Hip Dislocation
- Fysiobasen
- Sep 13
- 11 min read
Hip Dislocation: Hip joint dislocations are relatively rare and can be either congenital or acquired. They account for approximately 5% of all joint dislocations. The natural hip joint (as opposed to a prosthetic hip) is inherently stable and requires significant force to become dislocated, such as in motor vehicle accidents.¹
Classification of Hip Dislocations
Posterior dislocation (approx. 85%, most common):Occurs as a result of combined forces such as:
Hip flexion
Adduction
Internal rotation
Anterior dislocation (approx. 10%):Caused by combined forces such as:
Hyperabduction
Extension
Central dislocation:Always occurs in association with an acetabular fracture²
Clinically Relevant Anatomy
The Hip Joint
The hip joint is a ball-and-socket joint that is inherently stable due to its well-defined bony architecture and strong ligaments. This structural robustness allows the hip to withstand substantial mechanical stress. Hip stability is maintained by several anatomical components, including:
Acetabulum: The depth of the hip socket provides secure placement of the femoral head
Labrum: Enhances depth and stability of the acetabulum
Joint capsule: Provides mechanical support and protects against dislocation
Muscular support: Muscles such as rectus femoris, the gluteal muscles, and the short external rotators contribute to dynamic stability
Ligaments:
Iliofemoral ligament (anterior): One of the strongest ligaments in the body, resists hyperextension
Ischiofemoral ligament (posterior): Provides posterior support
The greater strength of the anterior ligaments explains why traumatic hip dislocations most often occur posteriorly, accounting for approximately 90% of cases.
Blood Supply
Understanding the vascularization of the hip joint is crucial, as trauma causing femoral head dislocation can compromise blood flow and lead to avascular necrosis (AVN).
External iliac artery: Gives rise to branches forming a ring around the femoral neck
Lateral femoral circumflex artery: Branches anteriorly
Medial femoral circumflex artery: Branches posteriorly and provides the main blood supply to the femoral head
Etiology
Acquired Hip Dislocation
Dislocation after hip replacement (THR):A complication of total hip replacement (THR), usually caused by:
Patient noncompliance with postoperative precautions
Malposition of the implant
Deficiencies in the soft tissues around the hip jointDislocation after THR often requires less trauma, such as a fall or movement into contraindicated positions that stress the capsule cut during surgery.
Traumatic hip dislocation:
Motor vehicle accidents: Over 50% of traumatic hip dislocations occur in relation to car accidents²
Falls from height: Another common mechanism for dislocationTraumatic hip dislocation is rarely isolated and often occurs together with:
Acetabular or femoral head fractures
Soft tissue injuries such as muscles, ligaments, and labrum
Nerve injuries, which may affect the sciatic nerve
Congenital hip dislocation:Now considered part of the spectrum of developmental dysplasia of the hip.
Focus on Traumatic Hip Dislocations
Traumatic dislocations often result in extensive injuries to the hip joint and surrounding structures. This highlights the importance of early diagnosis and treatment to prevent complications such as avascular necrosis and joint instability.
Mechanism and Classification
Mechanisms of Dislocation
Hip dislocation primarily occurs due to axial loading, with the direction of dislocation depending on the hip position at impact and the direction of the force vector.
