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Osteochondral Autograft Transplantation (OAT, Mosaicplasty)

A surgical technique for treating focal articular cartilage defects of the knee, talus, and other joints by harvesting cylindrical osteochondral plugs from non-weight-bearing donor sites and press-fitting them into the chondral defect; provides hyaline cartilage, immediate weight bearing, and durable repair for defects 1–3 cm².

Written by: Saygı Hospital Health Guide Editorial Board
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This content has been compiled by the Saygı Hospital Health Guide Editorial Board and is periodically reviewed by a specialist physician.

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What is Osteochondral Autograft Transplantation (OAT, Mosaicplasty)?

Osteochondral autograft transplantation (OAT, marketed as OATS by Arthrex; also called mosaicplasty when multiple smaller plugs are used to fill a larger defect, technique developed by Hangody) is a single-stage surgical technique for restoring focal full-thickness articular cartilage defects with the patient's own osteochondral tissue. The technique involves harvesting cylindrical osteochondral plugs (typically 4–10 mm diameter, 10–15 mm length) from non-weight-bearing donor sites and press-fitting them into the prepared defect.

Indications: focal full-thickness Outerbridge grade III–IV or ICRS grade 3–4 articular cartilage defects 1–3 cm² (single plug), 1–4 cm² (mosaicplasty with multiple plugs), in younger active patients with closed growth plates and limited osteoarthritis; ideal locations are medial and lateral femoral condyle, trochlea (knee), talar dome (especially OCD lesions of the medial talar dome), femoral head; defects must have intact subchondral bone (otherwise need allograft or matrix-based technique); ipsilateral knee donor sites used for talar OCD; contraindications are diffuse osteoarthritis, kissing lesions, defects > 4 cm² (better treated with osteochondral allograft transplantation OCA or MACI), uncorrected malalignment (must be corrected with osteotomy if > 5 degrees), inflammatory arthritis, untreated infection, instability without addressing underlying problem.

Donor sites and surgical technique: knee — superolateral trochlea, intercondylar notch (Hangody notch), inferomedial trochlea (less commonly); talus — ipsilateral knee for talar OCD; arthroscopic or mini-open approach; precision OAT instrument set with matched harvester and recipient drill creating plug 0.5–1 mm larger than recipient hole for press-fit interference; multiple plugs (mosaicplasty) for larger defects; perpendicular harvest to articular surface critical to avoid step-off; recipient hole must be perpendicular and slightly deeper than plug height for proper countersinking; sequential filling from periphery to center for better stability.

Symptoms

Activity-related knee, ankle, or hip pain localized to one compartment
Mechanical symptoms: catching, locking, giving way (loose body or large defect)
Joint effusion after activity
Decreased range of motion
History of OCD lesion or focal injury
Previously failed microfracture or other cartilage procedure
Failed conservative therapy (PT, NSAIDs, injections)
Young active patient with focal full-thickness defect on imaging
Persistent symptoms despite addressing alignment, stability, meniscal pathology
MRI showing focal full-thickness cartilage defect 1–3 cm² with viable underlying bone

Risk Factors

Defect size > 4 cm² (consider osteochondral allograft, MACI instead)
Diffuse osteoarthritis (poor outcomes — better with arthroplasty)
Kissing lesions (both articular surfaces involved)
Significant malalignment uncorrected (> 5 degrees varus / valgus — must be addressed)
Meniscal deficiency uncorrected
Ligamentous instability uncorrected
Inflammatory arthritis (rheumatoid, psoriatic)
Smoking (impaired healing)
Donor site morbidity (5–25 percent — anterior knee pain after talar OCD treatment with knee donor)
Older age (> 50 years — relative; outcomes inferior compared to younger patients)
Prior multiple knee surgeries
Active infection

When to See a Doctor?

If you experience any of the following symptoms, seek medical attention promptly:

  • Persistent activity-related knee, ankle, or hip pain in young patient
  • Mechanical symptoms (catching, locking, giving way)
  • MRI showing focal full-thickness cartilage defect 1–3 cm²
  • OCD lesion (juvenile or adult) with mechanical symptoms or detached fragment
  • Failed microfracture or other cartilage procedure
  • Failed conservative therapy (PT, NSAIDs, injections)
  • Young athlete wishing to return to sport with focal cartilage defect
  • Suspected loose body in joint
  • New trauma to previously known cartilage lesion
  • Discussion of cartilage restoration options

Treatment Methods

01
Pre-operative evaluation: comprehensive history (mechanism, prior treatments), physical exam (alignment, ligamentous stability, meniscal exam, range of motion), weight-bearing AP and lateral radiographs, long-leg standing alignment films, MRI (defect size, location, depth, subchondral bone status, exclude bone marrow edema indicating advanced disease), diagnostic arthroscopy if uncertain
02
Address concomitant pathology in same setting or staged: malalignment correction (high tibial osteotomy for varus, distal femoral osteotomy for valgus, > 5 degrees), ligamentous reconstruction (ACL, MCL, LCL), meniscal repair or transplant, lower-extremity malalignment for hip
03
Surgical approach: arthroscopic for talar OCD and small knee defects, mini-arthrotomy or open for larger knee defects or trochlear lesions; precise positioning and access to perpendicular harvest and recipient site
04
Donor site selection: lateral trochlea (most common, harvested from low-load area), intercondylar notch (Hangody), medial trochlea (least preferred — symptomatic donor site morbidity); avoid hyaline cartilage on weight-bearing surface in mature patient
05
Plug preparation: harvester drill perpendicular to surface 0.5 mm larger than recipient hole for press-fit; plug length matches recipient depth (typically 10–15 mm) with cartilage cap intact and subchondral bone segment for press-fit stability; multiple smaller plugs (3.5, 5, 6.5, 8, 10 mm) used for mosaicplasty
06
Recipient preparation: recipient drill perpendicular to articular surface, debride defect to stable margins, depth matches plug length; press-fit plug from periphery to center for larger defects
07
Plug insertion: tap plug gently with delivery tamp, ensuring articular surface flush (slight countersinking acceptable, no proud or sunken plug); confirm stability with arthroscopic probe
08
Postoperative protocol: 6 weeks non-weight-bearing on operated side (or partial weight-bearing per surgeon preference, recent trend toward earlier weight bearing for talar OAT), continuous passive motion for knee within first 2 weeks (5–6 hours daily) to promote chondrocyte nutrition and prevent stiffness, gradual return to weight-bearing at 6–8 weeks, return to running at 4–6 months, return to cutting / pivoting sports at 9–12 months
09
Adjunctive treatments: PRP or biologic augmentation (limited evidence), hyaluronic acid injection during postoperative recovery, addressing residual issues (alignment, meniscal pathology, ligamentous laxity) staged or simultaneously
10
Long-term follow-up: MRI at 6 months and 12 months to assess plug incorporation and surface congruence; clinical outcomes (Lysholm, KOOS, IKDC scores) at 6 months, 1, 2, 5, 10 years; 5- to 10-year outcomes show 70–85 percent good to excellent results for medium-sized defects in younger patients; conversion to arthroplasty rate 10–15 percent at 10–15 years
11
Multidisciplinary team: orthopedic sports medicine, physical therapy, athletic training, primary care sports medicine for return-to-play decisions

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Health Disclaimer: The information on this page is prepared for general informational purposes only. It does not replace medical diagnosis and treatment. Please consult your physician for your complaints. Saygı Hospital does not accept responsibility for actions taken based on the information on this page.