What it is.
Articular cartilage is the smooth white surface covering the ends of the bones. It is remarkable material: lower friction than ice on ice, and able to carry several times body weight for decades. It has one significant weakness. It has no blood supply and almost no capacity to repair itself.
A chondral defect is a localised area where that surface has been damaged or lost, usually from an injury, with healthy cartilage around it. An osteochondral defect involves the bone underneath as well.
A defect is not osteoarthritis.
This distinction governs everything that follows.
- A focal defect is a hole in an otherwise good surface, typically in a younger person after an injury. The cartilage around it is healthy. Repair or resurfacing of that area is potentially worthwhile because there is something intact to protect.
- Osteoarthritis is diffuse loss across a whole compartment, with changes in the underlying bone and the joint lining. There is no isolated hole to fill. Cartilage repair techniques do not work in this setting.
Untreated focal defects, particularly large ones in weight-bearing areas, are associated with progression to osteoarthritis over time, so the two are connected. They are simply not the same problem at the same moment.
Symptoms.
Often localised: pain in one specific part of the knee, worse with loading and twisting, with swelling after activity. If a fragment has separated, there may be catching, locking or giving way. Some defects are found incidentally during surgery for another reason and cause no symptoms at all.
Diagnosis.
MRI is the investigation of choice and shows both the cartilage and the bone beneath. Weight-bearing radiographs are still needed, to assess overall joint space and alignment, which determine whether the joint as a whole is arthritic and how the defect is being loaded.
Treatment.
Many small defects are managed without surgery: activity modification, physiotherapy to strengthen the muscles that control load through the knee, and weight management.
For symptomatic defects in younger knees with otherwise healthy cartilage, repair techniques exist, including microfracture, osteochondral grafting and cell-based cartilage implantation. Choice depends on size, location, depth and age, and this work is done by surgeons who specialise in cartilage repair. Where malalignment is loading the defect, an osteotomy to shift the load may be part of the plan.
Where the joint has become diffusely arthritic, repair is no longer the question and knee replacement is the operation that helps. If the damage is genuinely confined to one compartment with sound ligaments, a partial knee replacement may be appropriate.
Where this practice fits.
Professor Rodda's practice is focused on hip and knee replacement. He does not perform joint-preserving surgery such as arthroscopy or osteotomy. If your condition is at a stage where preservation surgery is the right option, you will be told that and referred to a colleague who does it, within Sunshine Coast Orthopaedic Group or elsewhere. Where the joint has reached the point that replacement is the reasonable option, that is the work done here.
Common questions.
Can cartilage grow back?
Not on its own in any meaningful way. Articular cartilage has no blood supply and very limited repair capacity. Repair techniques aim to fill the defect with something durable rather than to regenerate identical cartilage.
What is microfracture?
Small holes are made in the bone beneath the defect so marrow cells enter and form repair tissue. That tissue is fibrocartilage, which is less durable than the original. Results are better in smaller defects and tend to deteriorate over time in larger ones.
Is a cartilage defect the same as arthritis?
No. A focal defect is a localised hole in an otherwise healthy surface. Osteoarthritis is diffuse loss across a compartment with changes in the bone and joint lining. Repair techniques work for the first and not the second.
Will a defect turn into arthritis?
It can. Large defects in weight-bearing areas are associated with progression to osteoarthritis, which is part of the argument for treating symptomatic ones in younger patients.
Does Professor Rodda perform cartilage repair?
No. This practice is focused on hip and knee replacement. Cartilage repair is performed by surgeons who specialise in it, and you will be referred if that is the appropriate option.
References.
- Krych AJ, Saris DBF, Stuart MJ, Hacken B. Cartilage injury in the knee: assessment and treatment options. J Am Acad Orthop Surg. 2020;28(22):914-922.
- Houck DA, Kraeutler MJ, Belk JW, et al. Do focal chondral defects of the knee increase the risk of osteoarthritis? A systematic review. Am J Sports Med. 2018;46(12):3057-3063.
This page provides general information about a medical condition and a surgical procedure. It is not individual medical advice and does not replace consultation with a qualified practitioner. Outcomes vary between individuals and all surgery carries risk. A referral is needed for a consultation with Professor Daevyd Rodda; without one, you can start with the practice nurse practitioner, who can provide it.