Background and Etiology
The hip joint is one of the largest joints in the body. It is composed of one osseous (contains bone) joint. The hip is built for weight bearing and movement in several different planes. The stability of the hip joint comes from the capsule, ligaments, muscle and a cartilaginous tissue called the labrum.
Bone and Joint
The hip, like the shoulder, is a ball and socket joint. It is formed by the head of the femur (thigh bone), which sits in the acetabulum, a part of pelvis. The head of the femur (the ball) is large and the acetabulum (the socket) is shallow. This allows for a greater range of motion.
Articular cartilage covers the surface of the bones involved in the hip joint. The articular cartilage has a smooth and shiny surface that allows the ends of the bones to slide freely over each other.
Ligaments and Labrum
There are five major ligaments that provide stability to the hip joint. Ligaments are soft tissue structures that connect bone-to-bone. The capsule and ligaments provide passive stability to the hip joint, that allows for movement in different planes. The labrum of the hip is a fibrocartilaginous structure that is located around the acetabulum (the socket.) It provides added depth and stability to the joint.
Due to the inherent stability of the hip, dislocations are rare. When dislocations do occur, they are typically the result of trauma or extreme force. The hip can dislocate in either a posterior (back) or anterior (front) direction. A majority of hip dislocations, 70-80%, occur in the posterior direction, and 90% of these dislocations are sports related. Trauma due to motor vehicle accidents accounts for up to 70% of all hip dislocations.
Cause and Mechanism
Posterior dislocations are caused when a large force impacts the leg when the knee is flexed (bent,) the hip is flexed (bent,) the hip is adducted (moved toward the opposite leg) and the hip is internally rotated (turned in.) In the hip, the head of the femur will be pushed out of the joint in a posterior (backward) direction.
- This is common in motor vehicle accidents when the knee hits the dashboard. The use of a seat belt can help prevent a hip dislocation in this instance.
- A sudden fall while the leg is in the afore mentioned position
- High contact sports like rugby or football where the player is hit and lands hard on his or her knee.
- Anterior dislocations occur when a significant force impacts the leg while the hip is flexed (bent,) abducted (away from body,) and externally rotated (turned out.)
- Anterior dislocations may occur due to jumping sports like gymnastics, basketball, or skiing where the individual lands awkwardly.
- Pain that is severe in nature and may run down the leg to the knee, or into the back following a fall or forceful impact injury.
- Inability to walk or place weight on the knee
- Decreased ability to move the hip
- Weakness of the affected hip joint
- Numbness or tingling in the leg that may be associated with nerve involvement in the dislocation (likely the sciatic nerve.)
- The hip will appear shortened, rotated in and close to the other leg with a posterior dislocation.
- Pulse should be monitored because circulation may be effected by this injury.
- X-rays will be necessary to rule out an associated fracture, which may have occurred in addition to the dislocation.
- It may be important to assess the circulation of the hip joint following dislocation because avascular necrosis can be a complication.
A hip dislocation is a medical emergency. The hip needs to be put back in place, or reduced as soon as possible.
- If there are no complications the physician will administer anesthesia or a sedative and relocate or put the hip back in place.
- In more complicated situations surgery may be indicated. This is especially true if there are complications like a fracture, nerve involvement, or vascular involvement.
- Following reduction, the patient will be given anti-inflammatory and pain medication and ice will be applied.
- If the injury is more involved, traction to the leg may be necessary.
- Dislocations with fractures may require a period of bracing.
- Weight bearing is encouraged as soon as possible, initially with crutches.
- Physical Therapy will be initiated once the physician has given clearance for weight bearing.
A hip dislocation is a serious injury. Following relocation and reduction of pain, weight bearing should be initiated. Individuals will start partial weight bearing with crutches or a walker and then progress to full weight bearing. Initiation of weight bearing and progression of treatment will depend on the severity of the injury. Emphasis will be on reduction of pain, progression of weight bearing, improving range of motion, hip strength and stability.
- Gait and weight bearing activities may be used to help the patient wean-off assistive devices and progress to full weight bearing
- Range of Motion: restore range of motion, avoiding the position of dislocation while the ligaments and muscles heal
- Strengthening: Improve strength of the affected hip musculature and total leg strength.
- Stabilization: Work on the primary hip stabilizers in weight bearing functional positions to improve dynamic stability of the hip joint.
- Function: Progression to functional activities including daily life (stairs, kneeling, squatting, getting in and out of the car, etc.), or returning to high-level functions like sport performance.
Physical Therapy Interventions
Common Physical Therapy interventions in the treatment of Hip Dislocation include:
- Manual Therapeutic Technique (MTT): hands on care including soft tissue massage, stretching and joint mobilization by a physical therapist to improve alignment, mobility and range of motion of the hip. Use of mobilization techniques also help to modulate pain.
- Therapeutic Exercises (TE) including stretching and strengthening exercises to regain range of motion within safe parameters and strengthen muscles of the hip and lower extremity to support, stabilize and decrease the stress placed on the joint.
- Neuromuscular Reeducation (NMR) to restore stability, retrain the lower extremity and improve movement techniques and mechanics (for example, running, kneeling, squatting and jumping) of the involved lower extremity to reduce stress on the hip joint in daily activities.
- Modalities including the use of ultrasound, electrical stimulation, ice, cold laser and others to decrease pain and inflammation of the involved tendon and bursa.
- A home program that includes strengthening, stretching and stabilization exercises and instructions to help the person perform daily tasks and advance to the next functional level are an important part of physical therapy and eventual patient independence.
The prognosis for a full recovery depends on the severity of the injury, which may be complicated by nerve damage, loss of blood supply to the femoral head (aseptic necrosis) or associated fracture. Early reduction of the dislocation is important in limiting the chances of developing aseptic necrosis or neurological damage. The hip relocation should be done preferably in the first six hours following injury. Individuals without complications generally do well within four months. This is especially true for athletic dislocations.