Articular cartilage of the knee is the smooth but tough covering over the end of the femur (thighbone). It protects the joint and the bone. At the same time, it allows for smooth gliding and movement of the knee joint.
Injury to the articular cartilage is fairly common in young, active adults (younger than 40 years old). It's estimated that as many as 10 per cent of this group have such an injury. But articular cartilage injury can be silent with no symptoms at all for quite some time.
Pain, clicking, locking, and swelling of the knee are symptoms that occur when the injury is present over the load-bearing surface. In some cases, when the joint is bent to just the right angle, even minor injuries can cause symptoms.
There are several different grading systems for articular cartilage lesions. The International Cartilage Repair Society suggests a five-point grading scale from zero (normal) to four (severely abnormal).
The remaining grades (two, three, and four) describe progressively worse damage. Grade two is a tear that goes half way down through the depth of the cartilage. Grade three goes all the way through the cartilage but stops short of damaging the bone.
A grade four injury means the cartilage is torn clear through to the bone. A small piece of the bone attached to the torn cartilage is lifted away from the femur.
The tear may not get worse but the damage to the joint may progress. Without treatment, you may develop painful and limiting arthritis. Experts advise early diagnosis and treatment for these injuries.
Minor injuries can be repaired before pain and swelling reduce motion and function. It's best not to wait for it to get worse but rather, restore the joint surface as quickly as possible.