Can a Patient Order a Knee Ultrasound?
No, patients cannot independently order knee ultrasounds—imaging studies require a physician's order based on clinical evaluation and appropriate indications. Medical imaging, including knee ultrasound, must be ordered by a licensed healthcare provider who can determine medical necessity and ensure proper clinical context 1.
Clinical Context for Knee Ultrasound Ordering
When Knee Ultrasound is Appropriate
Knee ultrasound has specific clinical indications where it provides diagnostic value:
- Soft-tissue pathology evaluation: Ultrasound is rated as "usually appropriate" (7/9) for suspected periprosthetic soft-tissue abnormalities including quadriceps or patellar tendinopathy, tendon tears, and nerve impingement 1
- Confirmed infection with positive cultures: Ultrasound may be appropriate (4/9) as additional imaging following radiographs when joint aspiration cultures are positive 1
- Synovitis and effusion detection: Ultrasound effectively detects synovial thickening, joint effusions, and early degenerative changes 2, 3
- Bursitis and Baker's cysts: Common applications include evaluation of bursae and popliteal cysts 4
When Knee Ultrasound is NOT Appropriate
The American College of Radiology provides clear guidance on inappropriate uses:
- Asymptomatic total knee arthroplasty follow-up: Ultrasound is rated "usually not appropriate" (1/9) for routine surveillance 1
- Measuring component wear or rotation: Ultrasound is rated 1/9 for these indications—plain radiographs (9/9) and CT (9/9) are preferred 1
- Suspected periprosthetic infection: Ultrasound is rated only 3/9 for initial evaluation; joint aspiration (9/9) and radiographs (8/9) are the appropriate first steps 1
- Periprosthetic fracture evaluation: Ultrasound is rated 1/9; radiographs (9/9) and CT (8/9) are indicated 1
The Proper Ordering Process
Required Clinical Evaluation
A physician must:
- Perform clinical assessment to determine pretest probability and appropriate imaging modality 1
- Obtain plain radiographs first in most knee pathology scenarios, as these are rated 9/9 for initial evaluation 1
- Consider alternative imaging based on specific clinical scenarios—MRI without contrast is equivalent to ultrasound (both 7/9) for soft-tissue abnormalities 1
Common Pitfall to Avoid
The most critical error is ordering ultrasound when other modalities are more appropriate. For example, if evaluating for deep venous thrombosis in the lower extremity, complete duplex ultrasound with compression from thigh to ankle is the standard protocol 1, not a simple knee ultrasound. Similarly, for post-arthroplasty complications, radiographs must precede any advanced imaging 1, 5.
Why Physician Ordering is Necessary
- Medical necessity determination: Only a physician can assess whether imaging will change clinical management 1
- Appropriate test selection: Different clinical scenarios require different imaging approaches—ultrasound is not universally appropriate for knee evaluation 1
- Insurance coverage: Third-party payers require physician orders with documented medical necessity for reimbursement
- Patient safety: Proper clinical context prevents unnecessary testing and ensures timely diagnosis of serious conditions like infection 5
In summary, while ultrasound has valuable applications for specific knee pathologies—particularly soft-tissue evaluation—it must be ordered by a physician who can determine appropriateness based on clinical presentation, ensure proper sequencing of diagnostic tests (typically radiographs first), and select the optimal imaging modality for the suspected pathology.