Evaluation and Management of Worsening Pes Anserine Bursitis Post-Partial Knee Replacement
Given that the last cortisone injection was a year ago and symptoms have worsened, repeat ultrasound-guided corticosteroid injection is the most appropriate next step, as it provides superior accuracy and efficacy compared to unguided injection.
Initial Diagnostic Approach
Confirm the diagnosis with ultrasound imaging to:
- Visualize bursal inflammation and fluid collection
- Rule out prosthetic complications (infection, loosening, or mechanical issues)
- Guide therapeutic injection with 92% accuracy versus 17% for unguided approaches 1
Key clinical findings to assess:
- Medial knee pain and tenderness 2-6 cm below the joint line
- Pain worsening with stair climbing or rising from sitting
- Swelling over the pes anserine insertion site
- Night pain or rest pain (suggests infection requiring urgent evaluation)
Critical red flags requiring immediate workup:
- Fever, warmth, or erythema (infection must be excluded in all post-arthroplasty patients with persistent pain >6 months) 2
- If infection suspected: obtain ESR, CRP, and joint aspiration before any injection 2
Treatment Algorithm
First-Line: Ultrasound-Guided Corticosteroid Injection
Inject triamcinolone acetonide 40 mg under ultrasound guidance 3, 4, 5:
- Ultrasound guidance is essential—unguided injections miss the bursa 83% of the time 1
- Patients with confirmed ultrasonographic bursitis show the best response to injection 6
- Expect significant improvement in pain (VAS) and function (WOMAC scores) within 1 week 5
Important caveat: Corticosteroid effects are relatively short-lived with 20-40% recurrence rates 7. However, this remains first-line therapy given the rapid onset and established efficacy 8, 9.
If Inadequate Response or Recurrence After Corticosteroid
Consider PRP (platelet-rich plasma) injection as second-line therapy:
- PRP demonstrates superior long-term outcomes compared to corticosteroids at 8 weeks 10, 5
- Lower recurrence rates than corticosteroids 7
- Particularly effective for chronic, recurrent bursitis 10
Alternative: Oxygen-ozone injection shows comparable efficacy to PRP with longer-lasting effects than corticosteroids 10
Adjunctive Conservative Measures
Implement regardless of injection choice:
- Physical therapy with active supervised exercise (not passive modalities like ultrasound or heat) 11
- NSAIDs for additional anti-inflammatory effect if no contraindications 9, 8
- Weight reduction if applicable—reduces mechanical stress on the bursa 9
- Avoid overuse for 24 hours post-injection, but do not immobilize 12
Special Considerations in Post-Arthroplasty Patients
This is a recognized but uncommon complication of knee replacement 3, 4:
- Can occur years after surgery (reported case 13 years post-op) 4
- Often responds well to local corticosteroid injection 3, 4
- Must rule out prosthetic-related issues before attributing pain solely to bursitis
Repeated corticosteroid use concerns 13:
- Minimize frequency and dose to reduce bone loss risk
- Consider calcium/vitamin D supplementation and bisphosphonates if multiple injections anticipated
- Monitor for systemic effects if injections become frequent
When to Escalate Care
Refer to orthopedic surgery if:
- No response to 2-3 ultrasound-guided injections with different agents
- Evidence of prosthetic loosening, malalignment, or infection on imaging
- Progressive functional decline despite optimal conservative management
The key differentiator: Ultrasound confirmation of bursitis predicts treatment success 6. If ultrasound shows no bursal pathology despite clinical suspicion, investigate alternative pain sources including prosthetic complications, referred pain, or concurrent knee osteoarthritis progression.