Introduction
Hip or groin pain with discomfort is a frequent clinical manifestation associated with hip joint disorders. While sports injuries and musculoskeletal, or systemic, pathological conditions are considered common causes of hip pain, clinical studies have identified that mechanical hip labral tears and associated disorders are increasingly contributing to hip pathology in recent years.
These pathologies involving the hip labrum often go unnoticed or evade existing diagnostic methods, which becomes a considerable challenge for effective therapeutic interventions. Also, the clinical accuracy of labral tear detection tests needs to be better defined. The McCarthy test is a reliable physical assessment test for evaluating labral pathologies associated with the hip joint. This article explores the McCarthy test's indications, basic techniques, and benefits of the McCarthy test for hip labral disorders.
What Is McCarthy Test?
The McCarthy test is a clinical orthopedic physical examination to detect or assess hip joint problems such as hip labral tears and hip impingement. The prime purpose of the test is to see any tear or defect in the acetabular labrum by reproducing pain, provoking a click sound, or both during the physical evaluation.
Anatomical Relevance
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The acetabulofemoral joint, also known as the hip joint, is the most stable and the largest in humans.
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It belongs to the ball and socket type of joint, where the head (ball-shaped) of the femur (thigh bone) articulates with the acetabulum (cup-shaped cavity on the outer side of the hip bone).
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A soft connective tissue structure lines the rim of the acetabulum called the acetabular labrum. This labrum plays a crucial role in articulating the hip joint by providing lubrication, maintaining intra-articular (inside the joint) fluid pressure, and distributing the load.
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The seal of the labrum also ensures the stability of the hip joint. Also, several ligaments surround the hip joint to maintain intact articulation.
Clinical Relevance
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Structurally, few cadaveric studies have proved that acetabular labrum does not show age-related degeneration.
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Interestingly, clinical labral problems are reported more in younger populations, commonly manifested as groin pain triggered during flexion activities like squatting or driving.
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In some cases, a click sound accompanies specific hip movements.
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Some individuals also experience lumbar pain or pain at the back of the hip, which often starts during load-bearing activities or impact.
What Are the Indications of the McCarthy Test?
The McCarthy test helps detect mechanical injuries and risk factors associated with hip labral pathologies. Some of the primary indications for the McCarthy test are as follows -
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Hip Impingement - It is also referred to as femoroacetabular impingement (FAI). As the name suggests, it occurs when the femoral head compresses the acetabulum, eventually leading to labral damage.
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Hip Labral Tear - This occurs when the labrum tissue surrounding the ball and socket hip joint gets injured.
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Mechanical Injuries - Direct traumatic impacts such as falling or slipping involving hip joints, motor vehicle accidents, and hip dislocation lead to labral tears.
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Extreme Physical Activities - Sporting activities involving persistent lateral rotation (external movement) like ballet, running, sprinting, golf, soccer, and hockey cause a labral tear or hip impingement.
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Twisting movements involving torsion, hyperextension (with or without lateral rotation), and hyperabduction led to acetabular defects.
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Clinical Manifestations - Pain in the groin region, stiffness in the hip joint, and limping are commonly seen in acetabular tears or impingement.
How Is McCarthy Test Performed?
The techniques involved in conducting McCarthy Test are as follows -
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Position of the Patient - The individual should be supine, lying on a flat surface with their head supported, arms comfortably on their sides, and both feet freely rested.
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Position of the Examiner - The examiner, or clinician, stands at the side of the individual. With one hand supporting the knee and the other upholding the foot, the examiner passively takes the affected hip to the full possible flexion.
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Maneuver - The clinician adds external rotation to the affected hip when the leg is gradually moved down during extension.
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If a positive sign or response is not elicited, the procedure is repeated with internal rotation after the leg reaches its normal position.
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Positive Result - The hip pain or a click sound or both is reproduced, indicative of a labral defect.
What Are the Benefits of the McCarthy Test?
The McCarthy test considerably helps evaluate hip joint pathologies, commonly called symptomatic hip, that occur due to labral tear or impingement.
Some of the benefits of the McCarthy Test are as follows -
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In recent years, femoroacetabular impingements and labral tears are emerging disorders commonly seen in modern-day activities.
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Appropriate diagnostic methods and clinical evaluation are relatively new study areas that require more clinical evidence.
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Though McCarthy Test is non-specific for hip joint disorders, it becomes reliable for screening labral problems, especially in limited-resource healthcare settings.
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Surgical diagnosis remains the gold standard confirmatory tool for hip impingement. Imaging techniques such as MR arthrography are relatively less sensitive, and femoroacetabular impingement sometimes remains undetected.
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A positive McCarthy test significantly contributes to detecting hip joint pathologies such as FAI and labral tears. It could be considered an adjunct in diagnostic investigations involving history, clinical manifestations, physical test outcomes like the McCarthy test, and imaging methods.
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Some clinical studies have documented that the McCarthy test is also used to predict surgical outcomes. Reproduction of click or pain correlates with positive post-surgical response.
When Does the McCarthy Test Show a False Positive Response?
Since the McCarthy test is non-specific, a positive McCarthy response could be seen in other clinical conditions associated with hip pain but unrelated to the hip labrum. In such cases, further detailed investigations are required.
Some of the hip joint conditions that can give a false positive response in the McCarthy test are as follows -
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Fractures involving the hip joint.
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Tumors involving the hip joint.
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Infections.
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Inflammatory conditions like osteoarthritis
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Avascular necrosis involving the femoral head.
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Adductor tendinopathy.
What Are the Variations of the McCarthy Test?
Modified versions of the McCarthy test are developed through various clinical studies to enhance accuracy and ensure better evaluation.
Some of the variations of the McCarthy test are as follows -
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Snapping Hip Test (Active Version) - Also referred to as extension test or clicking hip test, helps to differentiate extra-articular problems (iliopsoas tendon snapping) from intra- articular labral defects. Here, the test is evaluated by active flexion of the hip joint.
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This McCarthy variant test is conducted to rule out hip problems such as Iliopsoas syndrome, inflammatory and degenerative arthritis of the hip joint, and hip arthroplasty.
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Maneuver - In the supine lying position, the individual actively flexes the affected hip, followed by adduction and internal rotation.
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The clinician positions their hand over the hip joint and palpates for snapping. On the other hand, the clinician guides the leg downwards to rest.
Conclusion
The McCarthy Test is a practical orthopedic screening test commonly performed to assess for an acetabular labral tear and Femoroacetabular impingement. This clinical test would greatly help physical therapists and clinicians to determine suspected hip pathologies like labral tears or impingement through physical examinations and further substantiate them through clinical diagnostic tests.
