The primary purpose of this study was to systematically review the literature for evidence of reliability and validity of functional performance tests used with a young, athletic population with hip dysfunction. The single-leg stance test, deep squat test, single-leg squat test, and SEBT demonstrated evidence of validity to be used in a population of patients with suspected hip dysfunction. The evidence for validity suggests that gluteal tendinopathy and function of the hip abductors may be assessed with the single-leg stance test,30
single-leg squat test,28,29
The deep squat test demonstrated evidence of validity as a functional performance test for evaluating patients with suspected FAI.27
Additionally, there were 20 tests that had evidence of reliability in healthy subjects with normative data provided to aide in score interpretation. Clinicians may use this normative data to identify impairments of patients with hip dysfunction that score outside the normal range of healthy subjects on the functional performance tests.
The authors of the current systematic review aimed to identify existing functional performance tests that demonstrated evidence for validity in a population of young, athletic patients with hip dysfunction. Only the single-leg stance test and deep squat test had evidence of validity in patients with confirmed hip dysfunction. The single-leg stance test was performed on subjects with greater than 4 months of lateral hip pain. Provocation of pain during 30-seconds of single leg stance had high sensitivity (100%) and specificity (97.3%) in detecting tendinopathy of the gluteus medius and minimus confirmed by magnetic resonance imaging (MRI).30
Based on the current evidence, the single-leg stance test has clinical value in ruling out other potential sources of lateral hip pain including lumbosacral, sacroiliac, or intra-articular pathology from gluteal tendinopathy, otherwise known as greater trochanteric pain syndrome (GTPS).30
The deep squat test was performed on subjects with radiologically confirmed FAI. The maximal squat depth in subjects with FAI (41% of leg length) was significantly less when compared to healthy controls (32% of leg length).27
Clinicians may test maximum squat depth in patients with suspected FAI to help confirm a diagnosis of FAI. Further studies are needed to determine how the single-leg stance and deep squat tests may compliment current clinical exam procedures to identify the presence of specific hip dysfunction.
While the single-leg stance and deep squat tests provided evidence of validity in subjects with hip dysfunction, the SEBT and single-leg squat test provided evidence of validity through an analysis of kinematics and muscle function in normal subjects. Three studies have related SEBT performance to kinematic and muscle function variables of the hip joint. Hip flexion range of motion was shown to explain a high percentage of variance (92–95%) in SEBT performance.32
Electromyographic study of the gluteus medius demonstrated the medial reach of the SEBT elicited the gluteus medius at 49% of maximal volitional isometric contraction.33
Hip abduction and extension strength also demonstrated a moderate correlation (r =.48 – .51) to posterior-medial and posterior-lateral reach distances of the SEBT.31
The moderate correlation implies that gluteal muscle strength only partially accounts for the variance of SEBT scores. The single-leg squat also demonstrated a relationship to hip abductor muscle function.29
However, the strength of this relationship has been disputed. DiMattia et al.28
reported poor association (r =.21) of the single-leg squat to hip abductor strength. The SEBT and the single-leg squat test have not been studied on a population of patients with hip dysfunction, but may have value to help clinicians screen for ROM and muscle strength impairments.28–33
ROM and strength deficits are commonly associated with hip pathology including FAI,34
A positive finding or asymmetry on the SEBT or single-leg squat test may lead the clinician to perform goniometry or dynamometry to further objectify ROM and strength deficits observed during the functional performance tests.
The reliability of a test is important to be able to confidently interpret the results. There were 2 movement, 4 balance, 11 hop/jump, and 3 agility tests with evidence of reliability in a young, healthy population. The Functional Movement Screen™ (FMS) is a series of seven individual movement tests that have been reliable in screening and evaluating athletes.37
Each test is graded on an ordinal scale based on the ability of the subject to perform specific motor functions.37
The FMS™ is designed to be a comprehensive cross section of functional movement and has been used to predict an athlete's risk for non-specific injury.38
The FMS™ is an intriguing tool for patients with varied hip dysfunction as it tests multiple movement patterns that require different components of hip ROM, strength, and trunk control. Such tests may elicit familiar symptoms or indicate impairments related to FAI, labral tears, osteoarthritis, or GTPS. Clinicians may use normative data established for the FMS™ as a guide to identify abnormal findings on the FMS™ for patients with hip-related dysfunction.37
Further study is needed to determine if the FMS™ is able to accurately predict hip-specific injuries.
Similar to the FMS™, hop/jump tests also demonstrated good to excellent reliability in normal subjects. Hop tests have also shown ability to discriminate injuredfrom uninjured lower extremities, particularly in the assessment of ankle instability and post-operatively following ACL reconstruction.39–42
Researchers have established normative, gender-specific values for hop tests19,43
in young, athletic subjects. These values may serve as benchmarks that may be helpful in interpreting an “abnormal” score for a subject with hip-related dysfunction. Field agility tests have demonstrated evidence of good reliability,19,43–45
but have not been able to discriminate injured versus uninjured limbs in the same manner as hop tests. This is likely because agility tests require bipedal movement. However, agility tests may have value in an athletic population as the tests may more closely mimic the dynamic requirements of sport activity. The reliability of hop/jump and agility tests measures have not been established on patients with hip dysfunction. It remains unclear how patients with hip dysfunction perform on these tests without further study. For patients with unilateral hip symptoms, hop tests may be used in comparison of the uninvolved side. Interpretation of agility test results is limited to a comparison of scores established on healthy subjects. Whether jump/hop tests or agility tests can be used to discriminate subjects with hip-related dysfunction remains unknown.
There are limitations of this systematic review that should be acknowledged. First, the authors established very specific inclusion/exclusion criteria for selection of functional performance tests included in this review. This included only exploring functional performance tests for a young and athletic population. Many tests were excluded because the studies were performed on elderly patients, or subjects with various neurologic or debilitating co-morbidities. Therefore, a number of articles that examined functional performance tests did not fit the inclusion criteria. It is possible some of these functionalperformance tests may have value in a population of subjects with musculoskeletal dysfunction. Given the volume of articles reviewed, it is also possible some functional performance tests were not identified. Significant variations in the descriptions of functional performance tests used by different authors were common. This may alter interpretation of the values attained for a specific functional performance test.
In conclusion, only the deep squat and single-leg stance test demonstrated evidence of validity in a population of patients with hip-related dysfunction. Specifically, diminished squat depth and provocation of pain during the single-leg balance test may be an indication for FAI and gluteal tendinopathy, respectively. The SEBT and single-leg squat test provided evidence of validity through an analysis of kinematics and muscle function in healthy subjects. There were 20 functional performance tests, including the FMS™, with evidence of reliability and normative data to help in score interpretation. None of the articles provided evidence of reliability in a group of subjects with hip-related dysfunction. Without established reliability for these functional performance tests it limits the ability of the clinician to confidently interpret test results and utilize the tests to measure patient progress. The results of the systematic review demonstrated few functional performance tests that have established validity and reliability to compliment traditional clinical exam procedures for patients with hip dysfunction. Further study is needed to establish the reliability and validity of existing functional performance tests or explore new, relevant functional performance tests to be used in a young, athletic population with hip dysfunction.