Cartilage Injury

Cartilage injury is damage to the tough but flexible tissue that covers the ends of bones in joints, most commonly affecting the knee, though it can also occur in the hip, ankle, shoulder, and elbow.

Table of contents

• What is Cartilage?
• Types of Cartilage in the Body
• How Do Cartilage Injuries Occur?
• Symptoms of Cartilage Injuries
• How Are Cartilage Injuries Diagnosed?
• Treatment Options
• Surgical Procedures for Cartilage Repair
• Recovery and Rehabilitation

What is Cartilage?

Cartilage is a strong, flexible connective tissue that plays a vital role in protecting your joints and bones. It acts as a shock absorber throughout your body, helping your bones move smoothly against each other without rubbing together when you use your joints^[6].

The specific type of cartilage that covers the ends of bones in joints is called articular cartilage (articular simply means “having to do with joints”). This tissue forms a smooth, durable covering at the end of each bone in the joint, with a consistency almost like linoleum^[1]. Fluid from within the joints lubricates this cartilage, allowing the opposing bones to slide over one another smoothly and with very little friction^[1].

Unlike other types of tissue in your body, cartilage does not have a blood supply. Because of this, damaged cartilage takes much longer to heal compared with other tissues that receive blood^[3]. This lack of blood supply means that once articular cartilage becomes damaged, it can rapidly deteriorate^[21].

Types of Cartilage in the Body

There are three types of cartilage found in the human body, each with different properties and functions^[3]:

• Hyaline cartilage is the most common type and is springy, tough, and elastic. It lines your joints and caps the ends of your bones. This is the type found between the ribs, around the windpipe, and between the joints^[3][6].
• Fibrocartilage is the toughest type of cartilage, able to withstand heavy weights. It is found between the discs and vertebrae of the spine and between the bones of the hip and pelvis. It also makes up the meniscus in your knee^[3][6].
• Elastic cartilage is the most springy and supple type. It makes up the outside of the ears and some of the nose. It can bend and move without causing injury before returning to its usual shape^[3][6].

• Knee
• Hip
• Ankle
• Shoulder
• Elbow
• Wrist

How Do Cartilage Injuries Occur?

While articular cartilage is strong and capable of bearing heavy loads and withstanding decades of use, it can become damaged by injury or overuse^[1]. Cartilage injuries are a common joint problem, especially among people who are physically active^[1].

Articular cartilage injuries can result from a number of causes, including^[1]:

• Forceful impacts to the joint as a result of sports injuries or a fall
• Repetitive smaller impacts to the joint
• Twisting the joint while it bears weight, for instance twisting the knee while the foot is planted
• Progressive wear and tear, usually over several decades of use
• Poor alignment of joints due to a birth abnormality or previous injury

According to research, approximately 60% of patients undergoing knee surgery were found to have high-grade cartilage defects involving 50% or more of the cartilage surface^[4]. The majority of patients who undergo routine knee surgery have evidence of some cartilage damage^[4].

Young athletes who tear their ACL (anterior cruciate ligament) or meniscus are most at risk for articular cartilage injuries. Without a secure ligament to keep the knee stable, or with a torn meniscus, the knee makes unnecessary motions that can cause cartilage to get damaged or be worn down more quickly^[21].

Symptoms of Cartilage Injuries

People with cartilage damage commonly experience joint pain, stiffness, and inflammation (swelling)^[3]. The symptoms of articular cartilage injuries can include^[1][7]:

• Joint pain or tenderness that gets worse when the joint is being used and is relieved by rest
• Swelling caused by inflammation in the joint tissue or an accumulation of liquid within the joint
• A feeling of “catching,” “locking,” or the joint getting stuck
• Stiffness and decreased range of motion
• Hearing a clicking, popping, or soft grinding sound in the joint when getting up from a seated position or while walking
• A feeling that the bones in the joint are rubbing together
• The affected limb not moving as freely and easily as it should

In severe cases, a piece of cartilage can break off completely from the underlying bone. This chip, called a loose body, may float in the joint, interfering with normal joint motion^[7].

How Are Cartilage Injuries Diagnosed?

Your doctor will perform a physical examination to look for altered range of motion, swelling, and alignment of the bones^[13]. They will take a full medical history and utilize imaging studies to determine the location and extent of the articular cartilage damage^[12].

Because cartilage is not calcified, it does not show up well on regular X-rays^[13]. However, diagnostic tests may include:

• X-rays to assess bone structure and joint alignment
• MRI (Magnetic Resonance Imaging) scans, which are often required to visualize cartilage damage. Advanced MRI technology allows surgeons to design a personalized treatment plan prior to surgery^[12]
• CT (Computed Tomography) scans for detailed bone and joint imaging
• Arthroscopy, which is used as the final determination for what technique may be best used. During this procedure, a surgeon makes small incisions and inserts a thin tube with a camera to view the inside of the joint^[13]

Treatment Options

While articular cartilage injuries can be painful and may make it difficult to go about your daily activities, there are several treatments available to both relieve bothersome symptoms and repair damaged cartilage^[1].

