Question 1

What is articular cartilage and why can't it heal naturally?

Accepted Answer

Articular cartilage is the smooth white tissue covering the ends of bones in joints - it provides frictionless gliding and shock absorption. Unlike most body tissues, articular cartilage CANNOT HEAL naturally once damaged, which is why cartilage injuries are so problematic. WHY CARTILAGE IS SPECIAL: Articular cartilage is different from fibrocartilage (meniscus) or elastic cartilage (ear). It is HYALINE CARTILAGE - smooth, glassy, low-friction surface. 2-4mm thick in knee (thicker in weight-bearing areas). Composed of: CHONDROCYTES (cartilage cells - only 1-5% of cartilage volume), EXTRACELLULAR MATRIX (95-99% of volume - collagen fibers for structure, proteoglycans attract water for shock absorption, water 60-80% by weight). WHY IT CANNOT HEAL: NO BLOOD SUPPLY: Cartilage is AVASCULAR (no blood vessels penetrate it). Nutrients diffuse from synovial fluid (joint fluid), not from blood. Without blood supply, cannot mount inflammatory healing response (no white blood cells, growth factors, platelets can reach injury site). MINIMAL CELL ACTIVITY: Adult chondrocytes have very LOW metabolic activity (divide very slowly or not at all). Once damaged, chondrocytes cannot replicate enough to fill defect. NO STEM CELLS: Unlike bone (which has abundant stem cells and heals excellently), adult articular cartilage contains NO stem cell population. ZONAL STRUCTURE: Cartilage organized in layers (superficial, middle, deep, calcified zones). Superficial zone injury may heal slightly (cells more active). FULL-THICKNESS injury (down to bone) CANNOT heal - defect remains permanently. WHAT HAPPENS TO UNTREATED CARTILAGE DEFECTS: Small defect (less than 1cm²) may remain stable for years but won't heal. Medium-large defect (more than 2cm²) progressively enlarges over time. Mechanical stress concentrates at defect edges causing surrounding cartilage to fray and detach. Exposed bone in defect becomes eburnated (polished, sclerotic) - very painful. Eventually entire joint surface degenerates → osteoarthritis → joint replacement. Timeline: 5-15 years from focal defect to severe arthritis depending on defect size, patient age, activity level. BOTTOM LINE: Articular cartilage damage is PERMANENT - it will NOT heal naturally. This is why cartilage repair surgery is needed for symptomatic defects - to fill defect with SOMETHING (fibrocartilage scar from microfracture, or transplanted cartilage from OATS/ACI) to prevent progression to arthritis.

Question 2

What are the different cartilage repair surgery options and how do I choose?

Accepted Answer

There are FOUR main surgical options for cartilage repair, each with different indications based on defect SIZE, patient AGE, and previous surgeries. DECISION ALGORITHM: DEFECT SIZE: Small (less than 2 cm²) → MICROFRACTURE (simplest, cheapest). Medium (2-4 cm²) → OATS (mosaicplasty) OR ACI. Large (more than 4 cm²) → ACI OR osteochondral allograft. PATIENT AGE: Under 30 years → Any procedure (best healing capacity). 30-40 years → Any procedure (good results possible). 40-50 years → Microfracture or OATS (ACI success declines). Over 50 years → Consider joint replacement rather than cartilage repair. PROCEDURE COMPARISON: 1. MICROFRACTURE (Bone Marrow Stimulation): Best for: Small defects 1-3 cm², young patients, first-time surgery. Surgery: 30-60 min arthroscopic day procedure. Recovery: 6-9 months return to sport. Result: Fills defect with FIBROCARTILAGE scar (inferior to normal cartilage). Success: 60-80% at 5 years, 40-60% at 10 years (deteriorates over time). Cost: $3,000-6,000 (lowest cost option). Pros: Simple, quick, cheap, can weight-bear sooner (6 weeks). Cons: Fibrocartilage less durable, results decline after 5 years, many need revision surgery. 2. OATS (Osteochondral Autograft Transfer): Best for: Medium defects 1-4 cm², failed microfracture, need durable repair. Surgery: 60-90 min arthroscopic or mini-open, 1-2 night hospital stay. Recovery: 6-9 months return to sport. Result: Transplants patient's own NORMAL HYALINE CARTILAGE. Success: 75-85% at 10 years (better long-term than microfracture). Cost: $8,000-15,000. Pros: Uses patient's own normal cartilage (best quality), good long-term results. Cons: Donor site pain 10-20%, limited by available donor cartilage (can't treat very large defects). 3. ACI (Autologous Chondrocyte Implantation): Best for: Large defects more than 4 cm², failed OATS, revision surgery. Surgery: TWO procedures - (1) Harvest arthroscopy 30 min, (2) Implantation open surgery 90-120 min 6-8 weeks later. Recovery: 9-18 months return to sport (longer than other procedures). Result: Cultured cells produce HYALINE-LIKE cartilage (high quality). Success: 70-80% at 10 years. Cost: $20,000-35,000 (most expensive - includes cell culture). Pros: Can treat LARGE defects, produces high-quality cartilage, good long-term results. Cons: TWO surgeries, second is OPEN (not arthroscopic), long recovery, very expensive, large gap payments. 4. OSTEOCHONDRAL ALLOGRAFT (Cadaver Graft): Best for: Massive defects more than 6-10 cm², bone + cartilage loss, failed ACI, salvage before joint replacement. Surgery: 90-150 min open surgery, 2-5 night hospital. Recovery: 9-12 months. Result: Transplants donor hyaline cartilage. Success: 65-80% at 10 years. Cost: $25,000-45,000 (graft tissue $10,000-20,000). Pros: Can replace huge areas of cartilage/bone. Cons: Limited availability (wait 3-12 months), risk immune rejection/disease transmission, high failure rate (30-50% at 15 years), very expensive. MY RECOMMENDATION APPROACH: Small defect under 2 cm², young patient (under 30), first surgery → MICROFRACTURE (simplest, if it fails can do OATS/ACI later). Medium defect 2-4 cm² → OATS (one surgery, good results, less expensive than ACI). Large defect more than 4 cm² → ACI (only option for very large defects besides allograft). Failed microfracture → OATS or ACI depending on size. Massive defect, failed ACI → Osteochondral allograft (salvage). BOTTOM LINE: Start with simplest procedure (microfracture) for small defects. Use OATS for medium defects or failed microfracture. Reserve ACI for large defects where OATS not feasible. Reserve allograft for salvage of massive defects.

Medical Disclaimer

Articular Cartilage Damage (Chondral Defects)

📖What is Articular Cartilage Damage (Chondral Defects)?

🔬What Causes It?

⚠️Risk Factors

You may be at higher risk if:

🛡️Prevention