Calcific tendonitis is a condition where calcium crystals build up inside a tendon, most commonly in the shoulder. It affects roughly 3% to 20% of the population, peaks in your 50s, and can range from completely painless to severely debilitating depending on which stage the deposits are in. The condition is self-limiting in many cases, meaning the body eventually reabsorbs the calcium on its own, but that process can take months and the resorption phase is often the most painful part.
Why Calcium Builds Up in Tendons
The process starts when a section of tendon loses adequate blood flow. This localized oxygen shortage triggers cells in the tendon to transform into a type normally found in cartilage or bone. These transformed cells then begin depositing calcium, specifically a mineral called hydroxyapatite, the same substance that makes up tooth enamel and bone.
One leading theory points to stem cells within the tendon itself. These cells normally maintain and repair tendon tissue, but under certain conditions they differentiate into the wrong cell type: cells designed to deposit calcium rather than maintain flexible tendon fibers. The result is a chalky deposit that grows inside the tendon over time, sometimes reaching a centimeter or more in diameter.
Who Gets It
Women are affected far more often than men. In a study of over 500 patients, 79% were female. The average age at diagnosis was 55, and nearly half of all cases occurred in people in their 50s. The 40s and 60s age groups each accounted for roughly 20% to 23% of cases, with smaller numbers in the 30s and 70s. In 10% to 20% of patients, calcium deposits appear in both shoulders.
Which Tendons Are Affected
The shoulder’s rotator cuff is by far the most common site. Within the rotator cuff, the supraspinatus tendon (the one running along the top of your shoulder blade to the top of your arm bone) accounts for about 80% of cases. The infraspinatus tendon, which sits just below and behind it, is involved in about 15% of cases. The subscapularis tendon at the front of the shoulder makes up the remaining 5%. Calcific tendonitis can occur in other tendons throughout the body, including the hip, elbow, wrist, and knee, but shoulder involvement dominates.
The Four Stages of Calcific Tendonitis
The condition progresses through distinct phases, and understanding which phase you’re in helps explain why your symptoms may suddenly worsen or improve.
Pre-Calcific Stage
Tendon cells begin transforming in response to reduced blood flow. No calcium is visible on imaging yet, and this stage rarely causes symptoms. Most people pass through it without knowing anything is happening.
Formative Phase
Calcium crystals actively accumulate within the tendon. The deposits tend to appear dense and well-defined on X-rays. Pain during this phase is usually mild or moderate, often described as a dull ache with overhead movements. Some people remain completely asymptomatic.
Resorptive Phase
This is the stage that typically sends people to the doctor. The body recognizes the calcium deposit as something that needs to go and launches an inflammatory attack. Immune cells called phagocytes swarm the deposit, and new blood vessels proliferate around it. The deposit softens and begins breaking apart, which shows up on imaging as fragmented, punctate, or cystic patterns rather than a solid mass. The resorptive phase lasts anywhere from 3 weeks to 6 months, and the pain can be intense: sudden onset, sharp, sometimes waking you at night, with significant loss of range of motion.
Post-Calcific Phase
The calcium is gradually cleared away and the tendon heals with new tissue. Pain subsides as the deposit shrinks, though some residual stiffness or soreness can linger as the tendon remodels.
What It Feels Like
The experience varies dramatically depending on the stage. During the formative phase, you might notice a nagging ache when reaching overhead, putting on a coat, or lying on the affected shoulder at night. Many people attribute it to general shoulder strain and don’t seek treatment.
The resorptive phase is a different experience entirely. Pain can escalate rapidly over hours, becoming constant and severe enough to prevent sleep. The shoulder may feel hot, swollen, and extremely tender to touch. Range of motion drops significantly. Because this acute flare-up often comes without an obvious injury, it can be alarming. Some people initially worry they’ve torn something. The pain pattern can also mimic frozen shoulder, and in some cases, calcific tendonitis and frozen shoulder occur together, with the inflammation from calcium resorption triggering shoulder stiffness that persists even after the deposit resolves.
How It’s Diagnosed
A standard shoulder X-ray is usually enough to identify calcium deposits. During the formative phase, deposits appear as bright, well-defined white spots. During the resorptive phase, they look cloudier and more diffuse. Ultrasound provides additional detail, showing increased blood flow around the deposit during active resorption and helping to determine whether the deposit is solid (harder to treat with needling) or soft and toothpaste-like (easier to aspirate). MRI is sometimes used to rule out other problems like rotator cuff tears but isn’t necessary for diagnosing calcific tendonitis itself.
Non-Surgical Treatment Options
Because many deposits eventually resorb on their own, initial treatment focuses on managing pain and maintaining shoulder function while the body does its work.
Anti-inflammatory medications and ice are the starting point for most people. Steroid injections into the subacromial space (the cushioned area above the rotator cuff) can provide significant short-term relief during acute flares, though the effect may be temporary. Physical therapy helps preserve range of motion and strengthen the surrounding muscles, which matters both for managing current symptoms and preventing compensatory injuries from favoring the shoulder.
Shockwave Therapy
Extracorporeal shockwave therapy (ESWT) uses focused pressure waves directed at the deposit through the skin. The goal is to break up the calcium and stimulate the body’s resorption process. Research suggests it works best with three sessions spaced a week apart. In clinical trials, shockwave therapy produced significantly better outcomes than placebo in roughly 80% to 88% of studies, making it one of the more reliable non-surgical options for deposits that aren’t resolving on their own.
Ultrasound-Guided Needling
A procedure called barbotage involves inserting a needle directly into the calcium deposit under ultrasound guidance. The clinician first tries to aspirate (suction out) the calcium crystals, then flushes the deposit with saline to break it up and draw out more material. This cycle of flushing and aspirating continues until a satisfactory amount of calcium has been removed. A local anesthetic and anti-inflammatory are typically injected afterward to manage post-procedure pain. The procedure is done in a clinic setting without general anesthesia, and most people can go home the same day. It’s particularly effective when the deposit has softened into the resorptive phase.
When Surgery Becomes Necessary
Most people improve with conservative treatment, but certain factors make surgical intervention more likely. Research from the Royal College of Surgeons identified several predictors of needing surgery: deposits larger than 10 millimeters, symptoms lasting longer than eight months, being female, and having only a temporary response to steroid injections. If you’ve already tried physical therapy and injections without lasting improvement, the probability of eventually needing a procedure goes up.
Surgery is typically done arthroscopically, meaning through small incisions using a camera and specialized instruments. The surgeon locates the deposit and removes as much calcium as possible while preserving the surrounding tendon. Recovery involves a period of limited shoulder use followed by a structured physical therapy program. Most people see meaningful improvement within a few months, though full recovery of strength and mobility can take longer depending on how much tendon tissue was involved.
Calcific Tendonitis vs. Frozen Shoulder
These two conditions overlap enough to cause confusion. Frozen shoulder (adhesive capsulitis) involves inflammation and tightening of the shoulder capsule itself, leading to progressive stiffness and pain that develops over months. Calcific tendonitis targets the tendon rather than the capsule, and its pain pattern tends to be more acute, especially during the resorptive phase. The key distinction on examination is that frozen shoulder restricts passive range of motion (someone else moving your arm for you), while calcific tendonitis primarily limits active movement due to pain but often preserves passive range until inflammation becomes severe. That said, calcific tendonitis can trigger frozen shoulder as a secondary complication, so having both simultaneously is not uncommon.