What is microfracture surgery for the knee?

From the Guidelines

Microfracture surgery is a recommended treatment option for small cartilage defects in the knee, particularly for patients under 40 with single lesions smaller than 2cm² and minimal existing arthritis. This procedure involves creating small holes in the bone beneath damaged cartilage, allowing bone marrow cells to access the injury site and form new cartilage-like tissue, as supported by the management of chondral defects of the knee with microfracture being well established, with favorable outcomes reported 1. The rehabilitation process is crucial and includes a progressive weight-bearing protocol starting with crutches for 6-8 weeks, followed by physical therapy focusing on range of motion exercises, strengthening, and eventually sport-specific training.

• Key considerations for microfracture surgery in the knee include:
  • Lesion size: smaller than 2cm²
  • Patient age: under 40
  • Existing arthritis: minimal
  • Rehabilitation protocol: progressive weight-bearing and physical therapy
• Pain management typically involves NSAIDs like ibuprofen (400-600mg every 6-8 hours) or naproxen (500mg twice daily) for the first 1-2 weeks, with prescription medications like tramadol used only if necessary for severe pain, although specific pain management strategies may vary depending on individual patient needs and medical history.
• The new tissue formed through microfracture surgery (fibrocartilage) is not as durable as original cartilage, so results may deteriorate after 5-10 years, particularly with high-impact activities, highlighting the importance of careful patient selection and post-operative management 1.

From the Research

Microfracture Surgery for Knee Cartilage Defects

• Microfracture surgery is a technique used to treat cartilage defects in the knee, where an awl is used to penetrate the subchondral bone, inducing fibrin clot formation and promoting the growth of fibrocartilage 2.
• The procedure is ideally suited for small, contained cartilage lesions, and most clinical studies show improvement in knee function in 70-90% of patients 2.
• However, the long-term results vary, with some studies showing a decline in activity levels after 1 year, especially in elite athletes, while others show good results for up to 7 years 2.

Predictors of Outcome

• Factors that impact the functional outcome of microfracture surgery include age, body mass index (BMI), time from diagnosis to surgery, size of the lesion, and the MOCART score 3.
• A higher BMI, longer time from diagnosis to surgery, and larger lesion size are associated with poor outcomes 3, 4.
• Younger patients and those with smaller lesions tend to have better clinical outcomes and quality of cartilage repair 5, 4.

Efficacy and Safety

• Microfracture surgery provides good function and pain relief in the mid-term, with failure rates ranging from 11-27% within 5 years and 6-32% at 10 years 6.
• Imaging analysis and second-look arthroscopies have shown that microfracture can lead to the growth of fibrocartilaginous repair tissue, although the quality of the repair tissue can be variable 2, 6.
• The technical simplicity, cost-effectiveness, and relatively low patient morbidity make microfracture an invaluable tool for the treatment of small full-thickness cartilage lesions 2.