Hip Microinstability

Other Names

• Hip Microinstability
• Hip Micro-instability
• Hip Instability
• Hip Laxity
• Idiopathic hip microinstability

---

Background

• This page refers to so-called instability or microinstability of the hip joint

History

• First case published by Philippon et al in 2009

Epidemiology

• One study found 91% of patients were female

---

Introduction

Infographic on hip microinstability

Illustration of traumatic hip instability

General

• Definition: extraphysiologic hip motion that causes pain with or without symptoms of hip joint unsteadiness
• Generally recognized but poorly understood and defined cause of hip pain
• Most commonly caused by inherent soft tissue and capsular laxity, sometimes iatrogenic
• No definitive preoperative diagnostic test, physical exam finding or imaging modality for diagnosis
• Clinician must have a strong suspicion for hip microinstability based on overall clinical picture

Etiology

• Capsular laxity secondary to generalized hypermobility
  • Secondary to capsular over-resection, lack of capsular closure or cam over-resection
• Iatrogenic capsular insufficiency

Pathophysiology

• Historically, the hip joint was thought to only exhibit rotational motion
• Modern research suggests the hip also exhibits some translational movement
• Etiology of translational movement seems to be multifactorial, labrum and capsule have been implicated
• Laxity, when present, has been shown to intensify rotation/translation of the joint
• Activity related proposed mechanism
  • Subtle anatomic abnormalities in the presence of repetitive hip joint rotation and axial loading
  • Sports at risk include golf, figure skating, gymnastics, ballet, martial arts, football, tennis and baseball
• Inherent ligamentous laxity and/or peri-articular muscular weakness
  • Results in increased movement of the femoral head relative to acetabulum
  • Eventual damage to labrum, cartilage, capsular structures

Associated Conditions

• Acetabular Labral Tear
• Ligamentum Teres Injury
• Connective tissue disorder
  • Ehlers Danlos Syndrome
  • Marfan Syndrome
  • Down Syndrome

Controversy

• Somewhat controversial, debate still exists as to whether this is a discrete clinically entity
• Mostly because the hip is thought of as a stable joint due to bony conformity of femoral head and acetabulum

Anatomy of the Hip Joint

• Traditionally modeled as highly constrained ball and socket joint
• More recent studies identify the relationship is more complicated, neither perfectly congruent or spherical
• Under physiologic loads, there is flattening/widening of the joint and translation of the joint
• Soft tissue structures include: acetabular labrum, ligamentum teres and capsuloligamentous complex

---

Risk Factors

Risk factors for microinstability<

• Female gender

---

Differential Diagnosis

Differential Diagnosis Hip Pain

• Fractures And Dislocations
  • Pelvic Fracture
  • Hip Fracture
  • Acetabular Fracture
  • Femoral Neck Stress Fracture
  • Pelvic Stress Fracture
  • Hip Dislocation
• Arthropathies
  • Osteitis Pubis
  • Avascular Necrosis of the Hip
  • Hip Osteoarthritis
  • Femoroacetabular Impingement
  • Transient Osteoporosis of the Hip
  • Hip Microinstability
  • Osteochondral Defect of the Hip
• Muscle and Tendon Injuries
  • Hip Flexor Tendonitis
  • Piriformis Syndrome
  • Hamstring Strain
  • Proximal Hamstring Tendinopathy
  • Adductor Strain
  • Greater Trochanteric Pain Syndrome
• Bursopathies
  • Iliopsoas Bursitis
  • Ischial Bursitis
• Ligament Injuries
  • Acetabular Labrum Tear
• Neuropathies
  • Meralgia Paresthetica
• Other
  • Snapping Hip Syndrome
  • Septic Arthritis
  • Gout
  • Leg Length Discrepancy
• Pediatric Pathology
  • Transient Synovitis of the Hip
  • Developmental Dysplasia of the Hip (DDH)
  • Legg-Calve-Perthes Disease
  • Slipped Capital Femoral Epiphysis (SCFE)
  • Avulsion Fractures of the Ilium (Iliac Crest, ASIS, AIIS)
  • Ischial Tuberosity Avulsion Fracture
  • Avulsion Fractures of the Trochanters (Greater, Lesser)
  • Iliac Apophysitis (AIIS, ASIS, Iliac Crest)
  • Idiopathic Chondrolysis of the Hip

