Chondral Defects


Although symptoms may not appear until later in life, articular cartilage problems are very common. Painful osteoarthritis develops when this smooth, gliding surface on the end of the bone has lost its cushioning, deformity develops, and bone rubs on bone. Damage may occur as the result of a sudden injury or wear and tear over many years. There are some people with damaged articular cartilage who display few symptoms and may not develop osteoarthritis until they are elderly.

The development of ostearthritis depends on several factors:

  • The patient's age when the degeneration starts
  • The patient's activity level and weight
  • The presence of ligament damage

Articular cartilage problems can be particularly difficult to treat because the onset, while occasionally sudden, often occurs gradually and thus is not immediately detected.

What is articular cartilage and what does it do?

There are two types of cartilage in the human knee:

  • Meniscus cartilage - This is the cartilage most commonly referred to when the term "torn cartilage" is used. These two rubbery shock absorbers sit between the upper bone of the thigh (femur) and the large bone in the lower leg (tibia).
  • Articular cartilage - This cartilage is the shiny, white surface that covers the ends of most bones. Articular cartilage protects the ends of bones and allows the joints to glide smoothly with less friction. It also helps to spread the loads applied to a joint. This covering is only a few millimeters thick and it has no blood supply to facilitate the healing process. Therefore, if it gets damaged, there is very little capacity for healing.

What is an articular cartilage injury?

An articular cartilage injury, or chondral injury, may occur as a result of a pivot or twist on a bent knee, similar to the motion that can cause a meniscus tear. Damage may also be the result of a direct blow to the knee. Chondral injuries may accompany an injury to a ligament, such as the anterior cruciate ligament. Small pieces of the articular cartilage can actually break off and float around in the knee as loose bodies, causing locking, catching, and/or swelling. More often, there is no clear history of a single injury. The patient's condition may, in fact, result from a series of minor injuries that have occurred over time. Articular cartilage also wears down as a person ages.

Chondral damage is graded from mild to severe, and all grades can have characteristics of osteoarthritis.

  • Grade I - The cartilage "blisters" and becomes soft in the earliest form of damage.
  • Grade II and III - As the condition worsens, the cartilage may become fibrillated (it has a shredded appearance). The grade of injury depends on the size of the involved area and how much of the cartilage thickness is worn down. Noise as the knee bends, called crepitus, may be present.
  • Grade IV - The cartilage may wear away completely, leaving the underlying bone exposed in small or widespread areas. When the involved areas are large, pain usually becomes more severe, causing a limitation in activity.

What are the signs and symptoms of an articular cartilage injury?

The symptoms of an articular cartilage injury are not as obvious as those of a meniscus tear or ligament injury.

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

How is articular cartilage damage diagnosed?

It can be difficult to diagnose an articular cartilage injury. Physical examination may show a swollen knee, but frequently the exam is normal.

Imaging may help the doctor make a diagnosis in some, but not all, cases. X-rays may be normal in most cases because only bone damage is visible on X-ray. One indication of advanced cartilage loss is a decrease in space between two bone surfaces. A loose bone fragment may be detected in a condition called osteochondritis dissecans (OCD), in which a portion of bone detaches with the articular cartilage.

An MRI (Magnetic Resonance Image) may reveal softened cartilage in many cases. This softening can be difficult to detect, however, and the diagnosis may require the most sensitive and highest quality MRI images, which may show changes in the underlying bone. Cartilage thinning or loss is also usually visible on MRI.

Articular cartilage damage is most reliably diagnosed with an arthroscopic examination of the joint. In this procedure, a tiny fiberoptic scope is inserted into the joint. The doctor uses this scope to visually assess the damage.


How is an articular cartilage injury treated?

Non-Operative Treatment

Articular cartilage degeneration is often treated without surgery. Some measures that the physician may recommend are:

  • weight loss.
  • exercises to strengthen the muscles around the joint.
  • shock absorbent shoe inserts.
  • changes in physical activity.
  • glucosamine and chondroitin supplements (not FDA regulated).
  • injections of hyaluronic acid to improve joint lubrication and reduce friction.

