Cartilage is the white, flexible but firm connective tissue, which covers the ends of the bones. Cartilage provides a smooth cushion, letting the bones of the joint to move effortlessly without painful contact. Although cartilage is tough, it can be damaged either suddenly due to an injury or degenerate from general wear and tear or due to any infection or inflammatory disease.
Pain and swelling in the knee joint. Locking sensation in the knee, which interferes with the ability to stand or walk. In some injuries, a piece of cartilage can be detached and behave like a “loose body” in the joint which affects the movement and causes pain.
The doctor will perform a physical examination and evaluate the symptoms. X-ray to see for any bone fracture or dislocation in cases of injury and reduced joint space and sclerosis of bone ends and osteophyte or loose body formation in degenerative cases. Cartilage is not seen on x-ray. MRI Scan is useful in some patients.
Non Operative – Rest, lifestyle modification and weight loss, anti-inflammatory medication, physical therapy to strengthen the muscles, changing footwear, taping or bracing.
Surgical Treatment – Injured cartilage typically does not heal on its own, so doctors have developed several surgical techniques that attempt to repair, regenerate, and replace cartilage.
Knee Cartilage Repair
A surgeon uses special tools to remove tattered and frayed cartilage and smoothen the remaining cartilage surface. This cartilage contouring decreases joint friction, which in turn may:
- Reduce knee pain
- Restore knee function
- Potentially slow down future cartilage degeneration
The clinical term for surgery to reshape the knee cartilage is called “knee chondroplasty”. While ‘Chondro’ denotes cartilage, ‘plasty’ means to mold or form. Chondroplasty can be done on the articular cartilage of the knee, meniscus, or both.
Knee chondroplasty is often performed together with debridement. During knee debridement the surgeon removes potential irritants to the joint, such as loose pieces of cartilage, and flushes the joint with a saline solution (lavage).
Knee Cartilage Regeneration
Cartilage tissue’s ability to repair itself is severely limited because it does not contain blood vessels, and bleeding is necessary for healing. A surgeon may encourage the growth of new cartilage by making small abrasions or cuts in the bone beneath the injured cartilage. The hope is that the blood from the damaged bone will facilitate new cartilage cell growth.
There are three common knee cartilage regeneration techniques that use bleeding to spur cartilage healing:
- Knee micro-fracture that needs the damaged cartilage to be cleared away completely. The surgeon then uses an awl, a sharpened tool, to pierce the bone.
- Knee drilling, which uses a drill or wire to make tiny holes the bone. There is some evidence that the heat from the drill can cause unnecessary injury to nearby tissue, which can eventually lead to bone cysts or other problems.3
- Knee abrasion arthroplasty, which requires the damaged cartilage to be completely cleared away. Then, the surgeon utilizes a special tool to scrape as well as roughen the affected surface of the bone.
Knee Cartilage Replacement
Most knee cartilage replacement surgeries are called OATs surgeries—either osteochondral autograft transplantation or osteochondral allograft transplantation surgeries. A third option is called autologous chondrocyte implantation.
Osteochondral autograft transplantation uses cartilage from the patient.
- The surgeon removes a small (<1cm), a round plug of healthy cartilage—and a tiny bit of underlying bone—from a non-weight-bearing area of the knee joint. The surgeon transfers the plug to the area being treated.
- This OATs procedure can be used to repair one or more relatively small cartilage defects in a knee. When more than one plug is used to treat a single cartilage defect, the procedure is called mosaicplasty.
- The surgery is usually done arthroscopically.
Osteochondral allograft transplantation uses cartilage from outside the patient, usually from a cadaver.
- The surgeon removes a circular plug of healthy cartilage from an outside donor.
- An allograft is usually used when cartilage defect being treated is too large for an autograft (≥2cm).
- This surgery usually requires an open incision.
Autologous chondrocyte implantation relies on newly grown cartilage cells. It requires two surgeries.
- First, the patient undergoes arthroscopic surgery to remove a small piece of healthy cartilage from a non-weight bearing area of the knee joint. That cartilage is cultured, allowing new cartilage cells to grow.
- Three to five weeks after the first surgery, a second surgery is performed to implant the newly grown cartilage cells into the affected knee joint.
- This second surgery can be done arthroscopically or sometimes it requires an open incision.
- This procedure may be recommended when the cartilage injury is large (up to several centimeters) or there are multiple cartilage injuries to repair.
What cartilage replacement procedure is used will depend on the size of the cartilage injury being treated as well as the surgeon’s expertise and recommendation.
Stem Cell And PRP Therapy
A surgeon preforming knee cartilage repair, regeneration, or replacement surgery may use stem cells or Platelet Rich Plasma(PRP) in hope of encouraging new cartilage cell growth.
Both stem cells and platelets are involved in the body’s natural healing process and the restoration of damaged tissue. Stem cell and PRP therapies are generally considered safe. Research regarding whether or not they are effective is ongoing.
While surgeries to repair, regenerate and replace the cartilage are becoming more common, they are not suggested for everyone. Generally, these surgeries are most successful in patients who are:
- Young, for instance, OATs microplasty procedures are very successful in patients younger than 40 years of age
- Experience pain for a relatively short time (a few months, not several years)
- Experience pain at rest
- Do not have problems with knee stability or alignment
- Have a localized cartilage damage
Two isolated injuries to the cartilage are called ‘localized cartilage damage’. Individuals with extensive cartilage damage, like that found in moderate-to-severe knee osteoarthritis, are generally not candidates for surgical repair, regeneration or replacement of the cartilage.
These surgeries are elective, meaning a physician may recommend surgery but it is left to the patient’s discretion whether or not to have it. They are typically performed on an outpatient basis.