Cartilage lesions in bone are common, and the great majority are entirely benign. Being told you have one is much more often a matter of confirming what it is than of needing treatment.
This page covers the three that are seen most: the enchondroma, inside the bone; the osteochondroma, growing outward from it; and the chondroblastoma, at the very end of a bone next to a joint. It also covers the uncommon inherited conditions in which these appear in numbers, because those are the situations where ongoing surveillance genuinely matters.
The malignant cartilage tumours these have to be distinguished from are covered separately in chondrosarcoma.
The essentials
- Most cartilage lesions in bone are benign and need no treatment, only a secure diagnosis.
- Pain is not a reliable warning sign. In published series, pain was more common with harmless enchondromas than with the low-grade tumours they can be mistaken for. Do not use pain as your reassurance either way.
- The features that matter on imaging are size, scalloping of the inside of the bone, any extension outside the bone, and, above all, change over time.
- A lump that starts growing again after you have finished growing is the single most important thing to report, particularly with an osteochondroma.
- One lesion and many lesions are different situations. A solitary osteochondroma carries around a 1% risk of malignant change; the inherited multiple form carries around 10%, and the multiple enchondroma syndromes higher again.
Enchondroma: the common incidental finding
An enchondroma is a benign island of cartilage sitting inside a bone. Most cause no symptoms and are found by accident, on an X-ray or scan arranged for something else entirely: a twisted ankle, a sore shoulder, an unrelated investigation.
For a lesion with the typical appearance and no symptoms, the usual course is no treatment. The question is not whether to remove it but whether the diagnosis is secure.
Telling an enchondroma from a low-grade tumour
This is the one genuine clinical issue with enchondromas, because a small number of lesions that look like one are in fact an atypical cartilaginous tumour, a grade 1 cartilage cancer, which does not spread but does grow locally and needs treating.
Two published series looked specifically at what separates them. The features that pointed towards the low-grade tumour rather than a harmless enchondroma were:
- Scalloping of the inner surface of the bone: the lesion eating into the bone from within
- Extension outside the bone into the surrounding soft tissue
- Larger size
- Older age
And one finding worth knowing because it runs against intuition: pain was more frequent in the patients who turned out to have ordinary enchondromas. Pain in the region of a cartilage lesion very often has nothing to do with the lesion: it comes from the tendon, joint or muscle that prompted the scan in the first place. It is neither a reason to panic nor a reason for reassurance.
In those series, every enchondroma treated was cured with no recurrence at all, while about one in ten of the low-grade tumours came back, which is why the distinction is worth the effort of getting right.
Where the appearance is not entirely typical, the usual approach is a repeat scan after an interval. Stability over time is genuinely reassuring; change is the thing that prompts action.
Osteochondroma: the bony lump
An osteochondroma, sometimes called an exostosis, is an outgrowth of bone capped with cartilage. It is the commonest benign bone tumour, and typically arises near the end of a long bone, growing outward.
Many cause no problems and are simply left alone. Removal is considered when the lump:
- is painful in itself
- rubs on a tendon, muscle or overlying tissue, causing irritation or an inflamed bursa
- presses on a nerve or blood vessel
- causes a deformity or a difference in bone growth
- is cosmetically or mechanically troublesome in a way the patient wants addressed
Surgery removes the lump at its base. Where a lesion sits somewhere awkward (the neck of the femur, for instance, or the shoulder blade), the operation needs more planning, both to reach it safely and because removing a large lump can leave the bone needing protection afterwards.
When to be concerned
The risk of an osteochondroma becoming a secondary chondrosarcoma is real but low: about 1% for a solitary lesion.
The changes that matter, and the reason patients are told what to watch for:
A lump that starts growing again after skeletal growth has finished, or one that becomes newly painful, needs assessment. Osteochondromas normally stop growing when you do.
On imaging, the feature specialists look at is the thickness of the cartilage cap. A cap that has become thick is the finding that raises concern.
Chondroblastoma: the young person’s lesion
Chondroblastoma is an uncommon benign cartilage tumour of young people. In a series of 48 patients the mean age was 18, with a male predominance.
It characteristically sits in the epiphysis (the very end of the bone, immediately next to the joint), which is what makes it both distinctive and awkward. Patients usually present with pain around the joint rather than a lump.
Treatment is to scrape the tumour out. The accepted approach is intralesional curettage, often with the cavity wall additionally treated (with a high-speed burr, or by cauterising it), and the defect then filled with bone graft or cement. Because the tumour sits against the growth plate in a child and against the joint surface in everyone, the operation is planned to protect both: published series in children describe careful approaches through the cartilage specifically to preserve the joint and the growing plate.
Results are generally good, though these lesions can come back locally, and follow-up after surgery is routine.
When there are many: the inherited and multiple conditions
A single benign cartilage lesion and a body full of them are different clinical situations, and the difference is mostly about surveillance.
Hereditary multiple exostoses
An inherited condition, passed on in an autosomal dominant pattern (meaning a parent with it has a one-in-two chance of passing it to each child), in which multiple osteochondromas develop from the ends of the long and flat bones. It is rare, affecting somewhere between 1 in 50,000 and 1 in 100,000 people, and is caused by changes in the genes EXT1 and EXT2. Diagnosis is usually made on X-rays, with two or more osteochondromas near the ends of the long bones; genetic testing is reserved for unclear cases.
Beyond the lumps themselves, it can cause differences in bone growth and limb alignment, fractures, inflamed bursae, and occasionally pressure on nerves or blood vessels. Much of the orthopaedic work in this condition is about those mechanical problems rather than about cancer.
But the cancer risk is the reason for long-term review: the risk of malignant transformation to a secondary chondrosarcoma is around 10%, against about 1% for a solitary osteochondroma. People with the condition therefore stay under specialist follow-up, with a clear instruction about what to report.
Ollier disease and Maffucci syndrome
Ollier disease is a rare condition in which multiple enchondromas develop, characteristically affecting one side of the body more than the other. It can cause significant bone deformity and differences in limb length. When the same condition occurs together with clusters of abnormal blood vessels in the skin and soft tissues, it is called Maffucci syndrome.
The lifetime risk of one of the lesions becoming a chondrosarcoma is substantially higher than for a solitary enchondroma. Published estimates range very widely, from around 5% up to 50%, and that range is worth reporting honestly rather than collapsing into a single number, because it reflects real uncertainty in a rare condition. What follows from it is not in doubt: whole-body imaging to map the lesions, and lifelong surveillance.
What this means for you
- If you have been told you have an enchondroma and it is not causing symptoms, the likely answer is no treatment, and confirmation that the appearance is typical.
- Do not use pain to judge risk in either direction. Report it, but know that pain near a cartilage lesion frequently comes from something else.
- If you have an osteochondroma, know the one thing to watch for: a lump that starts growing again after you have stopped growing, or becomes newly painful.
- If you have many lesions, or an inherited condition, expect lifelong review rather than discharge. That is the point of it.
- Report change between appointments rather than saving it. In every condition on this page, change over time is the finding that matters most.
Assessment of a bone lesion is set out in tests and diagnosis. If a cartilage lesion is causing symptoms, or has changed, referral for imaging and specialist review, before any attempt to remove it, is the most useful step.