What is the diagnosis and appropriate management of a high‑riding patella (patella alta) presenting with acute knee pain and inability to extend the knee?

High-Riding Patella: Diagnosis and Management

Primary Recommendation

A high-riding patella (patella alta) presenting with acute knee pain and inability to extend the knee indicates patellar tendon rupture until proven otherwise, requiring immediate surgical repair within days to weeks for optimal functional recovery. 1, 2

Clinical Diagnosis

The diagnosis is primarily clinical and should be suspected when the following triad is present:

• Palpable defect in the patellar tendon substance 1, 3
• Inability to actively extend the knee against gravity or maintain extension 1, 2
• Localized tenderness over the patellar tendon with visible/palpable soft tissue swelling 2, 3

Imaging Approach

Initial Radiographic Assessment

Obtain standard knee radiographs immediately (anteroposterior and lateral views at 25-30 degrees of flexion) as first-line imaging: 4

• Lateral radiograph will demonstrate patella alta, confirming extensor mechanism disruption 1, 3
• Look for suprapatellar soft tissue swelling and posterior tibial subluxation as additional radiographic signs of tendon rupture 5, 1
• Radiographs may also reveal bony avulsions or dystrophic calcifications within the tendon 5

Advanced Imaging When Needed

• Ultrasound or MRI should be obtained if the diagnosis is uncertain, to identify partial tears, or when the presentation is delayed and clinical findings are less obvious 1, 2, 3
• These modalities confirm the diagnosis and reveal associated injuries that may affect surgical planning 1

Management Algorithm

Complete Ruptures (Inability to Extend Knee)

Early surgical reconstruction is mandatory and represents the single most important prognostic factor for success: 2, 3

1. Timing is critical: Surgery should be performed within days to weeks of injury 2, 3

   • Delayed repair (>3-4 weeks) significantly compromises outcomes with loss of knee flexion and decreased quadriceps strength 3
   • Time to surgery remains the most important prognosticator for functional recovery 2

2. Surgical technique options include: 2

   • Transosseous tunnel repair through the patella
   • Suture anchor fixation
   • End-to-end tendon repair
   • Reinforcing cerclage suture for additional stability 3
   • Repair of torn extensor retinacula 3

3. Post-operative rehabilitation: 2, 3

   • Early range-of-motion exercises (aggressive program)
   • Protected weight-bearing initially
   • Progressive quadriceps strengthening
   • Return to sport expected by 6 months 2

Partial/Incomplete Tears (Some Extension Preserved)

Nonsurgical management with immobilization and progressive rehabilitation can be attempted for incomplete tears: 2

• Immobilization in extension initially
• Gradual progression to weight-bearing and range of motion
• Quadriceps strengthening program 6

Critical Pitfalls to Avoid

Do not delay surgical intervention in complete ruptures—every week of delay worsens the prognosis due to tendon retraction, quadriceps atrophy, and scar tissue formation 2, 3

Recognize predisposing factors that increase rupture risk: 3

• Chronic tendinopathy from repetitive microtrauma
• Systemic illness affecting tendon quality
• Local or systemic corticosteroid use
• Prior knee surgeries or devascularization 7

In post-total knee arthroplasty patients, patella alta may indicate extensor mechanism disruption requiring urgent evaluation, as the incidence of these complications is 0.17% to 2.5% but carries high morbidity 5, 7