What Is a Positive Sail Sign? Explained and Explored

After a traumatic event, such as a fall or a collision, the body can experience various forms of injury, and one particularly concerning consequence is the accumulation of blood in the intraarticular space. This space, located within a joint, plays a crucial role in ensuring smooth and painless movement. However, when blood fills this space, it can exert pressure on surrounding structures, one of which is the fat pad. The fat pad, also known as the haversian gland, is a cluster of closely packed fat cells that are encapsulated by fibrous tissue. Although it may seem like a relatively insignificant component, the fat pad can provide invaluable diagnostic information when it comes to identifying the extent of an injury. In cases where blood pushes the fat pad anteriorly, resulting in a positive sail sign, healthcare professionals can confidently conclude that there’s an underlying intraarticular fracture, even if a fracture line isn’t immediately detectable. This sail sign serves as a reliable indicator, helping medical professionals make informed decisions in diagnosing and managing traumatic injuries, ultimately promoting improved outcomes for patients.

Is Sail Sign Normal?

A sail sign on a chest X-ray is a radiologic finding that typically indicates left lower lobe collapse. This can be a result of various conditions such as pneumonia, atelectasis, or tumor obstruction. When the left lower lobe collapses, it creates a radiologic shadow that resembles a sail, hence the name sail sign. This finding is most commonly seen in adult patients and is usually concerning for underlying pathology.

However, in children, a sail sign can actually be considered normal and doesn’t necessarily indicate any pathology. In pediatric patients, the sail sign is often attributed to the presence of the thymus gland. The thymus is a specialized organ of the immune system located in the front part of the chest, behind the sternum. As it enlarges during childhood, it can create a radiologic shadow that resembles a sail on a chest X-ray.

The thymic sail sign, also known as the spinnaker-sail sign, is particularly relevant in the setting of pneumomediastinum. Pneumomediastinum refers to the presence of air within the mediastinum, the central compartment of the chest that contains the heart, great vessels, and various other structures. When pneumomediastinum occurs, the thymic lobes can become elevated, causing a sail-like appearance on imaging.

It’s important for radiologists and physicians to be aware of the presence of a sail sign and to interpret it in the appropriate clinical context. While it’s more commonly associated with left lower lobe collapse in adults, it can be a normal finding in children, reflecting the shadow of the thymus.

The sail sign on an elbow radiograph, also known as the anterior fat pad sign, is an important diagnostic finding that indicates the presence of an elbow joint effusion. This sign is characterized by the elevation of the anterior fat pad, creating a distinctive silhouette reminiscent of a billowing spinnaker sail from a boat. Understanding and recognizing the significance of the anterior sail sign can aid in the accurate diagnosis of elbow pathologies.

What Does Anterior Sail Sign Mean?

The sail sign, also known as the anterior fat pad sign, is commonly observed on an elbow radiograph. It refers to the elevation of the anterior fat pad, which creates a distinct silhouette resembling a billowing spinnaker sail on a boat. This sign is highly indicative of the presence of an elbow joint effusion.

When there’s an effusion or collection of fluid within the joint, such as blood or synovial fluid, it causes the anterior fat pad to be displaced. This displacement results in the sail-like appearance on the radiograph.

By identifying the presence of an anterior sail sign, they can conclude that there’s an effusion within the joint and potentially assess the extent of the injury. This information is essential for determining the appropriate course of treatment, whether it be conservative management or surgical intervention.

Source: Fat pad sign


In conclusion, a positive sail sign is a significant indicator of an intraarticular fracture following trauma, even when no visible fracture line is present. This sign occurs when blood accumulates in the intraarticular space and pushes the fat pad anteriorly.

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