Imaging for knee pain

For mild knee pain without trauma, swelling, or mechanical symptoms (locking, giving way), a trial of rest, ice, anti-inflammatories, and activity modification is reasonable for two to four weeks. Imaging is appropriate sooner when:

• The knee was injured with a twist, pop, or impact and there is swelling within a few hours
• The knee locks, gives way, or you cannot fully straighten or bend it
• You cannot bear weight
• Pain persists beyond a few weeks despite first-line treatment
• There is concern for infection (warmth, fever)

The Ottawa Knee Rules help clinicians decide who needs an X-ray after acute injury. ACR Appropriateness Criteria support starting with X-ray for most adult knee pain, then adding MRI when soft-tissue injury is suspected or symptoms persist.

Knee X-ray is the first-line study for acute knee pain after trauma, suspected fracture, or evaluating osteoarthritis. Weight-bearing views show joint space narrowing, which correlates with cartilage loss.

Knee MRI is the gold standard for evaluating menisci, cruciate ligaments (ACL/PCL), collateral ligaments, cartilage, and the patellar tendon. It also shows bone bruises that X-rays miss entirely.

Knee CT is useful for complex fractures, pre-operative planning, or when MRI is contraindicated.

Knee arthrogram (MR or CT) adds contrast directly into the joint to evaluate subtle cartilage defects, post-operative menisci (where prior surgery makes standard MRI hard to interpret), or unstable cartilage lesions. It is usually reserved for cases where a standard MRI did not give a definitive answer.

A knee MRI evaluates:

• Medial and lateral menisci for tears (radial, horizontal, complex, root tears)
• Anterior and posterior cruciate ligaments for sprain or rupture
• Medial and lateral collateral ligaments
• Articular cartilage on the femur, tibia, and patella
• Bone marrow for contusions, stress fractures, or avascular necrosis
• The patellar and quadriceps tendons
• The joint capsule for effusions, cysts (Baker's cyst), and synovitis

Meniscal tear — very common in adults; not all tears need surgery. Symptomatic locking or persistent mechanical symptoms may warrant arthroscopy.

ACL tear — usually requires surgical reconstruction in active patients; partial tears may be managed nonoperatively.

Osteoarthritis — joint space narrowing and cartilage loss. Managed with weight management, PT, injections, and ultimately joint replacement in advanced cases.

Patellar tendinopathy / jumper's knee — overuse injury of the patellar tendon, common in athletes.

Bone bruise / contusion — typically resolves over weeks; visible on MRI long before symptoms fully resolve.

Baker's cyst — fluid collection behind the knee, usually a marker of underlying joint pathology rather than a primary problem.

Routine reports are available within a day; STAT requests can be back in four hours or less. Many knee problems are managed without surgery — physical therapy, anti-inflammatories, bracing, and selective injections handle the majority. Surgical referral is appropriate for unstable ACL injuries in active patients, symptomatic mechanical tears, and end-stage arthritis.

Schedule online or by phone. Bring your physician's order and ID. A standard knee MRI takes about 30 minutes; an arthrogram requires an additional 30 minutes for the joint injection performed by a radiologist. Call 800-558-2223 for a transparent self-pay quote.