Knee Pain and MRI: What the Scan Finds

What Is a Knee MRI Scan and Why Is It Ordered?

A knee MRI scan is useful for assessing both acute and chronic knee pain; it simultaneously evaluates ligaments, menisci, cartilage, tendons, bone marrow, and soft tissues in one non-invasive session without ionising radiation.

• X-ray cannot visualise soft tissue structures or early cartilage changes; MRI detects bone marrow lesions, synovitis, and early cartilage degeneration that X-ray misses entirely. Most knee pain in India has a soft tissue origin.
• The assessment includes the menisci, ligaments, tendons, cartilage, bone marrow, soft tissues, bursae, and femorotibial and patellar alignment, all captured in a single scan without repositioning the patient.
• A knee MRI is ordered for knee pain, weakness, swelling, or bleeding in joint tissues, and to determine whether arthroscopy or surgery is needed, or to monitor post-surgical progress.
• Up to 76% of pre-consultation knee MRI scans ordered for patients over 55 years were found to be of no use to the orthopaedic surgeon ^[1]. In India, the correct pathway is X-ray first, then MRI when soft-tissue pathology is clinically suspected.
• MRI is an indispensable tool for diagnosing sports injuries, degenerative diseases, and joint inflammation, owing to its high resolution and superior soft-tissue imaging capabilities. No other non-invasive modality matches its diagnostic range for the knee.

Next, let’s understand how a knee MRI procedure is done.

What Does a Knee MRI Actually Show?

The knee is the joint most commonly assessed for internal derangement by MRI; ligaments, menisci, cartilage, bone marrow, and soft tissues are all evaluated in a single scan.

• ACL tears: MRI has a sensitivity of 88% and a specificity of 76% for ACL diagnosis against arthroscopy as the gold standard. In India, ACL tears from road traffic accidents and sports are the most frequent surgical indication following a knee MRI.
• Meniscal tears: MRI sensitivity for medial meniscal tears reaches 100% with a specificity of 89%, the most accurately detected finding on a standard knee scan ^[2]. A meta-analysis of 75 studies confirmed consistently high MRI accuracy for meniscal tears.
• Cartilage damage: MRI accuracy for grading chondromalacia patellae drops to 70% ^[3]. Arthroscopy remains the gold standard for precise cartilage assessment; MRI findings must always be read alongside clinical examination.
• Bone marrow findings: MRI detects bone marrow lesions and early cartilage degeneration invisible on X-rays. Bone marrow oedema and subchondral changes, precursors to fracture or OA progression, are exclusively visible on MRI.
• Additional findings: The assessment includes soft tissues, bursae, and femorotibial and patellar alignment. Popliteal cysts, synovitis, joint effusion, and tendon pathology are all assessed in the same scan.

Suggested Read: Silent MRI Scans: The Best Solution for Claustrophobia.

How Is a Knee MRI Done? The Step-by-Step Procedure

Understanding how a knee MRI is performed helps patients approach the scan without anxiety. A knee MRI follows a structured protocol designed to capture every relevant structure of the knee joint in a single session, without radiation or pain.

Here’s a step-wise process for a knee MRI:

Step 1: Screening and Preparation

MRI scanning begins with screening the patient for metallic foreign bodies and devices, such as pacemakers, that may represent a contraindication to imaging. The patient’s health conditions and allergies are also reviewed before entering the scanner room. Remove all metal objects, dental implants, jewellery, and belt buckles. No fasting is required for a standard knee MRI without contrast.

Step 2: Positioning on the Table

The technologist positions you on the movable exam table and may use straps and bolsters to help you stay still and maintain your position throughout the scan. For knee joint pain assessment, the patient enters the scanner feet-first while lying supine, a significantly less claustrophobic experience than head-first entry.

Step 3: Placing the Knee Coil

The knee is inserted into the coil with a slight bend of approximately 15 degrees, with the patella aligned to the centre of the coil; pads are used for fixation and immobilisation throughout the scan. The dedicated knee coil is critical; it receives the radiofrequency signal and directly determines image resolution and diagnostic quality.

Step 4: Image Acquisition

You will know when images are being recorded because you will hear tapping or thumping sounds when the coils generating the radiofrequency pulses are activated. You can relax between sequences but must maintain your position. Proton density fat-saturated sequences are the primary protocol; they highlight fluid, cartilage, and soft-tissue abnormalities, directly informing planning for knee pain relief. A complete protocol takes 30-45 minutes.

Step 5: After the Scan

The technologist will be able to see, hear, and speak with you at all times using a two-way intercom. You can resume all normal daily activities immediately after the scan is complete. A radiologist reviews and reports the images, typically within 24-48 hours. Your orthopaedic surgeon then interprets the report in the context of your symptoms and clinical examination to determine the next step.

With a clear understanding of the knee MRI process, let’s understand how to read MRI results for appropriate evaluation.

After Your Knee MRI: Reading Results and Next Steps

Receiving a knee MRI report without context is confusing for most patients. Moreover, understanding what the findings mean and what comes next is as important as the scan itself.

• Meniscal Grading: Grade 1 and 2 signals indicate intrasubstance degeneration without a true tear; Grade 3 indicates a tear communicating with the joint surface. Grade 3 is the finding that changes surgical decision-making.
• False Negatives Exist: Short peripheral tears in the posterior horn of the medial meniscus are characteristic false negative findings, missed on standard sequences and identified only at arthroscopy. A normal MRI does not rule out all pathology.
• Repairability Has Limits: MRI-based prediction of meniscal repairability showed reviewer accuracy of only 48-76% with poor interobserver reliability. Arthroscopic assessment, not the MRI report alone, determines surgical approach.
• Not All Findings Need Surgery: Accurate diagnosis requires combining MRI findings with the patient’s history and physical examination; not all meniscal tears require surgery. Degenerative tears in older patients are frequently managed with physiotherapy and pain-relief strategies.
• Radiologist Specialisation Matters: MRI scans should be reviewed by musculoskeletal radiologists who specialise in identifying knee injuries. At any MRI scan centre or MRI hospital, a specialist musculoskeletal radiology test report directly improves diagnostic accuracy for complex knee findings.