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Basics ⬇

Author(s): Sean T.Bryan, MD, FAAFP, CAQSM and Isaac P.Syrop, MD

Description

  • Overuse syndrome of the patellar and/or quadriceps tendons/knee extensor mechanism complex
  • Anterior knee pain worsened by activity such as jumping or running
  • Also termed “jumper’s knee”

Epidemiology

Prevalence

  • Commonly seen in athletes who participate in sports with excessive jumping or running (volleyball, basketball, soccer, track and field)
  • Prevalence is estimated to be 40–50% among high-level volleyball players and 35–40% among elite basketball players (1,2).
  • Affects males and females equally

Risk-Factors

  • Participation in a sport with excessive “jumping” (volleyball, basketball)
  • Risk increases with training volume and intensity (3).
  • Poor flexibility of quadriceps and hamstrings
  • Anatomic variants that can lead to abnormal repetitive biomechanical stresses such as patella alta, patella baja, or patellar malalignment/maltracking
  • Use of a fluoroquinolone antibiotic within the past 90 days (4)
  • Underlying connective tissue disease such as rheumatoid arthritis or ankylosing spondylitis (5)

Etiology and Pathophysiology

  • Histopathology shows (6):
    • Collagen degeneration and disorganization/disruption of normal parallel arrangement of fibrils.
    • Microscopic to macroscopic intrasubstance tendon tears can occur.
    • Increase in mucoid ground substance.
    • Fibroblast proliferation.
    • Neovascularization.
    • Intratendinous calcifications with gritty toothpaste-like consistency can occur.
  • More accurately termed tendinopathy which includes the full spectrum of disease from tendinitis (early stage lasting about 1 wk when inflammatory cells are present) to tendinosis (end stage after months to years when tendon is thickened and has central mucoid degeneration)

Diagnosis ⬆ ⬇

History

  • Anterior knee pain exacerbated by activity or by prolonged knee flexion
  • Participation in a sport with excessive jumping
  • A progressive condition of anterior knee pain (Blazina classification) (7):
    • Phase 1: pain after activity
    • Phase 2: pain during and after activity not affecting performance
    • Phase 3: pain during and after activity impeding performance

Physical Exam

  • Patellar tendinitis: localized tenderness at the patellar tendon origin (inferior pole of the patella), patellar tendon midportion, and/or patellar tendon insertion (tibial tubercle)
  • Quadriceps tendinitis: localized tenderness at the quadriceps tendon midportion and/or quadriceps tendon insertion (superior pole of the patella)
  • Both: pain reproduced with extension of the knee versus resistance and/or with maximal stretching of the quadriceps
  • Both: poor flexibility of the quadriceps and hamstrings

Differential Diagnosis

  • Patellofemoral pain syndrome
  • Hoffa disease (fat pad impingement)
  • Osgood-Schlatter disease
  • Sinding-Larsen-Johansson syndrome
  • Chondromalacia patella/patellofemoral osteoarthritis
  • Osteochondral lesions
  • Patellar subluxation/dislocation
  • Patellar stress fracture
  • Patellar tendon rupture (partial or complete)
  • Quadriceps tendon rupture (partial or complete)
  • Lumbar radiculitis/radiculopathy involving the L3 and/or L4 nerve roots

Diagnostic Tests & Interpretation

  • Patellar/quadriceps tendinitis remains a clinical diagnosis, and routine imaging is neither required nor recommended.
  • Plain film radiographs may show occasional intratendinous calcification.
  • Magnetic resonance imaging (MRI) may reveal increased signal within the patellar or quadriceps tendon and/or at the junction with the patella (6).
  • Ultrasound (US) may reveal focal hypoechoic areas in the patellar or quadriceps tendon and/or neovascularization on color Doppler flow (6).
  • The study of choice and relevance of abnormalities remain somewhat controversial.

Treatment ⬆ ⬇

Medication

  • Conservative measures typically include relative rest (reduction in amount or intensity of training to achieve pain-free state), ice, acetaminophen, and/or nonsteroidal anti-inflammatory drugs (NSAIDs).
  • NSAIDs are commonly used as analgesics and may be beneficial for acute symptoms; however, there is a lack of evidence showing benefits in chronic cases.
  • Topical nitroglycerin (patches/ointments) have been shown to reduce pain during activities of daily living in the acute and chronic phases and may help enhance tendon forces in the chronic phase (8).

Additional Therapies

  • Mainstay treatment is stretching and strengthening exercises for the quadriceps to improve flexibility and stimulate tendon tissue repair via mechanotransduction (9).
  • Eccentric strengthening exercises of the quadriceps, mainly single leg squats with a slow negative phase, have been shown to decrease pain and improve function in volleyball players after 3 mo and 12 mo, and doing these squats on a 25-degree decline board may provide additional clinical benefit at 12 mo in athletes participating with pain (10).
  • Correction of biomechanical abnormalities (if possible) and/or training errors
  • Wearing a patellar tendon strap has been shown to decrease localized tendon strain forces and may help reduce symptoms during sports participation (11).

