Joints are formed when the ends of two bones meet. For example, the knee joint is made up of the ends of the femur (thigh bone) and tibia (shin bone). Cartilage is the smooth elastic tissue that covers the ends of the bones at these joints. The cartilage allows for the joint surfaces to glide smoothly and painlessly against each other. Injuries to the cartilage can occur with acute traumatic injuries or with chronic repetitive injuries. Cartilage injuries can result in pain, swelling and stiffness of the joint.
The diagnosis of a cartilage injury within the knee is made after a thorough clinical assessment of the knee. MRI scans are done to confirm the diagnosis and to look for concomitant knee injuries, such as meniscal tears and ligament injuries.
Patients with small cartilage injuries may be treated non-surgically with a course of rehabilitation. However, patients with cartilage injuries, who develop persistent pain, swelling and loss of joint function, are candidates for surgical treatment.
Surgical treatment involves cartilage repair. Cartilage has a low potential for intrinsic repair because of its poor blood supply. Therefore specialized repair techniques are employed to repair this tissue. These include:
Bone marrow stimulation
Drilling or microfracture of the bone beneath the cartilage injury is performed so as to allow stem cells from the bone marrow to form new repair cartilage at the site of the cartilage injury
Autologous matrix-induced chondrogenesis (AMIC) (See Figures below)
In addition to drilling or microfracture, a tissue scaffold is placed within the cartilage defect to enhance the cartilage healing process
Osteochondral autograft transfer (OAT)
Fresh bone and cartilage from another part of the joint is harvested and transferred to the site of cartilage injury so as to restore its structure
Bone and cartilage tissue from a donor can be used to reconstruct large cartilage defects in the joint
At the same time, bone reshaping or osteotomy may also be performed to correct significant abnormalities in joint alignment that may affect the cartilage healing process. Such surgery is usually performed under general anaesthesia, using minimally invasive arthroscopic (keyhole) techniques. An overnight stay in hospital is usually required after the surgery and 4-6 weeks of crutch-assisted ambulation may be advised. The use of a continuous passive motion machine may also be beneficial.
The rehabilitation process after the surgery is generally supervised by a physiotherapist, and consists of progressive knee range of motion exercises, muscle strengthening exercises, and sport-specific drills. The whole rehabilitation process may last to 6-9 months following the procedure. The success rate of cartilage repair surgery has been reported to be about 70-90%. The complications of this procedure include knee stiffness, infection and cartilage reinjury.
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