Knee pain is one of the most common reasons that people go to the doctor. It can be caused by several things, including arthritis, ligament damage, and meniscus tears. An increasingly common cause of knee pain is damage to the articular cartilage.
- What is Articular Cartilage?
- Clinical and Radiological Assessment of Articular Cartilage Injury
- Etiology of Cartilage Knee Lesions
- Description of Chondral Lesions
- Treatment Modalities for Articular Cartilage Lesions
- Conservative Management
- Arthroscopic Lavage and Debridement; Chondroplasty; Abrasion Arthroplasty
- Subchondral Drilling or Microfracture (MFx)
- Osteochondral Autograft (OATS) and Mosaicoplasty
- Osteochondral Allograft Transplantation (OAT)
- Autologous Chondrocyte Implantation (ACI)
- Matrix autologous Chondrocyte Implantation (MACI)
- FAQ. Frequently Asked Questions
What is Articular Cartilage?
Healthy articular cartilage is a smooth, slippery substance that covers the ends of bones and helps them move smoothly against each other. Cartilage also acts as a shock absorber, protecting bones from the impact of movement.
Unfortunately, cartilage has poor blood supply and once injured, it does not heal readily. The scientific names for these injuries include phrases such as “articular cartilage defect,” “osteochondral defects,” and “knee cartilage defects.” However, they are often more simply referred to as “potholes” in the knee cartilage.
Traditionally, there were very few successful treatments for cartilage damage except for joint replacement surgeries, especially in weight-bearing joints. However, emerging technologies have allowed us to successfully perform several types of cartilage repair and cartilage restoration treatments.
Injuries to the articular cartilage can occur in isolation, or combined with other injuries. For instance, ACL injuries, PCL injuries, and meniscus tears are often associated with articular cartilage injuries. Occasionally, malalignment such as “knock knees” or “bow-legged” knees can contribute to cartilage injury. In these cases, it is important to address the underlying cause of the cartilage injuries where applicable. Weight-bearing joints (tibio-femoral joint) are usually more symptomatic than non-weightbearing joints (patella-femoral joint) For example, chondromalacia patella is more likely to be associated with asymptomatic lesions than full-thickness defects to the medial femoral condyle.
The difficulty in cartilage restoration lies in the method through which the body tries to heal cartilage. It often does not replace the injured cartilage with new hyaline cartilage, the normal type of cartilage found on the joint surface. Instead, the torn cartilage is often replaced with something known as “fibrocartilage” which is not as smooth or lubricated as regular cartilage. Newer treatment strategies have evolved in an attempt to improve clinical and histological outcomes.
Clinical and Radiological Assessment of Articular Cartilage Injury
MRI (magnetic resonance imaging) and x-ray (radiographs) are two common ways to assess articular cartilage injury. MRI is generally considered the gold standard for diagnosing articular cartilage injury, as it can provide detailed images of the cartilage and identify early changes that may not be visible on x-ray. MRI is also useful for assessing the extent of damage and determining whether the injury is confined to the surface or extends deeper into the cartilage and bone below the cartilage (subchondral bone).
X-ray, on the other hand, is better suited for assessing bone injury and identifying bony abnormalities that may be contributing to symptoms. Radiographs also provide a better view of the overall joint space narrowing (a sign of generalized arthritis). Sometimes a loose body may be seen on both x-ray and MRI of the affected limb.
It is important to note that MRI and x-ray are not perfect tools, and in some cases, additional imaging modalities such as CT or ultrasound may be necessary to fully assess the articular cartilage injury. Ultimately, the decision of which imaging modality to use should be made on a case-by-case basis by a qualified healthcare professional, such as a board-certified orthopedic surgeon and knee specialist.
Etiology of Cartilage Knee Lesions
The etiology (cause of disease or abnormal condition) of cartilage knee lesions is complex and multi-factorial. Various etiological factors have been implicated in the development of cartilage lesions, including mechanical, biochemical, and genetic factors.
Mechanical factors include knee joint trauma, overuse, and repetitive microtrauma. Biochemical factors for articular cartilage lesions include inflammatory mediators, such as cytokines and enzymes. Genetic factors include mutations in genes involved in chondrogenesis (making cartilage), such as COL2A1, SOX9, and aggrecan. Many factors likely contribute to the development of articular cartilage lesions, and further research is needed to further understand the underlying pathogenesis of these lesions.
