eMedicine Specialties > Sports Medicine > Hip

Hip Dislocation

Matthew Gammons, MD, Assistant Clinical Professor, Department of Family and Community Medicine, Medical College of Wisconsin; Medical Director, Castleton State College; Consulting Staff, Vermont Orthopaedic Clinic and Killington Medical Clinic
Contributor Information and Disclosures

Updated: Jun 10, 2008

Introduction

Background

Hip dislocations are relatively uncommon during athletic events.¹ Injuries to small joints (eg, finger, wrist, ankle, knee) are much more common. However, serious morbidity can be associated with hip dislocations, making careful and expedient diagnosis and treatment important for the sports medicine physician.

Large-force traumas (eg, motor vehicle accidents, pedestrians struck by automobiles) are the most common causes of hip dislocations.^{1, 2, 3, 4, 5} This type of injury is also associated with high-energy impact athletic events (eg, American football, rugby, water skiing, alpine skiing/snowboarding, gymnastics, running, basketball, race car driving, equestrian sports).^{5, 6, 7, 8, 9} Diagnosing and correctly treating these injuries to avoid long-term sequelae of avascular necrosis and osteoarthritis is imperative.

Hip dislocations are either anterior or posterior, with posterior hip dislocations comprising the majority of traumatic dislocations.

• Several classification systems are used to describe posterior hip dislocations.
  • The Thompson-Epstein classification is based on radiographic findings.
    • Type 1 – With or without minor fracture
    • Type 2 – With large, single fracture of posterior acetabular rim
    • Type 3 – With comminution of rim of acetabulum, with or without major fragments
    • Type 4 – With fracture of the acetabular floor
    • Type 5 – With fracture of the femoral head
  • The Steward and Milford classification is based on functional hip stability.
    • Type 1 – No fracture or insignificant fracture
    • Type 2 – Associated with a single or comminuted posterior wall fragment, but the hip remains stable through a functional range of motion
    • Type 3 – Associated with gross instability of the hip joint secondary to loss of structural support
    • Type 4 – Associated with femoral head fracture
  • Some case series have found that most posterior hip dislocations are type 1.

For excellent patient education resources, visit eMedicine's Breaks, Fractures, and Dislocations Center and Sports Injury Center. Also, see eMedicine's patient education article Total Hip Replacement.

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Frequency

United States

Up to 70% of all hip dislocations are due to motor vehicle accidents. Very little documentation concerning the occurrence of hip dislocations during sporting events exists. American football and rugby are the sports in which hip dislocations have been most widely reported.⁶ An estimated 3% of all football injuries involve hip fracture or dislocation. Rugby, followed by alpine skiing and snowboarding, is the sport with the second highest number of hip dislocations.⁶

One study found rates of hip dislocation with or without fracture of the hip joint significantly higher in snowboarders than skiers over a 10-year period (5 times higher in snowboarders than in skiers),⁷ and one case each of hip dislocation has been documented in the literature in competitive gymnastics and professional basketball.^{1, 5} Case reports also exist of hip dislocations and fractures in racecar drivers and equestrians.¹⁰

Functional Anatomy

The hip joint is based on the articulation of the femoral head and the acetabulum of the pelvis, and it is a synovial ball-and-socket type joint. The femur is held in the acetabulum by 5 separate ligaments as follows:

• The iliofemoral ligament attaches to the anterior inferior iliac spine of the pelvis and the intertrochanteric line of the femur.
• The pubofemoral ligament originates at the superior ramus of the pubis, also attaching to the intertrochanteric line of the femur.
• The ischiofemoral ligament connects the ischium to the greater trochanter of the femur.
• The transverse acetabular ligament consists of the labrum covering the acetabular notch.
• The femoral head ligament joins the femoral head with the transverse ligament and acetabular notch.

The relative strength of these ligaments joined together, along with the angulation of the proximal femur in relation to the acetabulum, make dislocation of the hip joint difficult. The large sciatic nerve lies just inferoposterior to the hip joint, whereas the femoral nerve lies just anterior to the hip. The proximal shaft of the femur and the femoral neck has a plentiful blood supply from the medial circumflex femoral artery and its branches. The femoral head, on the other hand, has an extremely tenuous blood supply from a small branch of the obturator artery that passes with the femoral ligament.

Sport-Specific Biomechanics

Two general categories of hip dislocations exist, anterior and posterior. Posterior dislocations compose 70-80% of all hip dislocations and 90% of all sports-related hip dislocations. Alpine skiing is an exception, with one study showing higher rates of anterior dislocations in skiers.⁷ In order to cause a posterior dislocation, a large force is required to strike the flexed knee with the hip flexed, adducted, and internally rotated. This injury occurs more commonly during contact sports (eg, American football, rugby) when a running player is tackled and falls out of control onto a flexed knee.

