Updated: 9/28/2018

Patella Tendon Rupture

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Introduction
  • Disruption of the tendon attaching the patella to the tibial tubercle (the patella is a sesamoid bone making this a tendon, not a ligament)
  • Epidemiology
    • incidence
      • < 0.5% of the US population per year
    • demographic
      • most commonly in 3rd and 4th decade
      • male > female 
    • location
      • quadriceps tendon rupture > patella tendon rupture
    • risk factors
      • weakening of collagen structure
        • systemic 
          • systemic lupus erythematous
          • rheumatoid arthritis
          • chronic renal disease
          • diabetes mellitus
        • local 
          • patellar degeneration (most common)
          • previous injury
          • patellar tendinopathy
        • other
          • corticosteroid injection
  • Pathophysiology
    • mechanism
      • tensile overload of the extensor mechanism
      • most ruptures occur with knee in flexed position
        • greatest forces on tendon when knee flexion > 60 degrees
        • ratio of patellar tendon force to quads tendon force >1 at <45° and <1 at >45°
          • at smaller flexion angle, patellofemoral contact point is at distal pole of patella, giving quads tendon a mechanical advantage
    • pathoanatomy
      • 3 patterns of injury
        • avulsion with or without bone from the proximal insertion/inferior pole of patella (most common)
          • strain at tendon-bone interface is 3-4x strain at midsubstance
        • midsubstance
        • distal avulsion from the tibial tubercle
    • biology
      • rupture is usually the result of end stage or long-standing chronic tendon degeneration
  • Outcome
    • most important factor is timing of repair
Anatomy
  • Extensor mechanism of the knee
    • quadriceps femoris muscles
    • quadriceps tendon
    • patella
    • patellar tendon
    • tibial tubercle
  • Forces in patellar tendon
    • ascending stairs is 3x body weight
    • to rupture a normal tendon is 17x body weight
  • Blood supply
    • infrapatellar fat pad 
    • retinacular structures (medial and lateral inferior geniculate arteries)
Presentation
  • History
    • sudden quadriceps contraction with knee in a flexed position (e.g., jumping sports, missing step on stairs)
  • Symptoms
    • infrapatellar pain
    • popping sensation
    • difficulty weight-bearing
  • Physical exam
    • inspection
      • elevation of patella height
      • usually associated with a large hemarthrosis and ecchymosis
      • localized tenderness
      • palpable gap below the inferior pole of the patella
    • motion
      • unable to perform active straight leg raise or maintain passively extended knee
      • reduced ROM of knee (and difficulty bearing weight) due to pain
        • if only tendon is ruptured and retinaculum is intact, active extension will be possible but will have extensor lag of a few degrees
Imaging
  • Radiographs
    • recommended views
      • AP and lateral of the knee
    • optional views
      • merchant or skyline 
    • findings
      • patella alta seen in complete rupture  
      • knee in flexion (ideally 30 degrees), the Insall-Salvati ratio is > 1.2 
  • Ultrasound
    • indications
      • suspected acute and chronic injuries
    • findings
      • effective at detecting and localizing disruption
      • operator and user-dependent
  • MRI
    • indications
      • differentiate partial from complete tendon rupture
      • most sensitive imaging modality
    • findings
      • site of disruption, tendon degeneration, patellar position, and associated soft tissue injuries
Treatment
  • Nonoperative
    • immobilization in full extension with a progressive weight-bearing exercise program
      • indications
        • partial tears with intact extensor mechanism
      • modalities
        • application of a removable knee splint 
        • early knee range of motion
  • Operative
    • primary repair q q q q
      • indications
        • complete patellar tendon ruptures
        • ability to approximate tendon at site of disruption
      • techniques
        • end-to-end repair
        • transosseous tendon repair
        • suture anchor tendon repair
    • tendon reconstruction
      • indications
        • severely disrupted or degenerative patella tendon
      • techniques
        • semitendinosus or gracilis tendon autograft 
          • free ends of the tendons are passed through transosseous hole of the patella, and then through a transosseous hole within the tibial tubercle to make a complete circle graft.
        • other options
          • central quadriceps tendon-patellar bone autograft
          • contralateral bone-patellar tendon-bone autograft
          • allograft
    • rehabilitation q
      • may weight bear early with protected knee extension brace
      • exercises to optimize range of motion and minimizes stress on the repair include
        • passive extension and active closed chain flexion (heel slides)  
        • prone open chain knee flexion 
Techniques
  • Direct primary repair
    • approach
      • longitudinal midline incision
      • expose rupture and adjacent retinacula
      • debride the ends of the rupture
    • end-to-end technique
      • approximate tendon at site of rupture
      • nonabsorbable sutures are woven with locking stitch
    • transosseous tendon repair 
      • suture the patellar tendon to the patella with a no.5 nonabsorbable transosseous suture
      • can be protected with a cerclage wire or nonabsorbable tape between patella and tibial tuberosity
    • postoperative care
      • immediate immobilization
      • weight-bearing status
      • rehabilitation
      • following acute primary repair with suture augmentation - immediate immobilization with full weight-bearing and controlled initiation of knee ROM at 7-10 days, goal of brace free ambulation, full knee extension, and 120 degrees of knee flexion by 6 weeks, and full return to sport at 6 months q
Complications
  • Stiffness (loss of knee flexion)
    • prevent this by starting early ROM and quads strengthening
    • treat this with MUA if flexion is <120° at 6-8wks
  • Decreased quadriceps strength
  • Quadriceps atrophy (does not compromise return of strength)
 

