What are the appropriate management steps for a patient experiencing left groin pain after left Total Knee Arthroplasty (TKA) surgery?

Management of Left Groin Pain After Left Total Knee Arthroplasty

Left groin pain after left TKA is an atypical presentation that requires immediate evaluation to exclude occult ipsilateral hip fracture, followed by systematic assessment for referred pain from the knee, nerve injury, or vascular complications.

Initial Diagnostic Approach

Immediate Imaging Requirements

• Obtain radiographs of the ipsilateral hip and pelvis immediately to exclude occult hip fracture, which can present as groin pain after lower extremity surgery 1
• If initial radiographs are negative but clinical suspicion remains high (pain with hip rotation, inability to bear weight), obtain MRI of the hip within 48-72 hours, as basicervical and femoral neck fractures may not be visible on plain films initially 1
• Obtain knee radiographs if not recently performed to evaluate for TKA-related complications that may refer pain 1

Critical Clinical Examination Points

• Assess for hip-specific pain: increased discomfort with internal and external rotation of the hip suggests hip pathology rather than knee-related issues 1
• Evaluate for signs of infection: night pain or pain at rest is characteristic of infection, whereas pain on weight bearing suggests mechanical loosening 1
• Check for vascular complications: repeated hemarthroses from synovial hyperemia or arteriovenous malformations can occur and may present with groin discomfort 1

Differential Diagnosis and Specific Evaluations

Hip-Related Causes (Most Critical to Exclude)

• Occult hip fracture: Most dangerous missed diagnosis, particularly basicervical or femoral neck fractures that may be radiographically occult initially 1
• Iliopsoas tendinitis/impingement: Can occur after lower extremity surgery, presents with groin pain and pain with hip flexion 2, 3, 4
• Stress fracture of the hip: May develop from altered gait mechanics post-TKA 4

Knee-Related Referred Pain

• Periprosthetic infection: Most serious TKA complication (0.8-1.9% incidence), can present with atypical pain patterns 1, 5
• Aseptic loosening: Most common late failure mechanism (39.9% of revisions) 5, 6
• Component malalignment or instability 5, 6

Neurologic Causes

• Lateral femoral cutaneous, ilioinguinal, iliohypogastric, or genitofemoral nerve injury can cause groin pain and may occur from positioning or surgical approach 7
• Femoral nerve complications from femoral nerve block (if used for analgesia) 1

Algorithmic Management Strategy

If Hip Fracture is Identified

• Immediate orthopedic consultation for surgical fixation 1
• VTE prophylaxis should be initiated 1
• Weight-bearing restrictions until surgical stabilization 1

If Hip Fracture is Excluded and Infection is Suspected

• Check ESR and CRP: CRP >13.5 mg/L has 73-91% sensitivity for prosthetic infection 1
• Perform knee joint aspiration for culture if infection suspected 1
• If aspiration is positive, proceed to surgery without additional imaging 1
• If aspiration is negative but infection still suspected, reaspiration is appropriate 1

If Iliopsoas Tendinitis is Suspected

• Diagnostic/therapeutic injection with local anesthetic into iliopsoas muscle under fluoroscopic guidance can confirm diagnosis 2
• Non-operative management includes physical therapy with high-grade joint mobilization and targeted exercise 3
• Botulinum toxin A injection (100 units) into iliopsoas muscle may provide significant relief 2
• Surgical iliopsoas tenotomy if conservative measures fail 4

If Vascular Complication is Suspected

• Angiography can diagnose arteriovenous malformations or synovial hyperemia causing repeated hemarthroses 1
• Embolization may be therapeutic 1

If Nerve Injury is Suspected

• Diagnostic nerve blocks can identify specific nerve involvement 7
• Surgical options include neurolysis for lateral femoral cutaneous nerve or resection for ilioinguinal, iliohypogastric, or genitofemoral nerves 7

Pain Management During Evaluation

• Multimodal analgesia with paracetamol plus NSAIDs or COX-2 inhibitors 1, 8
• Strong opioids for breakthrough high-intensity pain, weak opioids for moderate pain 1
• Avoid premature surgical intervention for unexplained pain, as reoperation without clear diagnosis is frequently associated with suboptimal results 5

Common Pitfalls to Avoid

• Never dismiss groin pain as "normal" post-TKA pain: This is an atypical location requiring thorough evaluation 1, 4
• Do not delay hip imaging: Occult hip fractures can worsen with continued weight-bearing 1
• Avoid attributing all pain to the surgical knee: 10-30% of TKA patients have ongoing pain, but groin pain specifically suggests alternative pathology 5, 6
• Do not proceed to revision surgery without definitive diagnosis: Unexplained pain with negative workup should not prompt surgical intervention 5