Anterior dislocations occur when an athlete's hip is flexed, with the leg abducted and externally rotated. These injuries are more common in sports (eg, basketball, gymnastics) where players are running at high speeds, jumping, and landing awkwardly with the knees flexed. This force drives the femoral head out of the acetabulum, tearing ligaments, and often fracturing the femoral head and/or acetabulum. The increased rates of dislocation in alpine skiing are likely due to the large rotational forces, abduction, and external rotation applied to the hip by the ski equipment during a fall.

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Acetabulum Fractures
Femoral Neck Fracture
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Related Medscape topics:
Resource Center Exercise and Sports Medicine
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Specialty Site Orthopaedics

Clinical

History

• The typical history of a hip dislocation during an athletic event involves 1 of 2 mechanisms.
  • Most commonly, an athlete is running and lands on the feet or flexed knees, striking the ground while the hip is flexed, adducted, and internally rotated. This type of injury has been well documented in contact sports where participants are tackled at high speeds and land out of control with other players piling on top of them (eg, football, rugby). A similar injury may occur during high-speed racecar driving accidents.
  • The second mechanism involves an athlete landing in the splits, with the hip flexed, abducted, and externally rotated. This type of injury is more likely to be seen during sports involving jumping and landing (eg, basketball, gymnastics). 
  • The mechanism in skiing and snowboarding injuries is not well described and complex, due to high speeds and additional equipment, but it is likely similar to the aforementioned mechanisms. 
• Patients often present in obvious severe pain in the hip region and upper leg. They may also complain of knee, lower leg, or even back pain.
• Patients usually complain of the inability to walk or move their leg about the hip joint.
• Patients may complain of numbness and/or tingling in the legs in cases involving neurovascular damage.

Physical

• Hip dislocations usually present with the athlete complaining of severe pain around the hip and proximal thigh.
• Anterior hip dislocations may present in 2 different ways.
  • Superiorly displaced dislocations present with the affected hip extended and externally rotated.
  • The inferior type of anterior dislocations presents with the affected hip flexed, abducted, and externally rotated.
• On the other hand, the affected limb of a posterior hip dislocation most commonly appears shortened, internally rotated, and adducted.
• In those patients whose mechanism of injury suggests a posterior hip dislocation but who have no evidence of a dislocation on examination, a traumatic posterior hip subluxation should be considered. This injury carries many of the risks of a true dislocation and may be overlooked.¹¹
• Assessing the neurovascular status of the injured leg is extremely important. Nerve injury, particularly neurapraxia, is not uncommon. The sciatic nerve and the common peroneal division of the sciatic nerve are most often injured in posterior dislocations. Simple observation and palpation for bony deformity, skin color, and temperature provides clues to the vascular status of the leg. Test reflexes, strength, and sensation in the affected leg, and palpate for femoral and distal pulses.
• The physician should also examine the patient carefully for other bony injuries. A significant amount of force is required to dislocate a hip. Studies of motor vehicle accidents have shown hip dislocations are commonly associated with knee injuries such as fractures, dislocations, and ligamentous damage. Whether or not sport-related hip dislocations have the same rates of associated knee injuries is not known; however, a careful knee examination should be performed on all patients with hip dislocations.

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Peripheral Nerve Injuries
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Causes

• High-speed, high-impact sports are the most common setting for hip dislocations.
  • Unsafe and poorly maintained playing surfaces may add to the risk of participating in high-impact sports. For instance, wet surfaces provide an environment where athletes are more prone to lose control of their bodies while running and jumping. However, no evidence exists to link these factors with an increased incidence of hip dislocations.
  • One case report describes a basketball player who slipped on a wet court and dislocated his hip.⁵
• Although warming up before an activity and stretching on a regular basis may help prevent some sporting injuries, no evidence suggests that this decreases the risk of hip dislocation.
• No correlation exists between athletic experience and hip dislocations.

Related Medscape topic:
Resource Center Exercise and Sports Medicine

References

• Contusions
• Femoral Head Avascular Necrosis
• Femoral Neck Fracture
• Femur Injuries and Fractures
• Hip Fracture
• Hip Pointer
• Slipped Capital Femoral Epiphysis
• Snapping Hip Syndrome
• Traumatic Hip Subluxation

• Breaks, Fractures, and Dislocations Center
• Sports Injury Center
• Total Hip Replacement Introduction
• Total Hip Replacement Preparation