Latest Facts About Osteonecrosis Of The Knee: Causes, Diagnosis, Risk Factors, Symptoms, Prognosis & Treatment

Blood supply to every organ and tissue in the body is very vital for optimal functioning. Loss of blood supply to a body part or organ leads to gradual death (necrosis) of that part or organ and can be very dangerous. Loss of blood supply to the brain leads to stroke; loss of blood supply to the heart leads to a heart attack; loss of blood supply to bone tissue leads to bone death (osteonecrosis).

knee bone

Osteonecrosis of the knee means bone death in the knee. It occurs mainly in the elderly, with women being more affected than men. Three types of osteonecrosis affect the knee: spontaneous osteonecrosis of the knee (SONK), secondary and post-arthroscopic.

Read also : PRP is no more effective for knee osteoarthritis than placebo

Knee anatomy

The knee is one of the two major articulating joints in the body, the elbow being the other. It is responsible for movement and very vital for weight bearing. The knee joint is the largest and most complex joint in the body. It is made up of three bones the lower end of the femur (thigh bone), the upper end of the tibia (tibia) and the patella (kneecap). Osteonecrosis of the knee usually occurs in the medial femoral condyle (inside the knee), however, the lateral femoral epicondyle (outside the knee) or the tibial plateau (the flat top of the tibia) can also be probable areas of occurrence.

The knee is vulnerable to injury; according to the National Institutes of Health database, it is the joint most commonly injured by adolescent athletes. In the elderly, it is prone to osteonecrosis of the knee, which, if not treated quickly, can progress to osteoarthritis.


The most common form of osteonecrosis of the knee is spontaneous osteonecrosis of the knee, SONK. It is mainly seen in people over the age of 50. On the other hand, secondary osteonecrosis has been observed to be more common in the younger population and it is linked to certain medical conditions such as sickle cell disease (SCD), alcohol consumption, corticosteroids, tobacco and drugs. myeloproliferative disorders. The last form, post-arthroscopic osteonecrosis, is a rare type. Reports show that it affected 4% of patients who underwent arthroscopic knee surgery, specifically meniscectomy.

Causes of osteonecrosis of the knee

When there is a lack of blood supply to the bone tissues, it leads to the death of bone cells, which leads to eventual collapse of the bone. This is the case with osteonecrosis. Osteonecrosis of the knee can cause the articular cartilage covering the ends of the bones to collapse, which can lead to arthritis.

Read also : TOKA a new 3D printed personalized plate for the treatment of knee osteoarthritis

Risk factors

The cause of the lack of blood supply is still unknown, but studies have linked the following risk factors to the development of osteonecrosis of the knee:

  1. Knee wound

Apart from pain and swelling, knee injuries such as dislocation or fracture can also damage blood vessels. The dislocation involves the bony ends; the fracture involves any bony part; Either way, both injuries can affect the blood vessels supplying the bone, thereby reducing blood flow to the dislocated/fractured bone. This is why immediate medical attention is needed. Sometimes an X-ray or MRI can be done to get a deeper view of the bone.

  1. Oral corticosteroid drugs

It is not known exactly why oral steroids cause osteonecrosis, but research shows there is a link between them. This is worrying because many diseases such as asthma and rheumatoid arthritis are treated with these drugs.

  1. Medical conditions

Certain medical conditions such as obesity, sickle cell anemia, and lupus are associated with the secondary form of osteonecrosis of the knee. HIV-positive patients are also diagnosed with it, as drugs for the treatment of HIV are also linked to the disease.

  1. Excessive alcohol consumption

Alcohol causes weight gain because it prevents the body from burning fat. Drinking too much alcohol increases fat accumulation in the body, which can lead to fatty tissue deposits that can block blood vessels and obstruct blood flow to the vessels.

  1. transplants

Studies show that osteonecrosis can occur after organ transplants, especially kidney transplants.

Read also : Duke University researchers create gel that could replace knee cartilage

Symptoms of Osteonecrosis of the Knee

The most common symptom associated with osteonecrosis of the knee is pain on the inside of the knee. The pain can be triggered by a specific activity or a minor injury and can become intense at night.

Other symptoms include: swelling in the front and inside of the knee, increased tenderness in the area, and limited movement of the knee due to pain.

Diagnosis of osteonecrosis of the knee

A proper diagnosis of osteonecrosis of the knee begins with a thorough history.

