What is the likely cause and recommended management for medial right‑knee pain and leg heaviness on standing after prolonged sitting in a patient who recently completed a course of prednisolone for minimal‑change disease and received two rituximab infusions, now practicing yoga?

Medial Knee Osteoarthritis with Corticosteroid-Related Musculoskeletal Effects

Your medial right knee pain with stiffness after prolonged sitting ("start-up pain") is most consistent with knee osteoarthritis, likely exacerbated by your recent prolonged prednisolone exposure for MCD, and should be managed with a structured exercise program as first-line therapy, combined with weight optimization if applicable.

Clinical Assessment

Your symptom pattern is classic for knee OA:

• Start-up pain: Pain when rising from sitting that improves with walking is pathognomonic for osteoarthritis 1
• Medial compartment involvement: Most common pattern in knee OA
• Leg heaviness: Consistent with deconditioning and possible mild effusion

Corticosteroid Considerations

Your 2-year prednisolone course for MCD creates additional concerns:

• Prolonged corticosteroid exposure can accelerate cartilage degradation and cause steroid-induced myopathy
• The rituximab you received 2 is appropriate for MCD management and helps minimize future steroid exposure 3, 4
• Leg heaviness may reflect steroid-induced muscle weakness, which improves with targeted exercise

Important caveat: While low-dose prednisolone (7.5 mg/day) can reduce knee OA pain short-term 5, you should NOT restart corticosteroids given your recent prolonged exposure and successful rituximab therapy for MCD.

Evidence-Based Treatment Algorithm

First-Line (Strongly Recommended) 1

1. Exercise program (strongest recommendation):

   • Start with low-impact activities: swimming, cycling, or yoga (which you're already doing—excellent)
   • Progress to strengthening exercises targeting quadriceps and hip muscles
   • Supervised programs enhance effectiveness

2. Weight management (if BMI >25):

   • Even 5-10% weight loss significantly reduces knee loading

3. Self-management education:

   • Understanding OA natural history
   • Activity pacing strategies

Second-Line Pharmacologic Options 1

For localized medial knee pain:

• Topical NSAIDs (strongly recommended for knee OA): Apply to medial knee 3-4 times daily
  • Lower systemic side effects than oral NSAIDs
  • Particularly appropriate given your renal history (MCD)

If topical therapy insufficient:

• Oral NSAIDs (strongly recommended): Use lowest effective dose for shortest duration
  • Critical: Monitor renal function closely given your MCD history
  • Consider gastroprotection if risk factors present

Alternative oral agents (conditional recommendations):

• Acetaminophen: Limited efficacy but safest profile
• Duloxetine: Consider if neuropathic component or concurrent depression
• Tramadol: Reserve for refractory cases due to addiction potential

Interventional Options 1

Intra-articular glucocorticoid injection (strongly recommended):

• Provides 4-12 weeks of relief
• Reasonable option for acute flares
• Can be repeated every 3-4 months if needed
• Note: Single injections are safe despite your steroid history

Avoid:

• Intra-articular hyaluronic acid: Not recommended in current guidelines 1

Yoga-Specific Guidance

Continue your yoga practice (conditional recommendation for yoga in knee OA 1):

• Modify poses that stress the medial knee (deep squats, lotus position)
• Focus on poses that strengthen hip abductors and quadriceps
• Avoid prolonged kneeling or deep knee flexion initially
• Use props (blocks, straps) to reduce knee stress

Red Flags Requiring Urgent Evaluation

Seek immediate assessment if you develop:

• Sudden severe pain or inability to bear weight
• Significant knee swelling or warmth (infection risk post-rituximab)
• Locking or true mechanical catching (suggests meniscal tear)
• Recurrence of proteinuria or edema (MCD relapse)

Monitoring Considerations

Given your immunosuppressed state (recent rituximab 2):

• Be vigilant for joint infections (septic arthritis can mimic OA flare)
• Any fever with joint pain requires urgent evaluation
• Continue monitoring for MCD relapse as planned with your nephrologist

Prognosis

With appropriate conservative management, most patients experience significant symptom improvement within 6-12 weeks 1. Your young age (implied by recent MCD diagnosis) and engagement in yoga are favorable prognostic factors. The "start-up pain" pattern typically responds well to regular exercise and activity modification.

Surgical referral (joint replacement) is only indicated for end-stage OA with minimal joint space and failure of all conservative measures—not applicable to your current presentation 1, 6.