Findings explained
What “patellar tendinosis” means on a knee MRI
Read Your Scan Editorial Team·Last updated ·5 min read
Written from published radiology references and reviewed for plain language. Not written or signed by a physician, and not a diagnosis. How we write these pages →
The short answer
Patellar tendinosis means the tendon below your kneecap has degenerated — its fibres have become disorganised and it holds more water than a healthy tendon, so it looks thickened and brighter on MRI. The word is chosen deliberately instead of tendinitis: tissue studies of these tendons find degeneration rather than inflammation, and that changes what actually helps.
- Tendinosis is degeneration. Tendinitis means inflammation. The report chose the first word on purpose.
- It matters because anti-inflammatories treat inflammation, and loading exercise treats degeneration.
- The classic site is the top of the tendon, right where it attaches to the bottom of the kneecap.
- It is called jumper’s knee for a reason — repeated explosive loading is the usual cause.
- Abnormal-looking tendons turn up on MRI in athletes with no pain at all, so the images alone do not decide it.
Why the report says tendinosis
For decades these tendons were called inflamed, and the condition was named tendinitis — the "-itis" ending means inflammation. Then people looked at the tissue itself. Samples taken from painful tendons showed remarkably little inflammation. What they showed was disorganised collagen, more ground substance holding water, and abnormal new blood vessels growing in.
That is degeneration, not inflammation, and it got its own word: tendinosis. Many radiologists now use the umbrella term tendinopathy, which commits to neither.
This is not a semantic exercise. If the problem were inflammation, anti-inflammatories would be the treatment. Because it is degeneration, the treatment with the strongest evidence is loading the tendon in a controlled way so it remodels — which is close to the opposite of resting it.
What the MRI is actually showing
A healthy tendon is dense, ordered collagen with very little free water. On MRI that makes it uniformly dark — almost black — on every sequence.
- Thickening. The affected part of the tendon is fatter than the rest of it, and fatter than the same tendon on the other side.
- Increased signal. The disorganised tissue holds water, so the dark tendon develops a brighter area inside it.
- Loss of the normal shape, usually at the top where the tendon meets the kneecap.
- Sometimes bone marrow edema in the lower pole of the kneecap, where the tendon pulls on it.
- In more advanced cases, small tears within the substance of the tendon.
The location is characteristic: the deep part of the tendon at its upper attachment, immediately below the kneecap. A report describing changes there in someone whose pain is in exactly that spot is a good match.
The finding without the symptom
Imaging studies of athletes have repeatedly found abnormal-looking patellar tendons in people with no knee pain whatsoever — in volleyball and basketball players, in particular, where the rates are substantial.
The reverse also happens: people with clear jumper’s knee whose tendon looks close to normal. The correlation between how bad a tendon looks and how much it hurts is real but loose.
So the MRI is confirmation, not the diagnosis. Patellar tendinopathy is diagnosed clinically — pain at the bottom of the kneecap, worse with jumping, landing, squatting and stairs, tender to press on that exact spot.
What actually helps
The treatment with the best evidence is progressive loading: exercises that put controlled, increasing load through the tendon so it rebuilds. Isometric holds, then slow heavy resistance work, then a graded return to jumping. It is supervised, and it takes months rather than weeks.
- Complete rest is generally unhelpful. An unloaded tendon does not remodel, and deconditioning makes the return harder.
- Anti-inflammatories may take the edge off symptoms but do not address the underlying tissue change.
- Corticosteroid injection into the tendon is avoided — it can weaken the tendon and there are reports of rupture.
- Load management matters: reducing jumping volume while strengthening, rather than stopping and then returning at full volume.
- Surgery is a last resort, for the small number who do not improve after a long, properly supervised rehabilitation.
The single most useful thing to bring to a physiotherapist is the phrase "my report says tendinosis". It tells them the imaging supports a degenerative picture, which is the picture their loading protocols are built for.
Frequently asked questions
- Is tendinosis worse than tendinitis?
- They are different processes rather than different severities. Tendinitis is inflammation, usually short-lived; tendinosis is degeneration of the tendon tissue, usually longer-standing. Tendinosis typically takes longer to resolve, but it responds well to the right kind of loading.
- How long does patellar tendinosis take to heal?
- Months, usually — commonly three to six with a supervised loading programme, sometimes longer. Tendon tissue remodels slowly. Progress is measured in tolerance to load rather than in how the MRI looks.
- Should I rest completely?
- Usually not. Complete rest does not stimulate the tendon to remodel, and the strength lost makes the eventual return harder. The usual approach is to reduce the aggravating load — jumping in particular — while starting controlled strengthening.
- Why does my MRI look bad when my knee barely hurts?
- Because tendon appearance and pain correlate loosely. Abnormal patellar tendons are found on imaging in plenty of athletes with no symptoms at all. Treatment follows what your knee does, not what the picture looks like.
- Is a cortisone injection a good idea?
- For this tendon it is generally avoided. Corticosteroid can weaken tendon tissue and tendon rupture after injection has been reported. Ask specifically about it if it is offered, and about what else has been tried first.
When you want a second read of the images themselves
Understanding your radiologist’s report is free. A Second Opinion is the other thing: an independent AI reading of your images, done from the pictures rather than from the report, with the differences called out and a Q&A on the result. It is informational — not a diagnosis, and not a substitute for your doctor.
Words on this page
Each of these has its own page in the report glossary.
Report glossary, A–Z →Sources
- Patient-facing procedure descriptions (MRI, CT, X-ray, ultrasound)RadiologyInfo.org — Radiological Society of North America & American College of Radiology
- MRI scan — overview, how it is performed and resultsNHS (United Kingdom)
- ACR Appropriateness Criteria and practice parameters for reportingAmerican College of Radiology
Keep reading
Read Your Scan is informational only — not a medical diagnosis, and not a substitute for a licensed radiologist or your doctor. This page explains what a report says and what a radiologist looks at; it cannot tell you what your own images show. If you have urgent symptoms, seek care.