Here, your doctor will talk about your medical history, ask you to describe your symptoms, and then examine your knee.

When examining your knee, your doctor looks for swelling in your joints, tenderness, redness, and joint instability.

You may be asked to move your knee to observe the range of motion of your knee joint.

Your doctor also looks for any signs of injury to the muscles, ligaments, and tendons around your knee.

After a physical examination of your knee, your doctor then confirms the diagnosis by taking an imaging study of your knee either with an X-ray study, magnetic resonance imaging (MRI), or bone scan. An imaging study is essential as it takes a deeper look at your bones and other aspects of your knee joint to identify the stage of osteonecrosis of the knee you have.

Read also : Still no effective cures for osteoarthritis, but there is hope

Staging of osteonecrosis of the knee

There are four stages of development of osteonecrosis of the knee:

Stage I: At this stage, the patient experiences symptoms that become intense and last for six to eight weeks. To be sure of the diagnosis, the doctor uses a positive bone scan, not just X-rays to get a better view of the knee. At this point, surgery is not needed for treatment, instead the doctor administers pain-relieving medications and other methods that focus on reducing weight-bearing.

Stage 2: From stage I to this stage takes several months. At this stage, x-rays can confirm the diagnosis, as the normally rounded medial femoral condyle flattens out and may be visible on x-rays. Other forms of imaging studies such as MRI, CT scan, or bone scan can also confirm the diagnosis.

Stage III: From stage I to this stage takes about three to six months, only x-rays can confirm the diagnosis. The articular cartilage that covers the bones begins to detach from the bone as the bone itself gradually dies. Surgical procedures may be required to treat the patient at this stage.

Stage IV: At this stage, the disease becomes very critical because the articular cartilage is now destroyed and the joint space narrows; severe arthrosis develops; joint replacement surgery becomes necessary.

Prognosis of osteonecrosis of the knee

When osteonecrosis of the knee is diagnosed early (stage I), a simple painkiller may be enough to treat it. The doctor may also advise reduced mobility of the affected knee. In advanced stages, surgery may be done to prevent further damage to the entire joint.

Treatment of osteonecrosis of the knee

The treatment option for osteonecrosis of the knee depends on certain factors, including the stage of the disease, the part of the bone affected, and the cause of the disease. Based on these factors, treatment may be non-surgical or surgical.

Read also : Scientists are successfully repairing bones by combining gene therapy and bioprinting

Non-surgical treatment option

If the disease is at an early stage and only a small part of the knee is affected, surgery may not be necessary. The doctor may suggest one of the following non-surgical treatment procedures:

  1. Use medication:

The doctor may prescribe nonsteroidal inflammatory drugs (NSAIDs) such as ibuprofen and naproxen to relieve knee pain and swelling. If the patient is young, the doctor may suggest bisphosphonates for treatment.

  1. Reduced loading:

For some patients, removing weight from their knees is enough to slow damage and allow healing. The patient may need to start using crutches for a while to reduce the weight on their knees.

  1. Exercise:

The patient may be asked to engage in certain physical activities that help strengthen the thigh muscles and allow for a range of motion in the affected joint. To avoid stress on the joint, water exercise may also be recommended for the patient.

  1. Amendment in certain activities:

The doctor may advise the patient to stop certain activities that cause pain.

Surgical treatment options

Your doctor may recommend surgery if there doesn’t seem to be any improvement after non-surgical treatment options or if the affected part of the bone is quite large. Some surgical procedures that may be recommended include:

  1. Total knee replacement:

Your doctor may opt for this procedure if the disease has progressed to stage IV, where the bone has been destroyed. The procedure involves replacing destroyed bone and cartilage with metal or plastic joint surfaces to restore knee function.

  1. Osteotomy:

In this procedure, the surgeon removes part of the tibia or femur or inserts a wedge of bone graft/synthetic bone to help take the weight off the damaged part of the knee. This is essential as removing weight from the affected area of ​​the joint will relieve the patient of pain and promote healing.

Other Surgical Procedures Your doctor may recommend osteochondral (bone and cartilage) bone grafting, central compression, arthroscopic debridement and microfracture, and autologous chondrocyte implantation (ACI).

Read also : Inflammatory joint diseases: actions and foods to consider to naturally relieve joint inflammation


Even though osteonecrosis of the knee is likely to occur in people over 50, it can be prevented and effectively treated when we know what it is and how to diagnose and manage it easily.