Overview
Microfracture is a marrow-stimulation procedure for selected focal articular cartilage defects. Small penetrations through the subchondral plate provide access to marrow elements and promote a reparative fill. The resulting tissue is predominantly fibrocartilaginous and should not be equated with restoration of normal hyaline cartilage (Campbell, Chapter 50).
The operation is relatively simple and inexpensive, but durability is limited in some patients. Appropriate defect selection, careful preparation, correction of adverse joint mechanics and rehabilitation are as important as making the perforations (Campbell, Chapters 50 and 56).
Assessment and Indications
Correlate pain, swelling and mechanical symptoms with the lesion. Begin with appropriate nonoperative measures, including load reduction, activity modification and muscle strengthening.
Use cartilage-sensitive MRI to estimate location, dimensions, grade and subchondral involvement. Arthroscopic inspection and probing refine the final assessment.
Chapter 50 describes marrow stimulation mainly for small lesions, generally under 2 cm², in lower-demand patients. Larger lesions or high-demand patients may be better served by restorative procedures.
Distinguish a cartilage-only defect from an osteochondral lesion with substantial bone loss or a salvageable osteochondral fragment. These are different reconstructive problems.
Assess alignment, ligament stability, meniscal support and the surrounding cartilage. Treating a defect in a mechanically unfavorable compartment without correcting the cause compromises the repair environment.
(Campbell, Chapters 50 and 56.)
Factors Affecting Selection
More favorable setting | Factors requiring reconsideration or another strategy |
|---|---|
Small, contained focal defect | Large or uncontained defect, bipolar disease or diffuse arthritic change |
Healthy surrounding cartilage and retained meniscal function | Substantial cartilage degeneration or meniscal deficiency |
Stable, appropriately aligned knee | Uncorrected instability or malalignment |
Patient able to follow protected rehabilitation | Inability to comply with the loading and motion plan |
Younger patient with suitable activity expectations | Older age, obesity, smoking and systemic disease that may reduce healing potential |
These factors inform a combined decision; they are not interchangeable absolute cutoffs. Campbell reports better microfracture results in patients younger than 40 and lists several adverse healing factors in Chapter 56, Box 56.9.
Positioning and Setup
Position supine for knee arthroscopy, with a padded post or holder that permits the degree of flexion required to reach the entire lesion.
Prepare a 30-degree arthroscope, probe, curettes, controlled debridement instruments and marrow-stimulation instruments.
Confirm an unobstructed working trajectory. The posterior extent of a condylar lesion may require changing knee flexion and portal access.
Review any planned realignment, stabilization or meniscal procedure before starting: the final rehabilitation plan must account for all interventions.
(Campbell, Chapter 56, knee setup and chondral lesion assessment; Chapter 50, treatment planning.)
Surgical Technique
Diagnostic Assessment
Perform a systematic examination of the knee, including the menisci, ligaments and opposing articular surface.
Inspect and probe the lesion to establish its true margins, cartilage stability and any subchondral bone involvement.
Measure and record the defect. Confirm that marrow stimulation remains appropriate after direct assessment; do not continue solely because it was the preoperative plan.
(Campbell, Chapters 50 and 56.)
Defect Preparation
Remove unstable cartilage while preserving healthy surrounding tissue.
Create stable, sharply defined vertical margins to contain the repair tissue.
Remove the calcified cartilage layer with a curette. Avoid abrasion or unnecessary removal of the underlying subchondral bone.
Recheck that the entire bed has been prepared and that no unstable cartilage remains at the border.
(Campbell, Chapter 50, factors affecting repair quality; Chapter 56, Box 56.8.)
Marrow Stimulation
Create controlled small penetrations through the prepared bed into the vascular subchondral bone.
Keep the holes separate. Chapter 56 describes approximately 1–2-mm holes spaced 2–3 mm apart; Chapter 50 emphasizes retaining a 1–2-mm bridge of bone between penetrations.
Avoid joining the holes or creating broad subchondral damage. The retained bone bridges support attachment of the reparative tissue to the defect base.
Complete the planned treatment of associated mechanical abnormalities and record the final defect dimensions, location and procedures performed.
(Campbell, Chapters 50 and 56.)
Postoperative Care
Protect the repair while maintaining motion. Campbell emphasizes early motion, including continuous passive motion in its microfracture discussion, and protected weight bearing tailored to the size and location of the lesion. Chapter 50 also cites a systematic review suggesting that earlier loading may be acceptable for selected lesions under 2 cm²; this should not be interpreted as permission for unrestricted loading of every microfracture repair.
A single loading or return-to-sport timetable cannot be applied to femoral condylar, trochlear and patellar lesions or to procedures combined with osteotomy, meniscal repair or ligament reconstruction. The rehabilitation plan should match the actual operative findings and the mechanical stresses at the repair site (Campbell, Chapter 50).
Pearls and Pitfalls
Select the procedure for the defect: small size alone does not overcome poor cartilage surroundings, bipolar disease or absent meniscal support.
Prepare the base carefully: retained calcified cartilage and excessive subchondral abrasion are both undesirable.
Maintain bone bridges: multiple holes are intended to provide marrow access, not to remove the entire subchondral plate.
Correct overload: significant malalignment should be addressed with the cartilage treatment.
Explain the tissue produced: marrow stimulation is reparative, while osteochondral grafting and cell-based procedures have different restorative aims.
(Campbell, Chapters 50 and 56.)
Outcomes and Limitations
Short-term symptom improvement is common, but the fibrocartilaginous repair may deteriorate. Chapter 50 describes deterioration beginning around 18 months in some reports and substantial functional decline at longer follow-up. Results vary with age, lesion characteristics and activity demands. Early improvement should therefore not be presented as proof of durable cartilage restoration.
For larger lesions, substantial bone loss or a demanding activity profile, consider the broader treatment options described by Campbell, including osteochondral autograft or allograft and matrix-induced autologous chondrocyte implantation. These procedures require their own selection criteria and operative plans (Campbell, Chapter 50).
References
Bernholt DL, Azar FM. Knee injuries. In: Azar FM, Sawyer JR, Throckmorton TW, eds. Campbell's Operative Orthopaedics. 15th ed. Elsevier; 2026. Chapter 50, articular cartilage injuries and marrow stimulation, pp. 2117–2120.
Bernholt DL, Mihalko MJ. Arthroscopy of the lower extremity. In: Azar FM, Sawyer JR, Throckmorton TW, eds. Campbell's Operative Orthopaedics. 15th ed. Elsevier; 2026. Chapter 56, chondral lesion assessment and treatment selection, pp. 2359–2362, Boxes 56.8–56.9.