Research
Diagnosis & Imaging
October 28, 2024
Hip Strength and Patient Outcomes in Longstanding Hip and Groin Pain
Introduction
It is recommended to prescribe exercise interventions in people with longstanding hip and groin pain. Although exercise can produce meaningful changes when specifically targeted at modifiable physical factors such as strength, range of motion, and movement patterns, we currently need to learn exactly how this works. This study examined how hip strength and patient outcomes are related. The purpose of the study was to provide understanding on how this patient group’s reported symptoms, pain, everyday activities, and general quality of life might be impacted by stronger hip muscles.
Methods
Participants with longstanding hip and groin pain were consecutively recruited from an orthopedic care setting. Both patients with unilateral or bilateral hip and groin pain for more than three months were eligible. The key exclusion criteria included severe osteoarthritis, hernia inguinalis, or other musculoskeletal disorders.
Hip functioning and quality of life was assessed using the Copenhagen Hip and Groin Outcome Score (HAGOS). The questionnaire includes six subscales in which scores range from 0 (worst) to 100 (best).
- Symptoms,
- Pain,
- Activities of Daily Living (ADL),
- Physical Function in Sports and Recreation (Sport/Rec),
- Participation in Physical Activities (PA),
- Quality of Life (QoL).
Isometric muscle strength in hip adduction and extension was evaluated using a hand-held dynamometer which was fixed using a belt. Strength was measured in Newton and normalized to body weight (Nm/kg). The following testing protocols were used:
- Hip Adduction: The patient was in a supine position with the contralateral foot on the table. The dynamometer was positioned 0.1 centimeters proximal to the medial malleolus. The patient was instructed to push maximally for 3-5 seconds while verbal encouragement was provided.
- Hip Extension: The patient lay prone, and the dynamometer was placed on the posterior aspect of the leg, 10 centimeters proximal to the medial malleolus. The pelvis was stabilized using a belt during the test. Maximum force from three repetitions was recorded for analysis.
Results
A total of 81 patients (40 women, 41 men) aged between 18 and 55 were included. Hip-related intra-articular pain or extra-articular pain was diagnosed using clinical criteria. Of the 81 included participants, 33 had hip-related pain, 37 had extra-articular pain, and 11 were not categorized due to missing data.
Patients indicated that their hip and groin pain mostly affected their physical activity and quality of life.
The mean hip adductor strength was 1.58Nm/kg and the mean extension hip strength was 2.08Nm/kg. The analysis found that greater hip adductor strength was associated with better HAGOS scores in the subscales pain and ADL. Greater hip extension strength was associated with better HAGOS symptoms, pain, and ADL outcomes.
Questions and thoughts
The choice for hip adduction and extension strength measurements were twofold. First, hip extension strength stabilizes the hip joint during the push-off phase of activities such as jogging, stair climbing, and squatting, while hip adduction strength stabilizes the hip joint and pelvis in the frontal plane, which is essential for side movements like cutting and changing direction. These functions are necessary for daily functioning and sports and recreation activities. Secondly, in a previous study on the same study cohort, no differences were seen in hip adduction and extension strength outcomes between people with intra- and extra-articular hip pathologies as included in the current trial. This makes comparison between two different causes of hip pain possible.
This study gives an important understanding of how physical impairments and patient-reported outcomes are related in people with longstanding hip and groin pain. This study distinguishes itself from others since a heterogeneous population of patients was studied, including both people with intra- and extra-articular causes of hip and groin pain. Previous studies have mostly included a very specific population or studied participants who were already scheduled for surgery or were in the post-operative phase. By including a heterogeneous population of regularly active people who are not (already) waitlisted for surgery, this study provides interesting insights in a population that may frequently present to physiotherapy practice. The results are therefore quite transferable to patients you may encounter. Important to note is that these people did not have moderate or severe hip osteoarthritis.
The authors indicate that a 37% increase in hip extension strength may increase the HAGOS subscale for pain by 10 points, which is within the minimum clinically meaningful change. Assessing hip strength and patient outcomes at baseline and targeting these physical impairments throughout rehabilitation may be an important driver for successful outcomes in physiotherapy.
Talk nerdy to me
Linear regression was used to analyze the association between hip muscle strength (adduction and extension) and the HAGOS subscales. Covariates such as sex, age, BMI, and activity level were included in the analysis to control for their potential impact on outcomes. While the non-adjusted model found associations between hip strength and patient outcomes, the adjusted model found none. This means that when the analyses are adjusted for sex, age, BMI, and activity level, no associations between hip strength and patient outcomes were found. It may indicate that sex, age, BMI, and activity levels of patients have an important influence on patient-reported outcomes. The duration of peoples’ complaints was not considered in this analysis.
Since a cross-sectional design was used, these associations were measured only at 1 specific point in time. No causal inferences can be drawn from such analyses, meaning that we can not exactly understand the mechanism behind the findings that exercise and strength training can reduce pain in this population.
Limitations of the study include an important 10% missing data regarding the categorization of peoples’ hip pain source.
Take home messages
More hip strength in adduction and extension was linked to less self-reported symptoms, reduced pain, and improved ADL function in recreationally active patients with longstanding hip and groin pain. Exercise programs in people with longstanding hip and groin pain who are affected by high symptomatology, pain, and high impact on daily functioning can be directed at improving hip adductor and extensor strength.
Reference
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