From the Guidelines
Computed tomography (CT) is not usually necessary for the initial evaluation of postoperative knee pain, and radiography is typically the first-line imaging modality. According to the most recent guidelines from the American College of Radiology 1, radiography of the knee is usually appropriate for the initial imaging of symptomatic or asymptomatic patients with a total knee prosthesis.
Initial Management
Initial management of postoperative knee pain should focus on conservative measures, including:
- Rest, ice, compression, and elevation (RICE protocol)
- Appropriate pain medications, such as acetaminophen or NSAIDs, if not contraindicated
- Physical therapy as prescribed by the surgeon
Indications for Imaging
Imaging studies, such as CT scans, are typically reserved for specific concerns, including:
- Suspected periprosthetic or hardware fracture, in which case CT knee without IV contrast is usually appropriate as the next imaging study 1
- Aseptic loosening or osteolysis or instability, where MRI knee without IV contrast or CT knee without IV contrast are equivalent alternatives 1
Red Flags
If pain is severe, worsening, accompanied by fever, significant swelling, warmth, redness, drainage from the incision site, or if there is limited range of motion beyond expected post-operative limitations, the patient should contact their surgeon promptly. In these cases, the surgeon may order imaging studies, but typically would start with plain X-rays rather than CT to assess for hardware complications, fractures, or joint effusion.
From the Research
Computed Tomography (CT) in Postoperative Knee Pain
- CT can be useful in evaluating postoperative tunnel positioning after ligament reconstruction 2
- Bone SPECT/CT can contribute to assessing overloading or biodegradation problems after ligament reconstruction 2
- After meniscal or cartilage surgery, SPECT/CT can help identify compartment overloading or nonhealing chondral or osteochondral lesions as a cause of pain 2
- SPECT/CT arthrography can assess cartilage damage at an early stage due to altered biomechanical forces 2, 3
Limitations of CT in Postoperative Knee Pain
- Conventional radiographs lack sensitivity to detect aseptic loosening and specificity in differentiating aseptic from infectious loosening 2
- Hardware-induced artifacts still hamper CT and MRI, despite improving and increasingly available metal artifact reduction techniques 2
- Bone scintigraphy is a proven useful adjunct to conventional radiography and MRI to reveal the pain generator and is less hampered by artifacts from metallic implants compared with CT and MRI 2, 4
Alternative Imaging Modalities
- MRI remains the reference standard for evaluating patients with pain after knee joint-preserving surgery 2
- SPECT/CT is increasingly recognized as a promising imaging modality for the investigation of patients with a painful knee after knee arthroplasty 5, 3
- SPECT/CT can be particularly helpful in patients with overloading problems, chondral or osteochondral lesions, and unhappy patients with ongoing pain after arthroplasty 3