Knee MRI: What It Shows, How to Prepare, and What to Expect

Knee MRI is the most frequently ordered MRI exam in the United States. If your knee was injured during sports, twisted awkwardly, or has persistent pain and swelling, MRI is likely the next step after X-rays.

Why MRI for the Knee?

X-rays show bones, but most knee problems involve soft tissues that only MRI can visualize. MRI reveals the four major ligaments (ACL, PCL, MCL, LCL), both menisci (the C-shaped cartilage shock absorbers), articular cartilage covering the bone surfaces, tendons (patellar, quadriceps), muscles around the knee, fluid collections and cysts, and bone marrow abnormalities (bruising, stress fractures).

Common Findings on Knee MRI

ACL Tear The ACL (anterior cruciate ligament) is the most commonly injured knee ligament, especially in sports involving cutting and pivoting. MRI is over 95% accurate for ACL tears. A complete tear usually requires surgical reconstruction in active patients.

Meniscus Tear The menisci are vulnerable to twisting injuries and degeneration with age. MRI shows the location and pattern of the tear, which helps your orthopedic surgeon decide between conservative treatment and arthroscopic surgery.

Cartilage Damage Articular cartilage damage (chondral injury) can result from acute trauma or chronic wear. MRI can show the extent and depth of cartilage loss, which is important for treatment planning.

Bone Bruise Bone bruises (bone marrow edema) are invisible on X-ray but clearly visible on MRI. They indicate impact injury and are often found alongside ligament tears.

Baker's Cyst A fluid-filled cyst behind the knee, often associated with meniscus tears or arthritis. Usually an incidental finding that does not require treatment.

How to Prepare

Knee MRI requires minimal preparation. Wear comfortable shorts or athletic pants with no metal zippers or buttons. Remove all metal from your body including jewelry and watches. You will be asked about any metal implants or devices. No fasting is needed, and you can take your medications normally.

What to Expect

1. You lie on your back on the MRI table
2. Your knee is placed inside a coil (a specialized antenna)
3. Your leg is positioned with padding for comfort
4. The table slides into the scanner
5. Stay still throughout — movement blurs the images
6. The scan takes 30-40 minutes
7. You may hear loud tapping and buzzing sounds (earplugs provided)

Most knee MRIs do NOT require contrast injection.

After the Scan

Resume all normal activities immediately. Results are sent to your referring physician within 48 hours. If your doctor needs a stat read for surgical planning, we can accommodate.

Call (727) 398-5999 to schedule your knee MRI.