Cartilage & Osteoarthritis

Cartilage is a specialized connective tissue that can be found in various parts of your body, such as joints, tendons, ligaments, ears, nose, windpipe, and intervertebral discs. It is made of cells called chondrocytes and a matrix that consists of fibrous tissue and various combinations of proteoglycans and glycosaminoglycans.

What type of cartilage exists?

There are 3 types of cartilage: hyaline cartilage, elastic cartilage, and fibrocartilage. Hyaline cartilage, also called articular cartilage, is the most common type of cartilage. It is usually found in the trachea, nose, sternum, between ribs, and at the ends of bones that form joints.

Histological section of the articular cartilage. The cartilage matrix is stained with a red day, and the underlying bone with blue.
(School of Medicine University of Zagreb, photo by Andreja Vukasović)

While covering the ends of long bones, it reduces friction between the bones, enabling us a smooth and painless joint motion, and serves as a cushion for the joints by absorbing the compressive forces created when we move. Therefore, articular cartilage is crucial for keeping your joints healthy and functional.

Elastic cartilage is more flexible and is most commonly found in the larynx, ear, epiglottis, and
eustachian tube.

Fibrocartilage can resist high degrees of tension and compression and is considered the
strongest and least flexible. It is commonly found in menisci, tendons, ligaments, and
intervertebral discs.

Is it difficult to treat damaged articular cartilage?

Unfortunately, articular cartilage can get damaged, resulting in pain, discomfort, swelling, and loss of motion.

Several conditions can affect cartilage, varying from localized cartilage defects to disease of the whole joint called osteoarthritis.

If your physician upon clinical exam suspects your cartilage has been damaged, imaging tests such as X-ray and MRI should be done to diagnose or rule out a cartilage disease.

Arthroscopic view of the knee cartilage defect.
(University Hospital Sveti Duh Zagreb, Photo by Alan Ivković)

What is osteoarthritis?

Osteoarthritis (OA) is the most common form of joint disease. It is a whole joint disease, affecting not only articular cartilage but also the tissues around it. Synovial inflammation and subchondral bone remodeling result in pain, joint stiffness, and impaired movement, significantly reducing the quality of life for over 500 million people worldwide.

X-ray of the patient with knee osteoarthritis. Black arrows point to the reduction of the joint spaces indicating cartilage loss.
(University Hospital Sveti Duh Zagreb, Photo by Alan Ivković)

What are the risk factors for developing OA?

Risk factors for OA include injury, aging, obesity, and diabetes. Inflammatory causes, genetic factors, or job-related overexertion can also predispose to OA development. The knee is the most commonly affected joint, accounting for 83% of the total OA burden, followed by the hips, spine, and hands.

Are there different types of OA?

There are three different forms of OA in the knee: tibiofemoral, patellofemoral (PFOA), and combined OA. Recent studies found that patellofemoral osteoarthritis (PFOA) is present in ~39% of people with knee pain aged above 30 years and is considered one of the earliest signs leading to the progression of full OA in individuals with symptoms of knee OA within 2-5 years (50-75% of the patients) and the ultimate need for a prosthetic implant.

X-ray of the patient with patellofemoral osteoarthritis (PFOA). Reduction of the joint space and bone spurs are indicative of a degenerative process.
(University Hospital Sveti Duh Zagreb, Photo by Alan Ivković)

How is patellofemoral osteoarthritis treated?

Most treatment strategies focus on the alleviation of symptoms and pain management, while surgical procedures such as joint replacement are required for severely affected cases. However, due to a lack of high-quality studies, none of these treatments is accepted as a gold standard for the treatment of PFOA under evidence-based criteria and clinical guidelines are often inconsistent with one another regarding the use of these treatments.

These findings underline the importance of isolated PFOA in the natural course of knee osteoarthritis and prompt a regenerative treatment strategy a) to improve patients’ pain and symptoms and b) to possibly delay the natural course leading to combined (tri compartmental) knee OA.

Are there any other options to treat PFOA other than joint replacement with endoprosthesis?

Cell-based regenerative therapies utilizing articular chondrocytes or adipose tissue-derived stem cells are a promising alternative approach, but none of those available are applicable for knee OA or kissing lesions, recommended for the elderly (above 55 years), nor has proven to be of clinical benefit in randomized clinical trials.

Autologous matrix-induced chondrogenesis (AMIC) is widely performed for treating patellofemoral full-thickness cartilage defects in early-stage PFOA, but there is only low-quality evidence with several case reports published.

What is the treatment strategy used by the ENCANTO consortium?

Currently, there is no treatment option available aiming at disease modification or providing structural regeneration of PFOA.

The ENCANTO will address this gap.

We propose two innovations:

the use of autologous nasal chondrocytes (NC) as cell sources superior to articular chondrocytes (AC), and
the implantation of a Nasal chondrocyte Tissue Engineered Cartilage (N-TEC) tissue for the regenerative treatment of PFOA to improve clinical outcome and potentially delay artificial joint replacement.