: Systematic review and random effects meta-analysis of control-case studies. Methods: A literature search of case-control studies that evaluated patellofemoral kinematics at or near full extension and were written in English was conducted using Embase, PubMed, Scopus, and Web of Science up to September 2019. Cases were defined as patients with patellofemoral pain. Studies were eliminated if they lacked quantitative findings; had a primary aim to assess therapy efficacy; or included participants with osteoarthritis and/or previous trauma, pathology, or surgery. A quality assessment checklist was employed to evaluate each study. Meta-analyses were conducted to determine the influence of confounding variables on measures of patellofemoral kinematics. Results: Forty studies met the selection criteria, with quality scores ranging from 13% to 81%. Patient characteristics, data acquisition, and measurement methods were the primary sources of methodological variability. Active quadriceps significantly increased lateral shift (standardized mean difference [SMD]shift = 0.33; P = .0102) and lateral tilt (SMDtilt = 0.43; P = .006) maltracking. Individuals with pain secondary to dislocation had greater effect sizes for lateral maltracking than had those with isolated patellofemoral pain (ΔSMDshift = 0.71, P = .0071; ΔSMDtilt = 1.38, P = .0055). Conclusion: This review exposed large methodological variability across the literature, which not only hinders the generalization of results, but ultimately mitigates our understanding of the underlying mechanism of patellofemoral pain. Although our meta-analyses support the diagnostic value of maltracking in patellofemoral pain, the numerous distinct methods for measuring maltracking and the limited control for cofounding variables across the literature prohibit defining a single quantitative profile. Compliance with specific standards for anatomic and outcome measures must be addressed by the scientific and clinical community to establish methodological uniformity in this field.

The Importance of Medial Patellar Shape as a Risk Factor for Recurrent Patellar Dislocation in Adults

“…As such, it is crucial that future studies clearly define the axial plane used to measure LTI so that results can be directly compared across studies. The reduced trochlear width and depth, 5 patella alta, 6 lateralized patella, 15 and increased TT-TG 6,47 all agree with findings of past reports. Direct reporting of the medial and lateral trochlear length could not be found; however, our results agree with the increased patellar trochlear ratio previously reported.…”

“…5 Similarly, the measures of patellofemoral alignment (shift, tilt, and alta) agreed with those previously reported. 15 The novel measure of anterior patellar displacement needs further study. With a decrease in trochlear depth, a decreased anterior displacement was expected.…”

“…Patellofemoral displacement (PFD), patellar subluxation, and PTA were measured following the definitions noted as PFD* (patellofemoral displacement, measured using multiple images), LPD2* (2D lateral patellar displacement, using multiple images), and PTA2* (2D patellar tilt angle using multiple images) by Grant and colleagues. 15 Lateral was defined as the positive direction. The tibial tuberosity to trochlear groove (TT-TG) distance 5,10,45 was measured using the epicondylar image (Figure 1C) and the axial image containing the patellar tendon's caudal tibial insertion (Figure 1E).…”

The effects of different taping methods on patellofemoral alignment, pain and function in individuals with patellofemoral pain: A randomized controlled trial

“…It has also been suggested that patellar maltraction causes a high level of mechanical stress on the subchondral bone due to the altered patellofemoral contact, thereby resulting in pain. 3,4 In 2018, the iPFRN published a consensus document concerning PFP management that specified a hip-and knee-focused exercise regimen to be the approach with the highest level of evidence regarding its effectiveness. Moreover, applications such as patellar taping, manual therapy, and foot orthoses are recommended in addition to exercise, albeit not as standalone treatments.…”

Differences in Patellofemoral Alignment Between Static and Dynamic Extension Positions in Patients With Patellofemoral Pain

“…29,27 A meta-analysis demonstrated that the assessment of patellofemoral alignment together with quadriceps activation improves the ability to diagnose maltracking. 17 However, the type (dynamic or static) and intensity of muscle contraction varied among studies. Although several studies have compared the patellofemoral joint alignment in knee extension with and without quadriceps contraction, 5,18 most studies included analysis of the patellofemoral joint alignment without knee motion and with quadriceps isometric contraction.…”