A hip that is “out of place” refers to a severe injury known as a hip dislocation, where the ball of the thigh bone (femoral head) is completely forced out of the hip socket (acetabulum). A less severe version, called a subluxation, involves the partial displacement of the joint. The hip joint is designed for immense stability, meaning that any displacement is a sign of significant force or underlying joint vulnerability. A full dislocation is a major orthopedic injury requiring immediate medical attention.
The Immediate Sensation of Severe Pain
The initial sensation of a hip dislocation is a sudden, acute, and excruciating pain that is overwhelming. This pain is localized deep within the hip joint and groin area, marking the moment the femoral head tears through the surrounding ligaments and joint capsule. The severity is typically so high that it immediately renders the person incapable of focusing on anything else.
The deep joint pain is commonly accompanied by intense, involuntary muscle spasms in the surrounding large muscle groups of the hip and thigh. These powerful muscles seize up in an attempt to stabilize the unstable joint, which paradoxically increases the pain profile. This combination of bony displacement and muscle contraction creates a throbbing, relentless ache that persists until the joint is relocated.
Physical Signs and Inability to Move
Beyond the internal pain, a hip dislocation produces several clear physical signs. A distinct visual deformity of the limb is usually immediately apparent to any observer. The entire leg on the affected side will often appear shorter than the uninjured leg.
The position of the leg will be fixed and unable to move voluntarily. In the most common type of injury, a posterior dislocation, the leg will be visibly rotated inward and pulled toward the body’s midline. Conversely, in a less common anterior dislocation, the leg will be rotated outward and slightly bent.
The person will have an absolute inability to bear any weight on the injured leg due to the mechanical disruption of the joint. Any attempt to move the leg or put pressure on the foot will result in a sharp increase in the agonizing pain. The joint itself may appear swollen, and in some cases, the displaced femoral head may be felt or seen as a prominent bulge near the buttock or groin.
Understanding the Severity (Why Immediate Help Is Needed)
A displaced hip is a serious medical event because of the potential for permanent damage to nearby structures. The femoral head receives its blood supply through fragile vessels that can be stretched or torn when the joint dislocates. If this blood flow is interrupted for too long, it can lead to avascular necrosis, which is the death of bone tissue.
To minimize the risk of this complication, the hip must be reduced—or put back into place—within a window of six to eight hours. Furthermore, the sciatic nerve runs directly behind the hip joint and can be compressed or stretched by the displaced femoral head. Sciatic nerve injury occurs in approximately 10% to 20% of posterior dislocations and can result in numbness, tingling, or weakness in the lower leg and foot.
If a hip dislocation is suspected, it is imperative to call emergency medical services immediately. The person should not be moved, and no one should attempt to manipulate the limb or force the joint back into place. Keeping the patient as still as possible helps prevent additional damage to the surrounding blood vessels and nerves while awaiting professional help.
How Hip Displacements Occur
The hip is a stable ball-and-socket joint, meaning a significant amount of force is usually required to cause a dislocation in a healthy joint. The most frequent cause of a hip dislocation is high-energy trauma, such as a motor vehicle collision or a severe fall from a height. In these incidents, the force transmitted up the thigh bone is sufficient to push the femoral head out of the acetabulum.
However, hip displacement can also occur from low-energy mechanisms in individuals with predisposing factors. People who have had a total hip replacement, for example, have an artificial joint that is more susceptible to displacement from simple movements like bending over or twisting. Also, those with underlying conditions like hip dysplasia, where the socket is naturally shallow, may experience a dislocation more easily.