Can the patella tendon cause exostosis of the right knee?

Patellar Tendon and Knee Exostosis: Relationship and Management

The patellar tendon can rarely cause exostosis of the right knee, particularly at the patellar insertion site, though this is an uncommon finding that requires careful diagnostic evaluation to distinguish from other causes of bony outgrowths. 1

Pathophysiology and Clinical Presentation

Exostosis related to the patellar tendon typically presents as:

• Localized pain and tenderness at the inferior pole of the patella
• Progressive bony outgrowth that may be palpable on examination
• Functional limitations, particularly with activities requiring knee extension

Documented Cases and Mechanisms

Research has identified several potential mechanisms for patellar tendon-related exostosis:

• Surgical findings have confirmed exostosis at the patellar insertion site in athletes with chronic patellar tendon pain 1
• Heterotopic ossification within the patellar tendon has been documented following trauma or surgical procedures 2, 3
• Abnormal mechanical loading of the patellar tendon can lead to localized strain that may contribute to bony changes 4

Diagnostic Approach

Imaging Evaluation

According to the American College of Radiology guidelines:

1. Radiographs should be the initial imaging modality for knee pain with:

   • Anteroposterior and lateral views as minimum requirement
   • Additional patellofemoral view for suspected patellar abnormalities 5

2. MRI is recommended for detailed evaluation when radiographs are inconclusive:

   • Superior for detecting bone marrow contusions and occult fractures
   • Excellent for evaluating associated soft tissue abnormalities
   • Can identify inflammatory changes in the tendon 5

3. CT may be beneficial for:

   • Better characterization of bony abnormalities
   • Assessment of cortical bone involvement
   • Detection of complications like intraosseous extension 6

Differential Diagnosis

When evaluating exostosis near the patellar tendon, consider:

• Bizarre parosteal osteochondromatous proliferation (BPOP) - particularly when growth occurs after skeletal maturity 7
• Heterotopic ossification within the patellar tendon - may occur following trauma or surgery 2, 3
• Calcific tendinosis - characterized by calcium hydroxyapatite crystal deposition 6
• Solitary exostosis - typically stops growing after skeletal maturity 7

Management Approach

Conservative Management

For symptomatic patellar tendon-related exostosis:

1. First-line treatments:

   • NSAIDs for pain and inflammation
   • Relative rest and activity modification
   • Physical therapy with eccentric strengthening exercises 6

2. Second-line treatments:

   • Corticosteroid injections (limited to 2-3 injections with 4-6 weeks between injections)
   • Extracorporeal Shock Wave Therapy (ESWT) for chronic cases 6

Surgical Management

Surgical intervention should be considered if:

• Pain persists despite 3-6 months of well-managed conservative treatment
• The exostosis causes mechanical symptoms or functional limitations
• There is evidence of progressive growth 6, 1

Surgical options include:

• Excision of the exostosis
• Repair of any associated tendon damage
• Addressing any underlying pathology 1

Prognosis and Follow-up

• Most cases respond well to appropriate management
• Regular follow-up every 4-6 weeks is recommended to assess progress
• Complete resolution typically requires 3-6 months even with optimal management 6

Important Caveats

• Exostosis in unusual locations or presenting at unusual ages should prompt consideration of rare conditions like BPOP 7
• Heterotopic ossification of the patellar tendon can occur late (years) after initial injury or surgery 2
• Mechanical factors, including knee flexion angle and tendon loading patterns, may contribute to the development of pathology at the patellar tendon insertion 4