The shoulder impingement that keeps coming back
8 min read · Uplevel editorial
You know this pain now the way you know a difficult neighbor — its specific character, the times it shows up, what sets it off. Overhead press: yes. Sleeping on that side: yes. Reaching back to buckle a seatbelt: sometimes. You did the six weeks of physical therapy. The exercises helped for a while, until they didn't. The cortisone injection gave you two months of near-normal, and you thought maybe that was it, and then it came back. Your orthopedist looked at the MRI and said some fraying, normal for your age, it's a degenerative thing, try to avoid the movements that aggravate it. That was a year ago. You've been managing around it since then.
The problem with "shoulder impingement" as a diagnosis is that it describes a location and a symptom but not a cause. The subacromial space — the gap between the head of the humerus and the acromion above it — is where the impingement is occurring. But why is it occurring? That question is where most shoulder diagnoses stop and where the useful work actually begins.
Rotator cuff tendinopathy is the most common underlying finding, and it exists on a spectrum. The rotator cuff is a group of four muscles — supraspinatus, infraspinatus, subscapularis, and teres minor — whose tendons converge around the humeral head to provide dynamic stability and guide shoulder movement. Any of these tendons can develop tendinopathy: a degenerative process driven by cumulative load, compromised blood supply to the tendon (the critical zone of the supraspinatus has notoriously poor vascularity), and failed healing response. The pain of supraspinatus tendinopathy in particular maps almost exactly onto what most people call impingement: pain with overhead reach, pain lying on the affected side, a painful arc when lifting the arm to the side through about 60 to 120 degrees. The tendinopathy is the structure in distress; the impingement is what happens to it every time the shoulder moves through that arc.
Partial thickness rotator cuff tears are worth distinguishing from tendinopathy because they can look identical clinically but have different healing trajectories. An MRI with arthrography — or sometimes a high-quality MRI without — can distinguish a partial tear from thickened tendinopathy. This distinction matters for rehabilitation design: some partial tears respond well to conservative management; others, particularly larger partial tears on the articular surface, are more likely to progress and may warrant a different conversation with an orthopedic surgeon. Living with the generic label "impingement" when you have a partial tear that's been there for a year means you're not having that conversation.
Biceps tendinopathy is frequently involved alongside rotator cuff pathology and often goes unaddressed because the treatment focus goes to the rotator cuff. The long head of the biceps runs through the shoulder joint and is loaded in many of the same positions that aggravate rotator cuff symptoms — overhead pressing, heavy lifting, reaching. Anterior shoulder pain, pain with resisted supination or elbow flexion, and tenderness directly over the bicipital groove all suggest biceps tendon involvement. A rehabilitation program that addresses the rotator cuff without addressing the biceps may leave a persistent pain generator untouched.
AC joint involvement is another commonly missed piece. The acromioclavicular joint — at the top of the shoulder where the clavicle meets the acromion — can develop osteoarthritis or capsular irritation that contributes to shoulder pain and limits certain movements, particularly horizontal adduction (reaching across your body) and overhead loading. Pain specifically at the top of the shoulder rather than in the deltoid region is a clue. The AC joint and the subacromial space are anatomically adjacent, and pathology in both is common.
Scapular dyskinesis is the functional diagnosis that explains why many people's impingement keeps coming back despite adequate treatment of the local structures. The scapula is the base from which shoulder movement occurs. It needs to rotate upward, tilt posteriorly, and externally rotate as the arm elevates — a coordinated movement that opens the subacromial space and allows the rotator cuff tendons to clear the acromion without impingement. When the muscles that control scapular motion — primarily the serratus anterior, lower trapezius, and middle trapezius — are weak, inhibited, or poorly timed in their firing, the scapula moves wrong. The acromion doesn't elevate the way it should. The subacromial space narrows during elevation. Every overhead movement grinds tissue through too small a gap. You can inject and stretch and rest the local structures and they will re-impinge the moment you start loading the shoulder again, because the movement pattern driving the impingement hasn't changed.
