A relatively rare cause of knee pain in older women is osteonecrosis, a pathological condition that results from the interruption of blood supply to the bone. Women are up to 3 times more likely to be infected than men, while the vast majority is patients over 60 years of age.
The medial femoral condyle is most commonly affected; however, osteonecrosis can also occur in other parts of the knee such as the lateral femoral condyle or tibia.
The exact causes of knee osteonecrosis are not yet known. According to a theory, small fatigue fractures combined with vigorous activity lead to changes in bone blood circulation. Another theory supports that the accumulation of fluid within the bone compresses the blood vessels and as a result blood circulation decelerates.
In addition, osteonecrosis of the knee is associated with certain pathological conditions such as obesity, sickle cell anemia, lupus erythematosus or even corticosteroid therapy. In particular, treatment with steroids affects more than one joint and young people.
Regardless of the cause, when osteonecrosis is not diagnosed and treated in a timely manner, it can lead to severe osteoarthritis.
- Sudden knee pain triggered by specific activities or minor injuries
- Increased pain during nighttime
- Edema on the anterior surface of the knee
- Increased sensitivity to palpation
- Restriction of movement due to pain
Knee osteonecrosis is classified into four stages, which are identified on the basis of symptoms and radiological imaging.
STAGE I: Symptoms are more severe at an early stage and may persist for 6 to 8 weeks and then subside. Given the fact that radiographs at this stage are normal, bone scintigraphy is useful for diagnosing the disease.
The treatment at this stage is conservative and is based on the weight discharge of the leg.
STAGE II: It takes several months for the disease to progress to stage II. X-rays depict a widening of the curved surface of the condyle. MRI and bone scintigraphy are usually diagnostic.
STAGE III: When the disease reaches this stage – 3 to 6 months after onset – the lesions are visible on X-rays and no further tests are needed. The articular cartilage is damaged and the underlying bone exhibits obvious signs of necrosis. At this point the treatment is surgical.
STAGE IV: At this stage, the bone collapses. The articular cartilage degenerates irreversibly, the articular space is reduced and osteophytes are created. This type of severe arthritic lesions is usually treated with joint replacement (total knee arthroplasty).
In the early stages of the disease, the treatment is not surgical. If the affected area is small, discharge may be all that is needed.
Treatment options include:
- Medication to reduce pain
- Weight discharge with the aid of a bracket
- Program for strengthening the muscles of the thigh
- Modification of activities
If more than half of the bone surface is affected, surgical treatment may be required.
There are several options, including:
- Arthroscopic knee washout
- Drilling of the articular surface to reduce pressure on the bone surface
- Interventions that discharge the affected area (osteotomies)
- Unicompartmental or total knee arthroplasty