Posterior dislocation:
Occurs when the leg is straight or when the hip and knee are flexed less than 90° with the hip adducted
Commonly accompanied by fractures of the posterior acetabular wall
Often referred to as a dashboard injury, where the knee strikes the dashboard in a car accident, forcing the femur upward
Anterior dislocation:
Occurs when the hip is abducted and externally rotated
Often results when the medial aspect of the knee is struck by external forces, such as contact with the steering wheel, dashboard, or seatback
Types of Traumatic Hip Dislocations
Traumatic hip dislocations are classified into three main types based on the position of the femoral head relative to the acetabulum:
Posterior dislocation:
Incidence: 85–90% of cases
Mechanism: Often caused by trauma to a flexed hip and knee
Additional detail: Frequently associated with posterior acetabular fractures
Anterior dislocation:
Incidence: ~10% of cases
Mechanism: Caused by external rotation and abduction under force
Central dislocation:
Mechanism: Always associated with an acetabular fracture, where the femoral head is driven through the acetabulum
Thompson–Epstein Classification of Posterior Hip Dislocation
This classification system from 1951 is used to subclassify posterior dislocations based on severity and associated injuries:
Type I: Simple dislocation, with or without an insignificant posterior wall fragment
Type II: Dislocation with a single large posterior wall fragment
Type III: Dislocation with a comminuted fracture of the posterior wall
Type IV: Dislocation with fracture of the acetabular floor
Type V: Dislocation with fracture of the femoral head
This classification is important for assessing the severity of the injury and for guiding treatment strategy.
Anterior Traumatic Hip Dislocations
Anterior hip dislocations account for approximately 10% of all traumatic hip dislocations (THD). They occur when a hyperextension force is applied to an abducted leg, causing the femoral head to be forced out of the acetabulum.
Mechanism
Typical situations:
Traffic accidents where the knee strikes the dashboard while the thigh is abducted
Severe fall from height
Strong blow to the back of a person in a squatting position
Result: The femoral head dislocates anterior to the acetabulum.
Epstein Classification of Anterior THD
This classification divides anterior dislocations into two main types based on location and associated fractures:
Type I: Superior dislocations, including pubic and subspinal dislocations
IA: No associated fractures
IB: Fracture or impaction of the femoral head
IC: Fracture of the acetabulum
Type II: Inferior dislocations, including obturator and perineal dislocations
IIA: No associated fractures
IIB: Fracture or impaction of the femoral head
IIC: Fracture of the acetabulum
Central Traumatic Hip Dislocations
Central hip dislocation is the rarest and most challenging form of hip dislocation.
Mechanism
Typical injury scenarios:
Direct blow to the greater trochanter, such as in traffic accidents or lateral falls
Result: The femoral head is driven through the acetabulum, often causing complex fractures.
Clinical Presentation
Patients with hip dislocation often present with a dramatic injury history, including a reported audible "crack" or "pop," immediately followed by intense pain. Visible signs and symptoms are marked and include both physical deformity and functional limitations.
Common symptoms and signs:
Deformity: Ipsilateral limb shortening with hip in flexion, adduction, and internal rotation
Inactivity: Inability to walk due to pain and swelling
Leg length discrepancy: Visible difference in leg length
Physical symptoms:
Pain: Severe hip pain exacerbated by attempted movement
Swelling: Local edema and hematoma due to periarticular bleeding
Reduced range of motion: Hip immobility with restricted active and passive movement
Neurovascular Complications
Hip dislocation may damage surrounding structures, including blood vessels and the sciatic nerve.
Vascular injuries: Hematoma and local pain
Nerve injuries:
Pain in buttock, posterior thigh, and calf
Altered sensation in the posterior leg and foot
Muscle weakness or loss of function:
Dorsiflexion (peroneal branch)
Plantarflexion (tibial branch)
Reduced or absent ankle deep tendon reflexes
Additional Injuries
Muscle and tendon avulsions: Damage to surrounding soft tissues caused by the femoral head leaving the acetabulum
Knee injuries: Concomitant knee injuries may also occur
Diagnostic Procedures for Hip Dislocation
Accurate diagnosis is crucial to confirm dislocation, evaluate potential associated injuries, and ensure successful reduction. A combination of X-ray and CT is used for comprehensive assessment.
