Your body is made up of hundreds of joints. These joints attach bones together and help your body move. The sternoclavicular joint is one of four joints in your shoulder. When the sternoclavicular joint is injured, it can cause pain and difficulty in everyday tasks.
What Is the Sternoclavicular Joint?
Joints are points in the body where two or more bones meet. Some joints are fixed, meaning they only serve to connect bone and don’t allow for movement. Other joints, like those in your ankles, elbows, and shoulders, are mobile joints.
The sternoclavicular joint (SC joint) is a joint within your shoulder. Your shoulder uses several different muscles, tendons, ligaments, joints, and bones to move properly. The sternoclavicular joint is one of these joints.
Your sternoclavicular joint connects your sternum and your clavicle. Your clavicles are your collarbones, two bones that stretch horizontally from the bottom of your neck to your shoulders. Your clavicles are sandwiched between the sternoclavicular joint and acromioclavicular joint, which connects the clavicle to the shoulder blade. The sternum is your chest bone. It starts between your clavicles and goes down the center of your ribcage.
The main job of your sternoclavicular joint is to support your shoulder. It’s the only joint that connects your arm to the rest of your body. Your sternoclavicular joint also helps your shoulders move properly. You use it when you:
- Shrug your shoulders up or pull them back down
- Pull your shoulder blades back and together
- Round your shoulders forward
- Rotate your arm around your shoulder
Types of SC Joint Injuries
While not very common, your sternoclavicular joint can have problems because of injury or other conditions. Injuries are usually caused by a strong force, such as a car accident or a hit in a contact sport like football.
Sternoclavicular joint injuries are divided into three types:
- Type 1: Sprain
- Type 2: Subluxation
- Type 3: Dislocation
Sprain.Sprains happen when ligaments, the connective tissues that hold bones and organs in place, are overstretched or torn. Many different ligaments support your SC joint, and these ligaments can be injured by a strong force, such as in a car accident, contact sports, or a fall. Sprains can be divided into three levels:
- Grade 1: A grade 1 sprain is mild and involves overstretching of ligaments.
- Grade 2: A grade 2 sprain is moderate and is the result of a partial tear to the ligaments.
- Grade 3: Grade 3 sprains are severe and happen when the ligament is completely torn. This type may only be fixable through surgery.
You may hear a “pop” sound at the time of injury. Other SC joint sprain symptoms include:
- Limited ability to move the shoulder
Subluxation. A subluxation of the SC joint happens when the sternoclavicular ligaments are torn, but the costoclavicular ligaments are still intact. The sternoclavicular ligaments connect the sternum to the clavicle, while the costoclavicular ligaments stretch from the first rib to the clavicle.
Dislocation.Dislocation happens when the two bones in the joint, in this case the clavicle and sternum, are separated at the joint. Sternoclavicular dislocations are divided into two categories, depending on which direction the collarbone was pushed.
- Anterior dislocation: Anterior dislocations of the SC joint result in the clavicle being pushed in front of the sternum. This is usually from a hard blow to the front of the shoulder, such as falling on an outstretched hand. Anterior sternoclavicular dislocations are more common than posterior sternoclavicular dislocations.
- Posterior dislocation: Posterior dislocations happen when a direct blow against the front of the clavicle pushes the end of the clavicle behind the sternum.
Posterior dislocations are rarer than anterior dislocations, but they are more of a medical emergency. Posterior sternoclavicular dislocations can lead to:
- Brachial plexus injury: Your brachial plexus is the group of nerves that send messages from the spinal cord to your arms, hands, and shoulders. Brachial plexus injuries can cause numbness, tingling, weakness, pain, and even complete lack of movement in the affected arm.
- Pneumothorax: A pneumothorax is a collapsed lung. This can happen if the clavicle pierces one of your lungs. It can cause pain and difficulty breathing. A pneumothorax is a medical emergency.
- Problems in the throat: If the clavicle presses into your throat, it can lead to difficulty swallowing and a hoarse voice.
- Vascular injury: A vascular injury happens when there is injury to an artery or vein. This can include the artery or vein being crushed, pinched, stretched, twisted, or pierced. Symptoms include bleeding, bruising, pain, swelling, and the development of a lump under the skin.
Types of SC Joint Disorders
Aside from injuries, certain medical conditions and disorders can cause issues with your sternoclavicular joint. These include:
- Condensing osteitis. Condensing osteitis is a rare condition that causes pain and swelling in the SC joint.
- Friedrich’s disease. Friedrich’s disease is a condition in which the end of the clavicle bone that makes up part of the SC joint begins to die.
- Gout. Gout is a type of arthritis that causes inflammation and significant pain in a joint. It usually affects the joint of the big toe but has been known to affect the SC joint.
- Infection. Infections in the SC joint are rare and usually caused by bacteria. Symptoms include discomfort, fever, redness, and swelling.
- Osteoarthritis. Osteoarthritis is the most common type of arthritis and happens when the cartilage at the ends of your bones wears down. One study showed that up to 89% of patients above age 50 had signs of osteoarthritis in their SC joint.
- Rheumatoid arthritis. Rheumatoid arthritis is an autoimmune form of arthritis. It happens when your body attacks the lining of your joints, which causes painful swelling and can eventually cause bone erosion and joint deformity.
- Seronegative spondyloarthropathies. Seronegative spondyloarthropathies are a group of autoimmune inflammatory diseases that often affect the joints. These diseases cause pain, stiffness, and swelling within the joints.
- Synovitis-Acne-Pustulosis-Hyperostosis-Osteitis (SAPHO) Syndrome. SAPHO is a condition that affects the musculoskeletal system and can lead to bone inflammation.
If you’ve sustained an injury to your shoulder or clavicle or notice that you’re having pain or difficulty using your shoulder, contact your healthcare provider.