There are two kinds of chondral injuries: focal lesions and degenerative lesions. Focal damage includes well-defined defects of the articular cartilage, usually caused by an injury, like a fall or a car accident. Degenerative defects are less well-defined and usually caused by something else, like ligament instability, meniscus injury, malalignment, or osteoarthritis.
Trauma is the most common cause of osteochondral (involving bone and cartilage) articular cartilage lesions and articular cartilage defects. This type of injury is usually caused by sports injuries or accidents. The force can break through the articular cartilage matrix and even the subchondral bone. A patellar dislocation can cause an osteochondral fracture in this way. It most often happens to young, active patients who are aged 20-40 years old.
Osteoarthritis is the most common cause of chondral lesions in people over 40 years old. The resultant degenerative articular cartilage defects are found in different depths and shapes. The subchondral bone and cartilage stiffen compared to healthy articular cartilage and lead to less shock absorption and cartilage breakdown.
Osteonecrosis is a condition where the bone tissue dies. This can happen for different reasons such as when the bone tissue doesn’t get enough blood. Although the cause is often unknown, risk factors include chronic corticosteroid use or alcohol abuse.
Osteochondritis Dissecans (OCD)
Osteochondritis dissecans is a condition where the cartilage on the end of the bone starts to break down. It was first described in 1888 by Konig. In some people, it results from recurrent microtrauma to femoral condyles, which is damage to the bone and cartilage on the side of the knee. It likely involves the blood supply to the articular cartilage and underlying bone. In many cases the causes are unknown, and it often develops during childhood or adolescence. 85% of cases are located on the lateral aspect of the medial femoral condyle.
Meniscus and Ligament Injury
People with tears in their meniscus or ligaments are also more likely to have knee cartilage injury. In the case of ligament tears, this is because their knee is not stable anymore. The lack of ligament stability results in increased shear forces and articular cartilage damage.
In the case of meniscus injury, the lack of cushioning provided by the meniscal connective tissue leads to increased forces on the affected joint. There is some debate about whether or not prophylactic therapy (preventative measures) is a good idea in these cases. Some think that there may be a small window of time when this type of therapy can help, but others are unsure.
Description of Chondral Lesions
To understand chondral lesions and the best way to treat them, it is important to have a simple classification system for the lesion.
Outerbridge Grading System
The grading system devised by Outerbridge is one of the most commonly used systems. It is based on accurate notation of the location (medial femoral condyle – MFC, lateral femoral condyle – LFC), size (surface area), shape (circular, rectangular), and description of the walls (contained, partially contained, or opened). The depth of the lesion is designated as mild (partial thickness), moderate (full thickness), or severe with involvement of the subchondral bone.
ICRS (International Cartilage Repair Society) Grading System
The ICRS grading system is also commonly used to assess cartilage damage, guide treatment, and predict prognosis. The system is divided into four grades, with Grade I being the least severe and Grade IV the most severe.
Grade I features cartilage damage that is only superficial in nature. Grade II features cartilage damage that is less than 50% of the total depth. Grade III includes cartilage damage that is between 50-100% of the total surface area. There is extensive deep cartilage loss, but there is no bone involvement. Grade IV includes full-thickness cartilage loss with exposure and involvement of bone. Grade V is osteochondritis dissecans and Grade VI is avascular necrosis.
Treatment Modalities for Articular Cartilage Lesions
As with most orthopedic conditions and musculoskeletal injuries, conservative treatment is always an option. In addition to basic RICE principles (rest, ice, compression, elevation), physical therapy and activity restrictions are often prescribed. A knee brace may be recommended, particularly those that are able to unload portions of the knee joint. Oral medications such as NSAIDS (non-steroidal anti-inflammatories) can help with the symptoms but won’t reverse or slow down the cartilage wear.
Injections can also be utilized. The most common injection performed is a corticosteroid injection. This type of treatment is usually able to effectively relieve symptoms and allow resumption of normal knee function. However, this effect is usually temporary. Consistent and repetitive corticosteroid injections can harm cartilage health.
Viscosupplementation, or visco injections, are another commonly utilized non-surgical treatment modality. These injections include a concentrated form of hyaluronic acid and provide physiological and biomechanical benefits to knee cartilage. Some research studies suggest that regular viscosupplementation injections may slow down the progression of cartilage wear, although further studies are needed.
When knee joint lesions are large, progressive, or don’t respond to non-surgical intervention such as physical therapy, surgical treatment may be indicated.
