Are Osteophytes (Bone Spurs) Seen on Knee Osteoarthritis X-rays Really a Foreign Body to Remove? — Dr. Moriwaki on Bone Spurs as Structures the Body Builds to Stabilize the Joint, and the Line Between What Stem Cell Conditioned Media Knee Injection Can and Cannot Do2026.08.16

“My knee hurt, they took an X-ray, and I was told I have osteophytes (bone spurs).” — Many patients feel anxious after being told this. The mental image of a bony spike growing where it shouldn’t naturally prompts thoughts like, “Shouldn’t they take it out?” or “If I shave it off, will the pain disappear?” However, osteophytes in knee osteoarthritis are not always a foreign body to remove. They are structures that appear as a result of the body reshaping itself to protect the joint, and at times they function as a device that stabilizes the joint. In this article, Dr. Moriwaki at AVAN TOKYO Ginza organizes the medical meaning of osteophytes in knee osteoarthritis and what stem cell conditioned media knee joint injection can and cannot target.

Key Points of This Article

・Osteophytes in knee osteoarthritis are not “the debris of joint destruction” but adaptive changes in bone shape that the body creates to distribute load and stabilize the joint

・It is limited how often the osteophyte itself is the main source of pain; more often, coexisting synovitis, joint effusion, and subchondral bone marrow edema generate the pain

・What stem cell conditioned media knee joint injection can target is the intra-articular inflammatory environment; it cannot shrink or remove the osteophyte itself

・When an osteophyte mechanically compresses nerves or soft tissue, or bony blocks range of motion severely, surgical removal becomes the appropriate indication

・Even with osteophytes present, if the main source of pain is synovitis or effusion, stem cell conditioned media knee joint injection can be an option within conservative therapy

What Are Osteophytes in Knee Osteoarthritis, and Why Do They Form?

An osteophyte is a structure that appears when bone proliferates and changes shape in response to cartilage wear and sustained stress on the subchondral bone. Bone formation progresses beneath the periosteum at the joint margins and, over time, takes on various shapes: spikes, lips, or shelves. It is by no means “a fragment of broken bone,” but part of active bone neoformation the body builds up to stabilize the joint and distribute the increased load.

Osteophytes Are Not “Debris from Joint Destruction”

Patients told about osteophytes for the first time often misunderstand: “the cartilage wore down and the fragments turned into bony spikes.” In reality, when the articular cartilage thins and the load on the joint increases, the periosteum at the joint margins responds, and osteoblasts create new bone — the process that produces an osteophyte. From a biomechanical standpoint, it is a rational change that broadens the load-bearing area and reduces pressure per unit area.

Osteophytes and the Severity Classification (KL Grade)

In the Kellgren-Lawrence (KL) classification used to grade knee osteoarthritis, the presence of an osteophyte is a criterion for Grade II or higher. The presence and size of osteophytes serve as an index reflecting the progression of osteoarthritis — but osteophytes themselves are not the “main body” of the disease. The meaning and treatment strategy differ greatly between KL Grade II, where only small osteophytes are visible, and KL Grade IV, which is accompanied by large lipping osteophytes and loss of joint space.

Are Osteophytes in Knee Osteoarthritis a Foreign Body to Remove?

The intuition that “pain occurs because of the osteophyte” or “remove the osteophyte and pain will disappear” does not always match medical fact. Many clinical reports show that arthroscopic shaving (osteophyte removal) did not necessarily reduce pain, and osteophytes are often a result rather than a cause.

The Osteophyte as a Joint-Stabilizing Device

In the knee, as cartilage wears and joint space narrows, joint stability declines. Osteophytes that appear at the edges of the femoral condyles or tibial articular surface can broaden the “receiving base” of the joint and dampen mediolateral and rotational instability. In medial-compartment knee osteoarthritis particularly, osteophytes formed on the medial tibial condyle often physically restrain meniscal extrusion. Removing osteophytes carelessly may increase joint instability and paradoxically worsen pain.

When Osteophytes Should — and Should Not — Be Removed

Cases where surgical removal is clearly considered are limited: (1) impingement-type osteophytes that bony-block extension or flexion, (2) osteophytes that mechanically compress nerves or tendons subcutaneously, and (3) bony fragments acting as loose bodies (“joint mice”) producing pain or catching inside the joint. Conversely, when “an osteophyte is visible on X-ray” is the only finding and there is no evidence it is directly causing pain, removal surgery is not the first choice. Much of the pain in knee osteoarthritis arises not from the osteophyte itself but from some combination of coexisting synovitis, effusion, subchondral bone marrow edema, and meniscal degeneration.

