Knee Cartilage Defect Surgery

A knee cartilage ulcer—clinically termed an Osteochondral Defect (OCD)—is a focal lesion involving the smooth hyaline articular cartilage and the underlying subchondral bone. Unlike generalized osteoarthritis, cartilage defects are localized, making them prime candidates for joint-preserving restorative surgery in young and active patients.

Surgical Indications

Surgical intervention is indicated when conservative measures (rest, targeted physical therapy, and intra-articular injections) fail after 3 to 6 months, or when patients present with:

Well-localized, load-dependent joint line pain.
Mechanical symptoms, such as painful clicking, catching, or acute locking due to loose chondral fragments.
Recurrent exercise-induced joint effusion.
High-grade focal lesions (ICRS Grade 3 or 4) confirmed via high-resolution MRI.

Types of Cartilage Restoration Procedures

Microfracture (Marrow Stimulation):

Technique: Arthroscopic micro-perforations into the subchondral plate release mesenchymal stem cells to form fibrocartilage repair tissue.
Indications: Small lesions ($< 2\text{ cm}^2$) in patients under 40.

Osteochondral Autograft Transfer System (OATS / Mosaicplasty):

Technique: Cylindrical osteochondral plugs are harvested from non-weight-bearing donor sites and press-fit into the defect, providing immediate mature hyaline cartilage.
Indications: Moderate focal lesions ($1\text{ to }4\text{ cm}^2$).

Autologous Chondrocyte Implantation (ACI / MACI):

Technique: A two-stage procedure involving an arthroscopic cartilage biopsy, in vitro cellular expansion, and secondary implantation on a collagen matrix scaffold.
Indications: Large, complex defects ($> 4\text{ cm}^2$) requiring high-quality hyaline-like regeneration.

Osteochondral Allograft Transplantation:

Technique: Fresh cadaveric donor graft used to reconstruct massive post-traumatic or structural defects.

Success Rates and Clinical Outcomes

Overall success rates range between 70% and 90%, heavily dependent on lesion size, chronicity, and patient age:

Microfracture: 80%–90% early success in small, contained defects.
OATS: High rate of graft incorporation with durable hyaline resurfacing.
MACI: 75%–85% long-term survivorship with superior structural tissue integration.

Potential Complications

Complication rates range between 3% and 8%:

Fibrocartilage Degradation / Integration Failure: Most common with microfracture over time (10%–20%).
Arthrofibrosis / Joint Stiffness (3%–7%): Preventable with early continuous passive motion (CPM).
Deep Vein Thrombosis (DVT): Mitigated by chemical thromboprophylaxis during non-weight-bearing phases.
Superficial or Deep Infection (< 1%).

Estimated Cost in Cairo (2026)

Costs vary based on surgical complexity, specialized graft handling, and facility tier:

Arthroscopic Microfracture: Starting from EGP 15,000 to EGP 35,000.

OATS / Mosaicplasty: Ranges between EGP 40,000 and EGP 75,000.
MACI / Advanced Cell Therapy: Can reach EGP 120,000 to EGP 150,000+ due to specialized external laboratory cell-expansion requirements.

Frequently Asked Questions: Knee Cartilage Defect Surgery (Osteochondral Repair Guide)

What is a knee cartilage defect and why does it require surgical repair?

A knee chondral or osteochondral defect is a focal, localized zone of full-thickness damage to the smooth articular (hyaline) cartilage and underlying subchondral bone plate. Because native hyaline cartilage is entirely avascular, aneural, and alymphatic, it lacks spontaneous regenerative potential. Surgical repair restores a congruent articulating surface, eliminates pain, and arrests progressive joint deterioration toward premature osteoarthritis.

What are the primary surgical techniques for knee cartilage repair?