X-ray examinations:
AP pelvis and lateral hip view:
Confirms the presence of hip dislocation
Evaluates potential associated fractures of the acetabulum, femoral head, or nearby structures
Used to confirm successful reduction after treatment
Provides follow-up on progression of chronic conditions such as hip dysplasia
CT scan:
Detailed assessment of structural injuries:
Rules out associated injuries in traumatic cases, especially in the acetabulum and femoral head
Identifies occult fractures or fragments not visible on X-ray
Spinal assessment:
CT is also used to evaluate the lumbar spine for potential concurrent injuries, particularly in severe trauma
Complications of Hip Dislocation
Hip dislocations can lead to both immediate and long-term complications, depending on severity, delay in treatment, and accuracy of reduction. Early recognition and treatment are essential to reduce risks.
Immediate complications:
Soft tissue injuries: Damage to muscles, ligaments, and tendons around the hip joint
Nerve injuries: Especially sciatic nerve injury, occurring in ~10% of posterior traumatic dislocations. Symptoms include pain, sensory loss, and weakness in dorsiflexion (peroneal branch) or plantarflexion (tibial branch)
Fractures: Most commonly of the femoral head or posterior acetabular wall, potentially leading to joint instability and impaired future function
Long-term complications:
Avascular necrosis (AVN):
Incidence: 1.7–40%, but reduced to 0–10% if reduction occurs within 6 hours of trauma
Caused by compromised blood supply to the femoral head
Post-traumatic osteoarthritis: Degenerative changes in the hip joint leading to pain and functional decline
Chronic dislocations: Inadequate or delayed treatment may prevent proper joint stabilization, resulting in chronic pain and dysfunction
Leg length discrepancy: May arise from improper reduction or damage to growth plates or bony structures
Differential Diagnoses for Hip Pain
Hip pain may result from both acute trauma and chronic or atraumatic conditions. Accurate diagnosis requires thorough evaluation of the patient’s history, physical examination, and often imaging. Below is an overview of differential diagnoses for hip pain based on etiology.
Acute Trauma
Femoral fractures:
Proximal fractures:
Intracapsular:
Femoral head fracture
Femoral neck fracture
Extracapsular:
Intertrochanteric fracture
Trochanteric fracture
Shaft fractures:
Subtrochanteric and midshaft fractures
Pelvic fractures:
Acetabular fractures
“Open book” fracture: Injury that opens the pelvic ring
“Straddle” fracture: Involves both pubic rami
Avulsion fracture: Most often seen in athletes
Chronic or Atraumatic Conditions
Hip bursitis: Inflammation of the bursae around the hip joint, often associated with overuse
Psoas abscess: A rare condition causing deep hip pain, often accompanied by systemic symptoms such as fever
Piriformis syndrome: Sciatica-like pain caused by compression of the sciatic nerve by the piriformis muscle
Meralgia paresthetica: Compression of the lateral femoral cutaneous nerve, causing pain or numbness on the lateral thigh
Septic arthritis: Infection in the hip joint requiring urgent treatment to prevent permanent damage
In children: Septic arthritis often presents acutely with fever and limping
Obturator nerve entrapment: Causes pain and weakness in the adductor muscles
Avascular necrosis (AVN): Often associated with prior trauma, steroid use, or alcohol abuse; may lead to collapse of the femoral head and progression to osteoarthritis
Outcome Measures
Harris Hip Score (HHS) is a specialized tool for assessing hip function, administered by clinicians. Originally developed by William Harris to evaluate hip function after total hip replacement (THR) [17], it has since been widely used to assess various hip conditions and treatments in adults, including osteoarthritis (OA) [18].
HHS consists of four domains: pain, physical function (covering daily activities and gait), absence of hip deformity, and hip range of motion (ROM). The score includes 10 items with a maximum of 100 points: pain (0–44 points), function (0–47 points across 7 items), absence of deformity (4 points), and ROM (5 points across 2 items) [19].
