Subchondroplasty

Understanding Bone Marrow Lesions

Knee bone marrow lesions are areas of increased fluid and stress within the bone just beneath the cartilage. They may occur due to overload, early degenerative change, or small insufficiency injuries.

How Bone Stress Develops

Bone stress in the knee can develop when the bone experiences repetitive force faster than it can adapt. Over time, microscopic changes in the bone’s internal structure may lead to swelling and discomfort.

Impact on Knee Function

Because the lesion sits directly under the joint surface, even small areas of swelling can influence weight acceptance and load transfer. This may lead to symptoms during stairs, prolonged walking, or uneven ground.

Why MRI Matters

MRI is the most accurate imaging tool for detecting BMLs. It highlights areas of oedema, stress reaction, or early insufficiency breakdown that may not be visible on plain X-rays.

When Subchondroplasty May Be Considered

Subchondroplasty may be considered when bone marrow lesions in the knee are contributing to persistent symptoms despite structured non-surgical care.

Features That May Suggest Suitability

Your surgeon may explore subchondroplasty when:

• The lesion corresponds directly with your symptoms
• Conservative care has not provided enough improvement
• The joint surface above the lesion remains reasonably preserved
• Loading activities consistently trigger deep discomfort
• MRI identifies a discreet, well-defined lesion

When It May Not Be Appropriate

Subchondroplasty is less suitable when:

• There is widespread joint degeneration
• Alignment issues significantly overload the affected area
• The lesion relates to instability rather than bone stress
• The knee has advanced cartilage loss

In these situations, alternative joint-preserving or reconstructive procedures may be discussed.

How Subchondroplasty Works

The subchondroplasty procedure aims to reduce bone stress by filling the affected area with a flowable, calcium phosphate bone substitute.

Mechanism Behind the Technique

The injected material acts as an internal support scaffold. Over time, the surrounding bone may remodel through natural biological processes, which may improve load tolerance.

Why the Material Is Used

Calcium phosphate is biocompatible, meaning it works safely within bone. It hardens into a structure that has a similar density to cancellous bone and gradually integrates during healing.

Performing the Procedure

Key steps may include:

• Small incisions reduce soft-tissue disruption
• A specialised guide pin ensures precise targeting of the lesion
• Imaging confirms accurate placement
• The bone substitute is injected in controlled volumes
• Excess material is avoided to prevent pressure within the bone

The technical accuracy of the procedure is important for optimal support of the affected region.

Assessing Suitability for Subchondroplasty

Your surgeon will consider several factors before recommending subchondroplasty treatment.

Evaluating the Location of the Lesion

Lesions under the tibial plateau or femoral condyles may respond differently depending on load patterns. Some locations withstand stress more effectively than others during healing.

Considering Alignment and Load Distribution

Even a small variation in alignment may significantly influence bone stress. If alignment contributes to the lesion, corrective strategies may be necessary to maintain long-term comfort.

Reviewing Associated Joint Changes

If meniscal tears, cartilage defects, or mild instability exist, your surgeon may address these during the same procedure or structure a staged plan depending on your goals.

Non-Surgical Options Before Considering Subchondroplasty

Most people initially trial conservative care.

Physiotherapy Principles

A physiotherapist may focus on strengthening the quadriceps, hamstrings, and hip muscles to reduce stress on the knee during daily activities.

Supportive Measures

Bracing or taping may be helpful in redistributing the load. Footwear and orthotics may also assist if altered mechanics contribute to stress on the lesion.

Monitoring Progress

If symptoms settle with conservative care, ongoing rehabilitation may be continued without surgery. If symptoms persist, further imaging may help clarify why discomfort remains.

What to Expect on the Day of the Procedure

Subchondroplasty is typically performed in a hospital under general or regional anaesthesia.

Before the Procedure

You will be reviewed by the surgical and anaesthetic teams. The affected knee is assessed again, and imaging is reviewed to finalise surgical planning.

During the Procedure

Fluoroscopy assists in guiding the cannula into the targeted region. Arthroscopy may be performed at the same time to assess the joint surface and address any associated issues.

Immediately After

Dressings are applied, and early mobilisation often begins with the support of nursing and physiotherapy staff.

Recovery After Subchondroplasty

Recovery varies depending on the lesion size, associated injuries, and whether arthroscopy was performed at the same time.

Early Symptoms to Expect

Some discomfort, swelling, or stiffness is normal in the early phase. These symptoms usually settle as weight-bearing tolerance improves.

Gradual Strengthening

Physiotherapy progresses in stages, focusing on restoring range of motion, improving muscle activation, and reintroducing controlled load.

Returning to Work or Sport

Desk-based roles may allow earlier return, while physical or high-demand tasks may require a longer recovery period. Timelines vary and depend on your response to treatment.

Potential Risks and Considerations

As with any procedure, subchondroplasty carries risks.

Understanding Possible Outcomes

Potential outcomes may include:

• Temporary increase in bone pain
• Leakage of material if the lesion is unstable
• Ongoing discomfort if symptoms arise from other structures
• In rare cases, infection or inflammatory reactions

Balancing Expectations

The aim is to support the affected region of bone, but outcomes vary depending on the underlying cause, joint condition, and individual factors. Your surgeon will discuss realistic expectations before planning treatment.

When to Seek Specialist Review

It may be helpful to arrange an assessment if you notice:

Symptoms That Merit Review

Common symptoms may include:

• Deep, localised bone pain
• Activity-related discomfort that persists
• Reduced walking tolerance
• Pain when using stairs or walking on uneven ground
• Swelling that recurs despite rest

When Imaging May Be Recommended

If your symptoms follow a fall, increased training load, or a period of repetitive strain, an MRI may clarify whether a bone marrow lesion is present.

A knee orthopaedic surgeon in Sydney, such as Dr Jonathan Negus, can help clarify the cause of your symptoms and discuss whether subchondroplasty in Sydney may be an appropriate option.

Next Steps

Knee discomfort related to bone marrow lesions can affect daily function, confidence on uneven surfaces, and overall joint comfort. Subchondroplasty may be considered a type of knee preservation surgery for selected cases when supported by clinical assessment and imaging.

If you would like guidance on whether this treatment may suit your situation, you can arrange a consultation with Dr Jonathan Negus for an individualised evaluation and advice.

This information is intended as a general guide only. It may not apply to every situation. Assessment and treatment recommendations vary depending on your individual circumstances. Please speak with a qualified health professional for advice specific to your condition.