Proximal mechanics during stair ascent are more discriminate of females with patellofemoral pain than distal mechanics

Highlights

• Greater peak hip adduction and rearfoot eversion exist in patellofemoral pain during stair ascent.

• Hip adduction possesses the greatest capability to identify patellofemoral pain.

• Reduced hip adduction and reduced knee flexion are associated to avoid knee valgus collapse.

• Proximally targeted interventions may be most important in patellofemoral pain management.

Abstract

Background

Several hypotheses have been proposed to explain the pathomechanisms underlying patellofemoral pain (PFP). Concurrent evaluation of lower limb mechanics in the same PFP population is needed to determine which may be more important to target during rehabilitation. This study aimed to investigate possible differences in rearfoot eversion, hip adduction, and knee flexion during stair ascent; the relationship between these variables; and the discriminatory capability of each in identifying females with PFP.

Method

Thirty-six females with PFP and 31 asymptomatic controls underwent three-dimensional kinematic analyses during stair ascent. Between-group comparisons were made for peak rearfoot eversion, hip adduction, and knee flexion. Pearson's correlation coefficients were calculated to evaluate relationships among these parameters. Receiver operating characteristic curves were applied to identify the discriminatory capability of each.

Findings

Females with PFP ascended stairs with reduced peak knee flexion, greater peak hip adduction and peak rearfoot eversion. Peak hip adduction (> 10.6°; sensitivity = 67%, specificity = 77%) discriminated females with PFP more effectively than rearfoot eversion (> 5.0°; sensitivity = 58%, specificity = 67%). Reduced peak hip adduction was found to be associated with reduced peak knee flexion (r = 0.54, p = 0.002) in females with PFP.

Interpretation

These findings indicate that proximal, local, and distal kinematics should be considered in PFP management, but proximally targeted interventions may be most important. The relationship of reduced knee flexion with reduced hip adduction also indicates a possible compensatory strategy to reduce patellofemoral joint stress, and this may need to be addressed during rehabilitation.

Introduction

Patellofemoral pain (PFP) is defined as an idiopathic anterior knee pain and is a common condition presenting to orthopedic and sports medicine practices (Witvrouw et al., 2014). The estimated prevalence of PFP among females aged 18–35 years is 13% (Roush and Bay, 2012). Moreover, the prevalence of PFP in females is 2.23 times more than males (Boling et al., 2010). Key symptoms include peri- and retro-patellar pain, but etiology remains debated with many biomechanical alterations reported in the literature (Lankhorst et al., 2013), highlighting the multifactorial nature of PFP. The consensus statement from the most recent international PFP retreat led by area experts grouped possible biomechanical factors into 3 mechanistic categories: proximal, distal, and local factors (Witvrouw et al., 2014).

The source of symptoms in PFP is highly debated and remains unclear (Witvrouw et al., 2014), although increased patellofemoral joint (PFJ) stress is frequently identified in people with PFP (Brechter and Powers, 2002, Heino Brechter and Powers, 2002). Several theoretical hypotheses have been proposed in an attempt to explain the pathomechanisms underlying PFP development (Barton et al., 2012). Distally, excessive rearfoot eversion is thought to lead to greater PFJ stress due to joint coupling more proximally (Powers, 2003, Tiberio, 1987). Specifically, during the stance phase of gait, an everted rearfoot may result in excessive internal rotation of the tibia due to joint coupling. Consequently, greater hip internal rotation and subsequent hip adduction may result to maintain normal sagittal plane mechanics of the knee, thereby increasing PFJ stress (Tiberio, 1987).

Proximally, weakness or delayed onset of hip abductor and hip external rotator muscles is thought to potentially contribute to excessive hip adduction during weight-bearing activities in individuals with PFP (Powers, 2003, Robinson, 2007). Importantly, greater hip adduction during running in females has been reported to be a risk factor for PFP development (Noehren et al., 2013). McKenzie et al., 2010 previously reported greater hip adduction during stair ascent and descent in individuals with PFP. However, distal mechanics were not evaluated, which could play an important role in the altered hip mechanics observed (Tiberio, 1987). Additionally, we recently reported greater rearfoot eversion range of motion during stair ascent in a cohort of females with PFP but did not evaluate peak ankles which are more commonly considered in clinical practice. Additionally, we did not concurrently evaluate hip kinematics (De Oliveira Silva et al., 2015a). Concurrent evaluation of proximal and distal mechanics during stair ascent in the same PFP population is needed to determine which may be more important to target during rehabilitation (Barton et al., 2009).

An important consideration when interpreting findings from cross-sectional research evaluating kinematics in individuals with PFP is the likely presence of kinesiophobia or fear of movement which may develop to limit stress on the PFJ (Domenech et al., 2013). In regard to stair ascent, which patients with PFP commonly report pain with, Crossley et al., 2004 reported reduced peak knee flexion in individuals with PFP. This compensatory strategy may reduce PFJ stress due to sagittal plane joint loading but may also alter frontal plane kinematics such as hip adduction and rearfoot eversion (Crossley et al., 2004).

To the best of our knowledge there is no study that has investigated distal (excessive rearfoot eversion) and proximal (increased hip adduction) kinematics alongside a well-known local kinematic protection mechanism (reduced knee flexion) in individuals with PFP during stair ascent. Furthermore, previous studies evaluating these variables separately have only reported between-group differences for peak hip adduction and rearfoot eversion, without any attempt to identify their ability to discriminate or identify individuals with PFP.

This study aimed to investigate (i) possible differences in peak rearfoot eversion, hip adduction, and knee flexion during stair ascent; (ii) the relationship between these variables; and (iii) the discriminatory capability of each in identifying individuals with PFP. It was hypothesized that compared to controls, those with PFP will demonstrate greater rearfoot eversion, hip adduction, and decreased knee flexion. It was also hypothesized that the hip will discriminate those with PFP better than local and distal factors evaluated.