Arthroscopic Lavage and Debridement; Chondroplasty; Abrasion Arthroplasty
First described in 1935, arthroscopic lavage was one of the first surgical treatments to address cartilage damage. It was thought to remove inflammatory mediators, loose cartilage, and collagen debris. It also involves debridement of cartilage to remove loose flaps or edges that might impinge on the joint. This can be done by curettage, mechanical debridement with a shaver, or thermal debridement with a radiofrequency wand.
Of note, overzealous arthroscopic debridement with a mechanical shaver might cause more damage to the cartilage matrix, and the use of the radiofrequency wand can destroy cartilage cells.
Although some sources have reported that chondroplasty is the repair of damaged cartilage, it isn’t repairing cartilage. Chondroplasty surgery of the knee involves trimming the torn edges of cartilage in an attempt to prevent further tearing of the unstable edges, as well as relieve symptoms.
A similar but more aggressive variation of this is known as abrasion arthroplasty. This arthroscopic procedure utilizes a mechanical shaver to contour the edges of the articular cartilage injuries to prevent further expansion and then debridement of the subchondral bone to help stimulate a fibrin clot that might help fibro-cartilage fill in the articular cartilage defects.
Subchondral Drilling or Microfracture (MFx)
Microfracture is a technique where the damaged articular cartilage is removed, and tiny holes are poked or drilled into the underlying bone. This allows the bone marrow to release healing factors (including mesenchymal stem cells, and possibly pluripotential stem cells) that ultimately replace the injured area with fibrocartilage. This new cartilage is not as useful or durable as regular articular cartilage, but it has reasonable survival rates of up to 5 years. Microfracture was widely used in the past, and then underwent a period of time where it fell out of favor. More recently, microfracture is considered to have a limited, but useful, role in very specific situations.
Osteochondral Autograft (OATS) and Mosaicoplasty
Osteochondral autograft is a technique that involves using the patient’s own cartilage and bone tissue to replace the defect from articular cartilage injuries. One significant benefit of this technique is that it uses the same type of bone and cartilage tissue for the graft as is needed in the defect, and the patient won’t have problems with antigenicity since it is their tissue.
The best patients for this procedure are young people with medium-sized lesions. Similar to most cartilage repair or restoration techniques, an osteochondral autograft is most successful in focal defects (isolated defects with good surrounding cartilage).
OATS involves harvesting a plug (or plugs) from a donor site in the affected knee joint and inserting it into the area of damage. After surgery, the patient is kept non-weight bearing for 3-6 weeks, depending on the location of the lesion, the size of the lesion, and surgeon preference. A physical therapist directs range of motion exercises and muscle strengthening exercises for several months. Mosaicplasty is a variation of this technique that utilizes several plugs to more completely cover the defect.
Studies have shown that osteochondral autograft results in healthy hyaline cartilage in the defect, with some fibro-cartilage filling in the edges.
Osteochondral Allograft Transplantation (OAT or OCA)
Osteochondral allograft transfer is a surgical procedure that uses donor tissue to repair cartilage damage. Allograft procedures involve transplanting cartilage from a donor who donated their body to medicine, or a cadaver.
Osteochondral allograft transfer can be used to treat cartilage damage caused by trauma, degenerative disease, or congenital defects. It can be used when there is substantial damage to the underlying subchondral bone. Benefits of allograft transplantation compared to autograft transplantation include the ability to treat larger defects and the lack of harvest site pain and morbidity. Downsides include the cost and availability of the graft.
Rare, but theoretical risks include lack of incorporation of the graft or disease transmission. The donors and grafts are screened. Fresh grafts are generally preferred over frozen grafts due to improved chondrocyte viability.
One example of osteochondral allograft transplantation is the Arthrex BioUni procedure, which utilizes specialized instrumentation to perform osteochondral allograft transplantation in large defects of the medial femoral condyle of the knee.
Autologous Chondrocyte Implantation (ACI)
ACI (also known as autologous chondrocyte implantation or autologous cartilage implantation) is a technique where the patient’s own cartilage cells are harvested and then replicated in the lab. This is a staged surgery, meaning that an initial arthroscopic surgery is followed by an open procedure to implant the new chondrocytes (cartilage-producing cells).
