Question 1

What is OATS mosaicplasty and how is it different from microfracture?

Accepted Answer

OATS (Osteochondral Autograft Transfer System) also called mosaicplasty is a surgical procedure that transfers cylindrical plugs of your own healthy cartilage and bone from non-weight-bearing areas of your knee to fill cartilage defects in weight-bearing areas. Think of it like moving tiles from the edge of a mosaic (where they're not needed) to fill gaps in the center (where they are critical). HOW OATS WORKS: Surgeon uses a specialized coring tool (hollow cylindrical drill) to harvest donor plugs 6-10mm diameter from non-weight-bearing areas of your knee. Common donor sites: Intercondylar notch (edges of groove between femoral condyles), Superior trochlea (upper edges of groove, minimal contact with kneecap), Peripheral femoral condyle (outer rim areas). Each donor plug includes: Cartilage surface (2-4mm thick) + Bone underneath (6-10mm deep) - total plug 10-15mm length. Surgeon creates matching cylindrical holes in your cartilage defect. Press-fits donor plugs into recipient holes in mosaic pattern. Critical to achieve flush surface (plugs level with surrounding cartilage). Multiple plugs arranged to maximize defect coverage. OATS VS MICROFRACTURE COMPARISON: CARTILAGE QUALITY: OATS transplants your own NORMAL HYALINE CARTILAGE (smooth, durable, identical to native cartilage). Microfracture creates FIBROCARTILAGE scar (inferior quality - more like meniscus tissue than normal cartilage, less durable, wears out faster). LONG-TERM RESULTS: OATS: 75-85% good results at 10 years (results stable over time). Microfracture: 60-80% good at 5 years, declining to 40-60% at 10 years (deteriorates over time as fibrocartilage wears out). PROCEDURE COMPLEXITY: OATS: 60-90 minutes, hospital 1-2 nights (sometimes day procedure), technically demanding. Microfracture: 30-60 minutes, day procedure, simpler technique. DONOR SITE ISSUES: OATS: 10-20% patients experience donor site pain long-term (harvesting plugs leaves defects in donor areas that don't regenerate). Microfracture: No donor site (only creates holes in damaged area). COST: OATS $8,000-15,000 vs Microfracture $3,000-6,000. INDICATIONS: OATS best for medium defects 2-4 cm², young active patients (under 40), failed microfracture, athletes requiring durable repair. Microfracture best for small defects under 2 cm², older patients (over 45), cost-sensitive patients. BOTTOM LINE: OATS produces HIGHER QUALITY repair using your normal cartilage, giving better long-term results (75-85% success at 10 years) but is more complex surgery with donor site morbidity risk (10-20% donor site pain). Microfracture is simpler and cheaper but produces lower quality fibrocartilage scar that deteriorates over 10 years. For medium defects in young active patients, OATS is preferred despite donor site risk.

Question 2

Where does the donor cartilage come from and will harvesting it cause problems?

Accepted Answer

OATS uses your OWN cartilage harvested from non-weight-bearing areas of your same knee - these are areas that don't contact the opposite surface during normal knee motion, so removing cartilage from there theoretically should not affect function. However, 10-20% patients do experience donor site pain long-term. DONOR SITE ANATOMY: Your knee has several non-weight-bearing areas where cartilage is present but doesn't serve load-bearing function: INTERCONDYLAR NOTCH MARGINS (most common donor site): The notch is the groove between your medial and femoral condyles where ACL attaches. The edges (margins) of this groove have cartilage but don't contact the tibia during knee motion. Surgeon can harvest 2-3 plugs from notch margins (one medial, one lateral, sometimes one central). SUPERIOR TROCHLEA (trochlear groove edges): The trochlea is the groove where your patella (kneecap) glides. The upper portion of the trochlea doesn't contact the patella (patella only covers lower two-thirds in normal motion). Can harvest 1-2 plugs from superior non-contact zone. PERIPHERAL FEMORAL CONDYLE: The outer edges of the condyle (medial or lateral) have minimal contact. Can harvest plugs but higher risk of donor site symptoms than notch or superior trochlea. HARVESTING PROCESS: Surgeon uses cylindrical coring tool (trephine) to cut donor plugs. Typical plug: 6-10mm diameter, 10-15mm depth. Leaves cylindrical hole in donor area. Harvest 1-4 plugs depending on defect size (more plugs = more donor site defects). WHAT HAPPENS TO DONOR SITES AFTER HARVESTING: The donor site holes DO NOT regenerate normal cartilage. Instead fill with fibrocartilage scar or fibrous tissue over 6-12 months. Bone beneath donor site remodels and fills in. Cartilage surface never regenerates to original hyaline cartilage. This is why donor site morbidity occurs. DONOR SITE MORBIDITY RISK: 10-20% patients experience donor site pain long-term. Usually MILD: Occasional ache with deep knee bending, squatting, prolonged kneeling. Rarely SIGNIFICANT: Persistent pain limiting function, unable to return to desired activities. Higher risk if: Multiple plugs harvested (more donor defects), Peripheral condyle used (some contact stress), Pre-existing patellofemoral pain (harvest from trochlea may worsen). CANNOT PREDICT who will get donor site pain - some patients with 4 plugs no pain, others with 1 plug significant pain. PATIENT CONSIDERATIONS: Most patients accept 10-20% donor site pain risk as trade-off for successful defect repair (benefits outweigh risks). Surgeon minimizes donor site morbidity by: Using intercondylar notch and superior trochlea (truly non-weight-bearing areas), Harvesting minimum number of plugs needed, Avoiding peripheral sites if possible. BOTTOM LINE: OATS uses your own cartilage from non-weight-bearing areas within same knee. These areas don't regenerate after harvest. 10-20% experience donor site pain (usually mild). Benefits of successful defect repair typically outweigh donor site morbidity risk, but patients must accept this trade-off when choosing OATS.