The treatment of cartilage injuries remains one of the most difficult challenges in medicine. Articular cartilage injuries are difficult to treat successfully and require technical expertise^[1]. Treatment depends on the pattern of the lesion and the clinical conditions of the patient^[14].

Non-Surgical Treatment

Initial treatment usually includes conservative approaches^[13][8]:

• Rest, ice, and elevation
• NSAIDs (nonsteroidal anti-inflammatory drugs) to reduce pain and swelling
• Physical therapy to strengthen muscles around the joint and improve range of motion
• Exercise programs designed to restore function
• Bracing and splinting for joint support
• Steroid injections to reduce inflammation
• Activity modification to avoid movements that worsen symptoms

Physical therapy can help keep your joints functioning at their best by strengthening the muscles that provide support, reducing weight gain that puts excess stress on joints, and improving balance to decrease your risk of falls and injuries^[19].

Surgical Procedures for Cartilage Repair

When conservative treatments don’t provide relief, surgery may be necessary for individuals with large cartilage lesions or significant joint dysfunction^[13]. The goal of cartilage repair surgery is to reduce pain, improve range of motion, slow the progression of damage, and delay the need for joint replacement surgery^[13].

All cartilage repair procedures can be broadly categorized into two main groups^[4]:

Marrow Stimulation Techniques

These procedures utilize the body’s own stem cells from bone marrow to create repair tissue consisting of fibrocartilage, which is different from the original hyaline cartilage^[4]. Options include:

• Microfracture: The most common marrow stimulation technique. During this procedure, several small holes are drilled into the bone beneath the damaged cartilage using a sharp tool. This creates a new blood supply that stimulates the growth of new cartilage^[5][13].
• Drilling: Similar to microfracture but uses a drilling instrument. This method is less precise and the heat produced during drilling may damage other tissues^[5].
• Abrasion arthroplasty: A high-speed tool is used to remove damaged cartilage from the injured joint surface^[5].

The main drawback of fibrocartilage repair tissue is its poor wear characteristics and questionable durability over time. Fibrocartilage is stiffer than articular hyaline cartilage, which means it does not offer the same shock absorption and force distribution as normal hyaline cartilage^[15].

Cartilage Restoration Techniques

These procedures aim to restore the injured area with normal or near-normal joint cartilage^[4]:

• Osteochondral Autograft Transplantation (OATs or mosaicplasty): Healthy cartilage tissue is taken from a non-weight bearing area of the patient’s own joint and transferred to the site of injury. This technique generally treats smaller lesions at 1.5 cm² to 4 cm²^[15][13].
• Osteochondral Allograft: Healthy pieces of both cartilage and bone tissue sourced from a donor are inserted into damaged areas. This technique addresses medium to large lesions (4 cm² to 10 cm²) with bone involvement. However, patients have a short window to implant the donor tissue after it becomes available^[15].
• Autologous Chondrocyte Implantation (ACI): A two-step procedure where healthy cartilage cells are removed from a non-weight bearing area, grown in a laboratory, and then implanted in the cartilage defect^[5][13].
• MACI (Matrix-Induced Autologous Chondrocyte Implantation): A third-generation ACI procedure that uses the patient’s own cells to create repair tissue with properties similar to hyaline articular cartilage. During the first stage, a surgeon gathers a biopsy of knee cartilage, which is sent to a laboratory where the cells are replicated to form new cartilage tissue that is later implanted^[15].

Many procedures to restore articular cartilage are done arthroscopically, meaning through small incisions using a camera and specialized instruments. In general, recovery from an arthroscopic procedure is quicker and less painful than from traditional open surgery^[11].

Recovery and Rehabilitation

Following surgery, rehabilitation procedures are essential to facilitate healing and restore normal functioning of the joint^[13]. Continual MRI readings taken after surgery allow for an objective assessment of the performed surgery and the application of a proper rehabilitation plan that facilitates a complete recovery^[12].

The ideal cartilage repair candidate is someone who suffers from an isolated articular cartilage defect with a relatively healthy joint and no generalized cartilage loss. The treated joint should be well-aligned and stable^[12].

Successful cartilage repair surgery reduces pain and restores function. Most important, it can delay or prevent the onset of arthritis^[11]. However, cartilage repair can be performed on people of all ages, and the suitability of each approach depends on each patient’s unique clinical problem^[12].