Once an adequate number of cartilage cells are grown, they are re-implanted in the area of your injured cartilage. A biologic membrane or collagen membrane is used to seal the defect and keep the cells in the right place until new cartilage grows. The autologous chondrocyte implantation technique is a good procedure for smaller lesions and injuries where the bone below the cartilage, or the subchondral bone, is not damaged. The downside is that it requires two operations – one to harvest the cells, and one to reimplant them.
Matrix autologous Chondrocyte Implantation (MACI)
Matrix autologous chondrocyte implantation (MACI) is a newer generation of the ACI procedure. Like ACI (autologous chondrocyte implantation), it uses the patient’s own cartilage cells to grow cartilage. It is an increasingly performed procedure for full-thickness lesions and focal damage – Grade 4 defects that have good cartilage surrounding them.
First, cartilage cells are harvested in a small procedure known as a cartilage biopsy. A cartilage biopsy is performed arthroscopically. At the time of arthroscopy, the defect is also measured, evaluated, and quantified more accurately than is possible with MRI alone. The harvested cells are then sent to a lab.
After the cells are multiplied in the lab, they are inserted into a collagen matrix (a solid collagen scaffold similar to a sponge pad made of special proteins). The collagen matrix, now embedded with the patient’s own cartilage cells (chondrocytes), is then placed into the cartilage defect in the affected joint. Preformed templates are available, or a custom template can be used to ensure a precise fit. Weight bearing is limited for 6-8 weeks to allow the chondrocytes to mature and start producing cartilage. Physical therapy is used to maintain soft tissue flexibility and muscle strength.
Similar to ACI, this procedure is not possible without good cartilage surrounding the cartilage defect, or if the bone underlying the cartilage (subchondral bone) is in too poor of condition (sometimes seen as a bone bruise on magnetic resonance imaging). Of note, the new cartilage generated with this procedure is often made of hyaline cartilage, similar to normal articular cartilage Grade 0. Compared to ACI, MACI is considered to be less technically complex, and the results are more consistent. This is likely due in part to the fact that the cells are evenly distributed throughout the collagen matrix. With the traditional ACI procedure, cells were known to clump and distribute unevenly.
FAQ. Frequently Asked Questions
How do Articular Cartilage Injuries Occur?
Articular cartilage lesions can occur due to repetitive stress, acute injury, or degenerative changes associated with aging or disease.
Repetitive stress injuries to articular cartilage commonly occur in athletes who participate in sports that involve repetitive joint motion, such as running, tennis, or golf. Over time, this constant stress can damage the cartilage, causing it to become thin, frayed, or cracked. Acute trauma to the joint can also cause articular cartilage lesions. This may occur due to a fall or direct blow to the joint. In some cases, the impact of the trauma can cause the cartilage to tear away from the bone completely.
In addition to repetitive stress and trauma, articular cartilage lesions can also occur due to degenerative changes associated with aging or disease. These changes often occur slowly over time and may not cause any symptoms until the damage from the articular cartilage lesions is severe.
How Are Articular Cartilage Injuries Diagnosed?
Articular cartilage injuries are diagnosed through a combination of medical history, physical examination, and imaging tests. A doctor will first ask about the nature of the injury and any symptoms that have been experienced. They will then perform a physical examination, checking for swelling, tenderness, and range of motion.
Imaging tests such as X-rays, MRI, and computed tomography (CT) scan can also be used to diagnose articular cartilage lesions and damage to the underlying bone. In some cases, a diagnostic arthroscopy may be necessary to confirm the diagnosis. Once an injury has been diagnosed, treatment can be planned accordingly. Conservative measures such as rest, ice, and elevation may be recommended for mild injuries. More severe injuries may require surgery to repair or replace the damaged cartilage.
What is a Chondroplasty of the Knee?
The conventional description is that chondroplasty of the knee is a surgery to repair damage to the cartilage and articular cartilage lesions. The cartilage is the smooth, white tissue that covers the ends of bones and allows them to move smoothly against each other. Damage to the cartilage surface can occur due to injury, arthritis, or overuse.
During chondroplasty, the damaged articular cartilage from the articular cartilage lesions is removed and the area is smoothed out. Chondroplasty is generally considered a safe surgery with a low risk of complications to treat articular cartilage injuries. Long-term effectiveness for full-thickness articular cartilage injuries is likely less than newer cartilage restoration procedures.
Should loose bodies in the knee be removed?
There is some debate amongst medical professionals as to whether or not loose bodies in the knee should be removed. Some doctors believe that the loose bodies can eventually be reabsorbed by the body and pose no threat.
