The Anatomy of a Floating Rib

The human rib cage is made up of 12 pairs of ribs, some of which attach to a bony process in the front of the chest called the sternum. The first seven ribs attach directly to the sternum through cartilage that forms at the end of each rib. Others attach indirectly because they are attached to the cartilage of the rib above.

The last two pairs of ribs at the very bottom of the rib cage do not attach to the sternum at all. These ribs are referred to as "floating ribs" as their only attachment is found at the back of the rib cage, anchored to the vertebrae of the spine. Due to their lack of attachment, these ribs are more prone to injury and have been associated with a painful, though rare, condition called "slipping rib syndrome."

Anatomy

The rib cage is a bony structure found in the chest (thoracic cavity). It is made up of 12 pairs of ribs. Each pair is numbered based on their attachment to the sternum, a bony process at the front of the rib cage which serves as an anchor point. The cartilage that forms at the end of each rib (costal cartilage) attaches either directly or indirectly to the sternum.

Structure

An individual rib has five parts: head, neck, body or shaft, tubercle, and angle.

Location

The ribs are located in the chest (thoracic cavity).

Anatomical Variations

The first seven ribs attach to the sternum directly and are called "true ribs." The first rib is above the clavicle and is shorter and more curved than the others. The next six ribs are both longer and become progressively more open (rather than curved) as the rib cage continues down the length of the torso.

Each of the seven "true" ribs attaches to the breastbone (sternum) at the front of the chest through cartilage, as well as to the vertebrae of the spine in the back.

The remaining ribs (8 through 12) are called "false ribs" as they do not attach to the sternum directly. Instead, they are attached to the costal cartilage of the sternum. However, the last two pairs of ribs at the very bottom, also known as "floating ribs," do not attach at the front of the rib cage at all—only to the vertebrae in the back.

Function

The human rib cage (thoracic cage) has the very important job of protecting the heart and lungs. The ribs are part of the axial skeleton and are classified as flat bones. The primary job of flat bones is to protect underlying structures. Other flat bones in the human body are found in the pelvis and skull.

Several layers of compact bone and marrow form flat plates. Red blood cells are made in the marrow of flat bones.

Due to its cartilaginous attachments and surrounding tendons, the rib cage is able to expand to accommodate the movement of the lungs and diaphragm when breathing. While most of this cartilage remains flexible throughout life, the bottom tip of the sternum—known as the xiphoid process—ossifies (becomes hardened) with age.

Broken or Bruised Ribs

As with any bone in the human body, ribs can fracture or break—though the terminology used to describe injuries involving the chest wall and rib cage can be confusing. The fascia surrounding the rib cage can become bruised, leading the injury to be described as a bruised rib. In terms of broken or fractured ribs, these two terms refer to the same injury or one that occurs in the bone.

The key difference between broken, bruised, and fractured ribs is whether the bones of the rib cage are involved or if the injury was primarily to the tissue of the chest wall. In some cases, both are involved. While a bruised rib might not sound as severe as a broken rib, injury to the tissues that surround and support the rib cage can be extremely painful.

Ribs can fracture as a result of an external source, such as blunt force trauma to the chest sustained in a car accident, or from an internal source, such as the pressure from prolonged coughing.

Slipping Rib Syndrome

While it is not as common as an injury to the chest wall, "slipping rib syndrome" is a curious ailment that can cause distress for people who have it but are not aware of why it occurs.

Slipping rib syndrome (also called Cyriax syndrome, painful rib syndrome, and interchondral subluxation) occurs when the cartilage of the lower floating ribs moves. The movement of these lower ribs is often felt as a slipping, clicking, or popping sensation. The sensation typically only occurs on one side of the rib cage (unilateral), but the pain may radiate to the back on the affected side. The sensation can be very painful or simply a source of discomfort.

Slipping rib syndrome may come and go. Movement such as rolling over in bed, lifting, and coughing can worsen the discomfort or lead to sharp, stabbing pain.

It seems to be reported most often by middle-aged women, though cases have occurred in men, women, and children of all ages. The exact cause of slipping rib syndrome isn't known, but factors such as having previous injury or surgery to the chest or having ligament hypermobility may make a person more likely to experience the condition.

Treatment

Most injuries to the chest wall and rib cage are treated the same way. Unlike with other bones of the body, such as an arm or leg, the chest cannot be immobilized if a bone is broken. Similarly, if a person has experienced trauma to the muscles or ligaments in the chest, there is not much that can be done to reduce movement—as the chest needs to move at least enough to expand as a person breathes.

The treatment for soft tissue injury and fractures is, therefore, the same and mostly focused on controlling pain and any exacerbating factors (such as a cough). Given adequate time and supportive care (including pain management), these injuries usually heal on their own. The healing period can be very uncomfortable, however, and maybe prolonged if the chest is further irritated or reinjured.

Slipping rib syndrome usually does not require treatment. A doctor may suspect a person has the condition after ruling out other causes for their symptoms, such as an injury to the fascia or bone. There is also a physical test they can perform in the office called the hooking maneuver that can help determine if the lower ribs are hypermobile.

If a person with slipping rib syndrome has continued pain that is not well controlled with over-the-counter pain relievers, physical therapy, and other interventions, a doctor may prescribe nerve blocks.

A Word From Verywell

While the condition can range from a mild annoyance to a painful interruption to one's activities, slipping rib syndrome does not put a person at greater risk for injury or a more serious condition involving the chest wall or rib cage. With proper management, awareness of the nature of the condition, and reassurance, most people who experience it do not suffer any complications.

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