Osteonecrosis, which literally means “bone death”, is a condition in which a segment of bone loses its blood supply. Without adequate blood, the bone cannot survive and begins to die.
Osteonecrosis of the knee is 3 times more common in women than men, and mostly affects people over the age of 60 years.
In your knee, it usually affects the end of your femur (thigh bone), called the femoral condyles.
If the bone dies and collapses, it can lead to osteoarthritis of your knee.
Symptoms
Some common symptoms are:
- A sudden pain, usually on the inside of the knee, triggered by a routine action or minor injury
- Restricted mobility due to pain
- Pain worse at night and during activities
- Swelling around the knee
- Sensitivity to the touch
Causes
There are a number of causes of Osteonecrosis of the Knee but in the majority of cases the cause is unknown. also known as idiopathic.
Osteonecrosis of the Knee is associated with:
- Sickle cell disease
- Thalassemia
- Systemic Lupus Erythematosus (SLE)
- Obesity
- Kidney transplant patients and dialysis patients
- Patients with HIV
- Steroid therapy-Usually seen in younger patients and affects many joints
There are a number of theories as to the exact mechanism of AVN of the knee. The two main theories are altered blood flow to the area due to trauma or blocked blood flow due to fatty globules causing reduced circulation.
Risk Factors
As mentioned earlier the risk factors for developing this condition are:
- Sickle cell disease
- Fractures/Major trauma
- Thalassemia
- Systemic Lupus Erythematosus (SLE)
- Obesity
- Kidney transplant patients and dialysis patients
- Patients with HIV
- Steroid therapy-Usually seen in younger patients and affects many joints
- Alcohol abuse
- Gauchers disease
- Being female gives you a higher chance of this condition than being a male
Investigations
The doctor will usually order you an x-ray to have a look at the bones in your knee. However, early on in this condition the abnormalities may not be able to be seen on x-ray. Changes may only be seen several months after the onset of this condition. Therefore, during the early stage (also known specifically as stage I) a bone scan or MRI should be done as these methods can show up changes in the knee even at this early stage.
Complications
The major complication that can arise after Osteonecrosis of the Knee is severe Osteoarthritis if not treated early.
Also during natural repair, normal weight bearing can cause an acute pain in the knee due to the appearance of subchondral fractures.
Treatment
Treatment is either non-surgical or surgical
Non-surgical
The focus here is pain relief, protected weight bearing and treating the underlying cause (if there is one).
- Pain medication
- Crutches
- Knee brace
- Physical training to strengthen your thigh muscles
- Modifying activities to reduce knee pain
- Bisphophonates (bone protecting medicine) can be used to prevent too much bone from being re-absorbed and so stops it from being weakened.
Surgical
If the the majority of the bone surface is affected, surgery is often considered. Also the patients age and level of activity must be considered. Some surgical options are:
- Using an arthroscope to clean the surface of the knee and get rid of debris
- Drilling which reduces the pressure on the bones surface
- Knee replacement
- Procedures which alter the dynamics of weight-bearing away from the affected areas
Seeking Advice
Your Family Doctor (GP)
Your Family Doctor will be able to diagnose and help treat your problem. He or she will be able to
- tell you about your problem
- advise you of the best treatment methods
- prescribe you medications
- and if necessary, refer you to Specialists (Consultants) for further treatment
Prevention
Although there aren’t any specific ways to prevent Osteonecrosis of the knee, some preventative measures could involve reducing and controlling the risk factors of this condition.
- Maintaining a healthy body weight
- Avoiding excessive alcohol
- Good control of conditions which can predispose to AVN of the knee ie Sickle cell disease, Thalassemia
F.A.Q. | Frequently Asked Questions
Can osteonecrosis spread from bone to bone?
Osteonecrosis can affect any bone but it doesn’t spread from bone to bone.
Does Rheumatoid Arthritis (RA) predispose to osteonecrosis?
In itself, RA doesn’t predispose to osteonecrosis, but the associated steroid therapy for RA is a risk factor for osteonecrosis.