II. Pathophysiology

  1. Patellar tendon inflammation at attachment of Patellar tendon insertion at inferior pole of Patella
  2. Common cause of Anterior Knee Pain

III. Epidemiology

  1. Males affected more often (6:1 ratio)
  2. Ages 25 to 40 most often affected
  3. Tendonitis without rupture occurs in teen boys
    1. Associated with jumping sport during growth spurt

IV. Risk factors

  1. Running
    1. Jumping or bounding are more common overall than Running
  2. Athletes in jumping sports
    1. High jump
    2. Basketball
    3. Football
    4. Gymnastics
  3. Comorbid conditions
    1. Overweight (increased BMI)
    2. Systemic Lupus Erythematosus
    3. Rheumatoid Arthritis
    4. Chronic Renal Failure
    5. Diabetes Mellitus
    6. Paget's Disease
  4. Injury and Iatrogenic Causes
    1. Knee Local Corticosteroid Injections
    2. Repetitive Trauma to knee extensor tendon
  5. Structural predisposition
    1. Ankle dorsiflexion Muscle Weakness (from prior ankle injury)
    2. Leg Length Discrepancy
    3. Pes Cavus
    4. Quadriceps tightness or weakness
    5. Hamstring tightness

V. Symptoms

  1. Anterior Knee Pain
    1. Inferior Patella
    2. Proximal Patellar tendon
  2. Timing
    1. Insidious overall onset
    2. Initially: Pain after Exercise, especially prolonged Exercise and with knee flexion
    3. Later: During Exercise and while at rest

VI. Signs

  1. Focal Tenderness
    1. Inferior pole of Patella
    2. Patellar tendon body
  2. Strength
    1. Knee extension weakness
    2. Predisposing findings
      1. Ankle Dorsiflexion Weakness
      2. Hamstring tightness
      3. Heel cord tightness
      4. Quadriceps Muscle tightness
  3. Pain and decreased depth on single leg decline squat (LR+ 4 and LR- 0.5)
    1. Extend unaffected knee
    2. Squat with affected leg

VII. Differential Diagnosis

  1. Patellofemoral Pain Syndrome
  2. Patellar tendon soft tissue lesion

VIII. Imaging

  1. Patellar tendon Ultrasound
  2. Knee XRay
    1. Patella inferior pole irregularity
  3. MRI Knee
    1. Patellar Tendonitis may appear as False Positive partial Patellar Tendon Rupture

IX. Management

  1. Relative rest
  2. Cold therapy (Cryotherapy)
  3. NSAIDs
  4. Patellar Tendon Strap (Patellar counterforce brace)
    1. May decrease pain and increase function
  5. Eccentric Exercises (decline knee bends)
    1. Flex and extend knees while standing on decline board
    2. Ankle dorsiflexion
  6. Flexibility
    1. Hamstring, heel cord and quadriceps flexibility
  7. Other non-surgical measures in refractory cases (45% of patients)
    1. Corticosteroid Injection
      1. Risk of Patellar Tendon Rupture (Exercise caution!)
    2. Topical Nitroglycerin Patch (one quarter of 5 mg patch)
    3. Extracorporeal shock wave therapy
  8. Avoid ineffective measures (Patellar Taping, extracorporeal shock wave therapy)
  9. Surgery may be considered in refractory cases
  10. Experimental techniques
    1. Autologous blood injection into the Patellar tendon

X. Complications

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