Dr. Ebraheim’s educational animated video describes osteonecrosis of the knee.
There are three types:
1-Spontaneous osteonecrosis of the knee
2-Post arthroscopic osteonecrosis of the knee
3-Secondary osteonecrosis of the knee.
1-Spontaneous osteonecrosis of the knee: Occurs in females more than 55 years old. Usually one joint and one compartment are affected (medial femoral compartment). No etiology could be found.
Symptoms: sudden onset of pain with decreased range of motion, swelling of the knee. X-ray is probably normal. MRI is helpful. You may find a crescent shaped lesion. The condition can cause arthritis. Severe knee pain in middle aged or elderly female patients with a negative x-ray, get an MRI to rule out osteonecrosis of the knee.
Ficat stages of knee osteonecrosis
•Stage I: x-ray appears normal
•Stage II: sclerosis of the condyle.
•Stage III: crescent sign, subchondral fracture.
•Stage IV: the collapse of the subchondral bone.
Treatment:
•Protected weight bearing, therapy, and NSAIDs.
•Arthroplasty when conservative treatment fails.
•Unicompartmental knee arthroplasty for a small lesion.
•Total knee arthroplasty for large lesions or collapse.
2-Post arthroscopy osteonecrosis of the knee: occurs in middle aged women after knee arthroscopy.
3-Secondary osteonecrosis of the knee: the patient is usually less than 55 years of age and has associated risk factors. Involves more than one compartment or the metaphysis of the knee. Bilateral in 80% of the cases. Multifocal lesion may be seen. There is a cause for it that’s why it can be bilateral, multiple and everywhere. The spontaneous type occurs in older patients with normal x-rays. You see it on MRI.
Risk factors:
•Alcohol use
•Sickle cell disease
•Steroid use
•Trauma
•Gaucher disease
•HIV medication
•Transplant patient
•Hypercoaguable states.
These patients should be screened for other joint involvement. The lesion is a sub condylar insufficiency fracture and the patient will have severe pain with weight bearing either standing or sitting.
X-ray wedge shaped lesion and MRI is a better study.
Differential diagnosis:
•Osteochondral dissections: located in the lateral aspect of the medial femoral condyle in younger patients.
•Occult trauma, bone bruise, and overuse.
•Transient osteoporosis: found more in middle aged men. Found more in the hip than the knee.
Treatment:
•NSAIDS
•Decrease activity/decrease weight bearing
•Physical therapy.
•Surgery: scope to remove loose fragments or core decompression for lesions not extending to the joint.
•Osteocondylar allograft for larger, painful lesion and if the patient is young.
•Total knee replacement: a larger lesion with collapse. Multiple compartments involved.
•Conservative treatment is not as good with secondary AVN. Without surgery, secondary AVN will advance to osteoarthritis.
•Bisphosphonates have no effect on the knee osteonecrosis.
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Background music provided as a free download from YouTube Audio Library.
Song Title: Every Step
![](https://i.ytimg.com/vi/8vUyNxJo2LY/mqdefault.jpg)