Avascular necrosis (AVN) is a condition in which bone loses its blood supply. In the knee, AVN usually affects the subchondral bone, which is the bone beneath and supporting the joint surface.
Without proper treatment, the affected bone can die, fracture, and eventually collapse. This can lead to collapse of the joint surface and painful arthritis.
What Is Avascular Necrosis (AVN) of the Knee?
Healthy tissue requires a healthy blood supply to function normally. With AVN, an area of bone loses its blood supply and begins to die.
There are two types of AVN: traumatic and atraumatic. Traumatic AVN may occur following an injury such as a dislocation. Atraumatic AVN can occur with certain diseases, blood disorders, or medications such as corticosteroids. Occasionally, AVN can develop for no discernible reason.
Causes and Risk Factors
Causes of AVN of the knee include:
- An injury such as a dislocation or fracture
- Blood disorders or diseases
- A reaction to corticosteroids
- Alcoholism
Risk factors include:
- Contact or collision sports
- Activities with a high risk of knee injury
- Taking prescription corticosteroids, which can damage bone
- Sickle-cell disease, clotting disorders, and other blood disorders
Symptoms
Common signs and symptoms include:
- Deep, throbbing, aching pain
- Pain that becomes more consistent and begins to occur at rest
- Crepitus, or a crunching or cracking sensation
Treatment
If detected early by MRI, some AVN lesions can heal with rest and activity restriction. Gentle physical therapy can help maintain motion during the rest period and restore strength and motion once the injury has healed.
More often, surgery is required to stimulate, revascularize, and repair the area of avascular necrosis. Dr. Chudik can perform arthroscopic surgery to evaluate the AVN lesion. The surgical method depends on the size and condition of the lesion.
Small loose fragments may be removed, and the surface of the bone can be stimulated to promote a healing response. Large lesions may be drilled, bone grafted to stimulate healing, or replaced.
If AVN is severe and the integrity of the joint surface is compromised, a knee replacement may be required.
Recovery and Outcomes
The goals of treatment are to restore blood supply to the bone, protect the bone from loading while it heals, maintain or restore the joint surface to help prevent arthritis, and regain range of motion and function.
Outcomes depend on the stage of the AVN. Early recognition may allow treatment to stimulate a new blood supply and healing of the bone, or allow bone grafting before the joint surface is compromised.
Following surgery, patients are required to remain non-weight bearing for six weeks to allow the bone time to heal. Physical therapy begins two days after surgery to restore range of motion while protecting the healing bone.
Potential complications include:
- Failure to save the bone, with progressive fracture and collapse of the joint surface
- Development of arthritis and the need for joint replacement surgery
- Persistent pain and inflammation of the knee without treatment
- Weakness and deconditioning of the knee because of pain and activity limitations
- Persistent pain following surgery
- Infection and bleeding following surgery, although these complications are uncommon
When to See Dr. Chudik
If you are concerned about avascular necrosis of the knee or your symptoms worsen, schedule an evaluation with Dr. Chudik.
Call 630-324-0402, request an appointment online, or email contactus@chudikmd.com.