A shoulder bone spur is a small, bony projection that grows along the underside of the acromion, the flat bone forming the roof of your shoulder joint. These spurs narrow the already tight space between the acromion and the rotator cuff tendons below, and when they pinch or irritate those tendons during arm movement, the result is pain, stiffness, and sometimes significant loss of function. Treatment ranges from physical therapy and corticosteroid injections to arthroscopic surgery that shaves the spur away, with the right approach depending on how much the spur is disrupting your daily life and whether surrounding structures like the rotator cuff have been damaged.
How Bone Spurs Form in the Shoulder
Bone spurs, technically called osteophytes, develop when the body lays down extra bone in response to mechanical stress or chronic irritation. In the shoulder, the most common location is the underside of the acromion, where the bone hangs over the rotator cuff tendons. Years of repetitive overhead movement, age-related wear, or even the natural shape of your acromion can create friction in this space. The body responds to that friction the way it responds to many forms of stress: by building more bone. The spur itself is not inherently painful, but because it grows into an already crowded corridor, it can compress the supraspinatus tendon and the subacromial bursa, triggering what clinicians call subacromial impingement syndrome.
Research has found that people who grow bone spurs at one joint tend to grow them at others as well. A study examining the relationship between osteophytes and enthesophytes (spurs at tendon-attachment sites) found a strong positive correlation between the two, even after accounting for age and sex.
Why Some Shoulders Are More Vulnerable Than Others
The shape of your acromion plays a major role in whether you develop subacromial problems. In the 1980s, researchers classified the acromion into three types: flat (Type I), curved (Type II), and hooked (Type III). The hooked type leaves less clearance above the rotator cuff and has long been associated with impingement. In a study of patients diagnosed with subacromial impingement syndrome, the hooked acromion was by far the most common shape observed, present in roughly two-thirds of cases.1European Journal of Anatomy. Association of subacromial impingement syndrome with acromial morphology and morphometry By contrast, in healthy shoulders the hooked shape appears in fewer than one in ten people, while the curved type accounts for the vast majority.2PubMed Central. Distribution and analysis of subacromial spurs and the relationship with acromial classification and angle in healthy individuals
That said, acromion shape is not destiny. One study found that while Type III acromions and mild degeneration of the acromioclavicular joint were more common in impingement patients, these differences did not reach statistical significance. What did strongly predict impingement was pathology in the supraspinatus and infraspinatus tendons and a reduced distance between the acromion and the humeral head.3PubMed Central. Acromion Shape and Degenerative Changes of the Acromioclavicular Joint as Risk Factors for Sub-Acromial Impingement Syndrome In other words, the spur and the acromion shape set the stage, but the real trouble starts when the soft tissues underneath begin to break down.
Recognizing the Symptoms
Most shoulder bone spurs announce themselves gradually. The classic pattern starts with a dull ache at the front or side of the shoulder that worsens when you raise your arm overhead or reach behind your back. Sleeping on the affected side often becomes uncomfortable. Over time, the pain can sharpen and begin radiating partway down the upper arm. If the spur has been irritating the rotator cuff long enough to cause tendon damage, you may notice weakness when lifting objects or difficulty with everyday tasks like reaching into a cabinet or putting on a coat.
A frustrating feature of bone spurs is that their size on an X-ray does not always predict how much trouble they cause. A large spur in someone with a roomy subacromial space may produce no symptoms at all, while a modest spur in someone with a curved or hooked acromion can cause significant impingement. That is why imaging alone rarely tells the whole story, and why many spurs are discovered incidentally on scans taken for other reasons.
Non-Surgical Treatment
Most people with a symptomatic shoulder bone spur start with conservative treatment, and a substantial number improve enough to avoid surgery entirely. The core of non-surgical management rests on three pillars: activity modification, targeted rehabilitation, and, when needed, injections to control pain.
Physical Therapy and Scapular Rehabilitation
Physical therapy for subacromial impingement focuses on strengthening the rotator cuff muscles and the scapular stabilizers, which are the muscles that control how your shoulder blade moves. When these muscles work well, they help keep the humeral head centered in the joint and prevent it from riding upward into the spur during overhead motion. A meta-analysis of rehabilitation programs that specifically targeted the scapular muscles found that these programs significantly reduced pain and improved shoulder function compared to standard care.4PubMed Central. Clinical Value of Scapular-Targeted Rehabilitation Within the Rotator Cuff Care Continuum: A Systematic Review and Meta-analysis of Conservative and Postoperative Evidence The approach is not about eliminating the spur; it is about training the surrounding muscles to compensate for the narrowed space so the tendon no longer gets pinched.