Others believe that loose bodies can cause inflammation and damage to the surrounding tissue, and should therefore be removed surgically. Ultimately, the decision of whether or not to remove loose bodies from the knee should be made on a case-by-case basis, in consultation with a qualified medical professional and orthopedic surgeon.
Is cartilage damage curable?
There are several ways to treat articular cartilage damage, depending on the severity of the injury. For minor cartilage lesions (such as cartilage grade II cartilage defects), rest and ice may be enough to allow the tissue to heal on its own. A physical therapist may be able to help with the symptoms. More severe injuries may require surgery to repair or replace the damaged cartilage (e.g. autologous implantation). In some cases, cartilage damage may be permanent, but there are still options for treatment that can help improve symptoms (such as joint pain in the affected joint) and prevent or slow down further damage to knee joints.
What are symptoms of knee cartilage damage?
Knee cartilage damage can lead to several problems, including swelling, pain, stiffness, and reduced range of motion. The most common symptom is pain, which can range from mild to severe. Depending on the extent of the damage, the pain may only occur when the knee is used, or it may be constant.
Stiffness is another common symptom, and it may be worse in the morning or after sitting for a long period. Reduced range of motion is another possible symptom, and it can make it difficult to perform everyday activities such as walking or climbing stairs.
Can you walk with cartilage damage in your knee?
Cartilage is a type of connective tissue that cushions the joints and allows them to move smoothly. It is essential for healthy joint function, but it can be easily damaged. When cartilage is damaged, it can lead to pain, stiffness, and decreased range of motion. In some cases, it may even be necessary to have surgery to repair the damage. However, walking is often still possible with cartilage damage.
Depending on the severity of the damage, walking may be painful or difficult. However, it is often still possible to walk with some cartilage damage. In fact, walking for exercise can actually help to improve joint function, reduce pain, and slow the spread of arthritis. Of course, it is always best to consult with a doctor before beginning any new exercise routine.
Do osteochondral lesions heal?
Osteochondral lesions are injuries to the cartilage that covers the ends of bones. The term “osteochondral” refers to the bone and cartilage, while “lesion” is a general term for an injury. These injuries can range from small, partial thickness fissures in the cartilage to large, deep lesions that extend into the bone. The definition of the term osteochondral means that it includes the underlying bone. In most cases, osteochondral lesions are caused by trauma, such as a fall or a direct blow to the joint. However, they can also be caused by overuse injuries or degenerative diseases.
There is no one-size-fits-all answer to the question of whether or not osteochondral lesions heal. In some cases, the body can repair the damage using its own natural healing processes. However, in other cases, the damage may be too extensive for the body to heal on its own. Full Full-thicknessilage lesions have been shown to not heal on their own. In these cases, surgery may be necessary to repair the damage. Additionally, some people may require ongoing treatment even after their lesions have healed to prevent future injuries.
How is osteochondral lesion treated?
Osteochondral lesion is a condition that affects the bone and cartilage. Osteochondral lesion occurs when there is damage to the bone and to the cartilage that covers them. The most common cause of osteochondral lesion is injury, but it can also be caused by diseases such as arthritis.
There are several ways to treat osteochondral lesions. The most important goals of treatment are to relieve pain, improve joint function, and prevent worsening. Treatment options include conservative treatment such as knee braces, modified weight-bearing, physical therapy, a healthy diet, maintaining a healthy body weight, over-the-counter anti-inflammatory medications, injections, and surgery. Physical therapy can help to strengthen the muscles around the joints and improve range of motion.
Medications can be used to reduce pain and inflammation. Injections of steroids or other medications such as viscosupplementation (hyaluronic acid) can also be helpful. Surgery is sometimes necessary to repair damaged tissue or to replace damaged joints.
Dr. Jeremy Burnham is a board-certified and fellowship-trained orthopedic surgeon who focuses on knee injuries and complex knee joint damage. He performs “non-knee replacement” surgical regeneration and cartilage replacement procedures of the joint surface, as well as evidence-based utilization of orthobiologics such as platelet-rich plasma (PRP), bone marrow aspirate (BMAC), and more. He has offices in Baton Rouge, Hammond, and Plaquemine, Louisiana and treats patients from Walker, Denham Springs, Livingston, Ascension, Prairieville, Gonzales, New Roads, St. Francisville, Zachary, Baker, Central, Woodville, Natchez, Lafayette, Opelousas, and Centreville (Mississippi) communities.