Why Does My Deltoid Muscle Hurt?

Shoulder pain is a common problem that may be caused by an injured deltoid muscle. It is often a result of overuse, leading to stretching or tearing of the muscle./span>

Because of the shoulder’s complex anatomy, pain can interfere with everyday activities like reaching for an object or brushing your teeth. But it’s a common problem — some studies estimate up to 26% of adults report experiencing shoulder pain.

This pain could result from many causes, like arthritis, neck problems, or other health issues. But if your discomfort is coming from the front, side, or back of your shoulder — especially when lifting your arm — you may have a deltoid muscle injury.

The deltoid muscle is a large, round muscle that connects your collarbone, shoulder, and shoulder blade to your upper arm, stabilizing the joint. When it’s working properly, this muscle enables the arm to lift and rotate, supporting the greatest range of motion in your body.

Physiotherapy can treat — and potentially prevent — most deltoid pain, but in some cases you may need a doctor’s intervention. This pain can sometimes mask more serious injuries that worsen if left untreated. It’s important to understand why your shoulder hurts to ensure the right course of action.

Deltoid pain can indicate that there’s been some sort of damage to the muscle tissue. Your symptoms, their duration, and level of discomfort usually:

• Point to how severe the damage is
• Guide the appropriate treatment
• Help identify another underlying cause, like injury to a different part of your shoulder 

Common signs of a deltoid strain include:

Muscle tightness, weakness, and soreness

A minor muscle injury can make your shoulder feel tight or ache for several days, even during rest. This may not affect normal activities whatsoever, or it could cause pain during certain movements like lifting heavy objects.  

Limited range of movement

More serious muscle damage can interfere with normal movement. 

If you struggle to comfortably lift your arm or move it 90 degrees to the side of your body, there may be an injury in the front of the muscle.

If it’s painful to lift your arm from your side upwards, you might have damaged the mid or top part of the deltoid muscle. 

Swelling and bruising

Deltoid injuries often result in a swollen shoulder that’s tender to the touch. Generally, the more visible swelling or bruising that you see, the severer the injury.

What symptoms you experience can indicate a deltoid injury’s severity. Medical professionals categorize this shoulder injury into three different grades: 

• Grade 1: a mild muscle sprain that still allows for normal function, but you may experience tightness, a dull ache, or swelling
• Grade 2: partial muscle tears that can cause sudden, sharp pain and restrict mobility
• Grade 3: a complete muscle tear that limits or totally prevents usual movement, often leading to severe pain, bruising, and swelling v

Deltoid pain is often a result of overuse, leading to stretching or tearing of the muscle. Your deltoid muscle may be hurting due to:

Repetitive movements

Adding weight or stress to your deltoid muscle for long periods of time — like carrying a heavy backpack — can damage the muscle and cause pain. Some sports, like swimming or tennis, or other activities that require repetitive movements also increase your risk of straining your deltoid muscle. 

Poor posture

Changes in your posture can impact the way your shoulder moves, affecting your shoulder blade’s position and how well the parts of the shoulder work together. Over time, this extra pressure can add strain to the muscle, causing discomfort and reduced mobility. 

Acute injury

Sudden pressure or trauma to the deltoid muscle can cause a tear. This can happen with movements like breaking a fall with an outstretched arm or lifting too much weight. 

In serious cases, shoulder pain might:

• Restrict all movement
• Cause a popping noise
• Continue for several weeks
• Cause extreme discomfort even when at rest 
• Impact your sleep

These symptoms could indicate a full muscle tear or other complications, so make sure to see your doctor if you experience ongoing or severe pain.  

Your doctor will be able to diagnose how severe a deltoid injury is by performing a physical exam and reviewing what activities in your life could have caused this pain. 

If your doctor suspects your pain results from a full deltoid tear or other serious injury, they’ll refer you to an orthopedic doctor who can direct the best course of action. 

Most people can treat Grade 1 and Grade 2 deltoid injuries at home by:

• Resting your shoulder
• Icing or heating the area
• Taking over-the-counter anti-inflammatory medication
• Performing light stretching 

Once your pain has decreased, you can add deltoid-strengthening shoulder exercises to your routine to help prevent future injuries. With any exercise or activity, make sure you’re warming up to protect your shoulder from damage.

Daily stretching also improves your shoulder’s flexibility, helping it to manage stress.

More severe deltoid tears may require surgery or a physiotherapy regimen under a doctor’s care to restore full shoulder functionality. If you treat an injured deltoid muscle at home and pain doesn’t subside after a week or two, make sure to visit your doctor.