What makes me a candidate for this surgery?
You are a candidate if you have patellar instability (kneecap dislocation) and damage to the cartilage in your knee. The cartilage is evaluated preoperatively using MRI and intraoperatively during the diagnostic arthroscopy performed at the beginning of your surgery (see Knee Arthroscopy).
What is cartilage, why is it important, and how is it injured?
Cartilage is the shiny, smooth coating at the end of bones. It protects the bone and allows the bones to move smoothly and efficiently. When cartilage thins, or has a piece missing, it puts more stress on the bone and causes pain. The mechanism of injury for a cartilage defect is usually related to trauma, such as a dislocation that causes the cartilage to scrape along bone, or chronic friction from a maligned knee. The body cannot regenerate this type of cartilage.
What does the surgery entail?
The area of damaged cartilage is debrided and restored using one of the methods described below.
How will my cartilage be repaired?
This depends on many factors including your age as well as the size and location of the cartilage defect. The surgeon will choose from one of the following procedures:
Microfracture
- During arthroscopy, the surgeon will first remove any defective and damaged cartilage tissue from the knee joint with small instruments. They will then create small holes at the site of your lesion to allow bleeding from the underlying bone which will stimulate the formation of new tissue. The new tissue that grows is a hybrid of fibrocartilage and another type of cartilage that is similar to the original cartilage in the joint. Although it is not exactly the same, this new type of cartilage is shown to be durable and to function similarly to the original articular cartilage. This procedure can be used on very small lesions successfully.
Particulated Juvenille Articular Cartilage (PJAC) AlloGraft
- Through an incision along the side of your patella, the surgeon will first remove any defective and damaged cartilage tissue from the knee joint. They will then patch the cartilage defect with the PJAC cartilage cells. This consists of juvenile donor cartilage which is able to incorporate alongside your native cartilage, rejuvenate and grow to fill the area of missing cartilage.
- You may require follow-up MRIs at 3 mo, 6 mo, 12 mo, and 24 mo after surgery to follow the growth and maturation of the cartilage graft.
OCA (Osteochondral Allograft)
- The surgeon will first remove any defective and damaged cartilage tissue from the knee joint. They will then patch the cartilage defect with a plug of allograft donor cartilage and bone. This does not rejuvenate, but is press fit into the bone. The body then grows into the plug and it becomes your own.
MACI (autologous cultured chondrocytes on porcine collagen membrane)
- This is a staged surgery. Stage 1- Using arthroscopy, the surgeon will first remove any defective and damaged cartilage tissue from the knee joint. Healthy cartilage is biopsied and sent to a lab where the cartilage cells will be grown into a patch. Stage 2- About 4-6 weeks later, the defect will be filled with your new patch of cartilage cells.
How long will I stay in the hospital?
This surgery is typically done as ambulatory surgery, meaning you will go home the same day of surgery.
What are the possible risks and complications of surgery?
While very rare, as with any surgery there is a risk of DVT, nerve damage, and postoperative infection. Recurrent or persistent instability can also occur as well as post operative stiffness or inability to regain your full knee range of motion. With any cartilage restoration procedure there is a risk that the cartilage restoration graft will not take or that it overgrows.
When can I drive?
You may not drive while taking pain medication. In addition, if it is your right knee that had surgery, you will not be able to drive for approximately 6 weeks after surgery or until the brace is removed. You must have approval from your surgeon before starting to drive after surgery.
When can I resume jogging?
You will not resume jogging until cleared by your physician. This typically is around 5-6 months after surgery. You will be allowed to begin biking without resistance once you have adequate range of motion and will begin this with your physical therapist. Once adequate quad strength is demonstrated you will transition to the Elliptical, then running is the next step after that. It is essential that you have restoration of your strength before attempting to run in order to not cause damage to other areas of your knee.
When can I return to my sport?
There are many factors in determining when you will be ready to return to sport after surgery. Most patients are able to return around 7-10 months after surgery but it is essential that you are cleared by your surgeon and physical therapist before returning. Please see Physical Therapy for more information on this condition.