Question 3

What are realistic expectations for returning to sport and long-term outcomes?

Accepted Answer

OATS has good long-term success rates (75-85% at 10 years) with most patients returning to sport, but recovery is gradual over 6-9 months and some activity modifications may be needed long-term. RETURN TO SPORT TIMELINE: Months 0-3: NO impact activities. Partial weight-bearing progressing to full. Gentle strengthening and range of motion. Swimming, cycling OK. Months 3-6: Begin low-impact sport-specific training. Light jogging (if pain-free). Elliptical, stair-climber. Progressive resistance training. Can often return to low-impact sports (cycling, swimming). Months 6-9: Running progression. Agility drills, cutting, pivoting. Sport-specific drills. Return to UNRESTRICTED sport at 6-9 months if: Pain-free, Full strength and range of motion, Surgeon clearance (sometimes MRI at 6 months to confirm plug integration). SPORT-SPECIFIC RETURN RATES: LOW-IMPACT sports (cycling, swimming, walking): 95%+ return at pre-injury level. MODERATE-IMPACT sports (tennis, golf, recreational jogging): 85-90% return. HIGH-IMPACT PIVOTING sports (basketball, soccer, netball, AFL): 70-85% return to competitive level (some reduction in level common - e.g., return to recreational not elite). Very high-impact (marathon running, ultra-endurance): 50-70% return (prolonged repetitive loading may accelerate plug wear). LONG-TERM OUTCOMES (10 YEARS): 75-85% have GOOD-TO-EXCELLENT results meaning: Pain significantly improved (2-3/10 vs 6-8/10 preop), Function restored (able to work, exercise, play sport without major limitation), Plugs intact on imaging (no subsidence or significant wear), Satisfied with outcome and would choose surgery again. 15-25% have FAIR-TO-POOR results: Persistent pain despite intact plugs (5-10%), Plug failure requiring revision (5-10%), Donor site pain limiting function (5-10%). COMPARISON TO OTHER PROCEDURES: OATS vs MICROFRACTURE: OATS 75-85% good results at 10 years, Microfracture 40-60% at 10 years (OATS significantly better long-term). OATS vs ACI: Similar results (both 70-80% at 10 years) but OATS single surgery vs ACI two surgeries. FACTORS AFFECTING YOUR OUTCOME: BEST PROGNOSIS (85-90% success): Age under 30 years, Single 10-12mm plug for 2 cm² defect, Isolated defect, No malalignment, Non-smoker, Compliant with rehab. INTERMEDIATE (75-80% success): Age 30-40 years, 2-3 plugs for 3-4 cm² defect, Well-aligned joint, Compliant patient. POORER PROGNOSIS (60-70% success): Age over 40, 3-4 plugs for 4+ cm² defect (at upper limit of OATS capacity), Uncorrected malalignment, Smoker, Early return to sport (before 6 months). ACTIVITY MODIFICATIONS LONG-TERM: Most patients return to full sport including high-impact. Avoid EXTREME activities: Marathon running (repetitive loading over 2-4 hours may accelerate plug wear), Heavy laboring (prolonged squatting, kneeling if donor site pain), Extreme sports (high risk of re-injury). Maintain healthy weight (obesity accelerates cartilage stress). WHAT IF OATS FAILS: Failed OATS (persistent pain, plug failure) → Revision options include ACI, osteochondral allograft, or joint replacement depending on age and defect size. Failed OATS doesn't preclude other options (can still do ACI or allograft as salvage). BOTTOM LINE: 75-85% patients have good results at 10 years with return to sport at 6-9 months. OATS is BETTER long-term than microfracture (doesn't deteriorate over time like fibrocartilage does). Most return to pre-injury activity level including high-impact sport. Donor site pain affects 10-20% but usually mild. OATS is good option for medium defects in active patients seeking durable repair.

Medical Disclaimer

OATS - Mosaicplasty (Transferring Your Own Cartilage Plugs)

📖What is OATS - Mosaicplasty (Transferring Your Own Cartilage Plugs)?

🔬What Causes It?

⚠️Risk Factors

You may be at higher risk if:

🛡️Prevention