Knee Microfracture Surgery for Cartilage Defects

By Kurtis Mullaney, PT, DPT, ATC/L

Microfracture Surgery

Damage to the cartilage of the knee can be very challenging to treat due to the very limited capacity for articular cartilage to heal on its own. Because of this, microfracture surgery needs to be done to reduce pain and improve function. The development of this technique was in the 1980’s by Dr. Richard Steadman. It is an arthroscopic procedure in which the surgeon will typically remove the deepest or calcified layer of cartilage in the area of the defect or lesion.  Then use an instrument known as an awl to poke holes (microfractures) into the bone to cause bleeding.

Microfracture Surgery Process

The blood and bone marrow that seep out of these fractures create a blood clot that contains mesenchymal stem cells that are able to differentiate into fibrocartilage.  Which can be an effective short term replacement from the original cartilage. The blood clot is very delicate after surgery and needs to protection.  In terms of time, the clot takes about 8 weeks to 15 weeks to convert to fibrous tissue. It is usually fibrocartilage by about four months post surgery.  Holding implications for the rehabilitation of these patients leading to very conservative postoperative treatment and restrictions. Surgeons perform this surgery at any area of the tibia, femur, or patella. However, it is most widely in use on the femoral condyles of the knee.

Fitness woman having pain in her knee

Image of Woman Having Pain in Her Knee

The major limitation of this is that articular cartilage is made from hyaline cartilage (which is great for resisting compression forces) and not fibrocartilage (which is in areas of the body that require greater resistance to shear and tensile forces). Because of this, the long term benefits of this surgical technique are limiting. Over time, it has been shown that the initial benefit of microfracture tends to decline between 18 and 36 months after surgery.  However, despite this deterioration, postoperative functional scores remain higher than preoperative scores. Long-term studies demonstrate improvements in knee function in 67% to 86% of patients at an average of 6–7 years after microfracture. Most surgeons will agree most the most benefit of this surgery last for 2-5 years.

Success Stories

Furthermore, there are several success stories with microfracture surgery, especially in professional sports. NBA stars Jason Kidd, John Stockton, Kenyon Martin, Amar’e Stoudemire, Zach Randolph, and Steve Yzerman, along with the MLB’s Grady Sizemore and Matt Kemp.  They were all able to return to pre-injury form following microfracture surgery. It has become a very popular surgery in sports medicine in the past 20-30 years because it is able to prolong the careers of athletes so they can compete for another 4-5 years. It has also gained more popularity in the non-sports world as of late. However, there are a few major factors that must be taken into consideration when deciding whether or not significant benefit from the surgery.

Overall, microfracture surgery can be very effective for treating cartilage defects in the knee for short-intermediate term improvement in function and decrease in pain. It can help to prolong the need for more invasive and complicated surgeries such as total and partial knee arthroplasties and cartilage implantation surgeries. However, success for microfracture surgery will depend on a number of factors including the quality of the repair tissue, the age and health and activity level of the individual, the size and localization of the articular cartilage defect, the surgical technique, and the postoperative rehabilitation and the adherence of these patients to following postoperative precautions implemented by their physician and physical therapist.


Theodoropoulos, J., Dwyer, T., Whelan, D., Marks, P., Hurtig, M., & Sharma, P. (2012). Microfracture for knee chondral defects: a survey of surgical practice among Canadian orthopedic surgeons. Knee Surgery Sports Traumatology Arthroscopy, 20, 2430-2437.

By: Kurt Mullaney PT/ATC

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