Microfracture Procedure or Abrasion Arthroplasty

These are arthroscopic procedures used to try and treat early trauma or wear-induced articular cartilage loss (early arthritic defects).  They attempt to stimulate the body’s natural healing powers to form a cartilage-like tissue (scar tissue) to replace the damaged and lost cartilage.  If successful, these procedures will delay the need for further surgery on the knee.  This is accomplished by releasing the underlying bone marrow cells into the defect.  Some of the marrow cells have capacity to turn into cartilage-like cushion on the bare bone.

The postoperative care is very important in obtaining a successful outcome.  The most essential part of the post-operative regimen is strict non-weight bearing (NWB) on the operative leg.  Weight on the leg may dislodge the important marrow cells from the defect.  NWB must be maintained for 8 weeks.  In addition to keeping the stresses on the knee low, the new (and old) cartilage-like cells need to be fed.  Cartilage gets its nutrients from the joint fluid.  Therefore, the knee must be moved frequently in order to get fresh nutrients to the healing defect.  This is accomplished by the use of a CPM machine for 6 to 8 hours per day. The range of motion allowed will be determined by the location of the defect.  If a CPM machine can’t be used, three sets of 500 repetitions per day of active-assisted leg-extension/flexion exercises may be substituted.  If the area affected was between the patella (the kneecap) and the trochlear groove (the groove in which the patella moves), a brace may be used post-operatively to restrict your motion.  After the 8 weeks of NWB, therapy will be ordered to start an exercise program. 

The exercise program will be established to progress you back to as normal function, as your knee will allow.  The first phase will emphasize regaining any motion you may have lost as well as getting you comfortable with walking full weight bearing (FWB).  It is important to avoid “pounding” activities, such as jogging, at this stage.  Once you have full range-of-motion (ROM) and are walking FWB, the second phase, a strengthening program can be initiated.  As your strength improves and no pain is noted with walking, the third phase, functional activities are added.  The final phase is return to normal activities without restriction.  (There will always be the note of caution, as the new scar tissue will never be as durable as the original cartilage.)  This whole process from surgery to return to normal activities may take up to a year.

Written by James A. Shapiro, MD