Updated: 5/14/2022

Patellar Tendon Rupture

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  • Summary
    • A traumatic rupture of the patellar tendon caused by a tension overload during activity in a patient at risk.
    • Diagnosis can be confirmed by physical exam and radiographs for complete tears. Partial tears may need an MRI to confirm the diagnosis.
    • Treatment for complete tears is timely surgical repair to optimize the chance of healing. Partial tears with an intact extensor mechanism may be treated with immobilization.
  • Epidemiology
    • Incidence
      • rare
        • affects < 1 per 100,000 people annually
    • Demographic
      • most commonly in 3rd and 4th decade
      • male > female
    • Anatomic location
      • quadriceps tendon rupture is more common than patella tendon rupture (2:1 ratio)
    • Risk factors
      • may see weakening of collagen structure
        • systemic diseases
          • associated with bilateral ruptures
            • diabetes mellitus
            • systemic lupus erythematous
            • rheumatoid arthritis
            • chronic renal disease
        • local
          • patellar degeneration (most common)
          • previous injury
          • patellar tendinopathy
        • other
          • corticosteroid injection
  • Etiology
    • Pathophysiology
      • mechanism of injury
        • tensile overload of the extensor mechanism
          • sudden quadriceps contraction with knee in a flexed position (e.g., jumping sports, missing step on stairs)
        • 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
      • pathobiology
        • rupture is usually the result of end stage or long-standing chronic tendon degeneration
    • Associated conditions
      • orthopedic conditions
        • tibial tubercle avulsion
        • patella fractures
        • TKA extensor mechanism rupture
  • Anatomy
    • Extensor mechanism of the knee
      • quadriceps tendon
      • patella
      • patellar tendon
      • tibial tubercle
    • Blood supply
      • infrapatellar fat pad
      • retinacular structures (medial and lateral inferior geniculate arteries)
    • Biomechanics
      • Forces in patellar tendon
        • ascending stairs is 3x body weight
        • to rupture a normal tendon is 17x body weight
  • Classification
    • Anatomic
      • incomplete tear
        • intact extensor mechanism
        • in some cases can be treated noperatively
      • complete tear
        • patella alta with palpable defect
        • treated with surgical repair
  • Presentation
    • History
      • history of jumping event with sudden quadriceps contraction with knee in a flexed position (e.g., jumping sports, missing step on stairs)
        • patient will often hear/feel a popping sensation
    • Symptoms
      • infrapatellar pain
      • immediate swelling
      • 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
        • 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
      • provocative tests
        • straight leg raise
          • unable to perform active straight leg raise or maintain passively extended knee
  • Imaging
    • Radiographs
      • recommended views
        • AP and lateral of the knee
          • knee in flexion (ideally 30 degrees)
      • optional views
        • merchant or skyline
      • findings
        • patella alta seen in complete rupture
        • various measurements indicating patella alta
          • Insall-Salvati ratio is > 1.2
            • normal between 0.8 and 1.2
          • Blackburne-Peel ratio > 1.0
            • normal between 0.5 and 1.0
          • Caton Deschamps ratio > 1.3
            • normal between 0.6 and 1.3
    • 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
    • Ultrasound
      • indications
        • suspected acute and chronic injuries
      • findings
        • effective at detecting and localizing disruption
        • operator and user-dependent
  • Diagnosis
    • Complete tears
      • can be confirmed by physical exam and radiographs for complete tears. 
    • Partial tears
      • partial tears may need an MRI to confirm the diagnosis.
  • Treatment
    • Nonoperative
      • immobilization in full extension
        • indications
          • partial tears with intact extensor mechanism
        • modalities
          • immobilization
            • hinged knee brace locked in extension for 6 weeks with weight bearing
          • rehabilitation
            • progressive active flexion / passive extension protocol
    • Operative
      • primary repair
        • 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
        • rehabilitation
          • locked extension brace with immediate weight bearing for 6 weeks
          • early motion protocol at 7-10 days with focus on passive extension and active flexion
        • outcomes
          • biomechanical studies have shown less gap formation with suture anchor repair compared to transosseous repair
          • clinical studies have shown a significant decrease in re-rupture rate with use of suture anchor compared to transosseous repair.
      • tendon reconstruction
        • indications
          • severely disrupted or degenerative patella tendon
          • chronic tears > 6-8 weeks out from injury
