Patellar Tendinopathy

Aka: Patellar Tendinopathy, Jumper's Knee, Patellar Tendonitis

1. See Also
   1. Patellar Tendon Rupture
2. Pathophysiology
   1. Patellar tendon inflammation at attachment of Patellar tendon insertion at inferior pole of Patella
   2. Common cause of Anterior Knee Pain
3. 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
4. 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
5. 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
6. 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
7. Differential Diagnosis
   1. Patellofemoral Pain Syndrome
   2. Patellar tendon soft tissue lesion
8. 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
9. 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
10. Complications
    1. Patellar Tendon Rupture
11. References
    1. Madden (2010) Netter's Sports Medicine, p. 425
    2. Arnold (2018) Am Fam Physician 97(8): 510-6 [PubMed]
    3. Kane (2019) Am Fam Physician 100(3): 147-57 [PubMed]
    4. Levine (1996) Postgrad Med 100(2): 241-246 [PubMed]