What are the signs and symptoms of an articular cartilage injury that may be treated with the microfracture technique?
Intermittent swelling - Loose fragments floating in the knee can cause swelling to occur.
Pain - Pain with prolonged walking or climbing stairs can occur.
Giving way - The knee may occasionally buckle or give way when weight is placed upon it.
Locking or catching - Loose, floating pieces of cartilage may catch in the joint as it bends, causing the knee to lock or have limited motion.
Noise - The knee may make noise (called crepitus) during motion, especially if the cartilage on the back of the kneecap is damaged. This noise is often described as "snap, crackle, and pop".
The microfracture procedure is done arthroscopically. The surgeon visually assesses the defect and performs the procedure using special instruments that are inserted through three small incisions on the knee. After assessing the cartilage damage, any unstable cartilage is removed from the exposed bone. The surrounding rim of remaining articular cartilage is also checked for loose or marginally attached cartilage. This loose cartilage is also removed so that there is a stable edge of cartilage surrounding the defect. The process of thoroughly cleaning and preparing the defect is essential for optimum results.
Multiple holes, or microfractures, are then made in the exposed bone about 3 to 4mm apart. Bone marrow cells and blood from the holes combine to form a "super clot" that completely covers the damaged area. This marrow-rich clot is the basis for the new tissue formation. The microfracture technique produces a rough bone surface that the clot adheres to more easily. This clot eventually matures into firm repair tissue that becomes smooth and durable. Since this maturing process is gradual, it usually takes two to six months after the procedure for the patient to experience improvement in the pain and function of the knee. Improvement is likely to continue for about 2 to 3 years.
Rehabilitation Protocol for Patients with Chondral Defects on the Femur or Tibia.
The patient begins passive flexion/extension (straightening and bending) of the knee with 500 repetitions three times a day.
The use of crutches, with only light touch-down weight allowed on the involved leg, is prescribed for 6 to 8 weeks.
Patients with small defect areas (less than 1cm in diameter) may be allowed to put weight on the leg a few weeks sooner.
Limited strength training also begins immediately after microfracture surgery.
Standing one-third knee bends with a great deal of the weight on the uninjured leg begin the day after surgery.
Stationary biking without resistance and a deep-water exercise program begin 1 to 2 weeks after surgery.
After 8 weeks the patient progresses to full weight bearing and begins a more vigorous program of active knee motion.
Elastic resistance cord exercises can begin about 8 weeks following surgery.
Free weights or machine weights can be started when the early goals of the rehabilitation program have been met, but no sooner than 16 weeks after surgery.
Patients must not resume sports that involve pivoting, cutting, and jumping for 4 to 6 months after a microfracture procedure.
Full activity may be resumed once the physician has examined the knee and given approval for the patient to return to sports activity.