The total score provides an overall assessment categorized as Excellent, Good, Fair, or Poor function [20]. Higher scores indicate better function:
<70 = Poor
70–80 = Fair
80–90 = Good
90–100 = Excellent
As pain and physical function were the main indicators for surgery in hip disorders during tool development, these domains are weighted heavily [17]. HHS has demonstrated excellent reliability and is easy to use without formal training [19]. It has also shown greater responsiveness than the Short Form 36 Health Survey in short-term evaluation (within one year) of hip function [18]. Despite concerns regarding ceiling effects in systematic reviews, HHS remains suitable for studies [21], especially when new treatments are not under evaluation.
Medical Treatment
Treatment of hip dislocations may be operative or non-operative. Many studies emphasize that the time to reduction is critical, as the risk of avascular necrosis increases the longer the hip remains dislocated.
Non-surgical Treatment
Closed reduction of the hip is performed by applying traction in the opposite direction of the dislocation, with the hip flexed to 90°. This should preferably be done under general or regional anesthesia with muscle relaxation to avoid further damage to cartilage and soft tissues [22]. The procedure may also be carried out in the operating room under anesthesia [14]. After reduction, the hip joint must be carefully tested for stability. Bed rest may be recommended depending on hip stability and the extent of soft tissue injury.
Surgical Treatment
Indications for surgery:
Failed conservative reduction
Instability after conservative reduction
Associated fractures of the femoral head or acetabulum
Loose bone fragments in the joint cavity after reduction
Hip arthroscopy can be used to evaluate intra-articular fractures and cartilage damage, as well as to remove intra-articular fragments. Hip replacement surgery may be considered if optimal stability cannot be achieved with reduction and fixation of associated injuries [16]. Dislocation after hip replacement surgery may indicate the need for revision surgery to ensure long-term hip stability.
Indications for open reduction [16]:
When reduction is challenging, or when obstacles such as loose fragments or soft tissue limit closed reduction
Worsened neurological symptoms after closed reduction (especially sciatic nerve function following posterior dislocation)
Cases with proximal femur fractures, where bone manipulation is contraindicated
Physiotherapy Treatment
Individuals with hip dislocation will require extensive physiotherapy. It is important to consider healing times for soft tissue (and bone in cases with associated fractures) during rehabilitation after hip dislocation. The orthopedic surgeon will provide guidance on weight-bearing restrictions that may be necessary after medical treatment of the hip. Complete rehabilitation following hip dislocation may take 3–6 months [14].
Physiotherapy measures:
Gait training: Begin with mobility aids such as a walker or crutches to limit weight-bearing, progressing as tolerated
Improving hip mobility: Including mobilization of the hip joint to increase range of motion
Strength training: Focus on strengthening the muscles around the hip, especially hip abductors, adductors, extensors, and flexors
Stretching: To maintain and improve flexibility
Gradual return to activity/sport: Stepwise adaptation to activity to ensure safe functional recovery without risk of re-injury
Clinical Conclusion
Acquired, or traumatic, hip dislocations are medical emergencies, and treatment should be sought as quickly as possible. Reduction should ideally occur within 6 hours of dislocation to reduce the risk of complications. Traumatic dislocations are treated either with closed or open reduction, and open surgery or arthroscopic intervention may be indicated in cases with associated fractures. Physiotherapy plays a key role in rehabilitation after hip dislocation, helping restore patient function and prevent recurrent dislocations.
Kilder:
Masiewicz S, Mabrouk A, Johnson DE. Posterior hip dislocation.Available:https://www.ncbi.nlm.nih.gov/books/NBK459319/ (accessed 7.1.2023)
Radiopedia Hip dislocation Available:https://radiopaedia.org/articles/hip-dislocation (accessed 7.1.2023)
Orthobullets THA Dislocation Available:https://www.orthobullets.com/recon/5012/tha-dislocation (accessed 7.1.2022)
S. Sanders, N. Tejwani, and K. A. Egol, “Traumatic hip dislocation—a review,” Bulletin of the NYU Hospital for Joint Diseases, vol. 68, no. 2, pp. 91–96, 2010.
