Hip flexor strain test: Thomas Test, FADIR, and clinical grading

Key Takeaways

Hip flexor strain test: the Thomas Test is the primary clinical tool for identifying iliopsoas and rectus femoris tightness or contracture, confirmed by a thigh that rises off the table when one leg is lowered.

Three grades of hip flexor strain exist; grading without imaging carries uncertainty, so clinical findings should be documented alongside functional limitations rather than isolated test results.

FADIR and manual muscle testing complement the Thomas Test; no single test rules in or out a hip flexor strain, and the combination of ROM, strength, and provocation findings builds the clinical picture.

Pabau’s structured patient records and digital intake forms help sports medicine and physiotherapy practices document Thomas Test findings, ROM measurements, and rehab milestones in a single workflow.

Hip flexor injuries are among the most frequently missed diagnoses in clinical musculoskeletal assessment. Anterior hip pain gets attributed to groin pulls, lumbosacral referral, or hip labral pathology, while the underlying hip flexor strain goes undocumented and undertreated.

A systematic review published in the journal Sports Medicine found that sports-related groin pain accounts for 12% to 18% of all sports injuries each year, and hip flexor pathology is frequently implicated alongside labral and adductor-related causes.

Clinicians working in sports medicine practice management know the diagnostic challenge well: the pain location is non-specific, the tests require precise technique, and symptom overlap with differential diagnoses is substantial.

This guide covers the full hip flexor strain test battery used in physiotherapy and sports medicine: the Thomas Test as the primary assessment, the FADIR as a provocation complement, and resisted hip flexion combined with ROM measurement to complete the clinical picture. It also covers grading criteria, differential diagnosis, documentation workflows, and treatment pathways by grade.

Hip flexor strain test: Anatomy and the muscles you are assessing

Running an accurate hip flexor strain test requires knowing which structures you are loading. Three muscle groups dominate the anterior hip and are most frequently strained.

• Iliopsoas (psoas major + iliacus): The deepest and most powerful hip flexor. It originates from lumbar vertebrae L1-L5 and the iliac fossa, inserts on the lesser trochanter of the femur, and is the primary target of the Thomas Test. Strain here typically presents as deep anterior hip pain that worsens with prolonged sitting or resisted flexion above 90 degrees.
• Rectus femoris: The only quadriceps head that crosses the hip joint. It originates from the anterior inferior iliac spine (AIIS) and is tested separately in the Thomas Test by observing knee extension when the thigh is lowered. Athletes who sprint or kick are most susceptible.
• Tensor fasciae latae (TFL): A secondary hip flexor that also abducts and internally rotates the hip. TFL tightness contributes to snapping hip syndrome and is palpable just distal to the anterior superior iliac spine (ASIS).

Hip flexor pain is typically felt in the anterior hip and groin region, often radiating toward the inner thigh. Psoas major involvement can refer pain into the lumbar spine, which frequently leads to misattribution as lumbosacral strain. Knowing the pain distribution of each muscle guides both test selection and interpretation.

Recognizing hip flexor strain symptoms and severity grades

Before performing any hip flexor strain test, establish the symptom profile. Symptom pattern and functional limitation help select the appropriate tests and guide how aggressively to load the structure during assessment.

Clinical grading without imaging carries uncertainty, since physical exam findings alone can underestimate the true extent of fiber disruption in a partial tear. Document functional limitations and ROM measurements alongside the clinical grade, and recommend ultrasound or MRI when Grade II or III is suspected.

A delayed diagnosis of a severe strain raises the risk of myositis ossificans developing at the injury site, billed under M61.9.

The Thomas Test: Step-by-step procedure and interpretation for hip flexor strain

The Thomas Test, named after British orthopedic surgeon Hugh Owen Thomas, remains the foundational hip flexor strain test in clinical practice. It identifies hip flexion contracture, iliopsoas tightness, and rectus femoris restriction through a controlled passive positioning maneuver.

How to perform the Thomas Test

1. Position the patient supine at the end of the examination table, with both hips and knees hanging off the edge at 90 degrees.
2. Flex both hips to chest: Ask the patient to pull both knees firmly to their chest to flatten the lumbar spine and eliminate compensatory lordosis. Confirm the lumbar curve is abolished before proceeding.
3. Lower the test leg: While the patient maintains the non-test leg against their chest, slowly lower the test leg toward the table. Instruct the patient to relax the limb completely.
4. Observe the thigh position: Note whether the thigh lies flat on the table, rises above horizontal, or adopts an abducted or externally rotated position.
5. Observe the knee angle: Note whether the knee flexes to approximately 90 degrees, extends beyond that, or flexes less. Extension suggests rectus femoris tightness.
6. Stabilize the pelvis: Palpate the ASIS bilaterally to detect anterior pelvic tilt, which can create a false negative result by allowing the hip to appear to extend through lumbar compensation.

