Subchondral Bone Explained: Sclerosis, Cysts and Bone Marrow Lesions
Radiology reports love the word "subchondral." This guide puts sclerosis, cysts and bone marrow lesions into plain English, covers what they can and can't say about your pain, and shows where a joint supplement fits.
Subchondral bone is the layer of bone directly under joint cartilage. Unlike cartilage, it has blood vessels and nerves, and in one MRI study of 401 people with knee osteoarthritis, about 78% of those with knee pain had lesions in it. Researchers still disagree about whether those bone changes start the damage or follow it.
What subchondral bone is
Look at the end of a thigh bone and you'll find a glossy cap of cartilage. Underneath it sits bone, and the top layer of that bone is called subchondral bone, which just means "below the cartilage." It comes in two parts. A thin, dense plate lies right against the cartilage. Beneath the plate is spongy trabecular bone that keeps remodeling for as long as you're alive (Bone Research, 2021).
The plate is threaded with blood vessels and nerve fibers. The cartilage above it has neither. So when a knee hurts under load, the pain signal originates somewhere other than the cartilage, and bone is one of the candidates.
- 1Articular cartilage. No nerves or blood vessels.
- 2Subchondral plate. Dense bone with blood vessels and nerve fibers.
- 3Sclerosis. The plate thickens and hardens, typically in later-stage osteoarthritis.
- 4Bone marrow lesion. An MRI signal change in the marrow, thought to be edema.
- 5Subchondral cyst. A fluid-filled cavity in the bone.
Joint marketing talks about the coating almost exclusively. The pan is what carries the load, and it's the part with the wiring. The bone won't be to blame in every sore knee, but it deserves a seat in the conversation.
Section 02
What does subchondral sclerosis mean?
Subchondral sclerosis means the bone just under your cartilage has thickened and hardened. It's a scan finding, most often spotted on an X-ray, and it usually turns up in later-stage osteoarthritis. It points to changes in the joint without amounting to a diagnosis.
The word is easy to take apart: sub is below, chondral is cartilage, sclerosis is hardening. Radiologists often find it by accident, alongside other signs of osteoarthritis such as joint space narrowing and bone spurs.
So why does the bone harden? Bone adapts to the loads it carries, which is normally a good thing. Trouble starts when the load turns abnormal: an old ligament injury, years of hard impact, a joint that tracks poorly, extra body weight. Researchers describe a sequence that begins in the bone itself.
- Turnover in the subchondral bone speeds up
- New blood vessels and nerve fibers grow toward the cartilage
- Microdamage appears in the bone and in the calcified cartilage above it
- Marrow lesions, thought to be edema, can show up on MRI
Sources: Bone Research (2021); Arthritis Research & Therapy (2013); Annals of Internal Medicine (2001).
The timing is where it gets interesting. The 2021 review notes that lesions in the bone can appear before the cartilage visibly breaks down. In the same paper, the authors say the exact role of subchondral bone in starting osteoarthritis is unclear. Both statements are true at once, and a page that hands you a cleaner story than that is tidying up the science.
| Stage | Subchondral plate | Bone beneath it | What it means |
|---|---|---|---|
| Early | Thinner and more porous | Lower density, thinner struts | Microdamage begins and cartilage starts to break down (Arthritis Research & Therapy, 2013) |
| Late | Thickened and hardened (sclerosis) | More bone volume and density, but under-mineralized | Denser isn't stronger. Reported gains run about 15% in bone mineral density and up to 30% in bone volume, with lower material stiffness (Frontiers in Cell and Developmental Biology, 2020) |
So "weak bones cause arthritis" oversimplifies things. Under an arthritic joint the bone can be thin early on and dense but poorly mineralized later, and neither state is the same thing as having osteoporosis.