What Stem Cell Conditioned Media Knee Injection Can and Cannot Target

Patients sometimes ask, “Can stem cell conditioned media dissolve the osteophyte?” But what stem cell conditioned media knee joint injection can target is not a change in the osteophyte’s shape, but modulation of the inflammatory cycle progressing inside the joint.

What It Can Target: The Intra-articular Inflammatory Environment

Stem cell conditioned media contains a diverse range of growth factors, cytokines, and exosomes, and when administered into the joint cavity, is thought to act on synoviocytes, chondrocytes, and immune cells. The aim is to calm the inflammatory cycle that drives joint destruction (IL-1β, TNF-α, MMPs, and so on) and to create a microenvironment favorable to tissue repair. Even in a knee with osteophytes, if the main source of pain is synovitis, effusion, or subchondral bone marrow edema, this intra-articular intervention may contribute to symptom relief. For general information on joint disease, please also refer to the Japanese Orthopaedic Association.

What It Cannot Target: The Bone Morphology Itself

On the other hand, stem cell conditioned media knee joint injection does not change the size or shape of the osteophyte. An osteophyte is the product of bone neoformation formed over years, and virtually nothing other than surgical removal can shrink it. When the chief complaint at the top of the list is “I want the bone spike gone,” stem cell conditioned media knee joint injection is not the answer. Sharing this boundary with the patient at the outset is the first step in preventing a gap in expectations. For further details, please see our page on stem cell conditioned media joint injection.

Practical Considerations When Contemplating Injection in a Knee With Osteophytes

Even with osteophytes present, some cases can reasonably be considered for injection, while others should first receive orthopedic evaluation. Cases where injection may be considered include those roughly at KL Grade II–III with joint space largely preserved, where pain is centered on inflammation-derived findings such as synovitis, effusion, or starting pain. Conversely, if range of motion is strongly bony-blocked, if there are locking symptoms from loose bodies, or if KL Grade IV shows nearly complete loss of joint space with bone-on-bone contact, orthopedic evaluation is prioritized first and the possibility that injection alone cannot address the situation is shared. Assessment combining X-ray (and MRI when appropriate) with range of motion, stability, and pain localization is the prerequisite.

Frequently Asked Questions

Q. If an osteophyte is large enough to show clearly on X-ray, does that mean it is definitely the source of pain?

Not necessarily. Even when an osteophyte is clearly visible on X-ray, it is not always the direct source of pain. In many cases, coexisting synovitis or subchondral bone marrow edema contributes more strongly to pain, and clinical experience in knee osteoarthritis shows that osteophyte size and pain intensity do not always correlate.

Q. Will stem cell conditioned media knee joint injection shrink the osteophyte?

It will not. What stem cell conditioned media can target is modulation of the intra-articular inflammatory environment; it has no action to change the shape of osteophyte bone tissue itself. If you wish to remove the osteophyte, discussing indications for surgical procedures such as arthroscopic excision or total knee arthroplasty with an orthopedic surgeon is the appropriate path.

Q. Can I still receive stem cell conditioned media knee joint injection if I have osteophytes?

The presence of osteophytes itself is not a contraindication. It can be an option in cases roughly at KL Grade II–III where joint space is preserved and pain is judged to be inflammation-driven. However, situations such as bony-blocked range of motion, locking from loose bodies, or end-stage bone-on-bone contact may not be addressable by injection alone, so pre-treatment imaging assessment and orthopedic evaluation are prerequisites.

Q. If I leave the osteophyte alone, will knee osteoarthritis progress further?

The issue is less that the osteophyte itself drives progression, and more that the load and inflammatory environment that caused the osteophyte to form continue. Reducing joint load through weight management, quadriceps strengthening, and activity modification — and, when appropriate, calming the inflammatory environment via stem cell conditioned media knee joint injection — is meaningful in slowing progression.

Q. How do you determine whether an osteophyte in knee osteoarthritis is actually the source of pain?

We combine history (which movements provoke pain), examination (tender points, range of motion, joint stability), and imaging (X-ray/MRI findings of synovial thickening, effusion, and bone marrow edema) to reach a comprehensive judgment. If the osteophyte is palpable subcutaneously and matches the site of tenderness, or if it clearly blocks range of motion mechanically, the osteophyte-derived component is likely strong. Otherwise, we begin with conservative therapy targeting intra-articular inflammation.

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Supervising Physician: Shin Moriwaki, M.D.

Member, Japan Society of Aesthetic Surgery (JSAS) / Member, American Academy of Aesthetic Medicine

ECFMG Certificate

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📍AVAN TOKYO Ginza Joint Regenerative Medicine

AVAN TOKYO Ginza Joint Regenerative Medicine

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