Rehab programs typically start with gentle range-of-motion exercises to maintain flexibility, then progress to resistance work for the rotator cuff and the muscles around the shoulder blade. The process usually takes several weeks to months, and consistency matters more than intensity. Skipping exercises or returning to aggravating activities too soon is one of the most common reasons conservative treatment stalls.
Corticosteroid Injections
When pain is severe enough to interfere with sleep or prevent participation in physical therapy, a subacromial corticosteroid injection can provide meaningful short-term relief. One retrospective study comparing corticosteroid injections, physiotherapy, and hyaluronic acid injections found that the corticosteroid group showed significantly greater improvement in pain, disability, and shoulder function scores at both three and six months.5Current Orthopaedic Practice. Comparison of the efficacy of physiotherapy, subacromial corticosteroid, and subacromial hyaluronic acid injection in the treatment of subacromial impingement syndrome Injections work quickly, often within days, and can create a window of reduced pain that makes rehab exercises tolerable.
There has been debate about how much volume of medication needs to go into the joint. A randomized trial comparing a very low-volume corticosteroid injection to a high-volume injection found no significant difference in pain relief, function scores, or range of motion at any follow-up point, while the larger volume carried a higher risk of side effects from the added lidocaine.6PubMed Central. Efficacy of high-volume vs very low volume corticosteroid subacromial injection in subacromial impingement syndrome If you are offered an injection, a smaller volume appears to work just as well with fewer potential complications.
The main limitation of corticosteroid injections is that their effects are temporary. Most people experience relief for several weeks to a few months. Repeated injections carry risks, including tendon weakening and cartilage changes, so most clinicians limit them to two or three per year in a given joint.
When Surgery Becomes the Right Choice
Surgery is generally considered when symptoms persist after several months of consistent conservative treatment, or when imaging shows that the spur has already caused a rotator cuff tear. The most common procedure for addressing a shoulder bone spur is arthroscopic subacromial decompression, sometimes called acromioplasty. It is one of the most frequently performed shoulder operations.
The procedure is done through small incisions using a camera and specialized instruments. The surgeon first clears out the inflamed bursal tissue from beneath the acromion, then exposes the bony undersurface of the acromion and uses a motorized burr to smooth it down and remove the offending spur.7PubMed Central. Arthroscopic Subacromial Decompression and Acromioplasty The goal is to widen the subacromial space so the rotator cuff tendons can glide freely without being pinched. If a rotator cuff tear is found during surgery, it can often be repaired at the same time.
Recovery after acromioplasty depends on whether the rotator cuff was also repaired. For a straightforward decompression without tendon repair, most people use a sling for a few days, begin gentle range-of-motion exercises within the first week, and progress to strengthening over the following weeks. Supervised physical therapy after surgery produces better outcomes than home exercises alone. A randomized trial comparing supervised strengthening exercises to home-based movement exercises after arthroscopic acromioplasty found that the supervised group had significantly better shoulder function and disability scores at six months.8Journal of Rehabilitation Medicine. Supervised strengthening exercises versus home-based movement exercises after arthroscopic acromioplasty Returning to full overhead activity typically takes about three to four months.
Platelet-Rich Plasma as an Alternative to Cortisone
In recent years, platelet-rich plasma (PRP) injections have gained attention as a longer-lasting alternative to corticosteroids for subacromial pain. PRP is made from a sample of your own blood, concentrated to contain a higher-than-normal level of platelets and growth factors. The theory is that these growth factors promote tissue healing rather than just suppressing inflammation the way cortisone does.
A double-blinded randomized controlled trial compared PRP to corticosteroid injections in patients with subacromial impingement and followed them for a year. At twelve months, the PRP group had significantly better pain scores, functional scores, and sleep quality. The overall failure rate was also much lower in the PRP group, at roughly one in eight patients, compared to nearly one in three for corticosteroids.9Journal of Shoulder and Elbow Surgery. Subacromial injection of platelet-rich plasma provides greater improvement in pain and functional outcomes compared to corticosteroids at 1-year follow-up The catch is that PRP is rarely covered by insurance and typically costs several hundred dollars out of pocket, and more high-quality trials are needed before it becomes a standard first-line option.
Who Is Most at Risk
Shoulder bone spurs and the impingement they cause are strongly linked to age. The subacromial space naturally narrows with decades of use, and the cumulative effect of small stresses adds up. People whose jobs or hobbies involve repetitive overhead motion are frequently affected. A study of 150 overhead workers including carpenters, construction workers, electricians, and painters found that age and years of experience were the strongest predictors of shoulder pain severity and disability, with a robust correlation between those factors and standardized pain scores.10Journal of Ecophysiology and Occupational Health. Prevalence of Shoulder Pain in Overhead Occupation Workers Associated with Impingement Syndrome Roughly a quarter of those workers reported very severe shoulder pain and disability. Interestingly, body mass index did not show a significant correlation in that study, though it is worth noting that the relationship between metabolic factors and shoulder pain remains an active area of investigation.