Interpreting a positive Thomas Test result

Published sensitivity and specificity figures for the Thomas Test vary considerably between studies, and neither should be treated as fixed. The test should not be used in isolation. Positive findings guide the next layer of testing, not the final diagnosis.

FADIR test: Complementing the hip flexor strain test battery

The FADIR (Flexion, Adduction, Internal Rotation) test primarily screens for femoroacetabular impingement and hip labral pathology, but it also reveals hip flexor and anterior capsule tightness as secondary findings. Use it whenever the Thomas Test is positive and anterior hip pain suggests labral involvement may coexist with the hip flexor strain.

FADIR procedure

1. Patient supine, hip and knee relaxed at neutral.
2. Passively flex the hip to 90 degrees, then adduct and internally rotate the femur.
3. A positive result is reproduction of anterior hip or groin pain, clicking, or apprehension at end range.
4. Note whether pain is sharp and localized (labral) or a dull aching pull (hip flexor/capsular).

The FADIR test carries a sensitivity of approximately 88% for labral pathology but is less specific. It should not be read as confirming a labral tear without imaging confirmation.

When both the Thomas Test and FADIR are positive, the clinical priority is to determine whether a labral tear is contributing before prescribing progressive loading rehab, because resisted exercises appropriate for hip flexor strain can aggravate labral pathology.

Clinicians should record both test results and their directional findings in the same session notes, the same way a positive Stinchfield test is documented alongside other hip provocation findings.

Additional hip flexor tests: Strength and range of motion assessment

Relying on a single hip flexor strain test misses the multidimensional nature of the injury. Combine the Thomas Test and FADIR with these additional assessments for a complete clinical picture.

Resisted hip flexion (manual muscle testing)

With the patient seated at the edge of the table, hip and knee at 90 degrees, place your hand on the distal thigh and ask the patient to flex the hip against resistance. Grade strength using the Medical Research Council (MRC) scale (0-5).

Pain on resisted flexion without significant weakness suggests a Grade I strain. Weakness with pain indicates Grade II or higher. Compare bilaterally: a side-to-side deficit exceeding 20% in hip flexion strength is clinically significant.

Passive and active ROM measurement

Measure hip extension range actively and passively. Normal passive hip extension is 20-30 degrees beyond neutral, and a restriction below 10 degrees correlates with iliopsoas tightness.

Also measure hip internal rotation with the patient prone, knee at 90 degrees. Reduced internal rotation alongside anterior hip pain widens the differential toward FAI or labral pathology. Document all ROM values in degrees using a goniometer so they serve as a baseline for tracking rehab progress.

Palpation

Palpate the ASIS and distal iliopsoas tendon just medial to the femoral triangle. Focal tenderness at the lesser trochanter insertion distinguishes iliopsoas tendinopathy from a mid-belly strain. Palpation findings, when recorded alongside provocation tests such as the resisted external derotation test, improve consistency between sessions and between practitioners.

Differential diagnosis: Ruling out other causes of hip flexor pain

Anterior hip pain has a wide differential. The hip flexor strain test battery helps narrow it, but several conditions share overlapping symptoms and require deliberate exclusion. Using clinical decision rules as a model, the aim is to reach a working diagnosis with a defined confidence level, not false certainty.

The NHS guidance on hip pain recommends considering referred lumbar pathology in all presentations of anterior hip pain before attributing symptoms to a local muscle injury. A positive Bragard’s test alongside a restricted straight leg raise strengthens the case for a lumbar source over a local hip flexor strain.

Documenting hip flexor strain assessment findings in clinical practice

Documentation is where consistency breaks down between sessions and between practitioners. A positive hip flexor strain test result is clinically useful only if it is recorded in a format that transfers cleanly from one visit to the next.