---

Clinical Features

The hyperextension–external rotation (HEER) test

Starting position of the prone instability test

History

• Patients report pain around the hip, groin and inguinal crease
• Onset is often insidious and subacute in nature, however trauma does not rule out the diagnosis
• May have sense of giving way or apprehension with gait/ activities
• 78% of patients report anterior hip pain, 81% subjective hip instability
• Inquire about mechanical symptoms such as clicking, locking, giving way, sensation of looseness
• Symptoms are typically provoked by activities and sport

Physical Exam

• Objective is to attempt to reproduce the patients symptoms
• Often not identified with direct palpation of structures around the hip joint
• Anterior apprehension when combined with hip extension, external rotation seen in 65% of patients
• Rule out spinal, abdominal, groin and knee related pathology

Special Tests

• C Sign: commonly positive in patients with hip microinstability
• Abduction Hyperextension External Rotation Test: In the lateral decubitus position, abduct extend and externally rotate hip
• Prone Instability Test: lay prone on table, extend hip from floor
• HEER Test: supine with leg hanging off table, contralateral hip flexed to chest
• Beighton Score: may be positive
• Anterior Hip Impingement Test: May be positive
• Posterior apprehension test: hip/knee flexed, apply a posterior force
• Log Roll Test: patient is supine, internally and externally rotate hip

---

Evaluation

A 32-year-old woman with dysplasia presents with left hip pain. a AP radiograph demonstrates moderate reduction in the superolateral femoral head coverage bilaterally and superolateral subluxation of the femoral head on the left with disruption of Shenton’s line (arrow). b Axial oblique fat-supressed PD MR image suggests subtle anterior shift of the femoral head is present with a posterior crescent of fluid (arrows)

Radiographs

• Standard Hip Radiographs
  • Screening tool
  • Often normal
  • Can identify other pathology such as dysplasia, FAI, previous trauma, degenerative changes
• Cliff Sign

MRI

• Gold standard for evaluation of the soft tissue structures
  • Angiography can increase diagnostic yield
• Potential findings
  • Dysplastic morphology
  • Anterior labral tear
  • Ligamentum teres tears

Hip Joint Injection

• Has diagnostic and therapeutic value
• Can be part of an arthrogram when obtaining an MRI

Examination Under Anesthesia

• Can be performed at the time of hip arthroscopy

Dynamic Fluoroscopy

• Can be used to evaluate the hip stability in positions of pain/ apprehension

---

Classification

• Not applicable

---

Management

General Approach

• Treatment depends on severity/ frequency of symptoms
• Depends on underlying cause

Nonoperative

• Indications
  • First line therapy in most patients
• Activity Modification
• Physical Therapy
• NSAIDS

Operative

• Indications
  • Directed at the underlying condition and associated intra-articular pathology
  • 8 to 12 weeks of conservative management without improvemtn
• Technique
  • Capsulorrhaphy
  • Hip micro-instability
  • Proximal capsular advancement
  • Capsular reconstruction
  • Plication of capsuloligamentous structures

---

Rehab and Return to Play

Rehabilitation

• Emphasis on
  • Strengthening iliopsoas, hip abductors, short external rotators, abdominal core muscles and low back

Return to Play/ Work

• Needs to be updated

---

Prognosis and Complications

Prognosis: Nonsurgical

• Currently, there are no published reports on the outcome of non-surgical treatment

Prognosis: Surgical

• When diagnosed and treated correctly, most patients demonstrate improvement in symptoms
• Following capsular repair/ plication of the hip
  • Two studies demonstrated significantly improved patient reported outcomes at 2 years

Complications

• Chronic hip pain
• Inability to return to sport

---

See Also

Internal

• Hip Pain Main
• Hip Anatomy Main
• Physical Exam Hip
• Groin Pain Main

External

• https://www.sportsmedreview.com/blog/hip-microinstability/

---