You reach up to grab a glass from the cabinet — and there it is again: that sharp, nagging pain in your shoulder. Shoulder pain affects roughly 16% of the population across countries, ages, and occupations (Lucas et al., 2022), making it one of the most common orthopedic complaints. Yet, many of my physical therapy clients know surprisingly little about how the shoulder works - and often carry misconceptions about it. From firsthand experience, I know how shoulder pain can impact your life. So, let’s break it down and start the process of healing.

TL;DR: What You Need to Know About Shoulder Pain

The shoulder is more than one joint — it’s a complex system of bones, joints, and muscles, relying heavily on muscular coordination for stability.
Muscle imbalance and poor posture are the most common causes of shoulder pain, often leading to impingement or nerve compression.
Most shoulder issues are treatable without surgery through strengthening, posture correction, and movement retraining.
See a doctor if you experience trauma, severe weakness, or signs of nerve (numbness or loss of movement) or heart involvement (chest pain, shortness of breath, or nausea/lightheadedness).

Get to Know Your Shoulders

One of the biggest misconceptions about the shoulder is that it's just a single joint — the glenohumeral joint. In reality, the shoulder is a complex system made up of three bones (the clavicle, scapula, and humerus) and four joints, collectively forming the shoulder girdle.

Fun fact: The only direct bony connection between your arm and the rest of your body is where the collarbone (clavicle) meets the breastbone (sternum). Everything else is held together by muscles. This is part of why the shoulder is so prone to pain and injury — it’s the least stable joint in the body. Unlike the hip, which is stabilized by deep bony sockets, the shoulder relies heavily on muscle coordination to maintain proper alignment and function.

When this coordination falters, issues arise. Ideally, the shoulder should glide smoothly in its joint cavity — like a dresser drawer on well-oiled tracks. But if alignment is off, it might get stuck, you may not be able to move it out so far, it might take more effort to move it, and you might wear down the “groove” abnormally over time. This can also disrupt the scapulohumeral rhythm, the intricate “dance” between the shoulder blade, collarbone, and upper arm. When one part is out of sync, the whole system suffers.

Common Issues

While shoulder pain has many causes, these are the four most common problems I see in my physical therapy practice:

1. Muscle Imbalance

By far, the most frequent issue I treat is shoulder pain caused by muscle imbalances. Since the shoulder relies on muscles for stability, weak or dysfunctional muscles quickly lead to poor tracking and pain.

I would argue that the most common shoulder dysfunction/pain is related to the tracking and the scapulohumeral rhythm. Because the shoulder is so dependent on muscles to keep it stable, when those muscles stop working well or are not strong enough to do their jobs, the shoulder becomes painful quickly. The usual pattern of muscle dysfunction seen is called upper cross syndrome, or otherwise referred to as forward head and rounded shoulder position. Essentially, the chest muscles and lower neck muscles (upper trap) get tight, and the shoulder blade muscles and interior neck muscles are not strong enough to do their job. This causes the body to slouch forward and the shoulder to track poorly in its groove.

The most common injury or diagnosis made related to muscle imbalances is called secondary impingement syndrome. This is when the shoulder sits forward in its groove (see the picture to the right), and the tendons between the shoulder blade and top of the upper arm (humeral head) get squished and then inflamed.

People with this issue often say:

“It hurts when I reach overhead.”
“It hurts when I drive.”
“It hurts when I move my arm to the side.”

Fortunately, this is one of the easiest shoulder injuries to treat, as once we “un-squish” the tendons by strengthening the surrounding muscles, the pain usually resolves and leaves no lasting issues.

2. Overuse Injuries

The body craves a diversity of movement. Think of the hunters and gatherers: they ran, they threw spears, they climbed trees, picked berries, sharpened rocks for weapons, etc. They did a lot of different movements throughout their day. As societies evolved, we went from performing dynamic and diverse movement to repetitive, often sedentary or standing movement throughout our day.

When we have occupations or hobbies that require this repetitive movement, our muscles are prone to inflammation and then become painful. The usual structures that become inflamed are tendons (where muscles attach to bone) and bursae (fat pads that reduce friction between the tendon and the bone). Overuse injuries are worsened if there are also muscle imbalances present (which there often are). The best way to treat this is to try to control the inflammation with either medication, taking a break from the movement if possible, or various modalities, such as laser therapy or ultrasound. Once the inflammation is under control, building up strength and learning proper ways to move is the best way to treat the overuse injury and prevent future flare-ups.

3. Acute Injuries

The vast majority of acute injuries are not serious. When a client tells me that pain just happened all of a sudden, it is usually a spasm (which does hurt a lot!). Spasms then leave the muscle sore for a few days and often leave behind trigger points (AKA muscle knots) that linger until massaged out. Spasms are usually caused by muscle imbalance, dehydration (especially low electrolytes), or if you are at the beginning of a new exercise program, or have just increased the intensity. I used to get spasms in the pool when I started swim team - they are not fun! While painful, they are 99% of the time not serious and resolve on their own with a little help.

More serious acute injuries include sprains, strains, or fractures, usually from trauma. If you can’t lift your arm above shoulder height, or you see swelling or bruising shortly after an injury, get it checked. When in doubt, get checked out. The worst thing you can do is have a serious injury and not get it corrected soon enough.