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Questions (7)
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(OBQ11.28) A 35-year-old male slips on a patch of ice and falls on a hyperflexed knee. He reports hearing a "pop" during the fall and was unable to bear weight on the knee immediately after the injury. He has a large knee effusion on examination. A radiograph is shown in Figure A. He undergoes operative repair of the injury with standard technique. Which of the active range of motion exercises is MOST appropriate in the immediate postoperative period? Review Topic

QID: 3451
FIGURES:
1

Leg extensions

10%

(328/3296)

2

Heel slides

83%

(2740/3296)

3

Standing squats

2%

(65/3296)

4

Rear lunges

1%

(25/3296)

5

Seated leg press

4%

(119/3296)

L 2

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(OBQ08.251) A 24-year-old basketball player feels a painful "pop" in his knee when landing from a rebound. He develops immediate swelling, pain, and inability to extend his knee. A lateral radiograph is shown in Figure A. Proper management should include which of the following Review Topic

QID: 637
FIGURES:
1

Physical therapy for range of motion followed by surgical reconstruction with patellar tendon autograft

2%

(62/2851)

2

Hinged knee brace locked at 30-degrees of flexion for 6 weeks followed by physical therapy for range of motion

1%

(21/2851)

3

Medializing tibial tubercle osteotomy with lateral retinacular release

0%

(6/2851)

4

Primary surgical repair

96%

(2746/2851)

5

Arthroscopy for debridement versus repair

0%

(11/2851)

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(OBQ07.152) A 40-year-old recreational basketball player injured his knee while jumping for a rebound. He felt a pop and developed immediate swelling. His radiographs are shown in Figures A and B. What is the recommended management? Review Topic

QID: 813
FIGURES:
1

Obtain an MRI

4%

(58/1444)

2

Ice, rest, and observation

1%

(10/1444)

3

Physical therapy to regain motion

0%

(5/1444)

4

Knee arthroscopy and repair

1%

(9/1444)

5

Open surgical repair

94%

(1359/1444)

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(OBQ06.122) Which of the following rehabilitation exercises provides for restoration of range of motion while limiting stress on the repair of a ruptured patellar tendon? Review Topic

QID: 308
1

Active open chain flexion, active closed chain extension

4%

(57/1578)

2

Passive flexion, active closed chain extension

23%

(359/1578)

3

Active closed chain flexion, active open chain extension

4%

(57/1578)

4

Active flexion, passive extension

66%

(1043/1578)

5

Passive flexion, active open chain extension

4%

(58/1578)

L 3

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