What is the recommended treatment for a patient with a history of left total knee replacement who presents with swelling, warmth, stiffness, and sharp pains after a recent fall, with X-ray results showing no abnormality?

Management of Post-TKR Symptoms After Fall

Periprosthetic joint infection (PJI) must be immediately excluded in this patient with swelling, warmth, and pain after total knee replacement, regardless of normal X-ray findings. 1

Immediate Diagnostic Workup

Laboratory Testing (First Priority)

• Obtain ESR, CRP, and serum interleukin-6 immediately to evaluate for occult infection—these are strongly recommended by the American Academy of Orthopaedic Surgeons for any patient with concerning post-TKR symptoms 2
• CRP has 73-91% sensitivity and 81-86% specificity for prosthetic knee infection using a cutoff of 13.5 mg/L 1
• Do not rely on peripheral WBC count—it is not elevated in most patients with infected prostheses and is meaningless for excluding infection 2
• When both ESR and CRP are negative, infection is unlikely 1

Clinical Assessment Details

• Characterize the pain pattern specifically: Night pain or pain at rest characteristically indicates infection, whereas pain on weight-bearing suggests mechanical loosening 1
• The combination of swelling, warmth, and sharp pains in this patient raises high suspicion for acute infection, as these findings are common in acute PJI 1
• Do not dismiss the absence of fever or erythema—chronic infections frequently present with pain alone 2

Imaging and Aspiration Algorithm

If Inflammatory Markers Are Elevated or Clinical Suspicion Remains High:

• Proceed immediately with knee joint aspiration for synovial fluid analysis (cell count, culture, and sensitivity) to definitively rule out or confirm PJI 2, 3
• The American College of Radiology recommends joint aspiration as the most useful tool alongside CRP for diagnosing infection 1
• Withhold antibiotics for at least 2 weeks prior to aspiration if clinically feasible to avoid false-negative cultures 2

Additional Imaging Considerations:

• The normal X-ray does not exclude significant pathology—radiographs cannot directly image periprosthetic soft-tissue abnormalities 1
• If infection is excluded and mechanical issues are suspected, CT without IV contrast is the imaging modality of choice for evaluating component positioning, periprosthetic fracture, or loosening 3
• MRI without contrast may be considered as an alternative for soft tissue evaluation 3

Management Based on Findings

If Infection Is Confirmed:

• Surgical management per AAOS guidelines with aspiration cultures positive for infection 3
• This is the most serious complication, occurring in 0.8-1.9% of TKAs, and infection was responsible for 37.6% of early revisions 1

If Infection Is Excluded:

• Stiffness and pain may represent arthrofibrosis or soft tissue impingement, particularly given the recent fall 4, 5
• Physical therapy and mobilization should be instituted first 4
• If symptoms persist beyond 3 months with adequate initial range of motion, consider arthroscopic lysis of adhesions 4, 5
• Closed manipulation is most successful within the first 3 months after TKR 4

Critical Pitfalls to Avoid

• Never assume normal X-rays exclude serious pathology—53% of infected knees were not obviously infected before revision arthroplasty 1
• Never delay infection workup based on the timing of the fall—late infections can occur years after surgery and may be triggered by trauma 1
• Infection should be excluded in all patients with pain persisting >6 months after joint replacement 1
• The recent fall may have introduced bacteria or unmasked a subclinical infection 1