Knee Cartilage Repair, Regeneration, and Replacement—Who Can Get It?

Surgeries to repair, regenerate and replace cartilage are becoming more common, but they are not recommended for everyone. Generally, these surgeries are most successful in patients who are:

• Young—for example, OATs microplasty procedures are most successful in patients younger than 40¹Canale ST, Beaty JH. Campell’s Operative Orthopaedics, 12th ed. Philadelphia, PA: Mosby, Inc; 2013:p2185.
• Active
• Have had pain for a relatively short time—several months, not several years
• Have pain at rest
• Do not have problems with knee alignment or stability
• Have a localized cartilage damage

“Localized cartilage damage” means one or two isolated injuries to the cartilage. People with widespread cartilage damage, like that found in moderate to severe knee osteoarthritis, are typically not candidates for surgical cartilage repair, regeneration or replacement.

See Types of Regenerative Medicine for Sports Injuries

These surgeries are elective procedures, meaning a doctor may suggest surgery but it is up to the patient to decide whether or not to have it. They are typically performed on an outpatient basis.

See Whether to Choose Regenerative Medicine Treatment

How Is Damaged Knee Cartilage Diagnosed?

Doctors will use a clinical examination and medical imaging to diagnose damage to knee cartilage.

Clinical examination and patient interview
A doctor will examine the affected knee and take note of any swelling and other symptoms. The doctor will also ask the patient about knee pain.

See Symptoms of Meniscal Tears

Damage to the knee’s articular cartilage typically occurs in one of two places: the bottom of the femur or the back of the kneecap.

• When the damage is at the bottom of the femur, a patient may complain about pain at the inside or outside of the knee. Pain usually worsens when weight is put on the knee, especially during high-impact activities such as running.
• When damage is at the back of the kneecap, a patient may report feeling pain during stair climbing or kneeling, or after sitting for a long time.

See Guide to Knee Joint Anatomy

Medical imaging
Damage to knee cartilage can usually be confirmed with an MRI. Before an MRI is ordered a doctor will often order X-rays, which are less expensive and time-consuming than an MRI. X-rays can help rule out other possible causes of pain.

Cartilage is not seen on X-rays, so cartilage fraying and localized injuries, such as isolated tears or divots in the knee cartilage, are not detectable. However, severely degenerated cartilage is detectable on an X-ray because the joint space between the bones appears shrunken.

If bones appear too close together, or are even touching, it indicates knee osteoarthritis.

What Are the Alternatives to Knee Cartilage Repair?

Not everyone is eligible for cartilage repair surgery, and not everyone who is eligible for cartilage repair surgery will choose to have it. People who want to reduce pain without surgery may try:

• Losing weight
• Changing activities—transitioning from running to biking, or from biking to swimming
• Physical therapy to strengthen muscles
• Changing footwear, such as avoiding high heels
• Taping or bracing

See Acute Injury: Additional Treatment Considerations

This list is not exhaustive, and individuals may find other non-surgical treatments that work for them. For example, some people find acupuncture or other alternative medicine treatments help reduce pain.

Why Is Cartilage So Important?

Cartilage is the strong, pliable, and slippery substance that covers bones at joints. (A joint is where two or more bones meet.) Cartilage has two primary functions:

• Eliminating friction between a joint’s bones during joint flexing and extending.
• Providing a protective cushion between bones during high-impact activities, such as running and jumping.

This slick, smooth articular cartilage can measure anywhere from less than 1 mm to more than 6 mm thick.²Frisbie DD, Cross MW, Mcilwraith CW. A comparative study of articular cartilage thickness in the stifle of animal species used in human pre-clinical studies compared to articular cartilage thickness in the human knee. Vet Comp Orthop Traumatol. 2006;19(3):142-6.^,3Pollock J, O'toole RV, Nowicki SD, Eglseder WA. Articular cartilage thickness at the distal radius: a cadaveric study. J Hand Surg Am. 2013;38(8):1477-81.^,4Cohen ZA, Mccarthy DM, Kwak SD, et al. Knee cartilage topography, thickness, and contact areas from MRI: in-vitro calibration and in-vivo measurements. Osteoarthr Cartil. 1999;7(1):95-109. The cartilage is bathed in a joint fluid, called synovial fluid, which further decreases friction and allows for pain-free range of motion.

See Soft Tissue of the Knee Joint

When bones are not protected by cartilage, they can undergo changes that make them more porous and weaker. They can also grow bone spurs, called osteophytes.

See What Is a Bone Spur?