The doctor usually prescribes medications to treat the symptoms and watches the patient's progress. Although there are medicines that can treat the symptoms associated with articular cartilage damage, there are no medications that can repair or encourage new growth of cartilage. Further treatment would require a surgical procedure.

Operative Treatment

In the past 10 years, there have been many exciting advances in the surgical treatment of articular cartilage defects. The most commonly used treatment involves smoothing the rough areas of the defect with a shaving technique; however, significant research in this area of medicine has led to the development of several new ways to address this difficult problem.
Factors that influence the choice of procedure include:

  • the size of the defect.
  • the location of the defect in the knee.
  • the age and weight of the patient.
  • the patient's future goals and activity level.
  • the patient's motivation and ability to participate in postoperative rehabilitation.
  • the patient's limb alignment: Is the patient bow-legged or knock-kneed?

The most commonly performed procedures for treating chondral defects are Shaving and Microfracture.

Shaving or Debridement

This arthroscopic technique has been popular for 20 years and has had very satisfactory results for over 75% of patients. It is a common treatment for patients with a cartilage defect that has not worn all the way down to the bone, especially under the kneecap. This procedure is also used in the more arthritic knee when other resurfacing techniques are not appropriate. Using special arthroscopic instruments, the physician smoothes the shredded or frayed articular cartilage. Ideally, this treatment will decrease friction and irritation, reducing the symptoms of swelling, noise, and pain.

Microfracture or Abrasion

This technique encourages the growth of new cartilage into a defect. This is a well-accepted technique that is a common procedure for patients with damage through the full thickness of articular cartilage, all the way down to the bone. Using an arthroscopic procedure, the base of the damaged area is scraped to create a bleeding bed of bone. Blood is essential for healing. Small holes are then "picked" into the defect with a special instrument, allowing blood vessels and bone marrow cells to be in contact with the exposed cartilage defect. Bone marrow then fills the defect promoting the formation of a clot, which will eventually mature into firm scar cartilage. Research has shown that this tissue is a hybrid cartilage. Although this newly grown cartilage is durable and can function for many years, it may not have the same durability or strength as the original hyaline cartilage that existed before the injury.

The following procedures to repair articular cartilage defects are currently being researched and evaluated. Although these newer techniques hold some promise, their effectiveness and long-term outcomes have not been established and only a few surgeons perform them. Some of these procedures can be very costly. The patient should check with the insurance company before proceeding with any of these techniques.

Osteochondral Autograft Resurfacing

Ideally, defects of the articular cartilage in the knee would be replaced with normal hyaline cartilage. This cartilage would withstand years of use and prevent the development of arthritis. Osteochondral autograft resurfacing offers some hope in achieving this goal. The advantage of this treatment is that the patient's own cartilage is used to repair the damaged area.

This procedure involves the transfer of normal cartilage from one area of the knee to another. Cartilage plugs are taken from areas of the knee that do not bear the weight of the body during walking, and then "planted" in the damaged areas with a technique that is similar to the one used for a hair transplant.

This procedure is best for defects smaller than 15-20mm in size because there is a limit to the number of plugs that can be harvested. It is not recommended for osteoarthritis, in which the cartilage is thinning around the defect. This procedure can be done arthroscopically except when multiple plugs are required. In the case of a larger defect, a small incision may be necessary to position the plugs correctly.

Autologous Chondrocyte Implantation

This procedure is most commonly reserved for defects over 20 mm in size or when the damaged site is too large to be reliably treated with other techniques. It is only recommended if there is no cartilage wear around the defect.

This treatment involves using the patient's own cartilage cells. The patient's articular cartilage cells are arthroscopically removed from the injured knee and grown outside the body in tissue culture. After a growth period of three weeks, a second surgical procedure is performed to implant these cells into the defect. Ideally, these cells will fill the defect with a new cartilage surface over time. The implantation process requires a large incision so that the cartilage cells can be properly placed on the bone surface and begin to grow. It takes two to three years for these new cells to mature completely.

