Osteochondral Defects (OCD) or Articular Cartilage Defects

Written and Edited by Aruna Seneviratne, M.D.

Osteochondral defects are injuries to the articular cartilage of a joint. While any joint can be affected, the most common joints affected are the knee and ankle (talus bone).

Symptoms:
The most common symptoms are pain and swelling in the affected joint. The pain is usually dull in nature, but can be sharp at times. Usually, there is joint swelling that is noticeable and can be a source of discomfort. Range of motion can be decreased due to the swelling. You may also notice a painful clicking or catching sensation.

Biology: Why does it occur?
In general OCDs have three different mechanisms that affect three different age groups.
  1. 10 year to 28 year age group - Osteochondritis Dissecans (the acronym is OCD also). Its mechanism is poorly understood, but results in a discreet cartilage defect usually in the knee. These may or may not be associated with trauma.
  2. 18year to 50+years - usually traumatic secondary to sports injuries. Usually associated with other injuries such as meniscal tears and ACL tears (knee), or ligament sprains in the ankle.
  3. 60+years - Spontaneous Osteonecrosis (SPONCRE) or Avascular Necrosis (AVN) leading to an OCD. This occurs due to a sudden loss of blood supply to a discreet area of the knee or hip due to unclear reasons. It results in loss of cartilage, and frequently leads to diffuse osteoarthritis of the affected joint quite rapidly.
Common Diagnostic Techniques:
History: Diagnosing the problem begins with a detailed history that your surgeon will obtain from you.
Physical Exam: A thorough physical examination is then conducted by your surgeon. X-Rays: Plain radiographs (X-Rays) are the most important diagnostic study that is performed initially. For the knee and ankle specialized views will be obtained by your surgeon. Usually these are weight bearing x-rays - i.e.: you will be standing for the x-rays.
X-Rays: Plain radiographs (X-Rays) are the most important diagnostic study that is performed initially. Several views will be obtained to diagnose the condition.
Bone Scan: In certain situations a bone scan maybe useful in making the diagnosis.

Treatment:
Treatment depends on which of the three variants you have.
Osteochondritis Dissecans - usually treated operatively as soon as diagnosis is made to make use of the healing response in the early phases of the injury. The surgery is usually performed arthroscopically, and is aimed at reinserting the loose OCD fragment to where it broke off from with bio-absorbable pins. Sometimes, the loose fragment grows in size and no longer fits the defect. In this situation it is removed, and an alternate method of resurfacing the defect is utilized. Please see the FAQ section for explanation of procedures.

Traumatic OCD - usually treated operatively as soon as diagnosis is made. The surgery is usually arthroscopic, and the choices are Microfracture, Mosaicplasty, or Autologous Chondrocyte Implantation (ACI) depending on the size and depth of the lesion. An Osteotomy might be necessary to realign the knee in certain patients.

Spontaneous Osteonecrosis - usually treated non-operatively with crutches to unload the knee for 6 weeks, medication to help with the pain and help regenerate bone (Calcitonin), and physical therapy for joint range of motion and edema control. If non-operative treatment fails, operative intervention is undertaken. Arthroscopy is usually not very successful unless there is other pathology within the knee such as a meniscus tear. Arthroscopy can make the symptoms worse, and lead to a more rapid degeneration of the articular cartilage. Microfracture maybe attempted in this situation, but the results are variable. Mosaicplasty and ACI are not indicated. The definitive operative procedure is a uni knee replacement (UKA) or a total knee replacement (TKA) for the knee, and total hip replacement (THA) for the hip.

After Surgery
Specific post op instructions can be found under each type of surgery. Briefly, if you had arthroscopic surgery for Microfracture or Mosaicplasty your weight bearing is protected for six weeks with crutches. In addition you will be using a continuous passive motion (CPM) machine at home for 6 hours a day for this six week period. These measures are essential for the success of the surgery. A similar regimen is used for Autologous Chondrocyte Implantation (ACI). You will require physical therapy to rehabilitate your joint for up to 6 months.
For joint replacements (UKA, TKA, and THA) - typically you will be in hospital for 1 to 4 days. You will be able to bear full weight usually with a cane or crutches. For the first six weeks you will be given medication to prevent blood clots in your legs (DVT). Usually this is Aspirin, but Coumadin or other medication maybe utilized. You will require physical therapy to rehabilitate your joint for up to 6 months.

FAQ's
What is cartilage (or articular cartilage)?
This is the lining on the ends of bones that articulate upon one another. Articular cartilage is composed of Hyaline cartilage a very smooth tissue that is one hundred times slicker than wet ice on wet ice. It provides a nearly friction free surface for the joint to move on. Fibrocartilage is another type of cartilage, typically seen in reparative tissue after procedures such as Microfracture and ACI.

What is the Microfracture Technique?
This is an arthroscopic surgical technique where small holes are created within the OCD with a sharp awl like instrument. This allows marrow cells to enter the defect and regenerate cartilage. The type of cartilage that is generated is fibrocartilage, not hyaline cartilage which is what articular surfaces are composed of.

What is Mosaicplasty?
This is a surgical technique where plugs of articular cartilage or articular cartilage substitutes are placed into the OCD to restore the defective surface to near normal. These plugs can be obtained from your own knee from areas of low contact, or from cadaveric tissues (allograft).

What is OATS?
OsteoArticular Transfer System (OATS) is a mosaicplasty technique that harvests Osteoarticular plugs from an area of the knee that is not under high contact, and transfers these plugs to the OCD. This technique restores hyaline cartilage to the defect at the cost of harvesting it from another site of the knee.

What is Osteoarticular Allograft Transplantation?
This is a technique where cadaveric osteoarticular tissue is transplanted into the OCD. The transplant tissue is obtained from a tissue bank and must be preserved with a technique called cryopreservation. Typically this tissue has to be implanted within 14 to 21 days of harvest to ensure viability of the chondrocytes (cells that maintain articular cartilage). There is a small risk of disease transmission and immune rejection with this type of surgery. This type of surgery is reserved for young patients with very large OCDs.

What is Autologous Chondrocyte Implantation?
This is a two-stage procedure. Stage one: Arthroscopic procedure to diagnose problem, and harvest a small amount of articular cartilage. This tissue is cultured and the chondrocytes are multiplied. Stage Two: Usually 4-6 weeks after stage one, the multiplied chondrocytes are placed into the defect. This is an open procedure where a thin layer of tissue called the periosteum is harvested from your tibia bone, and used like Saran Wrap to cover the OCD. Into this covered defect the chondrocytes are injected. The idea is that it will regenerate Hyaline cartilage. However, histological studies show fibrocartilage to be the predominant tissue that is regenerated. Newer techniques are on the horizon to make this an all arthroscopic procedure.

What is an Osteotomy?
A surgical procedure where normal alignment is restored by cutting the bone involved, and moving it to a slightly different orientation that alters the weight distribution through the joint. The bone is re-fixed with plates and/or screws. Types of osteotomies are High Tibial Osteotomy (HTO), Femoral Osteotomy, or Tibial Tubercle Osteotomy (e.g.: Fulkerson Osteotomy).

How are patellar (knee cap) OCDs treated?
This is an uncommon and more difficult subset of OCDs to treat. Typically the Microfracture technique is utilized for these defects. Weight bearing is not usually protected, but a CPM machine is utilized for 6 weeks.