Surgery/Other Procedures

  • Iontophoresis/phonophoresis
  • Percutaneous interventions for those who fail conservative therapy for >6 mo (under US guidance):
    • Needle tenotomy
    • Platelet-rich plasma (PRP)
    • Prolotherapy
    • Tendon scraping or hydrodissection, separating the peritenon/fat pad from the tendon, disrupting the neovessels and nerves
    • Ultrasonic tenotomy (Tenex procedure)
  • Extracorporeal shock wave therapy (ECSWT) directed at areas of tendinopathy
  • Open surgical tenotomy may be considered for patients who fail to respond to 6 mo of conservative measures and/or who fail to respond to the above-mentioned less invasive procedures.
  • No randomized trials have been able to clearly demonstrate superior efficacy of one procedure or surgical technique over others.
ALERT

Steroid injections into a tendon should be avoided due to the risk of tendon rupture.

Ongoing Care ⬆ ⬇

Corticosteroid injections into the patellar tendon or quadriceps tendon should be avoided due to the theoretical increased risk of tendon rupture.

Additional Reading ⬆ ⬇

  • Everhart JS, Cole D, Sojka JH, et al. Treatment options for patellar tendinopathy: a systematic review. Arthroscopy. 2017;33(4):861–872.
  • Schwartz A, Watson JN, Hutchinson MR. Patellar tendinopathy. Sports Health. 2015;7(5):415–420.

References ⬆ ⬇

  1. Bahr R, Fossan B, Løken S, et al. Surgical treatment compared with eccentric training for patellar tendinopathy (jumper’s knee). A randomized, controlled trial. J Bone Joint Surg Am. 2006;88(8):1689–1698.
  2. Lian OB, Engebretsen L, Bahr R. Prevalence of jumper’s knee among elite athletes from different sports: a cross-sectional study. Am J Sports Med. 2005;33(4):561–567.
  3. Peers KH, Lysens RJ. Patellar tendinopathy in athletes: current diagnostic and therapeutic recommendations. Sports Med. 2005;35(1):71–87.
  4. Hall MM, Finnoff JT, Smith J. Musculoskeletal complications of fluoroquinolones: guidelines and precautions for usage in the athletic population. PM R. 2011;3(2):132–142.
  5. Matschke V, Jones JG, Lemmey AB, et al. Patellar tendon properties and lower limb function in rheumatoid arthritis and ankylosing spondylitis versus healthy controls: a cross-sectional study. ScientificWorldJournal. 2013;2013:514743.
  6. Khan KM, Bonar F, Desmond PM, et al. Patellar tendinosis (jumper’s knee): findings at histopathologic examination, US, and MR imaging. Victorian Institute of Sport Tendon Study Group. Radiology. 1996;200(3):821–827.
  7. Blazina ME, Kerlan RK, Jobe FW, et al. Jumper’s knee. Orthop Clin North Am. 1973;4(3):665–678.
  8. Gambito ED, Gonzalez-Suarez CB, Oquiñena TI, et al. Evidence on the effectiveness of topical nitroglycerin in the treatment of tendinopathies: a systematic review and meta-analysis. Arch Phys Med Rehabil. 2010;91(8):1291–1305.
  9. Khan KM, Scott A. Mechanotherapy: how physical therapists’ prescription of exercise promotes tissue repair. Br J Sports Med. 2009;43(4):247–252.
  10. Young MA, Cook JL, Purdam CR, et al. Eccentric decline squat protocol offers superior results at 12 months compared with traditional eccentric protocol for patellar tendinopathy in volleyball players. Br J Sports Med. 2005;39(2):102–105.
  11. Lavagnino M, Arnoczky SP, Dodds J, et al. Infrapatellar straps decrease patellar tendon strain at the site of the jumper’s knee lesion: a computational analysis based on radiographic measurements. Sports Health. 2011;3(3):296–302.

Clinical Pearls ⬆

  • Patellar/quadriceps tendinopathy remains a clinical diagnosis, and the mainstay of treatment is strengthening of the quadriceps muscles via one-legged squats emphasizing the eccentric (negative) phase for a prolonged period of time (6 mo to 1 yr) which promotes the slow and gradual process of microscopic tendon repair via mechanotransduction.
  • Evidence suggests that topical nitroglycerin decreases pain in the acute and chronic phases of patellar tendinopathy and may help increase patellar tendon forces in the chronic phase.
  • If the diagnosis is in question or if the patient is not responding to an appropriate course of conservative measures including eccentric quadriceps strengthening exercises, then patellar/quadriceps tendinopathy can be confirmed by either MRI or US.
  • If the patient is not responding to an appropriate course of conservative measures after 6 mo and patellar/quadriceps tendinopathy is confirmed by either MRI or US, then ECSWT or minimally invasive US-guided procedures (percutaneous needle tenotomy [PNT], PRP, prolotherapy, or Tenex) or open surgical tenotomy can be considered.