Frequently asked questions

We hope you find the following questions helpful when researching treatment options.

Is the articular cartilage the same throughout the knee joint?

No, the articular cartilage varies throught the joint. Not only is the cartilage thickness varied in different areas of the joint, but the composition of the matrix is also different. In fact, the orientation of the collagen bundles in the matrix is somewhat like a fingerprint for each area of the joint. These variations must be strongly considered and respected when transplanting cartilage from one site of the knee to another.

What does medial and lateral mean?

Medial and lateral are anatomical terms used to describe location or position. Medial is used to describe a position on the inside of the leg (e.g., medial femoral condyle or medial meniscus), while lateral describes a position on the outside of the leg (e.g., lateral femoral condyle, lateral meniscus).

What is the difference between autograft and allograft?

An autograft is tissue taken from one's own body and transplanted to another area to replace damaged tissue. The patient is both the donor and recipient of the graft. An allograft, however, is tissue obtained from a cadaver to be implanted and replace a patient's damaged tissue.

Will health insurance cover cartilage implants?

Each carrier is different. To check for coverage, visit your insurance carrier's website and enter "medical policy for cartilage procedures" in the search option.

How long does it take to grow cartilage cells for MACI?

The living cartilage biopsy tissue is sent to a laboratory. The cells released from the cartilage tissue are called chondrocytes. With cell culturing techniques the numbers are greatly multiplied, from a few hundred thousand to over 10 million. The entire process takes approximately 3 to 4 weeks after harvest and varies from patient to patient.

Is "chondromalacia patellae" a disease?

The International Patellofemoral Study Group and orthopedic surgeons, in general, no longer use the term to describe a clinical (office) diagnosis. Quite simply, the term means "soft cartilage" and can only be used when directly inspecting the cartilage either in an open or arthroscopic manner or as viewed on an MRI or CT arthrogram. In the past, the term was applied quite freely and inaccurately to any pain in the front aspect of the knee. In fact, the amount of cartilage softening does not correlate with symptoms. Therefore, the term as a clinical diagnosis is for historical purposes only. The current goal is to identify the anatomic source of pain and to use that in the formation of a specific diagnosis. The most common form of pain in the region of the patella is muscular and soft tissue imbalance for the desired level of activity: imbalance patellofemoral pain.

What is knee malalignment?

With regards to the knee, the term "alignment" in orthopedics refers to the relative positions of the bones as they meet at the joints. Just as with a car, which has a wheel out of alignment that leads to wear on one side of a tire, so to, in a human, being "out of alignment" can potentially cause problems. This is usually refered to as malalignment or "excessive positioning" and can involve both the long bones and/or the kneecap. With malalignment, the forces through the joint may be altered to the point that can result in joint pain and/or degenerative joint disease changes over time. When considering joint and/or cartilage restoration, an important step is to restore proper alignment and thus improve loads (forces) through the knee. Said another way, if you have a car wheel out of alignment that causes tire (cartilage) wear, it does not make sense to simply replace the tire (cartilage) without correcting the alignment to stop the abnormal wear.

Are all meniscal tears repairable?

Unfortunately, the meniscus has a poor blood supply and the opportunity for healing is low for most unstable tears. The area near the attachment sites at the outer margins of the meniscus (periphery) do have a better blood supply and thus opportunity for healing in this area is better. Nevertheless, for all patients and all tear types the number of repairable tears is typically reported in the range of 10 to 15 percent.

What is a discoid meniscus?

Typically, menisci are "C" or crescent shaped and semicircular. They are positioned between the femur and tibia and thus leave the central part of the top of the tibie (tibial plateau articular surface) uncovered as it meets with the femur. In some people the meniscal cartilage forms differently. The meniscus may be wider than usual and in some cases it is so wide that instead of resembling a crescent, it coveres the entire plateau of the tibia and appears to be a full disc of tissue, hence the name discoid meniscus. This variant occurs more frequently on the lateral (outside) meniscus. It is usually without symptoms, but may be torn as with any meniscus.

What is orthobiologics?

Orthobiologics are natural tissue-derived products that orthopedic surgeons use that may help injuries heal quicker and may delay major surgery. These injuries and conditions may include arthritic joints, broken bones or injured muscles, tendons or ligaments.

The orthobiologic substances consist of cells, proteins, glycoproteins and complex carbohydrates that are naturally found in the body. When orthobiologics are used, they may enhance the healing process by decreasing inflammation, pain and stiffness and improving the patient’s ability to function. 

What are tissue and cell therapies?

Unlike specialized, differentiated cells such as cartilage cells, bone cells, fat cells, etc., tissue and cell therapies are undifferentiated. Responding to various stimuli, they can differentiate into specialized cells. That capacity represents the common public conception: tissue and cell therapies can regenerate damaged or lost tissues. In the proper setting, this can occur.  However, in most current applications, they are “modulating” cells that help to re-balance the imbalance of pro-inflammation/anti-inflammation and/or tear down/regrowth that may exist, for example, in an arthritic knee.

