II. Pathophysiology

  1. Patellar tendon inflammation at attachment of Patellar tendon insertion at inferior pole of Patella

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. Systemic Lupus Erythematosus
    2. Rheumatoid Arthritis
    3. Chronic Renal Failure
    4. Diabetes Mellitus
    5. Paget's Disease
  4. Other associated factors
    1. Knee Local Corticosteroid Injections
    2. Repetitive Trauma to knee extensor tendon
    3. Ankle dorsiflexion Muscle Weakness (from prior ankle injury)

V. Symptoms

  1. Anterior Knee Pain
    1. Inferior Patella
    2. Proximal Patellar tendon
  2. Timing
    1. Initially: Pain after Exercise
    2. 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 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. Eccentric Exercises (decline knee bends)
    1. Flex and extend knees while standing on decline board
    2. Ankle dorsiflexion
  2. Flexibility
    1. Hamstring, heel cord and quadriceps flexibility
  3. Avoid ineffective measures (Patellar Taping, extracorporeal shock wave therapy)
  4. Surgery may be considered in refractory cases
  5. Experimental techniques
    1. Autologous blood injection into the Patellar tendon

X. Precautions

  1. Do not inject Corticosteroid (risk of Patellar Tendon Rupture)

XI. Complications

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Ontology: Patellar tendonitis (C0158317)

Concepts Disease or Syndrome (T047)
ICD9 726.64
ICD10 M76.5 , M76.50
SnomedCT 268089006, 156662006, 37785001
English Patellar tendinitis, patellar tendinitis (diagnosis), patellar tendonitis, patellar tendinitis, Patellar tendinitis, unspecified knee, Patellar ligament desmitis, Patellar tendonitis, Patellar tendonitis (disorder), patella; tendinitis, tendinitis; patella
Dutch tendinitis van patella, patella; tendinitis, tendinitis; patella, Tendinitis van patellapees
French Tendinite rotulienne
German Tendititis der Patella, Tendinitis der Patellarsehne
Italian Tendinite del rotuleo
Portuguese Tendinite rotuliana
Spanish Tendinitis rotuliana, tendinitis rotuliana (trastorno), tendinitis rotuliana, tendinitis patelar
Japanese 膝蓋腱炎, シツガイケンエン
Czech Patelární tendinitida
Korean 무릎뼈 힘줄염
Hungarian Patella tendinitis