What is the best course of treatment for a 53-year-old female with a history of left knee replacement, depression, hypertension, fluid retention, nausea, allergies, overactive bladder, chronic eczema, gastroesophageal reflux disease, vitamin D deficiency, and macrocytic anemia, who presents with persistent left knee pain that worsened after prolonged walking and standing, and has a small open wound with minimal drainage at the surgical site?

Management of Post-Knee Replacement Pain with Wound Concerns

This patient requires urgent orthopedic evaluation for possible prosthetic joint infection (PJI), and the oral antibiotic already prescribed should be continued while awaiting specialist assessment. 1

Immediate Infection Risk Assessment

The combination of a dehisced surgical wound with drainage, even minimal, in the context of a knee replacement warrants serious concern for PJI, which occurs in 0.8-1.9% of total knee arthroplasties and represents the most serious complication. 1

Key Clinical Features Present in This Case:

• Persistent pain (described as "piercing") is the most common presenting symptom of infection, though it is nonspecific 1
• Wound dehiscence with drainage (yellow to clear, 2mm opening) represents a potential portal for bacterial entry and possible ongoing infection 1
• Recent scab manipulation increases infection risk through breach of healing tissue 1
• Pain at rest or night pain is more characteristic of infection than mechanical loosening (pain on weight-bearing suggests mechanical issues) 1

Critical Diagnostic Steps Required:

Laboratory testing should include:

• C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are the most useful initial tests for diagnosing PJI 1
• CRP has 73-91% sensitivity and 81-86% specificity when cutoff ≥13.5 mg/L is used 1
• ESR is abnormal in infected patients but can also be elevated in uninfected patients 1
• Peripheral leukocyte counts are typically NOT elevated in most patients with infected prostheses 1

Imaging should include:

• Plain radiographs are appropriate for initial evaluation of suspected periprosthetic infection 1
• Look for signs of loosening, lucency around components, or early osteolysis 1

Antibiotic Management

The prescribed oral antibiotic (appears to be 500mg BID for 7 days) should be continued as empiric coverage for potential wound infection or early PJI. 1

Important Considerations:

• Oral antibiotics at day 7 are non-inferior to 6 weeks of IV therapy for bone and joint infections, with lower complication rates (fewer catheter-related infections) 1
• If PJI is confirmed, antimicrobial therapy duration depends on surgical management strategy 1
• Staphylococcus aureus and coagulase-negative Staphylococcus (including S. epidermidis) are the most common organisms in post-TKA infections 1

Pain Management Strategy

Do NOT increase gabapentin dose at this time until infection is ruled out, as the pain may be infection-related rather than neuropathic. 1

Appropriate Pain Control While Evaluating for Infection:

• Acetaminophen should be the preferred first-line analgesic (maximum 4 grams/day) 1
• Topical NSAIDs can be applied for localized pain relief with minimal systemic exposure 1, 2
• Oral NSAIDs at the lowest effective dose for shortest duration if acetaminophen insufficient 1, 2
• Continue alternating heat/cold therapy and elevation 1

Critical Caveat:

Only 15% of TKR patients report severe-extreme persistent pain at 3-4 years post-surgery, and 44% report some persistent pain of any severity. 3 However, infection must be excluded in all patients with pain persisting >6 months after joint replacement. 1

Wound Care

The small open area requires:

• Daily inspection for signs of worsening infection (increasing redness, warmth, purulent drainage, foul odor) 1
• Keep clean and dry 1
• Avoid further manipulation of the healing tissue 1
• Monitor for systemic signs (fever, chills) 1

Urgent Orthopedic Referral Indications

This patient meets criteria for urgent (not routine) orthopedic evaluation because:

• Wound dehiscence with drainage in post-TKA patient 1
• Persistent pain despite conservative measures 1
• Need for potential joint aspiration if clinical suspicion and laboratory markers suggest infection 1

The scheduled orthopedic appointment should be moved up rather than waiting for the routine appointment date. 1

Common Pitfalls to Avoid

• Do not dismiss minimal drainage as insignificant in a post-TKA patient—even low-grade chronic infections may present with pain alone 1
• Do not delay infection workup based on absence of fever, warmth, or elevated white blood cell count—these are often absent in chronic PJI 1
• Do not attribute all post-TKA pain to overuse without excluding infection, especially with wound concerns 1
• Do not increase neuropathic pain medications (gabapentin) without first ruling out infection as the pain source 1
• Do not rely solely on clinical examination—CRP and ESR are essential diagnostic tools 1

Additional Management Considerations

For the generalized knee swelling and non-pitting edema:

• This may represent inflammatory response to infection or mechanical irritation 1
• Elevation and compression when appropriate 1
• Avoid aggressive physical therapy until infection excluded 1

Regarding the patient's multiple comorbidities:

• Depression is associated with worse persistent post-surgical pain outcomes 3, 4
• Fluid retention and hypertension require careful NSAID selection if needed (consider topical over oral) 1, 2
• Macrocytic anemia may limit certain antibiotic choices if prolonged therapy needed 1