This is why physical therapy for shoulder impingement varies so dramatically in its outcomes: PT that focuses on rotator cuff strengthening exercises without addressing scapular mechanics is incomplete. PT that includes specific serratus anterior and lower trapezius activation, scapular upward rotation work, and movement retraining does something fundamentally different. The difference between these is not minor. If the PT you did didn't meaningfully improve your scapular mechanics, there's a reasonable argument that the most important work wasn't done.
Cervical spine referral is worth considering, particularly if there's any neck component to your history. The C5 and C6 nerve roots refer to the shoulder and outer arm in patterns that can overlap significantly with rotator cuff symptoms. Cervical disc pathology, foraminal stenosis, or upper cervical joint dysfunction can produce shoulder pain that mimics — or coexists with — local shoulder pathology. If your shoulder pain has any radiation into the arm, if it's associated with any neck stiffness or headaches, or if shoulder treatments haven't produced the improvement they should have, cervical evaluation is appropriate.
Thoracic mobility limitations produce apparent shoulder problems through a related mechanism. The thoracic spine needs to extend to allow full shoulder elevation with proper mechanics. If thoracic mobility is limited — common in people with desk postures, in people who don't regularly work through thoracic extension, and increasingly common with age — the shoulder compensates by demanding more range from the glenohumeral joint and more upward rotation from the scapula than either structure can comfortably produce. This results in earlier impingement and more limited overhead function than the shoulder structures themselves would predict. A thoracic extension deficit is often visible in someone with recurrent shoulder impingement and often completely absent from their treatment plan.
Calcific tendinitis is its own entity within the shoulder impingement differential. Calcium deposits within the rotator cuff tendon — most commonly the supraspinatus — can cause episodic severe pain, particularly during the resorptive phase when the calcium is being broken down. Plain X-rays can identify calcific deposits, and the treatment (often ultrasound-guided needling or lavage) is different from standard tendinopathy management. If your shoulder has periods of acute severe pain interspersed with more manageable chronic pain, calcific tendinitis is worth ruling in or out.
Early adhesive capsulitis — frozen shoulder — is in the differential for shoulder pain with significant stiffness. It's often initially diagnosed as impingement until it becomes apparent that the range of motion limitation is global rather than arc-specific, and that passive range of motion is as limited as active. It has a natural history (inflammatory phase, frozen phase, thawing phase) that spans one to three years, and early intervention with appropriate PT and sometimes corticosteroids or hydrodilatation can meaningfully shorten that trajectory.
Where peptide approaches may have a supporting role in established tendon pathology is in the context of tissue remodeling — as an adjunct to a rehabilitation program that's addressing the underlying mechanics, not as a substitute for it. BPC-157 has been researched for its effects on tendon healing in preclinical models — it appears to upregulate growth factor signaling and fibroblast activity relevant to collagen organization in healing tendons. TB-500 has been studied for its roles in cell migration and tissue repair. GH-axis support through peptides like sermorelin or CJC-1295 has a general collagen synthesis rationale — growth hormone increases IGF-1, which supports connective tissue remodeling. All of this research is preliminary relative to the established interventions; these are adjuncts for someone who's doing the structural work and looking to optimize healing biology, not a bypass for the structural work itself.
The foundational approach to recurring shoulder impingement starts with imaging that answers the specific structural questions: Is there a partial tear, and how large is it? Is there AC joint pathology? Is there calcific tendinitis? Then it moves to functional assessment by a physical therapist with specific competence in shoulder mechanics: What is the scapular kinematics pattern? Where is the thoracic mobility limitation? What is the serratus anterior and lower trapezius function? Ergonomic and lifestyle review — what movements are loading the shoulder repeatedly throughout the day, and are any of those modifiable — is the final piece that often goes undone.
What recurring shoulder impingement is signaling is not primarily that the shoulder is degenerating and needs to be managed around. It's that something in the mechanical picture hasn't been adequately identified or addressed. The cortisone injection works for six weeks because it reduces inflammation enough to take the pain out of the equation — and then the mechanics that were producing the impingement resume, and the tissue re-irritates, and you're back. The cycle ends when the mechanism driving the impingement is found and corrected, not when the symptoms are suppressed again.
Impingement that keeps coming back is a diagnostic adequacy problem before it's a treatment problem. The question worth asking your provider isn't "what else can we try for the impingement." It's "do we know yet what's actually causing it."
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