Articular Cartilage Injuries of the Knee
Defects or injury to the articular cartilage encompass a range of types, from smaller, focal defects to advanced degenerative disease of the articular cartilage. Articular cartilage damage occurs in the setting of acute trauma or chronic repetitive overload. Impaction of the cartilage results in softening of the cartilage, fissuring, flap tears and/or delamination. Unfortunately, cartilage injuries have a limited capability of healing, an often worsen over time.
Classification: Outerbridge Arthroscopic Grading System
- Grade 0: Normal cartilage
- Grade 1: Softening and swelling
- Grade 2: Superficial fissures
- Grade 3: Deep fissures, without exposed bone
- Grade 4: Exposed subchondral bone
Physical Examination and Work-up
On presentation, an effusion, pain and mechanical symptoms of locking, catching or clicking may or may not be present. X-ray is essential to assess overall alignment, to quantify joint space narrowing and to evaluate for degenerative changes. MRI is the most sensitive technique to evaluate for focal cartilage defects. A CT scan may be indicated to evaluate for bone loss.
Management of Cartilage Injuries
Non-operative care includes rest, NSAIDs, physical therapy, and injections are the first line of treatment for mild symptoms. Additionally, an unloader brace may be recommended for focal compartment joint space narrowing/cartilage injury. If conservative treatment does not reduce symptoms, surgery may be considered. The approach to cartilage surgery is a patient-specific, and recommendations are based on the extent and location of injury, age and skeletal maturity, activity level, and alignment. Surgical techniques include arthroscopic debridement, fixation of unstable osteochondral fragments, osteochondral autograft, and osteochondral allograft transplantation.
Fixation of Unstable Osteochondral Fragments
If adequate subchondral bone exists on an unstable fragment, the fragment is fixed with absorbable or nonabsorbable screws or devices back in place.
Fixation of unstable osteochondral fragments may be performed via an arthroscopic technique or through a mini-open incision depending on the size and location of the fragment. The cartilage injury site is first adequately prepared, then the fragment is fixed back into place, often with a screw.
Recovery is closely guided, and physical therapy begins in the days following surgery. Physical therapy begins immediately to assist with edema control, to reduce quadriceps atrophy and promote range of motion.
Osteochondral Autograft Transfer System (OATS)
A cartilage defect in a high weight bearing area is replaced by a cartilage bone plug from a lower weight bearing area within the knee joint.
Cartilage is transferred from a healthy, non-weight bearing area of the knee to the damaged area. OATS is typically recommended for individuals under the age of 50 and without extensive cartilage damage throughout the knee. The procedure itself commences with an arthroscopic examination in the operating room to examine the cartilage defect and transfer area closely.
Once confirmed the transfer is appropriate, an incision is made to expose the area of damage.
Next, the damaged area is prepared and precisely sized. A tool is used to core out a cartilage plug of the precise size in the area of healthy, non-weight bearing transfer site. This cartilage is then transferred into the prepared area of cartilage damage. Recovery is closely guided, and physical therapy begins in the days following surgery. Physical therapy begins immediately to assist with edema control, to reduce quadriceps atrophy and promote range of motion.
Osteochondral Allograft (OCA) Transplantation
The cartilage defect is replaced by an osteochondral allograft (donor tissue containing bone and cartilage).
This procedure is performed via an open incision overlying the site of cartilage damage. The cartilage defect size is precisely measured, and the defect site is prepared for transplant. A fresh allograft (donor) is prepared on the operating room back table to match the size of the defect.
The allograft is then press-fit into the defect site with or without additional hardware to assist stabilization. The incision site is then closed and dressed in sterile dressing. Recovery is closely guided, and physical therapy begins in the days following surgery. Physical therapy begins immediately to assist with edema control, to reduce quadriceps atrophy and promote range of motion.