Treatment selection is customized to defect morphology, surface area, and depth:

Microfracture / Marrow Stimulation: Inducing subchondral bleeding for small, contained lesions (<2 cm²).
Osteochondral Autograft/Allograft Transfer (OATS / Mosaicplasty): Transplanting viable bone-cartilage cylindrical plugs into medium-to-large defects.
Autologous Matrix-Induced Chondrogenesis (AMIC): Combining marrow stimulation with synthetic or biological collagen matrices.
Matrix-Induced Autologous Chondrocyte Implantation (MACI): Two-stage cell harvesting, laboratory expansion, and bio-scaffold reimplantation for large defects (>3–4 cm²).

How does Microfracture stimulate cartilage regeneration?

During arthroscopic microfracture, an orthopedic awl introduces multiple small perforations (2–4 mm deep) through the debrided subchondral plate into the cancellous marrow. This channels pluripotent mesenchymal stem cells and growth factors into the defect site, producing a "super-clot" that differentiates over several months into a dense, load-bearing fibrocartilage matrix predominantly composed of Type I and Type II collagen.

What is the difference between OATS (Mosaicplasty) and MACI?

OATS is a single-stage mechanical replacement that transplants mature hyaline cartilage and underlying bone plugs taken from a non-weight-bearing area of the joint (or a deceased donor allograft). MACI is a cellular biological process requiring two stages: an initial arthroscopic biopsy of healthy cartilage, ex-vivo laboratory cell proliferation, and a second-stage procedure to suture or glue the chondrocyte-seeded collagen membrane into the prepared defect.

Who is an ideal candidate for osteochondral repair surgery?

Optimal candidates present with:

Focal, unipolar Outerbridge Grade III or IV chondral lesions.
Age younger than 45–50 years with high functional demands.
Competent, stable ligaments (especially intact ACL and collateral ligaments).
Normal mechanical axis alignment (or willing to undergo concurrent realignment osteotomy).
Absence of diffuse multi-compartmental joint space narrowing.

Why is non-weight-bearing (crutch use) mandatory after cartilage repair?

Early excessive axial loading and shearing forces can mechanically destroy fragile chondrocyte matrices, shear off biological membranes, or displace osteochondral plugs before bone-to-bone osseointegration occurs. Strict adherence to non-weight-bearing or feather-touch loading with crutches for 4 to 6 weeks provides the protected microenvironment essential for matrix solidification.

What is the role of the Continuous Passive Motion (CPM) machine in recovery?

The CPM machine facilitates passive range of motion without muscular contraction or joint impact. By gently cycling the joint, it enhances intermittent hydrostatic pressure, optimizes synovial fluid diffusion (which provides the primary metabolic nutrition for the avascular repair site), minimizes intra-articular scarring, and promotes preferential differentiation into hyaline-like repair tissue.

What is the expected timeline for returning to sports and athletic activities?

Rehabilitation progresses in structured biological phases:

Weeks 0–6: Graft protection, passive motion, non-weight-bearing.
Weeks 6–12: Progressive full weight-bearing, gait normalization, stationary cycling.
Months 3–6: Closed kinetic chain strengthening, elliptical trainer, swimming.
Months 6–9: Controlled straight-line running and functional agility drills.
Months 9–12: Full clearance for contact sports, cutting, and high-impact loading after objective muscle and balance testing.

What are the common risks and complications of cartilage defect surgery?

While safe and effective, potential complications include:

Incomplete repair or biological graft failure (graft delamination or subsidence).
Donor-site morbidity, discomfort, or patellofemoral irritation in autograft harvesting.
Joint stiffness and arthrofibrosis requiring arthroscopic lysis of adhesions.
Deep vein thrombosis (DVT) secondary to temporary limb immobilization.

What is the overall long-term success rate of knee cartilage repair procedures?

Contemporary clinical studies and orthopedic registries indicate an overall success rate of 80% to 90% at 5 to 10 years of follow-up. Successful outcomes correlate directly with accurate pre-operative lesion characterization, correction of background biomechanical malalignment, and strict adherence to stage-specific physical therapy protocols.