Should you try to preserve your knee, or is replacement more realistic?

If the cartilage damage is localised and the rest of the knee is still in reasonable condition, joint preservation is worth exploring. If the knee is worn throughout, with advanced arthritis across much of the joint, replacement may be the more realistic and reliable route to pain relief and function.

This decision is not made by age alone. A younger person with diffuse, end-stage osteoarthritis may not be a good candidate for cartilage restoration. Equally, an older person with a focal cartilage defect, good leg alignment, stable ligaments and a healthy meniscus may still have preservation options.

The key distinction is between a focal cartilage defect and a knee that is generally worn out. With a focal defect, treatment may aim to repair, restore or unload the damaged area so the native joint can continue to work. With advanced osteoarthritis, the whole joint environment may no longer support a repair, and knee replacement may offer a more predictable option.

Doctors therefore look at the pattern of cartilage damage, the amount of established arthritis, your symptoms, activity goals, leg alignment, meniscus and ligament status, and the condition of the bone beneath the cartilage.

Preservation and replacement are not rival camps. They are different tools for different stages of disease. Injections such as PRP, BMAC or hydrogel treatments may help symptoms in selected patients, but they do not replace a proper assessment of whether the knee is structurally preservable.

How doctors decide: the tests and findings that matter most

An MRI is important, but it is not the whole decision. The treatment recommendation usually comes from putting together your symptoms, examination findings, imaging, previous treatments and what you need the knee to do.

The assessment often starts with practical questions: where is the pain, does the knee swell, catch, lock or give way, and which activities have become difficult? Examination then checks movement, stiffness, swelling, tenderness, stability and how your leg loads through the knee.

MRI helps define the cartilage injury: its size, depth, location and whether the bone beneath it is involved. X-rays are often added when arthritis, joint-space narrowing or limb alignment need to be assessed.

Doctors also look beyond the cartilage surface. A damaged meniscus, unstable ligament, malalignment, persistent swelling, stiffness, bone bruising or established arthritis can all change the plan. The same MRI finding may therefore lead to different advice in two people. One person may suit rehabilitation or injection-based symptom management; another may need cartilage restoration with correction of alignment; another may be better served by replacement.

The aim is to answer three questions: is the joint still preservable, which category of treatment fits best, and are there co-problems that must be corrected for any cartilage procedure to make sense?

What counts as ‘non-surgical’ knee cartilage treatment? PRP, BMAC, MFAT and Arthrosamid explained

Non-surgical knee cartilage treatment usually means an injection-based option aimed at reducing symptoms or improving the joint environment. It should not be assumed to mean that new, normal cartilage is being regrown in a focal defect.

PRP

PRP, or platelet-rich plasma, is made from a sample of your own blood. The blood is processed to concentrate platelets, then injected into the knee. PRP is most often discussed for knee osteoarthritis-type pain and function, rather than as a stand-alone structural cartilage repair. Trial and meta-analysis evidence supports symptom improvement in some patients, although results vary because PRP preparations and platelet doses are not all the same.

BMAC

BMAC, or bone marrow aspirate concentrate, is prepared from bone marrow taken from the patient. It contains a mixture of cells and signalling proteins and sits within the wider orthobiologics field. It is sometimes used in knee osteoarthritis or cartilage-related treatment pathways. Evidence suggests possible short- to mid-term symptom and function improvement in some settings, but preparation methods, injection techniques, delivery sites and patient selection are still not fully standardised.

MFAT

MFAT, or micro-fragmented adipose tissue, is derived from processed fat tissue. It is another orthobiologic option. In this research packet, direct evidence specific to MFAT for knee cartilage repair is limited, so it should be described cautiously as a biologic treatment option rather than as proven cartilage restoration.

Arthrosamid

Arthrosamid is different again. It is an injectable hydrogel implant used primarily for knee osteoarthritis symptom relief. It is not a cell-based treatment and should not be presented as a procedure that regrows damaged cartilage.

These options may have a role in symptom modification or as part of a broader preservation plan, but they are not interchangeable with MACI or other cartilage-restoration operations.

When MACI enters the conversation—and how it differs from injections

MACI becomes relevant when the main problem is a cartilage defect that may be suitable for structural repair, rather than a painful arthritic knee needing symptom control alone.