There are two main types of tissues and cells: adult cells, or tissue and cell therapies, and embryonic stem cells. We DO NOT USE embryonic stem cells. Embryonic cells are pluripotent meaning they can develop into almost any type of cell in the body.

We use only adult tissue and cell therapies.  One type is amniotic fluid cells, which are cells floating in the amniotic fluid and usually discarded at birth. Adult tissue and cell therapies are more tissue-specific than embryonic and the most commonly studied are hematopoietic (blood forming cells) and medicinal signaling cells (MSCs), formally know as mesenchymal stem cells, which form cartilage, bone, muscle, fat, etc.

For orthopedics, we are interested in the latter, the tissue and cell therapies, as they form the tissues of interest to us. Once again, at present, the “organ modulation” properties are currently of more interest for managing osteoarthritis symptoms than tissue regeneration though preclinical studies are ongoing and we are in communication with researchers outside the US involved in tissue and cell therapy cartilage regeneration.

Do tissue and cell therapies decrease arthritis symptoms?

Our center has been involved with two recent studies investigating tissue and cell therapies in arthritis and the outcomes are promising. The orthopedic literature is rapidly evolving in this area.

Journal of Bone and Joint Surgery (American). 2014. Authors: Vangsness CT, Farr J, Boyd J, Dellaero DT, Mills CR, LeRoux-Williams M.

Adult human tissue and cell therapies delivered via intra-articular injection to the knee following partial medial meniscectomy: a randomized, double-blind, controlled study

“Patients with osteoarthritic changes who received mesenchymal stem cells experienced a significant reduction in pain compared with those who received the control, on the basis of visual analog scale assessments.”    “…..clinical outcomes at intervals through two years’”


Journal of Knee Surgery. 2015. Authors: Vines JB, Aliprantis AO, Gomoll AH, and Farr J.
Cryopreserved Amniotic Suspension for the Treatment of Knee Osteoarthritis.

“Patient-reported outcomes including International Knee Documentation Committee, Knee Injury and Osteoarthritis Outcome, and Single Assessment Numeric Evaluation scores were collected throughout the study and evaluated for up to 12 months. Overall, this study demonstrates the feasibility of a single intra-articular injection of ASA for the treatment of knee OA and provides the foundation for a large placebo-controlled trial of intra-articular ASA for symptomatic knee OA.”


What is platelet rich plasma?

Blood is composed of a fluid component called plasma that can be separated from the small, solid components (red cells, white cells, and platelets). During tissue injury the platelets aid in clotting blood and as the “first responders” to injury, they contain over a 1,000  proteins called growth factors. These growth factors aid in initiating the healing response.

Platelet Rich Plasma simply means the prepared plasma has many more platelets per volume than the patient’s own whole blood. The concentration of platelets  can be 2 to 10 times greater (or richer) than the patient’s blood and thus more of the growth (and healing) factors.

To prepare PRP, blood is drawn from the patient. The platelets are separated from other blood cells and are concentrated by spinning at high speeds in a centrifuge. The concentrated platelets are then available with the plasma portion for injection.

Does PRP decrease arthritis symptoms?

British Journal of  Sports Medicine. 2015. Authors: Laudy ABBakker EWRekers MMoen MH.
Efficacy of platelet-rich plasma injections in osteoarthritis of the knee: a systematic review and meta-analysis.

  • Comprehensive, systematic literature review.
  • Ten trials were included.
  • In these, intra-articular PRP injections were more effective for pain reduction compared with placebo at 6 months post-injection.
  • Intra-articular PRP injections were compared with hyaluronic acid and showed a statistically significant difference in favour of PRP on pain.
  • Almost all trials revealed a high risk of bias.

"On the basis of the current evidence, PRP injections reduced pain more effectively than did placebo injections in OA of the knee (level of evidence: limited due to a high risk of bias). This significant effect on pain was also seen when PRP injections were compared with hyaluronic acid injections (level of evidence: moderate due to a generally high risk of bias). More large randomized studies of good quality and low risk of bias are needed to test whether PRP injections should be a routine part of management of patients with OA of the knee."

What is a knee replacement?

The term "knee replacement" is a broad term describing the replacement of one or more parts of the knee joint with artificial parts. A total knee replacement involves replacement of the entire knee joint, while a partial knee replacement (unicompartmental knee replacement, patellofemoral knee replacement or bicompartmental knee replacement) involves replacement of only a portion of the knee joint. 

How long does a knee replacement last?

According to current literature, more than 90 percent of total and partial knee replacements are still well functioning after 15 years. Adhering to post-operative activity modification and rehabilitation protocols greatly influences the durability and life of a total or partial knee replacement.