Microfracture surgery (MFS) is a common procedure used to address isolated damage to the articular cartilage in joints, most frequently the knee. Articular cartilage, the smooth tissue covering the ends of bones, does not heal well because it lacks a direct blood supply. MFS is designed to stimulate the body’s natural healing response to fill the defect. Deciding whether to undergo MFS requires careful consideration of surgical limitations, the quality of the repair tissue, and the intense commitment required for rehabilitation.
The Procedure and Candidate Selection
Microfracture surgery is performed arthroscopically, using small instruments inserted through tiny incisions. The surgeon prepares the damaged area by removing unstable cartilage until a stable rim of healthy tissue surrounds the defect. A small, sharp pick is then used to create several microfractures in the subchondral bone, the hard layer just beneath the cartilage.
Penetrating the subchondral bone allows blood and bone marrow contents to seep into the cartilage defect. This releases pluripotent stem cells and growth factors, forming a “super clot” that serves as the foundation for the new repair tissue. The ideal candidate is typically a younger patient, generally under 45 years of age, who has a small, well-defined cartilage defect resulting from acute trauma rather than widespread arthritis.
The size of the defect is a significant limiting factor; best outcomes are observed for lesions smaller than 2 to 4 square centimeters. Patients with poor knee alignment, such as “knock-kneed” or “bow-legged” anatomy, are not considered good candidates unless alignment is corrected concurrently. If the defect is too large or the surrounding edges are not well-contained, the blood clot may not adhere properly, compromising the healing process.
Expected Post-Surgical Outcomes
The primary goal of MFS is to relieve pain and improve function, but the resulting tissue is predominantly fibrocartilage, which is distinct from native hyaline cartilage. Hyaline cartilage is highly resilient and allows for smooth, low-friction joint movement. Fibrocartilage is scar-like, containing Type I collagen rather than the more durable Type II collagen found in native tissue.
Because fibrocartilage is mechanically inferior and less resilient than hyaline cartilage, it may break down more easily under the repetitive forces of daily activities. While initial results can be very positive, with good to excellent results reported in 67% to 80% of carefully selected patients, the durability of this repair tissue is a known limitation. Functional scores and activity levels can begin to decline between two and five years post-surgery for some patients.
The success of MFS is defined by its ability to provide substantial pain relief and allow a return to low-impact activity, not by achieving perfect anatomical restoration. The procedure’s effectiveness can be compromised over time due to the limited quality of the repair tissue. Patients must weigh the short to medium-term functional improvement against the possibility of needing further intervention years later.
The Rehabilitation Commitment
Post-operative rehabilitation for MFS is highly structured and demanding, requiring a significant commitment from the patient. The initial phase focuses on protecting the developing fibrocartilage scaffold through a strict non-weight-bearing period. Patients are typically restricted from putting full weight on the operated leg for four to eight weeks, relying on crutches for mobility.
During this time, a Continuous Passive Motion (CPM) machine is often prescribed for several hours daily to gently move the joint. This continuous motion helps nourish the cartilage and encourages the formation of a smoother, more organized repair tissue. Poor adherence to the non-weight-bearing and CPM protocol significantly jeopardizes the final outcome, as premature loading can damage the fragile clot.
Following the protected phase, rehabilitation progresses through months of rigorous physical therapy aimed at restoring range of motion, strength, and balance. A return to full, high-impact activities or sports typically takes a minimum of six to nine months, sometimes longer, underscoring the long-term investment required. The success of MFS is highly dependent on the patient’s compliance.
Comparing Treatment Options
Microfracture surgery sits within a spectrum of treatments for cartilage defects, ranging from non-surgical management to more complex reconstructive procedures. For less severe issues, non-surgical options like physical therapy, bracing, and injections may be considered first to manage pain. These approaches carry minimal risk and no extensive recovery period, but they do not address the underlying cartilage defect.
More advanced surgical alternatives are reserved for larger defects where MFS is less likely to succeed. The Osteochondral Autograft Transfer System (OATS) involves transplanting plugs of healthy bone and hyaline cartilage from a non-weight-bearing area of the joint to the defect site. OATS provides superior hyaline cartilage tissue but is limited by the size of the defect it can treat and the potential for donor-site issues.
Another option is Autologous Chondrocyte Implantation (ACI), a two-stage procedure where the patient’s own cartilage cells are harvested, cultured, and then reimplanted into the defect. ACI is capable of regenerating hyaline-like cartilage and is often used for larger lesions, sometimes up to 22 square centimeters, but it requires a longer rehabilitation period than MFS. While MFS is less invasive and less costly than ACI or OATS, these alternatives may offer a better quality of repair tissue and more durable long-term results for specific patient profiles.