What is articular cartilage?
Articular cartilage is the shiny, white surface that covers the ends of most bones. Articular cartilage protects bones during movement by dispersing the force applied to a joint and allowing the joint surfaces to glide smoothly with less friction. This covering is only a few millimeters thick, and has no blood supply to facilitate the healing process. Therefore, if it gets damaged, there is very little capacity for healing.
What is an articular cartilage defect in the shoulder?
An articular cartilage injury (also known as a chondral injury) may occur due to injury, such as a direct impact injury, or may be seen in the setting of shoulder instability and dislocation. However, it may also be due to wear and tear of the shoulder joint. If chondral injuries are left untreated, it is likely to progress to osteoarthritis of the shoulder joint over time. Cartilage defects may accompany concomitant pathology in this patient population, such as traumatic shoulder instability, labral tears, or rotator cuff tears.
What are the symptoms of a cartilage defect?
The symptoms of an articular cartilage injury in the shoulder are typically more likely to remain asymptomatic until they are further progressed. Some of the symptoms might include:
- Swelling and stiffness
- Shoulder pain that is worsened with activity
- Popping or clicking with shoulder movement
- Difficulty lying on affected side
How is articular cartilage damage diagnosed?
Articular cartilage injuries can be difficult to diagnose. Physical examination may show a swollen knee, but typically the exam is normal. X-ray may show a decrease in joint space, indicating advanced cartilage loss, and MRI imaging may reveal thinning or softened cartilage. Articular cartilage damage is most reliably diagnosed with shoulder arthroscopy where a camera is used to visually assess the damage.
Chondral damage is graded from mild to severe, and all grades can have characteristics of osteoarthritis.
- Grade 1 – The cartilage becomes soft in the earliest form of damage
- Grades 2 and 3 – As the condition worsens, the cartilage may become fibrillated with a shredded appearance. The grade of injury depends on the size and thickness of the defect
- Grade 4 – The cartilage may wear away completely, leaving the underlying bone exposed. When the involved areas are large, pain usually becomes more severe and causes limitations in activity
What is the treatment for articular cartilage defects?
The treatment of chondral damage in the shoulder typically depends on the specific location, size of the defect, severity of patient symptoms, and coexisting pathology within the shoulder. Once a symptomatic cartilage defect has been identified, initial treatment typically consist of conservative management. This includes rest, activity modification, anti-inflammatory medications, and strengthening in physical therapy.
In patients who have failed non-operative treatment with persistent pain and symptoms, surgical treatment may be considered. For patients with large or advanced cartilage defects, surgical intervention may be necessary to prevent further joint damage. The procedure chosen varies greatly on the location and overall size of the defect. Articular cartilage repair surgeries include:
- Microfracture – Creating small holes in the subchondral bone to allow for healing cells to flow into the defect and stimulate fibrocartilage formation. This is typically the first-line treatment in patients with a small symptomatic cartilage defect who place relatively low physical demands on their shoulder.
- Autologous Chondrocyte Implantation (ACI) – This is a two-step procedure where articular cartilage is biopsied from the patient’s knee during the initial arthroscopy and sent to a lab where the chondrocytes (cartilage cells) are processed and grown. When ready, the cells are re-implanted into the cartilage defect under a special patch to facilitate healing.
- Osteochondral autograft/allograft transfer (OATS) – Replaces the defect with a plug of bone and cartilage from a donor (allograft). This procedure is ideal for large defects and in situations where the underlying bone is damaged along with the cartilage.