Overview
Imaging is an essential part of evaluating knee problems. Different studies answer different questions and help determine the diagnosis and most appropriate treatment. Unlike the shoulder, where the MRI often provides the majority of the diagnostic information, the X-ray is usually the foundation of knee evaluation, with MRI serving as an important complementary study.
X-rays
Routine knee X-rays typically include standing AP (front), lateral (side), and patellofemoral (sunrise) views, usually obtained on both knees for comparison.
Standing AP View
- Overall alignment
- Joint-space narrowing
- Arthritis
- Bone spurs
- Previous fractures
- Bone quality
Lateral View
- Patellofemoral arthritis
- Patellar height
- Patellofemoral relationship
Sunrise (Patellofemoral) View
- Patellar alignment
- Trochlear groove anatomy
- Trochlear dysplasia
- Patellofemoral arthritis
MRI
MRI is particularly useful for evaluating meniscus tears, cartilage injuries, ligament injuries, loose bodies, tendon injuries, occult fractures, and bone bruising.
In my practice, there are three primary reasons to obtain an MRI:
- To determine whether operative treatment or continued conservative treatment is the most appropriate course.
- To better predict the postoperative course, including the anticipated restrictions, recovery timeline, and expected time away from work or other activities when that information is important to the patient.
- To better understand unusual anatomy or pathology when additional detail will change treatment planning.
CT Scan
A CT scan provides outstanding detail of the bony anatomy and is particularly useful for evaluating subtle fractures, fracture healing, and bone architecture. It is also an essential part of MAKO robotic-assisted knee arthroplasty. A preoperative CT scan is used to create the three-dimensional surgical plan that provides the information necessary for robotic guidance during surgery.
MR Arthrogram
MR arthrogram is rarely necessary in the knee but may occasionally be useful following previous surgery or in selected postoperative situations.
Ultrasound
Ultrasound has a limited role in my knee evaluation. It is most commonly used to evaluate patients with calf pain or swelling when there is concern for a deep vein thrombosis (DVT).