Your deltoid muscles cover the top of your shoulder. They help you lift your arm to front, side and back. Deltoid muscle pain can affect swimmers, pitchers or anyone who performs repetitive overhead arm movements.
Your deltoid muscles are in your shoulder, which is the ball-and-socket joint that connects your arm to the trunk of your body. Deltoid muscles help you move your arms in different directions. They also protect and stabilize your shoulder joint.
Like most other muscles in your body, the deltoids are skeletal muscles. Tendons attach them to bones. Skeletal muscles are voluntary muscles, meaning you choose to move them. Skeletal muscles are different than smooth, or involuntary, muscles (such as your heart) that work without you having to think about it.
Your deltoid muscles crown your shoulder, covering the front, side and back of the joint. They’re superficial, which means they’re close to the surface of your skin. The deltoid looks like an upside-down triangle. Tendons connect each of the three side to bones.
The base of the deltoids connects to the upper part of your scapula (shoulder blade) and the side of your clavicle (collarbone). The point of the deltoids attaches to the side of your humerus (the arm bone between your shoulder and elbow).
The deltoid muscles have three parts, or heads:
Like other muscles in your body, deltoid muscles in your shoulder contain elastic fibers. These fibers make the muscles flexible, so they can perform lots of movements. Skeletal muscles are red and white, making them appear striated (striped or streaked).
Conditions that may affect your deltoid muscles include:
Shoulder muscle conditions are common. One study suggests that 18 to 26% of adults experience shoulder pain at some time in their lives. But problems affecting the deltoid muscles aren’t quite as common as other shoulder conditions, such as rotator cuff injuries.
Anyone can have problems with their deltoid muscles. But they’re more common in athletes that perform a lot of overhead arm movements, such as:
Your risk for shoulder muscle conditions increases if you:
Deltoid muscle conditions may cause:
Your healthcare provider reviews your symptoms and performs a physical exam. They may ask you to lift your arm to the front, side and back, possibly against some resistance. If your deltoid muscles are working properly, your provider should be able to feel the muscle contract when you lift your arm.
If you can’t lift your arm, it doesn’t always mean you have a deltoid muscle injury. Arm muscle weakness can also be the result of:
Most deltoid muscle conditions heal with nonsurgical treatments, including:
Serious deltoid muscle injuries, such as a muscle tear, might require surgery. Your healthcare provider may recommend open surgery or minimally invasive arthroscopic shoulder surgery depending on your injury.
Like any surgery, shoulder surgery carries risks of infection, bleeding, blood clots and scar tissue formation. But it’s also important to note that any shoulder surgery can affect your deltoid muscles. Since these muscles run across most of your shoulder and are near the surface of your skin, surgeons often cut through these muscles when they perform rotator cuff repairs, tendon surgeries or other procedures.
Surgical complications specific to your deltoid muscle can include:
Take care of your deltoid muscles by:
Contact your doctor right away if you:
A note from Cleveland Clinic
Your deltoid muscles play an important role in helping you move your arm in different directions. They also stabilize your shoulder joint and protect it from injuries such as dislocations. People who perform a lot of repeated overhead movements, such as swimmers, pitchers or mechanics, are at risk of injuring their deltoid muscles. Most deltoid muscle injuries heal with nonsurgical treatments.
Last reviewed by a Cleveland Clinic medical professional on 09/24/2021.
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