Tendonitis: why sore tendons need loading, not just rest
Last updated September 3, 2026.
Tendonitis, now more accurately called tendinopathy, is the umbrella term for a tendon that has been overloaded beyond its ability to repair: at the shoulder, elbow, wrist, hip, knee (jumper's knee), or Achilles. The modern understanding changed the treatment: it is a failed-healing overload problem more than an inflammation problem, which is why progressive loading beats rest, and why the old response (total rest plus repeated steroid shots) prolongs it.
What does it feel like?
Pain localized to a specific tendon, typically stiffest and worst first thing in the morning or after sitting, warming up somewhat with movement, then flaring after too much activity (the next-morning payback is a hallmark). The tendon may be thickened and tender to press. It builds over weeks, though a sudden burst of activity can make it feel acute. Which tendon is involved gives it its local name: Achilles, patellar (jumper's knee), tennis and golfer's elbow, rotator cuff, De Quervain's at the wrist.
Why does it happen?
The tendon is asked to do more than its current capacity: a training ramp-up, a new job or sport, extra weekend DIY, or reduced capacity from age, inactivity, or certain medications (fluoroquinolone antibiotics are a specific tendon risk). Load exceeds repair, the tendon structure disorganizes, and pain becomes the governor. It is mechanical, not a sign of general ill health.
What actually heals it?
- Modify, do not stop: reduce the aggravating load to a tolerable level (mild discomfort that settles by the next day) rather than resting completely; total rest deconditions the tendon.
- Progressive loading: isometric holds for pain relief, then slow heavy strengthening (eccentric work has the longest evidence base), progressed over 8-12 weeks; physiotherapist-guided is the reliable route.
- Isometrics as painkillers: 30-45 second holds against resistance reduce tendon pain for hours, letting you function and train.
- Be careful with injections: steroids give short-term relief at the cost of worse long-term tendon health in trials; other injections (PRP) have mixed evidence.
- Fix the driver: training errors, workstation setup, footwear, or technique: whatever overloaded it gets corrected or the tendon re-flares.
When is it an emergency?
Tendinopathy is a chronic condition, but a tendon rupture is urgent: a sudden pop or snap with immediate weakness (a heel you cannot stand on tiptoe with, a shoulder that suddenly will not lift) needs same-week, and for Achilles ruptures same-day, assessment because early treatment decisions matter. A hot, red, swollen, febrile tendon area needs same-day review for infection. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
Should I completely rest a sore tendon?
No, and this is the single most important update in tendon care. Total rest calms pain temporarily but weakens the tendon further, so symptoms rebound the moment you reload, trapping people in a rest-flare-rest cycle for years. The correct approach is relative rest: reduce the aggravating activity to a level that produces at most mild, short-lived discomfort, keep everything else moving, and add progressive strengthening so the tendon regains capacity. The tendon heals by being loaded correctly, not by being left alone.
Why is it called tendinopathy now instead of tendonitis?
Because biopsies changed the picture: chronic sore tendons show disorganized, failed-repair tissue rather than the inflammatory cells the -itis name implies. That is why anti-inflammatory-heavy strategies (long NSAID courses, repeated steroid injections) disappoint long-term: the fire they aim at is mostly not there. The practical translation: brief anti-inflammatories can help a flare, but the treatment that rebuilds the tendon is progressive mechanical loading.
How long does a tendon take to heal?
Tendons remodel slowly: expect meaningful improvement over 6-12 weeks of consistent loading work, and full resolution over three to six months, sometimes longer for stubborn sites like the Achilles insertion or gluteal tendons. The jagged upward trend is normal: flare after a big day, recover, net progress. Quitting the program at week four because it is not fixed yet is the main way people stay sore for a year.
Are steroid injections a good idea for tendons?
The evidence has hardened against them as a default: steroids reliably relieve tendon pain for a few weeks, but trials repeatedly show worse outcomes at 6-12 months and higher recurrence, plus a small tendon-rupture risk with repeated injections near load-bearing tendons. Selective uses remain (a short-term need, or pain blocking all exercise), but if a plan is steroid-first, ask about the loading program that should be the actual foundation.
Which medications should I worry about with tendon problems?
Fluoroquinolone antibiotics (ciprofloxacin and relatives) carry a specific, well-documented tendon risk, including rupture, especially over 60, with steroids, or with kidney problems: if you need an antibiotic while managing tendinopathy, mention it. Long-term oral steroids also weaken tendons. Statins occasionally cause tendon aches, usually settling on a swap. On the helpful side: no supplement has strong evidence for tendon repair; load is the medicine.
Can I exercise at all while it heals?
Yes, and you should: the skill is choosing loads the tendon tolerates. Swap, do not stop: cycling or swimming while the Achilles calms, upper-body work while the elbow recovers. The working rule: mild discomfort during exercise is acceptable if it settles back to baseline by the next morning; pain that escalates during the session or leaves a next-day hangover means reduce the dose. Your physiotherapist will periodically retest and raise the ceiling as the tendon adapts.