Obakponovwe, O., Morell, D., Ahmad, M., Nunn, T., & Giannoudis, P. V. (2011).Traumatic hip dislocation. Orthopaedics and Trauma, 25(3), 214-222.
S. Sanders, N. Tejwani, and K. A. Egol, “Traumatic hip dislocation—a review,” Bulletin of the NYU Hospital for Joint Diseases, vol. 68, no. 2, pp. 91–96, 2010.
S. Sanders, N. Tejwani, and K. A. Egol, “Traumatic hip dislocation—a review,” Bulletin of the NYU Hospital for Joint Diseases, vol. 68, no. 2, pp. 91–96, 2010.
Obakponovwe, O., Morell, D., Ahmad, M., Nunn, T., & Giannoudis, P. V. (2011).Traumatic hip dislocation. Orthopaedics and Trauma, 25(3), 214-222.
Yang, & Cornwall, R. (2000). Initial treatment of traumatic hip dislocations in the adult. Clinical orthopaedics and related research (377), 24-31
Pallia CS, Scott RE, Chao DJ. Traumatic hip dislocation in athletes. Curr Sports Med Rep. 2002 Dec;1(6):338-45
Hung NN. Traumatic hip dislocation in children. Journal of Pediatric Orthopaedics B 2012;21(6):542-51.
pallia CS, Scott RE, Chao DJ. Traumatic hip dislocation in athletes. Curr Sports Med Rep. 2002 Dec;1(6):338-45
Larson DE. Gezin en gezondheid. Cambium BV:Zeewolde, 1995.
Ortho Info. Developmental Dislocation (Dysplasia) of the Hip (DDH). Available from: https://orthoinfo.aaos.org/en/diseases--conditions/developmental-dislocation-dysplasia-of-the-hip-ddh (accessed 08/08/2020).
Bucholz R, Heckman JD. Rockwood e Green fraturas em adultos. In: Rockwood e Green fraturas em adultos, 2006: pp. 2263-2263.
Lima LC, Nascimento RA, Almeida VM, Façanha Filho FA. Epidemiology of traumatic hip dislocation in patients treated in Ceará, Brazil. Acta ortopedica brasileira 2014;22(3):151-4.
Nilsdotter, A., & Bremander, A. (2011). Measures of hip function and symptoms: Harris Hip Score (HHS), Hip Disability and Osteoarthritis Outcome Score(HOOS), Oxford Hip Score (OHS), Lequesne Index of Severity for Osteoarthritis of the Hip (LISOH), and American Academy of Orthopaedic Surgeons (AAOS) Hip and Knee Questionnaire. Arthritis Care & Research, 63(S11), 200-207.
Shi, H. Y., Mau, L. W., Chang, J. K., Wang, J. W., & Chiu, H. C. (2009). Responsiveness of the Harris Hip Score and the SF-36: five years after total hip arthroplasty. Quality of Life Research, 18(8)
Hoeksma, H., Van den Ende, C., Ronday, H., Heering, A., Breedveld, F., & Dekker,J. (2003). Comparison of the responsiveness of the Harris Hip Score with generic measures for hip function in osteoarthritis of the hip. Annals of the Rheumatic Diseases, 62(10), 935-938.
Garellick, G., Herberts, P., & Malchau, H. (1999). The value of clinical data scoring systems: are traditional hip scoring systems adequate to use in evaluation after total hip surgery? The Journal of Arthroplasty, 14(8), 1024-1029.
Wamper, K. E., Sierevelt, I. N., Poolman, R. W., Bhandari, M., & Haverkamp, D. (2010). The Harris hip score: Do ceiling effects limit its usefulness in orthopaedics? Acta Orthopaedica, 81(6), 703-707.
Medscape. Hip dislocation. Available from: https://emedicine.medscape.com/article/86930-overview (accessed 09/08/2020).