        • techniques
          • ipsilateral semitendinosus or gracilis autograft
          • central quadriceps tendon-patellar bone autograft
          • contralateral bone-patellar tendon-bone autograft or allograft
  • Techniques
    • Nonoperative Treatment - Immobilization
      • protocol similar to post-operative protocol below
    • Direct primary repair
      • approach
        • longitudinal midline incision
        • expose rupture and adjacent retinacula
        • debride the ends of the rupture
        • for subacute tears (> 2 weeks out from injury)
          • quadplasty or scar tissue release to facilitate tendon approximation
      • technique
        • 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 #5 non-absorbable transosseous suture
          • drill 2 trans-patellar bony tunnels and pass the sutures through tunnels and tie over the top of patella
          • can be protected with a cerclage wire or nonabsorbable tape between patella and tibial tuberosity
        • suture anchor tendon repair
          • number of anchors debatable
            • most authors advocate for at least 2 anchors
      • postoperative rehabilitation
        • weight bearing
          • may weight bear early with protected knee brace locked in extension
          • goal of brace free ambulation by 6 weeks
        • early motion
          • begins at 7-10 days
          • controlled initiation of knee ROM at 7-10 days
          • 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
          • goal of brace free ambulation, full knee extension, and 120 degrees of knee flexion by 6 weeks, and
        • return to sport
          • full return to sport at 6 months
    • Tendon reconstruction
      • approach
        • retracted patella may require extensive surgical release
          • quadplasty
          • release of scar tissue
      • technique
        • graft sources
          • autograft
            • ipsilateral gracilis, semitendinous, and quadriceps autografts have all been used
          • allograft tendon or ligament
        • technique
          • 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
  • Complications
    • Knee stiffness
      • incidence
        • most common complication
      • risk factors
        • delay in surgical treatment
        • delay in initiating post-operative range of motion
      • treatment
        • manipulation under anesthesia (MUA)
          • if flexion is <120° at 6-12 weeks post-op
        • lysis of adhesions
          • if flexion is < 120° after >12 weeks post-op
    • Re-tear
      • incidence
        • ~8% with transosseous direct primary repair
          • 1-2% following suture anchor repair
      • treatment
        • primary repair
          • if acute and adequate tendon quality remains
        • reconstruction
          • chronic lesions
          • poor tendon quality
    • Infection
      • incidence
        • ~2% following surgery
    • Quadriceps atrophy
      • incidence
        • 2nd most common complication
          • does not compromise return of strength
      • treatment
        • physical therapy
  • Prognosis
    • Outcome with treatment
      • excellent outcomes seen with early repair
    • Prognostic variables
      • most important prognostic factor for complete tears is timing of repair
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Questions (8)
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(OBQ16.51) A 67-year-old man feels a pop and has an immediate onset of pain and swelling after awkwardly stepping off of a curb. Preoperative Xrays are shown in figure A. He undergoes the surgery depicted in Figure B. What would be the most likely finding pre-operatively?

QID: 8813

Insall-Salvati ratio of 1



Insall-Salvati ratio of 0.7



Insall-Salvati ratio of 1.3



MRI showing complete quadriceps tendon rupture



Maintained ability to perform a straight leg raise



L 2 B

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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?

QID: 3451

Leg extensions



Heel slides



Standing squats



Rear lunges



Seated leg press



L 2 C

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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

QID: 637

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



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



Medializing tibial tubercle osteotomy with lateral retinacular release



Primary surgical repair



Arthroscopy for debridement versus repair



L 1 D

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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?

QID: 813

Obtain an MRI



Ice, rest, and observation



Physical therapy to regain motion



Knee arthroscopy and repair



Open surgical repair



L 1 C

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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?

QID: 308

Active open chain flexion, active closed chain extension



Passive flexion, active closed chain extension



Active closed chain flexion, active open chain extension



Active flexion, passive extension



Passive flexion, active open chain extension



L 3 C

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Evidence (46)
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