Microfracture Surgery for the Treatment of Cartilage Defects in the Knee
By Kurtis Mullaney, PT, DPT, ATC/L
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 is sometimes warranted to reduce pain and improve function. This technique was first developed 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 and will then use an instrument called an awl to poke holes (microfractures) into the bone to cause bleeding. 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 be protected. In terms of time, the clot takes about 8 weeks to 15 weeks convert to fibrous tissue and 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 have been known to perform this surgery at any area of the tibia, femur, or patella, but it is most widely seen performed on the femoral condyles of the knee.
The major limitation of this is that articular cartilage is made from what is known as 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 longterm benefits of this surgical technique are very limited. Over time, it has been shown that the initial benefit of microfracture tends to decline between 18 and 36 months after surgery, but despite this deterioration, postoperative functional scores remain higher than preoperative scores. Long-term studies demonstrate improved 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 lasts for 2-5 years.
With this being said there are several well known success stories regarding 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 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 considered when considering whether or not significant benefit will be achieved with the surgery. These are listed in the chart below.
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.
An example of a cartilage defect on the medial femoral condyle:
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.