Lower-limb work during high- and low-impact activities in hip-related pain: Associations with sex and symptom severity

Highlights

• Symptomatic women have reduced ability to absorb energy at the knee.

• Sex had minimal effect on the relationship between work and hip-related pain burden.

• Hip-related pain burden was associated with work done at the hip-joint.

Abstract

Background:Hip-related pain (HRP) is described as a movement-related disorder. However, little attention is given to the way people with HRP move, especially in populations still participating in sport. Thus, limiting our understanding of movementbased impairments in HRP and their potential relationships with pain/symptoms.

Research Question: (1) What are the differences in absolute and relative amounts of positive and negative lower-limb joint work during walking and the single-leg drop jump (SLDJ) in football players with and without HRP? (2) What are the relationships between lower-limb joint work and HRP burden?

Methods:88 football players with HRP and 30 control football players were recruited. Positive and negative work done by the hip, knee, and ankle (and each joint’s relative contribution to total work done) were calculated. The effect of sex on the relationship between HRP and work done, as well as the association between work done and International Hip Outcome Tool (iHOT33) scores, were assessed using linear and beta regressions models.

Results:Walking: No joint work variables were significantly different between groups, nor were any relationships with iHOT33 scores evident. SLDJ: The knee’s relative contribution to total lower-limb negative work done was 37.7 % and 42.4 % for women with and without HRP, respectively (P = 0.04). The iHOT33 was significantly associated with positive (P = 0.03 to <0.01) and negative (P = 0.02 to <0.01) work done by the hip as well as negative work done by the ankle (P = 0.03 to 0.01), independent of sex.

Significance:Only one significant between-group comparison was revealed, involving the knee in female football players. In addition, football players with a greater selfreported burden of HRP tended to display lower hip joint work during the SLDJ. Rehabilitation programs could be targeted to address these impairments and normalize work done during high impact tasks in the management of HRP.

Introduction

Hip-related pain (HRP) is the second most common lower-limb musculoskeletal pain experienced by active adults [1] and is particularly burdensome, as it often affects people when they have high familial, societal, and employment responsibilities. It negatively impacts quality-of-life (QoL), physical activity, and work participation [2,3]. Hip-related pain describes non-arthritic hip pain and symptoms in young and middle-aged active adults [4] and encompasses three clinical classifications: (i) femoroacetabular impingement (FAI) syndrome; (ii) acetabular dysplasia and/or hip instability; and, (iii) HRP without distinct osseous morphology [4]. Irrespective of the classification, little attention has been given to the way these people move [5], limiting our understanding of movement-based impairments in HRP.

Previous studies investigating movement biomechanics in people with HRP have most commonly focused on FAI syndrome [6,7]. People with FAI syndrome have a reduced squat depth and lower peak hip extension angle during walking [7,8]. However, these studies have typically utilised small samples of individuals who have ceased sport participation and are seeking surgical intervention [7]. Thus, results may not apply to people with HRP who are still physically active [7]. Moreover, studies investigating groin pain in athletes have observed unique biomechanical profiles during high-impact tasks, such as cutting and hopping [[9], [10], [11], [12]]. These findings demonstrate the potential for athletes who are experiencing hip and/or groin symptoms, but are still participating in sport, to display altered movement biomechanics during high-impact tasks.

Our recent study of movement biomechanics in football players with and without HRP [13] revealed very few between-group differences in lower-limb joint angles and moments during walking and the single-leg drop jump (SLDJ). It is possible that impairments in lower-limb joint angles and moments may only become evident with more severe presentations of HRP [13]. Importantly, when differences were revealed, they were found to be sex-specific [13], highlighting the potential for the relationship between HRP and movement biomechanics to be modified by sex. As a result, previous findings from research utilising male-dominated HRP cohorts may not be applicable to women [8,14].

Other biomechanical metrics such as joint work might offer some additional insight into the functional impairments displayed by people with HRP. For example, people with hip osteoarthritis (OA) have been shown to have a reduction of up to 50 % in the positive and negative work done by the hip during the stance phase of walking compared to healthy controls [15]. It is therefore reasonable to suggest that lower-limb joint work might differ between football players with and without HRP pain during functional tasks. Moreover, as impairments in joint mechanics during functional tasks seem prominent in people with more severe presentations of HRP [13], associations may exist between lower-limb joint work and the burden of football players’ HRP.

The aims of this exploratory study were twofold: (1) to compare the absolute and relative amounts of positive and negative work done by the hip, knee, and ankle during two contrasting functional tasks (walking and SLDJ) in football players with and without HRP; and (2) to evaluate the relationship between the work done by the hip, knee, and ankle and the burden (severity) of HRP. We hypothesised that relative to walking the high impact nature of the SLDJ would amplify any between-group differences and reveal relationships between joint work and the burden of HRP.