Section 03
Other terms on your scan report
Sclerosis is one of five terms that come up again and again in knee and hip reports. The table below lines them up.
| Term | What it means | Seen on | Worth knowing |
|---|---|---|---|
| Subchondral sclerosis | Thickened, hardened bone under the cartilage | X-ray | A scan sign, not a diagnosis. Usually goes with later-stage osteoarthritis. |
| Subchondral cyst (geode) | A fluid-filled cavity in the bone under the cartilage | X-ray or MRI | One of the bone changes seen in osteoarthritis. |
| Bone marrow lesion (bone marrow edema) | A patch of altered signal in the marrow, thought to be edema | MRI | Linked to knee pain in osteoarthritis, and also found in some knees that don't hurt. |
| Osteophyte (bone spur) | A bony outgrowth at the edge of the joint | X-ray or MRI | Often appears alongside joint space narrowing. |
| Subchondral insufficiency fracture | A microfracture in the bone beneath the cartilage | MRI often needed | Sudden knee pain with no injury. Worth a prompt exam. |
Two things about scan findings are worth holding onto. Findings and symptoms often part ways: in the Felson study below, 15 of 50 people with pain-free knees still had a bone marrow lesion. Doctors, for their part, tend to treat the symptoms and the osteoarthritis behind them rather than X-ray changes alone.
Section 04
Bone marrow lesions and knee pain
of people with painful knee osteoarthritis had a bone marrow lesion on MRI, against 30% of people with pain-free knees. (Felson et al., 2001, Annals of Internal Medicine)
Felson's team ran that study in 2001. It was one of the earliest to look at bone marrow lesions in osteoarthritis, and the numbers still stand out. Below is what they did and, more to the point, what the design couldn't show.
401 people with knee osteoarthritis on X-ray, average age 66.8, drawn from Veterans Affairs clinics and the community. 351 had knee pain and 50 had none. Each person had an MRI of one knee, and the researchers scored the size of any bone marrow lesion.
It was a snapshot, not a follow-up, so it can't say whether lesions cause pain, whether painful knees get loaded differently and grow lesions as a result, or whether both simply travel with more advanced arthritis. Lesions did get more common as X-ray severity rose, which makes that third possibility hard to wave away.
- Lesions in 77.5% of the painful group (272 of 351) against 30% of the pain-free group (15 of 50)
- Large lesions in 35.9% of the painful group against 2% of the pain-free group
- Lesion frequency climbed with X-ray grade, from 48% at the mildest grade to 100% at the most severe
A 2022 mini review from Melbourne researchers offers a wiring explanation for the association: sensory neurons that supply bone can signal pain and become sensitized in osteoarthritis. It's a reasonable mechanism, not a demonstrated cause.
Section 05
What the research hasn't shown yet
Most joint supplement pages skip this part. We searched for a trial showing that glucosamine, MSM, hyaluronic acid, boswellia or curcumin shrinks a bone marrow lesion or rebuilds subchondral bone, and came up empty.
What those trials do measure is pain, stiffness, physical function and blood markers of inflammation, and even there a 2025 meta-analysis that pooled 21 randomized trials of curcumin in knee osteoarthritis flagged high variation in regimens, control groups and disease grade. One small pilot of a branded boswellia extract reported changes on X-ray, including joint gap and bone spurs. That's a measurement at the edge of the joint, not a look at the bone under the cartilage.
The only supplement trial we found with MRI bone-lesion outcomes tested vitamin D. Fifty people took 800 IU a day for two years, and lesion volume showed no significant difference from placebo (Perry et al., 2019). Vitamin D sits outside the Joint Axis Pro formula. We mention it as the closest supplement test of the bone-lesion idea, and it showed no effect.
Section 06
Where Joint Axis Pro fits
Joint Axis Pro isn't a bone product, and we don't sell it as one. It's a 6 in 1 formula built around the parts of the joint a supplement can plausibly support: cartilage building blocks, lubrication and the everyday inflammatory response.
Glucosamine sulfate is the building block for cartilage structure. Hyaluronic acid supports the synovial fluid that lubricates the joint, and MSM is a sulfur compound used for connective tissue support. Boswellia serrata extract and curcumin extract sit on the inflammatory side, both traditionally used to support a balanced response and everyday joint comfort. Black pepper extract (piperine) is in there to improve absorption of the others, curcumin especially.
