How to Understand Your Knee MRI Results
Updated: 4 days ago
To understand your knee MRI results, it helps to know three kinds of words: the names of the knee's parts, the words that describe damage or wear, and the names of common conditions. Once you know those, most of the report starts to make sense. This guide explains the terms patients see most often on knee MRI reports, so you can have a clearer talk with your doctor.
What a knee MRI shows
MRI uses a strong magnet and radio waves, not X-rays, to make detailed pictures of the knee. It shows bones as well as soft tissues like cartilage, ligaments, tendons, and the meniscus. A radiologist, a doctor trained to read medical images, reviews the pictures and writes a report for the doctor who ordered the scan.
The report usually lists findings structure by structure and ends with an impression, which is a short summary. For how the sections fit together, see MRI results explained: how to read your radiology report.
Common terms in knee MRI reports
Anatomical terms
Femur: the thigh bone, which forms the top of the knee joint
Tibia: the shin bone, which forms the bottom of the knee joint
Fibula: the thinner bone on the outer side of the lower leg
Patella: the kneecap
Meniscus: two C-shaped pads of cartilage (medial and lateral) that cushion the joint
Articular cartilage: the smooth layer covering the ends of the bones
ACL and PCL: the anterior and posterior cruciate ligaments, which cross inside the knee
MCL and LCL: the medial and lateral collateral ligaments, on the inner and outer sides
Patellar and quadriceps tendons: tendons below and above the kneecap
Medial means the inner side of the knee (toward the other knee). Lateral means the outer side.
Descriptive terms
Tear: a rip in a structure; it can be partial or complete (full-thickness)
Sprain: a stretched or partly torn ligament
Degeneration or degenerative changes: wear over time, often age-related
Effusion: extra fluid inside the knee joint
Edema: swelling in soft tissue or bone
Signal: how bright or dark a structure looks; "abnormal signal" means it looks different from normal
Intact: the structure looks whole and not torn
Specific conditions
Meniscal tear: a tear in the medial or lateral meniscus
Ligament tear: a partial or complete tear of the ACL, PCL, MCL, or LCL
Osteoarthritis: wearing down of joint cartilage, sometimes with bone spurs
Chondromalacia patellae: softening or wear of the cartilage under the kneecap
Patellar tendinopathy: irritation or wear of the tendon below the kneecap, sometimes called jumper's knee
Bone bruise: an area of bone edema, often after an injury
Baker's cyst: a fluid-filled sac at the back of the knee
Bursitis: swelling of a bursa, a small fluid sac that reduces friction
What these terms mean in more detail
Meniscal tear
The report will say which meniscus is torn (medial or lateral) and which part, such as the front (anterior horn), middle (body), or back (posterior horn). It may also describe the tear's shape. Common words include horizontal, vertical, radial, complex, and bucket-handle.
You may also see "intrasubstance signal" or "degeneration" in the meniscus without a tear. This means some wear inside the meniscus that doesn't reach its surface. It is common, especially with age. To learn when imaging helps, read when to get an MRI for knee pain.
Ligament tear
Ligament findings are often described by how much of the ligament is affected. Words you might see include sprain, low-grade or high-grade partial tear, and complete tear. A report may say "ACL is intact," which means it looks normal. Ligament injuries are often seen with other findings, like a bone bruise or joint effusion.
Osteoarthritis
With osteoarthritis, the cartilage that covers the bone ends gets thinner over time. The report may describe cartilage thinning, fissures (cracks), or full-thickness cartilage loss, plus bone spurs (osteophytes). Radiologists often describe how much cartilage is affected and where, such as the medial compartment or the area behind the kneecap.
Patellar tendinopathy
This describes irritation or wear of the tendon below the kneecap. You may see the older words tendinitis (suggesting inflammation) or tendinosis (suggesting longer-term wear). The report may describe thickening or abnormal signal in the tendon.
Chondromalacia
Chondromalacia patellae means the cartilage under the kneecap has softened or worn. Some reports give a grade to show how much of the cartilage is affected, from mild surface changes to deeper loss.
Effusion and edema
A joint effusion is extra fluid in the knee. It's often described as small, moderate, or large and can happen with injury, arthritis, or irritation. Bone marrow edema (sometimes called a bone bruise) is swelling inside the bone that shows up well on MRI, often after a twist or impact.
Cartilage and joint space
You may see words about the space between the bones. On X-rays, doctors often talk about joint space narrowing. On MRI, the radiologist can look at the cartilage directly and describe thinning or loss. Both point to how much wear the joint has.
How to use this information
Knee MRIs often show more than one finding, and some, like mild degeneration, are common in people with no pain at all. That's why your doctor reviews the images along with your exam and symptoms. Bring questions such as:
Which findings are most important for my knee?
Do these findings explain my pain or symptoms?
Is anything torn, and is it partial or complete?
Do I need more tests or a specialist?
What are my next steps?
Your doctor or specialist is the right person to talk about care options.
Frequently asked questions
What does joint effusion mean on a knee MRI?
It means there's extra fluid inside the knee joint. It's often a sign that the knee is irritated, injured, or affected by arthritis. Your doctor will explain the likely cause.
How serious is a meniscal tear?
It depends on the tear's size, shape, location, and your symptoms. Some tears cause few problems, while others may need more care. Your doctor will explain what yours means.
What's the difference between tendinitis and tendinosis?
Tendinitis suggests inflammation in a tendon. Tendinosis suggests longer-term wear without much inflammation. Many reports now use the broader word tendinopathy.
What is a bone bruise on an MRI?
It's swelling inside the bone, often from an injury like a twist or a hit. MRI shows it well even when an X-ray looks normal.
Can a knee MRI find every problem?
MRI shows the knee in great detail, but no test finds everything. Your doctor may use your exam and other tests to get the full picture.
Related reading
Schedule an MRI at Millenium MRI
Millenium MRI has centers in Ocala, Largo, and Tamarac, Florida, and in North Little Rock, Springdale, Jonesboro, and Marion, Arkansas. Board-certified radiologists read every scan, and results are usually sent to your referring doctor within 24 hours. Same-day appointments are often available, and we accept most insurance plans, workers' compensation, personal injury cases, and self-pay. Call your nearest center or request an appointment online.
This article is for general information and is not medical advice. Talk with your doctor about your specific situation.
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