The most commonly injured ligament in the knee is the anterior cruciate ligament (ACL). This ligament is most responsible for stabilizing the knee. People of all ages, physical ability, and conditions are susceptible to tearing this ligament; although ACL injuries are more commonly seen in athletes.

An ACL injury typically happens as the result of an individual or athlete stopping suddenly and changing direction. Nearly two-thirds of ACL injuries are "non-contact" injuries and often occur in conjunction with other injuries to the knee, such as damage to the meniscus.


In a healthy joint, bone ends are covered with a cushion of cartilage and the joint is protected by synovial fluid, a lubricant fluid in the joint. Arthritic joints are swollen, or inflamed, usually because the cartilage has been damaged or worn in some way. Individuals with arthritis typically suffer from stiffness, pain and swelling in the affected area or areas

The knee is the joint most commonly affected by osteoarthritis. A breakdown of cartilage causes the bones to rub against each other, which results in pain and loss of movement in the joint. It is this breakdown of the joint cartilage that can lead to joint pain, swelling and inflammation. Arthritis is diagnosed after an evaluation of the patient’s symptoms, a physical exam and one or more diagnostic imaging tests.


Avascular necrosis (AVN), also known as osteonecrosis, is a condition resulting from significant blood supply loss in a particular area of bone tissue. Most often AVN affects the knee, though it can occur in any bone in the body.

Loss of circulation in the affected joint or bone causes bone tissue to die and, in rare instances, can result in a collapse of the bone structure. AVN can also lead to advanced progression of osteoarthritis.

AVN can occur as the result of a trauma which cuts off blood supply, the use of systemic steroids or inflammatory diseases such as lupus or sickle cell anemia.

Symptoms of AVN usually begin with sudden knee pain, which can be triggered by routine activity. Other symptoms include swelling in the knee, limited range of motion and sensitivity to pressure or touch.


When joints are healthy, articular cartilage, a smooth cushion that lines bones where they connect with the end of joints, allows bones to shift and move normally with little friction. However, when the cartilage is torn or becomes worn down, either by trauma or disease, pain and weakness can occur in the joint. When this happens, treatment is often required to replace some of the missing cartilage in order to protect the joint surface.

Non-surgical treatments for cartilage injuries and disorders include immobilization of the knee, physical therapy and non-steroidal, anti-inflammatory medicines (NAISDs). Depending on the extent of the injury or disorder, a physician may determine that surgery is necessary to repair the damage.

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