Cartilage is about 100 times more slippery than ice

Sitting at Joe Louis Arena several weeks ago, I spent intermission avoiding concession lines and let myself become hypnotized as the Zamboni transformed the beat-up ice into a glistening, smooth surface once again. Then the Wings came out and promptly carved it up (and unfortunately were also carved up in OT by Calgary). Watching the players and the puck glide across the ice made me wonder how there could be a substance smoother than ice. Indeed there is, and it's a part of the human body.

Cartilage is a substance that coats the ends of each bone, where one bone meets another to form a joint. Normal cartilage has a coefficient of friction two orders of magnitude lower than ice — simply put, cartilage is about 100 times more slippery than ice. This is what allows each joint to move smoothly over the course of a lifetime — hopefully. Imagine how many times you bend and straighten a finger during the course of a lifetime and imagine how smooth that movement remains through the years. Cartilage is indeed a very unique and important material in the human body and damaged cartilage can cause major problems.

Injuries to cartilage occur commonly in athletes, typically in noncontact injuries of the knee. Although the injury itself does not involve contact, there is usually a violent collision inside the knee between the two smooth joint surfaces which can damage the cartilage and even break a piece off. This can also occur in the ankle with a severe sprain or in the thrower's elbow as a result of repetitive, forceful use of the arm.

Standard first-line treatment of this problem involves the “microfracture” procedure which has become such a dirty and dreaded word in professional sports. In reality, the procedure and the rehab are very simple though recovery is lengthy. The dread lies not in the procedure but in the nature of the injury as, once the smooth cartilage surface is damaged, the body lacks the ability to repair it. These dents or craters are generally small areas of the otherwise normal joint surface, analogous to a pothole on an otherwise well-paved road.

Microfracture is a minimally invasive arthroscopic procedure in which small, two-millimeter punctures are made in the defect left behind when the smooth cartilage covering the bone is lost. The goal of the surgery is to stimulate “scar” cartilage to fill in the defect from the holes that are punched in the base of the pothole. This scar cartilage is not normal but can often do an adequate job, similar to the asphalt used to repair small potholes in the road. If the joint pothole is extremely large, more extensive surgery is usually required.



Until recently, the only way to absolutely repave a damaged area of cartilage was to repave it with a brand new surface, namely a joint replacement. Joint replacement would be a colossal overkill for these injuries but the potholes also are too problematic to be ignored.

A recent development in cartilage surgery is a technique in which the patient's own cartilage is harvested, grown in a laboratory and then reimplanted into the defect. While microfracture is still considered the best first line of defense for cartilage injuries, it is now routine to take a sample of the patient's cartilage at the time of the microfracture to hold in a tissue bank should the microfracture fail to provide relief. It is essentially an insurance policy for the cartilage. Although it is still considered experimental by some insurers, this potent new procedure is now thought of as the most reliable way to replace and repair damaged areas of cartilage and will continue to be refined at least until a Zamboni machine for the knee is developed.

Dr. Sean Bak is a Novi resident and an orthopaedic surgeon who specializes in sports medicine and shoulder reconstruction. Dr. Bak takes care of the athletes of several area universities and high schools. His practice, Porretta Center for Orthopedic Surgery, is located at the Novi Orthopaedic Center on the campus of Providence Park Hospital