Athletes in overhead sports like swimming, baseball, tennis, and volleyball face similar risks. The repetitive motion of a tennis serve or a swimming stroke creates the same kind of cumulative stress as years of painting ceilings. Weekend warriors who suddenly ramp up overhead activity after a long period of inactivity are also vulnerable, because their rotator cuff and scapular muscles may not be conditioned to stabilize the joint under load.
Metabolic Factors and Shoulder Health
There is growing interest in whether systemic metabolic conditions contribute to rotator cuff problems and the shoulder pain that bone spurs aggravate. A systematic review examined the potential link between metabolic syndrome and rotator cuff-related shoulder pain.11BMJ Open Sport & Exercise Medicine. Is there an association between metabolic syndrome and rotator cuff-related shoulder pain? A systematic review The biological rationale is plausible: conditions like diabetes and dyslipidemia can impair blood flow to tendons and promote chronic low-grade inflammation, which could make rotator cuff tendons more susceptible to damage in an already narrowed subacromial space. If this link is confirmed by stronger evidence, it could mean that managing blood sugar and cholesterol might be part of keeping your shoulders healthy, not just your heart.
An Evolutionary Perspective on the Vulnerable Shoulder
If you have ever wondered why human shoulders seem so prone to problems, you are not alone. Researchers have looked at this question from an evolutionary standpoint and found that the answer is not as simple as “we were not designed for overhead work.” A comparative anatomy study examined ten features commonly associated with subacromial impingement and rotator cuff tears in humans and compared them to other species. None of those features were significantly more pronounced in humans than in the other animals studied.12PubMed Central. Human evolution and tears of the rotator cuff
That said, the human shoulder has evolved some characteristics that may leave it less suited for the overhead demands we place on it. Compared to great apes, humans have a relatively small suprascapular fossa, a laterally facing acromion, and a clavicle that does not flare upward at its outer end. The angle at which the muscles that stabilize the scapula attach is more similar to that of four-legged primates than to our closest evolutionary relatives. These subtle differences may make the human shoulder less naturally equipped for sustained overhead work and sporting activities.13Physiotherapy. Subacromial impingement syndrome: Has evolution failed us? In essence, the shoulder traded some overhead robustness for the extraordinary range of motion that lets us throw, climb, and manipulate objects with precision. Bone spurs in that tight subacromial corridor are one consequence of asking a joint optimized for mobility to also withstand decades of repetitive load.
Common Misconceptions About Shoulder Spurs
One of the most persistent misunderstandings is that a bone spur must be surgically removed as soon as it is found. In reality, many spurs are asymptomatic and discovered accidentally. If a spur is not causing pain, impingement, or tendon damage, there is no reason to operate. Treatment targets the symptoms, not the X-ray appearance.
Another common belief is that once a spur is shaved away surgically, the problem is permanently solved. While acromioplasty has good success rates and most people experience lasting relief, the underlying mechanical and biological forces that produced the spur in the first place do not vanish. The body is still capable of laying down new bone at the same site, particularly if the factors that caused the original spur, such as repetitive overhead stress or poor scapular mechanics, are not addressed through rehabilitation and activity modification. Post-surgical physical therapy is not optional padding in your recovery plan; it is one of the most important factors in a lasting outcome.
A third misconception is that cortisone injections “fix” the problem. Cortisone is a powerful anti-inflammatory that can dramatically reduce pain, but it does nothing to address the bony spur, strengthen the rotator cuff, or change the mechanics that led to impingement. Used strategically as part of a broader treatment plan, injections are valuable. Used as a standalone solution, they tend to provide a cycle of temporary relief followed by recurrence.
How the Acromioclavicular Joint Fits In
Bone spurs do not exclusively grow from the underside of the acromion. The acromioclavicular (AC) joint, where the collarbone meets the top of the shoulder blade, is another common site. AC joint spurs can grow downward and encroach on the subacromial space from above, producing symptoms that mimic or compound standard impingement. If you have been diagnosed with subacromial impingement but your symptoms do not fully resolve with treatment aimed at the acromial spur, AC joint involvement is worth investigating. During arthroscopic decompression, surgeons sometimes need to address spurs from both the acromion and the AC joint to fully open the space.
AC joint degeneration is extremely common with age, and many people develop spurs there without ever having symptoms. The challenge for clinicians is distinguishing the AC joint spur that is genuinely contributing to impingement from the one that is merely an incidental radiographic finding. Clinical tests that isolate the AC joint, such as the cross-body adduction test, can help sort this out, but the distinction is not always clean-cut. This ambiguity is one reason that a thorough evaluation including both physical examination and imaging is important before committing to a treatment plan.