The ends of the femur and tibia, the knee bones, are capped with a gristle which is called cartilage.  Cartilage is a remarkable organ because it can withstand a significant amount of impact and shear-type activities over time.

Causes of Chondral Defects of the Knee

An articular cartilage injury, or chondral injury, may occur as a result of a pivot or twist on a bent knee, a direct blow to the knee, or wear and tear as a patient gets older. In some cases, chondral injuries may accompany an injury to a ligament such as the anterior cruciate ligament (ACL). Small pieces of the articular cartilage can break off and float around in the knee as loose bodies, causing locking, catching and/or swelling. For most patients, there is no clear history reported of a single injury. This type of injury can result from a series of minor injuries that have occurred over time.

When cartilage becomes damaged, it is called chondromalacia.  This is basically a “kind term” for osteoarthritis.  Even young patients can develop chondromalacia, which means that they have damage to the cartilage on the ends of their bones.  Once damage occurs, it is invariably progressive and can lead to pain and swelling, which are the main signs of osteoarthritis, and the development of bone spurs and stiffness of the knee over time.

Symptoms of Knee Chondral Defect

The symptoms of a chondral injury are not as obvious as those of a meniscus tear or ligament injury.

  • Swelling is often the only symptom. The loose cartilage fragments floating in the knee can cause swelling.
  • Pain with prolonged walking or climbing stairs can occur.
  • The knee may occasionally buckle or give way when weight is placed upon it.
  • Loose, floating pieces of cartilage may block the joint as it bends, causing the knee to lock.
  • The knee may make noise during motion, especially if the cartilage on the back of the kneecap is damaged.

There are many factors which need to be thoroughly investigated for patients who have symptoms from chondral defects.  Ligament tears of the knee can cause and accelerate chondral defects and may need to be reconstructed either before or at the same time as a cartilage resurfacing procedure to slow down the progression of arthritis.  If patients have alignment problems, where they are bow-legged or knock-kneed into the site of their defect, the use of an unloader brace or straightening the bone through an osteotomy may be indicated depending upon their age and the amount of arthritis present in the knee.  Finally, patients who develop cartilage lesions because of the lack of a meniscus will most likely not have a successful cartilage resurfacing procedure unless a new meniscus is placed.  In these circumstances, the proper evaluation and workup for a potential meniscal transplant may prove beneficial.

How to Diagnose Knee Chondral Defect?

The majority of patients who have problems with chondral defects of the knee have pain and swelling with activities.  This is a sentinel sign that we rely on for those patients that are symptomatic.  Diagnosis of these problems can be used with standing x-rays which may show joint space narrowing, or the use of a high-quality MRI scan.  Many of the lower signal strength MRI scans are not equipped to be able to reliably demonstrate articular cartilage defects of the knee.  Therefore, we recommend the use of a 3-Tesla MRI scanner to best determine the location of a chondral defect of the knee.  In addition, this information can determine if there is any deeper bony defect, such as a cyst or swelling of the bone, which may indicate that this involves not only the cartilage, but also the bone itself.  The MRI can also be useful to determine the volume of the meniscus to ensure that there is enough cushion to protect any future cartilage procedure, and can also evaluate other areas of the knee to determine other problem pathologies that may be present.

Chondral Defect Knee Treatment

The treatment of chondral defects of the knee can depend upon the location and size of the defect.  In general, those that are on the end of the thigh bone, the femur, are the ones that are easiest to treat and have the best outcomes.  Those on the tibia and kneecap (patella) are harder to treat and the results are not as reliable.  For those patients who have a surface defect of the cartilage, with a flap or crack in it, a cleaning out or shaving of a defect, called a chondroplasty, can be performed.  This may be useful to alleviate the catching and painful symptoms from a cartilage flap, but they do not cure the underlying chondral defect.  In effect, it is resurfacing the defect and it is important the patient be careful about returning to the activities which caused the cartilage flap in the first place or it could happen all over again.

For those patients who have very deep cartilage defects, which extend all the way down to bone, the treatment of these can depend upon the location and overall diameter of the defect.  For smaller lesions, a technique called a microfracture, which tried to rely on the patient’s own stem cells and healing to form a fibrocartilage cap over the “pothole”, can be useful.  In other instances where the bone under the cartilage defect is also damaged, replacement with a plug of bone and cartilage from another portion of the knee can also be useful.  This is called an autograft osteochondral transfer.  For deeper or larger cartilage defects, one of the more reliable techniques in indicated patients is a fresh osteoarticular allograft.  This is a cadaver graft, donated from a recently deceased young donor, which can be used to replace the whole bone and cartilage unit.  These are the most predictable ways for us to treat cartilage defects of the knee, but obviously the donor supply is limited so it cannot be used in all patients.

Nonoperative Treatment of Chondral Defect of the Knee

In some instances, the chondral defects of the knee may be small enough to trial a period of rehabilitation.  In these circumstances, there may not be any large cartilage flaps demonstrated on the MRI scan and there may just be softening of the cartilage surface.  These patients may benefit from a program of rehabilitation, focusing on low-impact strengthening, primarily the quadriceps mechanism, to increase one’s absorption and overall strength.  This has been found to be very beneficial in these patients.  In addition, for patients who may have a lot of joint space irritation, called synovitis, a steroid injection or a platelet-rich plasma injection (PRP) may be indicated.  For patients who choose not to want surgery and who have more extensive chondromalacia, the use of an unloader brace to take the stress off a malaligned joint which has the weightbearing fall through the cartilage defect, or the use of further injections, such as viscosupplementation with hyaluronic acid or PRP may be indicated.

Chondral defects of the knee are important to thoroughly evaluate to determine the best treatment regimen.  Both operative and nonoperative treatments may be indicated.  In addition, assessment of alignment may indicate if an unloader brace may help alleviate a patient’s symptoms and review of newer biologic or corticosteroid or viscosupplementation injections may be indicated.

Chondral Defect of the Knee Recovery

The recovery process and rehabilitation requirements vary significantly among the different operative procedures used to repair articular cartilage damage. The patient’s commitment level to the rehabilitation process is an important factor in determining which treatment may be the best choice.

Knee Chondral Defect FAQ

What are the most important things a person can do to limit chondral or cartilage damage in the knee?

While there is not one specific thing that can prevent cartilage damage in the knee, there are a few measures that can be taken to delay the process.

  • Since excess weight can cause damaged cartilage to wear down more quickly, losing extra pounds may be helpful.
  • A person with cartilage damage should avoid high impact activities, such as prolonged running or jumping sports. These are very hard on the knee and can speed the progression of cartilage damage.
  • Even those with significant joint damage will benefit from mild to moderate activities, such as walking, bicycling, or running in water.

My doctor has told me that I have arthritis and will need an artificial knee in the next few years. Would I be a candidate for growing my own cartilage so I won’t need an artificial knee?

The newer techniques involving cartilage growth will not work if a patient is very bowlegged, knock-kneed, or has bone rubbing on bone. The newly grown cartilage would be quickly rubbed away by the worn surfaces. At some point in the progression of arthritis, only a total knee replacement can offer pain relief.

Will glucosamine and chondroitin make new cartilage?

Most studies of the effects of glucosamine and chondroitin have been done in animals, and most of the reported effects are based on hearsay rather than scientific evidence. Human studies are currently underway and reported results do show some promise that these substances can relieve the inflammation caused by arthritis in 60-70% of patients. It is doubtful, however, that they can cause new cartilage to grow. Diabetics and individuals taking blood thinners should not use these medications without a doctor’s approval.

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