Osteochondral Allograft Resurfacing

This procedure is used if there is bone damage in combination with articular cartilage defects. It requires the transplantation of fresh cartilage and bone from a donor, soon after that person's death. One large graft is implanted into the damaged area. (The tissue banks that provide grafts carefully screen the donors for infectious diseases, including AIDS and hepatitis.) Although this procedure has been done for over 20 years, it has only recently gained popularity because fresh grafts have become more readily available.

What types of complications may occur?

None of the above procedures are perfect, but each one may be helpful for patients with painful articular cartilage defects. Although the results have not been evaluated in controlled trials, these techniques have been shown to be safe and effective with positive results in the 70-80% range. The success rate seems to be time dependent. Some patients may have relief from symptoms for a short time, but find that symptoms gradually reoccur. Long-term results are still not available for some of the procedures. Joint stiffness, infection, and continued pain may sometimes follow surgery, as can happen with any major knee operation.

The decision to choose any of these procedures should be made only after the patient and physician have carefully discussed all the options. Adequate training and experience in the use of any of these techniques is important to the success of the chosen procedure.


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.

Shaving or Debridement

  • Crutch use is minimal.
  • Rehabilitation is started immediately after surgery.
  • Regular activities are often resumed within 4 - 6 weeks.


This procedure involves the growth and remodeling of cartilage and a restrictive period of rehabilitation and crutch use for 6-8 weeks, with only touch-down weight bearing of approximately 30 pounds permitted. Continuous passive motion (CPM) is suggested by some physicians. Recovery to full activity that is pain free may require 6 months or longer.

Following is an example of a recommended rehabilitation program. Programs may vary from doctor to doctor.

  • A CPM machine is used for 6 - 8 hours in a 24 hour period (usually at night) for 6-8 weeks.
  • Crutches are required for 6 - 8 weeks following surgery.
  • The patient must put no more than 30 pounds of weight on the injured leg for 6 - 8 weeks, depending on the physician's recommendation (some physicians may recommend no weight at all).
  • Pool exercises can be started as soon as the incisions have healed, usually two weeks after surgery.
  • Full activity resumes in 3 - 6 months, depending on the size of the cartilage damage.

Osteochondral Autograft Resurfacing

The long-term effects on the harvested area are still unknown, as is the long-term performance of the transplanted cartilage.

  • Crutch use is required for 4 - 6 weeks after surgery.
  • Pool therapy and bicycling are usually started within 2 weeks.
  • Recovery to full activity generally takes 4 - 6 months.
  • Return to running and impact sports depends on the number of grafts taken.

Autologous Chondrocyte Implantation

Rehabilitation is a very lengthy process with this treatment.

  • Crutches and touch-down weight bearing on the operative leg for 6 weeks, with increasing weight bearing to full weight bearing at 12 weeks.
  • Pool therapy and bicycling can be started within 6 weeks.
  • Weight can be put on the leg starting about 6 weeks after surgery. The patient's exact rehabilitation time frame set by the physician may vary as the time to full weight bearing is dependent on the size of the area resurfaced. Progressive strengthening continues as the patient's range of motion and muscle strength permits.
  • Return to sports often takes 6 - 12 months.

Osteochondral Allograft Resurfacing

  • Crutches and limited weight bearing for two weeks on the operative leg, followed by full weight bearing in a long leg cast brace for one year.
  • Pool therapy and bicycling are usually started within 2 weeks.
  • Recovery to full activity usually occurs when the cast brace is discontinued.
  • Return to running and impact sports depends on the number of grafts used.

 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.


1. Rodrigo J, Steadman JR. Improvement of full thickness chondral defect healing in the human knee after debridement and microfracture using CPM. Am J Knee Surg. 1994; 7:109-116.

2. Bugbee, W. Fresh osteochondral allografting. Operative Techniques in Sports Medicine. 2000;Vol 8, No 2 (April),158-167.

3. Minas, T. Current concepts in the treatment of articular cartilage defects. Orthopedics. 1997;20:525-538.

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