If your pain is coming mainly from the bone, a supplement like this is unlikely to be the whole answer. You should know that before you buy anything.
Section 07
When to see a clinician instead of shopping
Some knee pain belongs with a clinician, not on a supplement shelf.
- The pain came on suddenly, even with no injury. One cause is a subchondral insufficiency fracture, where early diagnosis matters
- The joint is hot, red or visibly swollen
- The knee locks or gives way
- The pain is getting worse, or wakes you at night
- You take prescription medication, a blood thinner for example, and want to add a supplement. Ask your prescriber or pharmacist first
Section 08
People also ask
Clinical evidence
What the research says
Section 09
Frequently asked questions
References
Sources
- Felson DT et al. (2001). The association of bone marrow lesions with pain in knee osteoarthritis. Annals of Internal Medicine, 134(7):541-549.
- Bone marrow lesions in osteoarthritis: characterising genetic and histological changes (PubMed Central review). Secondary source for lesion frequency by X-ray grade in the Felson cohort.
- Johns Hopkins Arthritis Center: news summary of the Felson 2001 study (source for the large-lesion percentages).
- Bone Research (2021). Subchondral bone microenvironment in osteoarthritis and pain.
- Arthritis Research & Therapy (2013). Subchondral bone in osteoarthritis: insight into risk factors and microstructural changes.
- Frontiers in Cell and Developmental Biology (2020). Subchondral bone remodeling: a therapeutic target for osteoarthritis.
- Alterations of subchondral bone progenitor cells in human knee and hip osteoarthritis lead to a bone sclerosis phenotype (PubMed Central). Source for sclerosis being a common feature of advanced disease with less-mineralized new bone.
- Morgan M et al. (2022). Mini review on innervation of subchondral bone in osteoarthritis pain. Frontiers in Endocrinology.
- Subchondral insufficiency fracture of the knee: review of current concepts and radiological differential diagnoses (PubMed Central).
- Subchondral insufficiency fracture of the medial femoral condyle treated conservatively with early non-weightbearing (PubMed Central). Source for MRI often being required to diagnose.
- Healthline: Subchondral sclerosis (secondary source for the term breakdown and for sclerosis being an incidental imaging finding).
- Healthgrades: What to know about subchondral sclerosis and sclerosis bone lesions (secondary source for sclerosis being a radiological sign, not a diagnosis, and for other X-ray signs of osteoarthritis).
- St. Joseph's Healthcare Hamilton: orthopedic researchers to test novel procedure for treating knee pain (source for proposed causes of bone marrow lesions).
- Perry TA et al. (2019). Effect of vitamin D supplementation on synovial tissue volume and subchondral bone marrow lesion volume in symptomatic knee osteoarthritis. BMC Musculoskeletal Disorders, 20:76.
- BMC Complementary Medicine and Therapies (2025). Effects of curcumin on serum inflammatory biomarkers in patients with knee osteoarthritis: a systematic review and meta-analysis of randomized controlled trials.
- Pilot randomized, double-blind, placebo-controlled trial of a branded Boswellia serrata extract in knee osteoarthritis (48 participants, 120 days). Open access via PubMed Central.
- Abrams GD, Harris JD, Cole BJ. Subchondral Bone Treatment. In: Biologic Knee Reconstruction: A Surgeon's Guide (CRC Press). Source for sclerosis and cysts being visible on plain X-ray.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This content is for educational purposes only and does not constitute medical advice. Consult a qualified healthcare provider, particularly if you have a diagnosed joint condition, take blood thinners or other prescription medications, or are pregnant or nursing.
Joint Axis Pro: 6 in 1 Joint Support
A 6 in 1 joint support supplement with glucosamine sulfate, MSM, hyaluronic acid, boswellia, curcumin and black pepper extract, formulated to support cartilage, joint lubrication and everyday comfort. 120 capsules, a 30-day supply.
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