Bone Spurs in the Knee: What They Are and What They Actually Mean

Few phrases on a radiology report worry patients more than “bone spurs.” It sounds like something sharp is growing inside the knee and cutting into it with every step. That is not what a bone spur is, and understanding what it actually represents changes the entire conversation about what to do next.

A bone spur in the knee — its medical name is an osteophyte — is extra bone the body forms along the edges of the joint as cartilage wears away. It is a response to years of abnormal loading, not a separate disease. In almost every case it is a marker of arthritis, not the cause of your pain.

What is a bone spur in the knee?

Bone is living tissue that constantly remodels in response to the forces placed on it — a principle known as Wolff's Law. When the cartilage cushioning the femur and tibia thins, the load across the knee is no longer distributed evenly. The bone senses that concentrated stress and does the only thing it can: it builds more bone at the margins of the joint, trying to widen the surface and stabilize a knee that is no longer moving normally.

This is also why bone spurs are found in nearly every arthritic knee. They are not an unusual or alarming finding. They are what an arthritic knee looks like on an X-ray. For the bigger picture across both joints, see what bone spurs really mean in the hip and knee.

What causes bone spurs in the knee?

The overwhelming cause is knee osteoarthritis. Spurs follow the pattern of wear, which is why their location on an X-ray tells us where the knee is failing:

Alignment is the thread running through all of it. A knee that is even slightly bow-legged concentrates force on the inner compartment with every step, and over decades that compartment wears out first while the outer half stays relatively healthy. Long-standing malalignment is its own subject — see knee osteotomy for how alignment drives single-compartment wear in younger patients.

Patients often ask whether something they did caused the spurs — running, kneeling, an old sports injury, being on their feet for work. Usually the honest answer is that the dominant factors are alignment, genetics, and time. Activity did not cause this.

Symptoms: what do bone spurs in the knee feel like?

On their own, most knee spurs cause no symptoms at all. When patients do have symptoms, they are almost always the symptoms of the underlying arthritis:

• Aching pain with activity that eases with rest
• Stiffness after sitting, driving, or first thing in the morning
• Swelling after a long day or a lot of walking
• Grinding, catching, or a sense that the knee is not moving smoothly
• Pain going down stairs or getting out of a low chair

There is one exception worth knowing about. A very large spur can create a mechanical problem of its own — most often physically blocking the knee from straightening all the way. Patients describe a knee that will not go flat, and that loss of full extension is genuinely disabling because it makes walking cost far more energy. That is a finding I take seriously on examination.

Spurs along the inner edge of the knee can also grow large enough to feel through the skin as a hard, fixed bump. A firm prominence that does not move is usually bone. A soft, squishy swelling behind the knee is more likely a fluid-filled cyst — a different problem covered in swelling behind the knee.

Are bone spurs causing my knee pain?

Usually not directly. This is the single most important point on this page. The pain of knee arthritis comes from:

• Loss of cartilage and bone-on-bone contact
• Inflammation of the joint lining (synovitis)
• Irritation of the sensitive bone just beneath the worn cartilage
• Deformity and abnormal mechanics as the knee shifts out of position

Bone itself has nerve endings, but the osteophyte sitting at the rim of the joint is rarely where the pain is generated. It is a bystander that happens to be visible on the X-ray — which is exactly why it gets blamed.

Can bone spurs be removed from the knee?

They can be. The more useful question is whether doing so accomplishes anything, and for an arthritic knee the answer is generally no.

Arthroscopic “clean-out” surgery — shaving spurs, trimming cartilage, and washing out the joint through small incisions — was once performed very commonly for arthritic knees. It has since been tested in high-quality randomized trials, and those trials found that it does not outperform non-surgical treatment. Professional guidelines now recommend against it for osteoarthritis of the knee.

The picture is different if the knee has a genuine mechanical block or a true locking meniscus tear in a knee that is not broadly arthritic. Those are specific situations decided by examination and imaging together — not by the words on a report.

How knee bone spurs are actually treated

Because the spur is a marker of arthritis, treatment targets the arthritis. For the large majority of patients that means non-surgical care for as long as it keeps working:

None of these remove the spur, and none reverse the arthritis. What they do is reduce the load and the inflammation driving the pain — which is the part that actually determines how your knee feels.

What happens to bone spurs during knee replacement?

When arthritis has progressed to the point that a knee replacement is the right answer, the spurs are removed as a routine part of the operation. But removing them is not the point of the surgery. The point is to replace the worn surfaces and restore the knee's alignment and mechanics — which eliminates the abnormal loading that produced the spurs in the first place. In practice that means:

If you want to see the operation step by step, read what happens during a knee replacement.

When to see a surgeon

Not because you have spurs. Bone spurs on an X-ray are not, by themselves, a reason to have surgery — and I have told many patients with dramatic-looking films that they do not need an operation. The decision is driven by how much the knee is costing you:

The related question of whether a severe X-ray means surgery is covered in detail in bone-on-bone arthritis: do you need knee replacement? — and the honest thresholds are laid out in signs you may need a knee replacement.