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Fixed flexion deformity of hip

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Fixed Flexion Deformity of the Hip

Definition

A fixed flexion deformity (FFD) of the hip is a contracture in which the hip cannot be fully extended — it is held in a position of flexion, which cannot be passively or actively overcome. The limb is fixed in a flexed posture relative to the pelvis.

Causes

CategoryConditions
DegenerativeOsteoarthritis of the hip (most common)
InflammatoryRheumatoid arthritis, ankylosing spondylitis
InfectiveSeptic arthritis, tuberculosis of the hip
NeurologicalCerebral palsy, stroke (spastic hip flexion), poliomyelitis
CongenitalDevelopmental dysplasia of the hip (DDH)
Post-traumaticNeglected femoral neck fracture, avascular necrosis
Soft tissueIliopsoas or hip flexor contracture
In ankylosing spondylitis, FFD of the hip is a classic finding, often associated with chin-on-chest deformity and lumbar kyphosis. — Miller's Review of Orthopaedics, 9th Edition

Pathomechanics

  • The iliopsoas is the primary hip flexor responsible for contracture.
  • A fixed flexion deformity tilts the pelvis anteriorly, producing a compensatory lumbar lordosis — this masks the true degree of hip flexion deformity when the patient is standing.
  • On lying flat, the lumbar spine remains lordosed; the contralateral hip must be maximally flexed to flatten the lumbar lordosis before the deformity can be measured accurately.

Clinical Assessment — Thomas Test

The Thomas test is the gold standard for detecting and measuring FFD of the hip.

Technique

  1. Patient lies supine on the examination table.
  2. The contralateral (normal) hip is fully flexed — bringing the knee to the chest — until the lumbar lordosis is obliterated (confirmed by placing a hand under the lumbar spine).
  3. This pelvic correction unmasks the FFD on the affected side.
  4. The angle at which the affected thigh lifts off the table = degree of fixed flexion deformity.

Interpretation

  • If the thigh remains flat → No FFD.
  • If the thigh rises off the table → FFD is present; the angle is the degree of deformity.
  • Positive Thomas test for hip flexion → Diagnostic of iliopsoas or hip flexor contracture. — Miller's Review of Orthopaedics, 9th Edition

Consequences of Untreated FFD

  1. Antalgic/abnormal gait — compensatory mechanisms lead to increased energy expenditure
  2. Lumbar hyperlordosis — chronic low back pain
  3. Knee flexion — secondary crouched gait pattern
  4. Pelvic obliquity and scoliosis (if bilateral asymmetry)
  5. In severe cases (e.g., AS): chin-on-chest deformity, inability to maintain horizontal gaze

Management

Non-operative

  • Physiotherapy: Stretching of hip flexors, muscle strengthening of extensors
  • NSAIDs / analgesics: For underlying inflammatory or degenerative conditions
  • Orthotics / walking aids: Compensatory strategies

Operative

Deformity CauseSurgical Option
Spastic hip flexion (CP)Psoas tenotomy or psoas recession
Hip osteoarthritis / RATotal hip arthroplasty (THA) — corrects deformity mechanically
Ankylosing spondylitis with kyphosisCorrection of hip disorder first, then spinal osteotomy
Crouched gait (CP)Lengthenings at hip, knee, and ankle
In ankylosing spondylitis, correction of hip and lumbar disorder should be performed before cervicothoracic osteotomy. — Miller's Review of Orthopaedics, 9th Edition

Key Points to Remember

FeatureDetail
Diagnostic testThomas test
Primary muscle responsibleIliopsoas
Compensatory changeLumbar hyperlordosis (masks deformity in standing)
Common cause in adultsHip osteoarthritis / AS
Common cause in childrenCerebral palsy
Surgical correction (CP)Psoas tenotomy / recession
Surgical correction (OA)Total hip replacement

Test for Iliotibial band contracture

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Ober test iliotibial band contracture

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Ober's Test — Test for Iliotibial Band (IT Band) Contracture

Purpose

Ober's test detects tightness or contracture of the iliotibial band (ITB) and the tensor fasciae latae (TFL) muscle. It is the primary clinical test used to diagnose iliotibial band syndrome.

Anatomy Basis

The iliotibial band is a lateral thickening of the fascia lata, running from the iliac crest proximally to Gerdy's tubercle on the lateral tibial condyle distally. It is tensioned by two muscles:
  • Tensor fasciae latae (TFL)
  • Gluteus maximus (lower fibres)
During knee flexion–extension, the ITB slides over the lateral femoral condyle — repetitive friction causes inflammation (ITB friction syndrome). A contracted/tight ITB restricts hip adduction. — Miller's Review of Orthopaedics, 9th Edition

Technique

Position: Patient lies in the lateral decubitus position (on the unaffected side), with the bottom (uninjured) hip and knee flexed to 90° for stability.
Steps:
  1. The examiner stands behind the patient.
  2. One hand stabilises the pelvis (superolateral aspect) to prevent compensatory pelvic tilt.
  3. The other arm supports the affected (upper) limb — hip is abducted and extended to stretch the ITB, knee is extended (or flexed to 90° in the modified version).
  4. The examiner then releases the limb, allowing gravity to adduct the hip passively.
Positive test: The leg fails to adduct to the neutral/table level, or remains in abduction — indicating a tight/contracted ITB. Reproduction of lateral knee pain indicates ITB inflammation. — Rosen's Emergency Medicine
Ober's Test variations showing lateral decubitus positioning with different contralateral hip angles. Green markers show degree of adduction achieved.

Interpretation

FindingMeaning
Hip adducts fully to tableNegative — ITB normal
Hip cannot adduct (stays elevated)Positive — ITB contracture / tightness
Lateral knee pain reproducedITB inflammation (friction syndrome)

Modified Ober's Test

In the original Ober test, the knee is extended during the drop. In the modified version, the knee is flexed to 90° — this is considered more reliable as it relaxes the biceps femoris, isolating ITB tension more accurately.

Important Technical Point

The pelvis must be stabilised throughout — failing to do so allows the pelvis to tilt, falsely allowing adduction and giving a false-negative result.

Clinical Associations

ConditionRelevance
ITB friction syndromeClassic indication; common in long-distance runners and cyclists
Gluteal muscle contracturePositive Ober's in bilateral contractures
Cerebral palsyHip flexion + ITB tightness contributing to crouched gait
Snapping hip (external)ITB snapping over the greater trochanter
Positive Ober's test (panel b) in gluteal muscle contracture — the upper leg remains abducted and cannot adduct to the table; panels c and d show pre-operative positive test, corrected postoperatively.

Management of ITB Contracture

  • Conservative (first-line): Relative rest, NSAIDs, ITB stretching, physiotherapy (hip abductor and TFL strengthening)
  • Steroid injection: For refractory inflammation at the lateral femoral condyle
  • Surgical: Excision of an ellipse of the ITB, or arthroscopic release — reserved for cases failing conservative management — Miller's Review of Orthopaedics, 9th Edition
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