Microfracturing surgery repairs damaged joint cartilage by stimulating the body’s natural healing processes. This technique encourages the growth of new cartilage-like tissue, aiming to restore a smoother joint surface, reduce pain, and improve joint function in specific, localized areas.
Understanding Cartilage and Its Damage
Articular cartilage is a smooth tissue covering bone ends, enabling nearly frictionless movement and acting as a shock absorber. This specialized tissue has a limited capacity for self-repair due to its lack of direct blood supply and nerves.
Damage to articular cartilage can cause pain, swelling, stiffness, and restricted movement. Such damage often results from acute injuries or repetitive stress, manifesting as focal cartilage defects, meaning the damage is localized.
When a cartilage defect extends to the underlying bone, the body’s natural healing response can begin. However, without intervention, the repair tissue that forms is often inferior to the original cartilage. Untreated lesions can worsen, potentially leading to osteoarthritis.
The Microfracturing Procedure Explained
Microfracturing is a minimally invasive surgical technique performed arthroscopically. A small incision is made in the joint, and an arthroscope (a thin tube with a camera) is inserted, allowing the surgeon to view the joint’s interior on a monitor.
Additional small incisions are made for specialized tools. The surgeon first removes unstable or damaged cartilage from the defect, ensuring a stable rim of healthy cartilage remains.
Next, a pointed tool called an awl creates tiny holes, or microfractures, in the subchondral bone, the hard bone layer beneath the defect. This allows blood and bone marrow from the deeper, more vascular bone to seep into the cartilage defect.
The bone marrow contains mesenchymal stem cells and growth factors. These cells, along with the blood, form a “super clot” that covers the damaged area. This clot provides the biological foundation for new tissue to form as stem cells differentiate and produce cartilage-like tissue over several months.
Post-Procedure Recovery and Rehabilitation
Recovery after microfracturing surgery typically involves a structured rehabilitation protocol that can last 6 to 8 months. Immediately following the surgery, patients are usually advised to follow a non-weight-bearing or partial weight-bearing regimen for 6 to 8 weeks, using crutches to protect the newly forming tissue.
Physical therapy begins promptly after surgery with gentle range-of-motion exercises to prevent stiffness and promote nutrient diffusion to the healing cartilage. A continuous passive motion (CPM) machine may be prescribed for 6 to 8 hours daily during the initial weeks to encourage cartilage growth and maintain joint mobility. As healing progresses, strengthening exercises are introduced.
The rehabilitation program gradually advances, with a transition from partial to full weight-bearing as the repair tissue gains strength. Patients progressively work on restoring full range of motion, improving muscle strength, and enhancing joint function through tailored exercises. Activities that involve impact loading are introduced gradually, with a return to sport-specific activities potentially occurring around months 4-6, depending on individual progress and the size of the treated defect.
Long-Term Outlook and Patient Suitability
The long-term success of microfracturing surgery is influenced by several factors, including the size and location of the cartilage defect, the patient’s age, and their adherence to the rehabilitation program. The new tissue formed after microfracturing is often fibrocartilage, which differs structurally and mechanically from the original hyaline cartilage. Fibrocartilage is generally less durable and resilient, and it may not withstand the same demands as native hyaline cartilage.
While initial improvements in pain and function are common, the durability of the repair tissue can sometimes diminish over time, potentially leading to a recurrence of symptoms, especially with continued high-impact activities. Studies have indicated that clinical outcomes may see a gradual decline after 2 to 5 years post-procedure, with some progression of osteoarthritis changes observed in a percentage of knees.
Ideal candidates for microfracturing are generally younger, active individuals with small, contained cartilage defects, typically less than 2 to 4 square centimeters in size. The procedure tends to be less effective in older patients, those with larger lesions, or individuals with widespread degenerative conditions like advanced arthritis. Patient outcomes are also better when the defect is addressed in its early stages.