Anatomy of the Knee
The bones of the knee, the femur and the tibia, meet to form a hinge joint.
The joint is protected in front by the patella (kneecap). The knee joint
is cushioned by articular cartilage that covers the ends of the tibia
and femur, as well as the underside of the patella. The lateral meniscus
and medial meniscus are pads of cartilage that further cushion the joint,
acting as shock absorbers between the bones.
Ligaments help to stabilize the knee. The collateral ligaments run along
the sides of the knee and limit sideways motion. The anterior cruciate
ligament, or ACL, connects the tibia to the femur at the center of the
knee. Its function is to limit rotation and forward motion of the tibia.
(A damaged ACL is replaced in a procedure known as an ACL Reconstruction.)
The posterior cruciate ligament, or PCL (located just behind the ACL)
limits backward motion of the tibia.
These components of your knee, along with the muscles of your leg, work
together to manage the stress your knee receives as you walk, run and jump.
Normal knee function requires a smooth gliding articular cartilage surface
on the ends of the bones. This surface is composed of a thin layer of
slippery, tough tissue called hyaline cartilage. This cartilage also acts
to distribute force during repetitive pounding-like movements such as
jumping or running.
A severe knee cartilage injury can radically change an active adult's
lifestyle. Symptoms such as locking, catching localized pain and swelling
often affect your ability to work, play, and even perform normal activities.
A cartilage lesion appears as a hole or divot in the cartilage surface.
Since cartilage has minimal ability to repair itself, even what may seem
like a small lesion (ranging from the size of a dime to a quarter), if
left untreated, can hinder your ability to move free from pain, and cause
deterioration to the joint surface.
Treatment with Autologous Chondrocyte Implantation (ACI)
Although cartilage is unable to repair itself on its own, advanced FDA-approved
technology allows cartilage cells, known as chondrocytes to be harvested
from your knee and cultured and multiplied. The fresh chondrocytes are
then re-implanted in your knee and cause hyaline cartilage to regenerate.
This biological repair is known as ACI. When you successfully complete
ACI and rehabilitation, you should be able to resume all normal activities,
ACI, also known as Carticel treatment, restores the articular surface and
regenerates hyaline cartilage without compromising the integrity of healthy
tissue or the subchondral bone. Carticel has demonstrated important benefits
in patients with a type of lesion called a femoral focal lesion. If your
orthopedic surgeon has determined that you have this type of lesion, then
Carticel may be an appropriate treatment option. The procedure consists
of two steps. The first is the harvesting of some healthy cartilage from
your knee through an arthroscope. This sample of cartilage is used to
create new chondrocytes, which take 3-4 weeks that are then re-implanted
in your knee. The second step is the reimplantation of the cultured chondrocytes,
or Carticel. This procedure is done through an arthrotomy, and is depicted below.
Implantation of Carticel:
- Step 1: An arthroscopic biopsy - First, the surgeon examines your knee
through an arthroscope - a small device that allows the doctor to see
into your knee joint. If a lesion is detected, a tiny biopsy of healthy
cartilage tissue will be removed.
- Step 2: Cell culture processing - The cartilage sample is then sent to
Genyzme Tissue Repair (GTR), where it is cultured. Cell culturing takes
about 4-5 weeks, during which time your cells multiply significantly.
About 12 million cells will be supplied to your surgeon at the time of
- Step 3: A surgical procedure is performed, and the damaged cartilage is removed.
- Step 4: Periosteum, skin that covers the bone, is sutured over the prepared defect.
- Step 5: Surgical implantation - The cultured cells are then implanted into
the lesion. Here, the cells may continue to multiply and integrate with
surrounding cartilage. With time, the cells will mature and fill-in the
lesion with hyaline cartilage.
To derive maximum benefit from ACI, you should adhere strictly to the personalized
rehabilitation plan recommended by your physician. This will include progressive
weight-bearing, range of motion, and muscle strengthening exercises which
may begin as early as the day after surgery.