Knee Joint Bone Infarct — including image, cause, reason, symptoms, and treatment 👇

Knee Joint Bone Infarct — including image, cause, reason, symptoms, and treatment 👇

🦴 Knee Joint Bone Infarct (Osteonecrosis / Avascular Necrosis)

Definition:
A bone infarct is a localized area of bone tissue death (necrosis) caused by an interruption of the blood supply to the bone.
When it occurs in the knee joint, it commonly affects the distal femur or proximal tibia.

Example MRI Image (Illustration)

Source: Radiopaedia.org — T1 MRI showing serpiginous low-signal rim typical of bone infarct.

CT MRI AND XRAY SHOWING BONE INFRACT

Causes / Reasons

1. Reduced Blood Flow (Ischemia):

   • Trauma or fracture damaging blood vessels.

   • Surgery near the knee joint.

2. Medical Conditions:

   • Sickle cell disease

   • Systemic lupus erythematosus (SLE)

   • Gaucher’s disease

3. Medication & Lifestyle Factors:

   • Long-term steroid (corticosteroid) use

   • Excessive alcohol intake

   • Smoking (reduces circulation)

4. Idiopathic (Unknown cause):

   • Sometimes, the exact cause is not identified.

Pathophysiology (What Happens Inside)

• Blood flow to part of the bone is reduced or stopped.

• Bone cells die due to lack of oxygen.

• The dead bone becomes weak and may collapse.

• Overlying cartilage can get damaged → leading to arthritis and pain.

Imaging Findings

X-Ray:

• Early stage: often normal

• Late stage: shows sclerotic (dense) and lucent (light) areas with serpentine border.

MRI:

• Most sensitive test.

• T1: low-signal serpiginous line

• T2/STIR: high-signal central marrow (due to edema)

MRI IMAGE PDFS SAG AND PDFS COR

Symptoms

• Deep, aching pain in the knee (especially while walking).

• Swelling or tenderness around the joint.

• Reduced range of motion.

• Pain worsens at night or after activity.

Treatment

Conservative Management (Early Stage):

• Rest and reduced weight-bearing

• Pain relief: NSAIDs (e.g., ibuprofen)

• Physiotherapy to maintain joint mobility

• Stop alcohol & steroid use if possible

Medical Options:

• Bisphosphonates (to slow bone damage)

• Vasodilator or anticoagulant therapy (to improve blood flow)

Surgical Treatment (Advanced Stage):

• Core decompression: relieves pressure & improves circulation

• Bone grafting: replaces dead bone

• Osteotomy: reshapes bone to reduce stress

• Total knee replacement: if joint is severely damaged

Prognosis

• Early detection + conservative treatment = good recovery.

• Late-stage infarcts may cause collapse of bone → osteoarthritis and need joint replacement.

Prevention Tips

• Avoid long-term steroid use unless necessary

• Limit alcohol

• Manage chronic diseases properly

• Maintain healthy body weight

• Regular exercise to improve circulation