Lastly, adhesive capsulitis (frozen shoulder) deserves special mention. It’s extremely painful and usually affects menopausal women, especially those with diabetes or thyroid issues. The hallmark sign: you literally can’t move your arm past a certain point — not just because of pain, but because something is stopping it. This requires early diagnosis and treatment.

4. The Rotator Cuff

The rotator cuff gets a lot of press but not too many people know what it actually is. The rotator cuff is a group of four muscles that essentially keep the head of your upper arm (humeral head) suctioned into the groove on the shoulder blade (glenoid). The rotator cuff is a predominant player in the stability of the shoulder, and when it is injured, it can cause a lot of issues (hints all the press).

There are three common injuries:

Tendinopathy: Inflammation from repetitive use or poor mechanics
Partial thickness tear: Some fibers of the tendon are torn
Full thickness tear: The tendon is completely torn, often requiring surgery

Most tendinopathies and partial tears resolve with strengthening and therapy. Full tears may require surgical repair depending on severity and patient goals.

When to See a Doctor

While most shoulder pain isn’t an emergency, some red flags warrant immediate care:

Heart attack: Shoulder pain, especially with chest discomfort, shortness of breath, nausea, or lightheadedness, could be cardiac-related. Don’t ignore it.
Nerve involvement: Sudden or worsening numbness, or total loss of arm movement, may mean nerve compression. Call your doctor or go to urgent care.
Severe trauma: After a fall or accident, if your shoulder looks misshapen, won’t move, or shows rapid swelling, get it checked right away.

Imaging Options

There are three types of imaging commonly performed for shoulder pain: X-rays, CT scans, and MRIs. X-rays are almost always performed first. The sole purpose of an X-ray is to check for major fractures. If these are negative, you likely will get an MRI, which looks at the soft tissue (muscles, tendons, bursae, ligaments, etc.). Occasionally, you may also get a CT scan, which provides a closer, more detailed view of bone and can be used to look at the joint itself more closely.

Home Remedies

There are many treatment options you can try on your own without a doctor or physical therapist to guide you.

Heat and Ice:
I get asked all the time which one is better, and the answer is: it depends. If you have a recent injury, swelling, or significant inflammation, ice is better. If you have muscle pain, spasms, muscle knots, or general tightness, heat is better. Sometimes I even advise clients to ice the injury area and heat the tight muscles around it.
Massage:
There are plenty of off-brand Theraguns available now for a decent price. I love to recommend these to clients as you can massage out muscle knots or sore muscles while watching Netflix or winding down for the night. You can also try a Theracane, which is even better than a Theragun to get your back and the back of the shoulder blade.
Keep it moving!:
The biggest mistake I see people make with shoulder injuries is that they immobilize it in a sling. This is a BIG no-no. Immobilizing your shoulder makes it stiff, and it is incredibly difficult to loosen a stiff shoulder. If you are nervous about moving your shoulder, try pulleys - they hang over your door and you can gently move your shoulder up and down with the assistance of the other arm. Most people like this after they get used to it and find it feels better than the sling.
Posture correctors:
I get asked about these all the time. Overall, my opinion is not to waste your money. I tend not to like them because people become dependent on the corrector to keep their shoulders back and not on the muscles that should be doing that job. I do not believe posture has to be perfect all the time, but the stronger your postural muscles are, the better your posture will be. The exceptions to this are if someone has a disease like Parkinson’s that pulls them forward and they cannot stop it, or if someone is hypermobile and the posture corrector helps to keep their joints in place, then absolutely use it. But for the average person, I would recommend focusing on strengthening.

Muscles to Strengthen

If you’re looking to address shoulder pain, these muscles should be part of your plan:

Middle/lower trapezius
Rhomboids
Latissimus dorsi
External rotators (infraspinatus, supraspinatus, teres minor)
Pectoralis major
All heads of the deltoid
Biceps and triceps
Deep neck flexors (e.g., longus colli)

Head over to my Shoulder Pain Workout Plan for a guided program with progressions and cues.

*Sarah’s dog, Kaja, modelling the Gentle Leader (no affliation)*

Prevention Tips

Improved Ergonomics:
This is a whole topic on its own but it deserves a mention. So many clients have come to me with either shoulder or back injuries due to poor lifting techniques or poor work ergonomic habits. For instance, lifting should always occur from the legs. No matter how strong your shoulders are, your arms will never be as strong as your legs. Repetitive lifting from the shoulders is inevitably going to result in an injury.
Frequent Breaks:
Taking a quick 30-second break to stretch, walk away from the task at hand to reset yourself, can give your muscles time to re-oxygenize and help remind you of your posture and mechanics. Additionally, you could request a variety of positions if you work in a repetitive job - instead of boxing all day, see if you could box, then label, then load the truck, etc. I know some places will not go for this but it never hurts to ask!
Dog Walking:
So many shoulder injuries result from a dog pulling on their leash. If you are walking your dog on a normal leash, never wrap it around your wrist - just hold it in your hand. If you dog spazzes and bolts, you will never get the wrap off in time and your wrist or shoulder will pay for it. If you have a pulley dog who cannot (or will not) stop pulling, I recommend getting a gentle leader so you have more control over them and they cannot pull you down. My dog uses one, and it has been a lifesaver when she sees a squirrel or a cat.

Final Thoughts

Shoulder pain can be frustrating, but it’s often very treatable with the right knowledge and approach. By understanding how your shoulder works and what throws it off, you can take practical steps toward long-term relief and injury prevention.

Understanding Shoulder Pain: What’s Really Happening and How to Heal