It sounds like you might have had a procedure called autologous chondrocyte implantation (ACI). In this technique, a number of healthy chondrocytes (cartilage cells) are harvested (removed) from a nonweight-bearing area of the joint.
These chondrocytes are then taken to the lab where they can be stimulated to grow even more healthy cells. When there are enough intact and healthy chondrocytes to patch up the hole, surgery is done to implant them in and around the lesion. This is the favored method of repair for large, full thickness, painful cartilage lesions.
For you, the first step is to go back to your orthopedic surgeon for an examination. It’s easy to assume that any new symptom or recurrence of knee pain is from the previous injury and repair. But that might not be the case at all, so an evaluation is needed.
If your surgeon determines that a look at the repaired cartilage is in order, there are several ways to do it. But evaluating the quality of tissue after cartilage repair isn’t easy.
The surgeon can go back in with an arthroscope and take a look but this requires another surgery and is invasive. During the arthroscopic procedure, the surgeon takes a small piece of the healing tissue to examine it under a microscope. No one knows if this procedure (which disturbs the healing or healed tissue) might cause problems later.
MRIs have been used because it is a noninvasive way to look inside the joint. But standard MRIs don’t show the cellular structure of the cartilage in enough detail to really assess the repair tissue.
There is a newer MRI technique under investigation right now. It’s called dGEMRIC– dGEMRIC stands for delayed gadolinium-enhanced MRI of cartilage. The radiologist puts a dye into the knee joint — that’s the gadolinium compound (short for gadolinium diethylene triamine pentaacetic acid or Gd-DPTA).
The gadolinium spreads throughout the joint and into the cartilage. The gadolinium seeps in the best wherever there is healthy cartilage tissue with plenty of glycosaminoglycans (GAG). GAGs form an important component of connective tissues. They attract water, which helps keep the cartilage healthy and slippery for joint motion.
High levels of gadolinium indicate healthy articular cartilage. Low levels are a sign of damage to the joint surface, usually from osteoarthritis. Before undergoing expensive imaging tests, see your orthopedic surgeon and find out what he or she recommends. A simple X-ray may be all that’s needed for the problem at hand.