Effective documentation of a hip flexor strain test assessment covers four elements:

• Test findings: Thomas Test result (negative / positive; thigh angle in degrees if measurable), FADIR result, and whether rectus femoris or TFL findings complicated the picture.
• Strength data: MRC grade for resisted hip flexion, bilateral comparison, and whether pain was provoked or just weakness noted.
• ROM measurements: Hip extension (active and passive) in degrees; hip internal rotation in degrees; note side-to-side differences.
• Strain grade and rationale: State the working clinical grade (I, II, or III), the features driving that assessment, and whether imaging is recommended to confirm.

Structured SOAP note documentation provides the framework, but content specificity determines whether a second treating clinician can pick up the case without starting from scratch. Guidelines on writing safer clinical notes stress that measurement values, not descriptive adjectives, are the standard for musculoskeletal assessments.

Practices using physical therapy EMR software can build structured templates for hip assessments that pre-populate field labels (Thomas Test: positive/negative; hip extension ROM: ___ degrees), reducing the time to document while standardizing the output across the team.

Practice management software like Pabau offers structured patient records and digital intake forms that let sports medicine and physiotherapy practices capture hip flexor strain test findings, ROM baselines, and rehab milestones in a single workflow, with full session history visible at the next appointment.

For practices with physiotherapy clinic compliance requirements, structured outcome measure recording is not optional. Regulators and insurers in the UK and Australia expect progressive documentation that demonstrates clinical reasoning and measurable change over time.

Streamline your sports medicine documentation

Pabau helps physiotherapy and sports medicine clinics capture structured assessment findings, track ROM baselines, and manage rehab milestones without switching between tools. See how it works for your practice.

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Hip flexor strain treatment and rehabilitation by grade

Confirm the working strain grade before prescribing a rehab pathway. Treatment diverges significantly between grades, and advancing a Grade II strain too quickly is a common cause of re-injury.

Acute phase (0-72 hours, all grades)

Apply the PEACE & LOVE framework. PEACE stands for Protection, Elevation, Avoid anti-inflammatories, Compression, and Education. LOVE stands for Load, Optimism, Vascularization, and Exercise, introduced progressively once the acute phase settles.

Avoid aggressive stretching in the first 72 hours. For Grade I, relative rest is sufficient, and the athlete can typically continue low-load activity. For Grade II and III, non-weight-bearing or reduced loading with crutch support may be necessary.

Sub-acute phase: Mobility and strength (days 4 onwards)

Begin gentle active ROM in pain-free range, progressing to resisted hip flexion at low loads. Key exercises in this phase include supine hip flexion slides, standing hip flexor activation with resistance band, and hip extension bridging to address antagonist weakness.

Progress is gated by pain response, not time alone. A clinician-monitored approach, informed by physiotherapy clinic management workflows, means each progression is assessed against the previous session’s ROM and strength measurements.

Rehabilitation milestones and return to sport

Recovery timelines vary by grade and individual. Grade I strains typically resolve within 1-3 weeks. Grade II injuries commonly require 4-8 weeks of structured rehabilitation. Grade III tears, particularly complete psoas avulsions, may require 3-6 months and surgical consultation.

The American College of Sports Medicine, or ACSM, recommends that return-to-sport decisions be clinician-guided and criterion-based rather than time-based. Three criteria matter most:

• Full pain-free range of motion
• Symmetric hip flexion strength within 10% of the uninjured side
• Sport-specific loading tolerance, confirmed with an objective measure such as the Illinois Agility Test

A structured return-to-sport protocol for physical therapy provides the progressive loading framework for athletes returning to running after hip flexor strain.

Conclusion

Anterior hip pain is easy to misattribute. The hip flexor strain test battery, anchored by the Thomas Test and supplemented by FADIR provocation, manual muscle testing, and goniometric ROM measurement, gives clinicians the evidence base to make a graded clinical diagnosis with confidence. No single test is sufficient; the combination builds the picture.

Documentation is where continuity of care is easiest to lose. Pabau’s physical therapy EMR gives sports medicine and physiotherapy practices structured templates that capture Thomas Test results, ROM baselines, strain grades, and rehab milestones in one place, making the handoff between sessions and between clinicians seamless.

To see how Pabau supports musculoskeletal assessment workflows, review this physiotherapy clinic setup guide, or speak with the team directly.

Continue your research

Need another provocation test for hip and sacroiliac pain? Gaenslen’s test covers how to perform and interpret this SI joint assessment alongside the Thomas Test and FADIR.

Building out a broader special-test toolkit? The alar ligament test explains how to assess craniocervical ligament stability using the same structured documentation approach.

Assessing vascular provocation in another region? The hand elevation test walks through thoracic outlet syndrome screening step by step.

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