MACI stands for matrix-induced autologous chondrocyte implantation. In broad terms, cartilage cells are taken from the patient, grown in a laboratory and implanted on a matrix into the cartilage defect. It is a surgical cartilage-repair technique, usually considered for selected defects, including larger or multiple chondral lesions, when the rest of the knee environment is good enough to justify repair.

That is the main difference from PRP, BMAC, MFAT and Arthrosamid. These treatments are usually discussed as injections for symptom relief, biologic modulation or support within a broader plan. MACI is intended as structural cartilage restoration. It is not a quick injection, and it requires careful selection, surgery and rehabilitation.

MACI may help some patients preserve the native knee and delay knee replacement, but it is not a guaranteed alternative to arthroplasty. Suitability depends on the lesion, the biology of the knee, rehabilitation adherence and any co-existing problems. If the leg is malaligned, the meniscus is deficient, the knee is unstable or arthritis is already widespread, the cartilage repair may be overloaded or less likely to succeed unless those issues are addressed.

For this reason, MACI is usually discussed as part of a joint-preservation pathway: define the defect, assess the whole knee, correct the mechanical environment where needed, and then decide whether restoration is realistic.

MACI recovery: what patients usually need to plan for

MACI recovery is usually a staged rehabilitation process, not a quick return to normal activity. The exact plan depends on the defect location, defect size, associated procedures and your surgeon’s protocol.

The early phase is normally about protecting the repair. This may involve crutches, restricted weight-bearing, swelling control, pain management and careful range-of-motion exercises. The aim is to keep the knee moving enough to reduce stiffness, while avoiding excessive load on the repair site.

Rehabilitation then usually shifts towards restoring walking mechanics, improving range of movement and rebuilding muscle control. Strengthening progresses over time, often starting with controlled exercises before moving towards more demanding gym-based, balance and functional work. Swelling, pain and movement quality matter; pushing too fast can be counterproductive.

Driving, work and exercise are therefore individual decisions rather than fixed calendar dates. A desk-based worker may return sooner than someone with a physical job. A small, contained defect may be managed differently from a large lesion, or from MACI combined with an osteotomy, meniscal procedure or ligament reconstruction.

Return to running, pivoting sport or high-impact activity is typically slower than patients expect. The decision should be based on graft protection, symptoms, strength, confidence, movement control and review by the surgical and physiotherapy team.

Follow-up imaging may be used in some pathways. MRI after cartilage repair can be assessed with structured systems such as MOCART, which are designed to evaluate repair tissue rather than relying on a casual scan impression. Precise week-by-week milestones, including exact crutch duration, swelling timelines or return-to-sport dates, would need a procedure-specific rehabilitation source and should not be inferred from this packet alone.

What to ask in consultation if you want to avoid or delay knee replacement

If your goal is to avoid or delay knee replacement, the most useful consultation question is: “Is my knee structurally preservable, and what would preservation realistically achieve?”

Helpful follow-up questions include:

• Is my cartilage damage focal, or is the arthritis widespread?
• How much joint-space loss or established osteoarthritis is already present?
• Is my leg alignment suitable, or is one side of the knee overloaded?
• Are my meniscus and ligaments healthy enough to support a repair?
• Am I a candidate for rehabilitation, injections, MACI, another preservation procedure, or replacement?
• Is the aim symptom relief, better function, structural repair, or a possible delay to arthroplasty?
• What are the limitations and uncertainties of the option being proposed?

No single treatment suits every knee, and strong claims that one option is always superior are rarely justified. The right plan depends on the whole joint, not just one MRI phrase.

Specialist joint-preservation assessment is available at the London Cartilage Clinic on Harley Street, the London access point for advanced cartilage and joint-preservation care. Professor Paul Y. F. Lee, internationally recognised cartilage and regenerative-medicine surgeon, leads care at LCC and is the originator of the Lee Liquid Cartilage (LLC) protocol. The team provides selected cartilage and regenerative-medicine procedures for patients hoping to preserve the native knee where appropriate.

1. [1] Treatment of complex multiple lesions in the knee with MACI (autologous cultured chondrocytes on porcine collagen membrane). (2024). https://doi.org/10.1177/26350254241272105 https://doi.org/10.1177/26350254241272105