Introduction
Background
Blazina et al first used the term jumper's knee (patellar tendinopathy, patellar tendinosis, patellar tendinitis) in 1973 to describe an insertional tendinopathy seen in skeletally mature athletes,1 although Sinding-Larson, Johansson, and Smillie once described this condition. Jumper's knee usually affects the attachment of the patellar tendon to the inferior patellar pole. The definition was subsequently widened to include tendinopathy of the attachment of the quadriceps tendon to the superior patellar pole or tendinopathy of the attachment of the patellar tendon to the anterior tuberosity of the tibia. The term jumper's knee implies functional stress overload due to jumping.
For excellent patient education resources, visit eMedicine's Foot, Ankle, Knee, and Hip Center and Sports Injury Center. Also, see eMedicine's patient education articles Knee Pain Overview, Knee Injury, and Tendinitis.
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Frequency
United States
Jumper's knee is certainly one of the more common tendinopathies affecting skeletally mature athletes, occurring in as many as 20% of jumping athletes. With regard to bilateral tendinopathy, males and females are equally affected. With regard to unilateral tendinopathy, the male-to-female ratio is 2:1.
Functional Anatomy
The rectus femoris and 3 vasti muscles (ie, the vastus medialis, vastus lateralis, and vastus intermedius muscles) join in a common quadriceps tendon that inserts on the patella, the largest sesamoid bone in the human body. This same tendon is known as the patellar tendon from the inferior pole of the patella to its distal insertion at the tibial tuberosity.
Radiologic and histologic studies have shown that the posterior proximal fibers of the patellar tendon appear to be most commonly affected in jumper's knee.2 Counter to these findings, however, biomechanical research has demonstrated that these posterior fibers can withstand greater tensile strains before failing, compared with the anterior fibers.3
Sport-Specific Biomechanics
Jumper's knee is believed to be caused by repetitive stress placed on the patellar or quadriceps tendon during jumping. It is an injury specific to athletes, particularly those participating in jumping sports such as basketball,4,5,6,7,8 volleyball,7,8,9,10 or high or long jumping.7,10 Jumper's knee is occasionally found in soccer players, and in rare cases, it may be seen in athletes in nonjumping sports, such as weight lifting and cycling.
Investigators have implicated sex, greater body weight, genu varum and genu valgum, an increased Q angle, patella alta and patella baja, and limb-length inequality as intrinsic risk factors.11 However, the only biomechanical impairment prospectively linked to jumper's knee is poor quadriceps and hamstring flexibility. Vertical jump ability, as well as jumping and landing technique, are believed to influence tendon loading.4,10,12
Overtraining and playing on hard surfaces have been implicated as extrinsic risk factors.
Interestingly, the patellar tendon experiences greater mechanical load during landing than during jumping because of the eccentric muscle contraction of the quadriceps. Therefore, eccentric muscle action during landing, rather than concentric muscle contraction during jumping, may exert the tensile loads that lead to injury.13
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Clinical
History
Jumper's knee (patellar tendinopathy, patellar tendinosis, patellar tendinitis) commonly occurs in athletes who are involved in jumping sports such as basketball and volleyball. Patients report anterior knee pain, often with an aching quality. The symptom onset is insidious. Rarely is a discrete injury described. Usually, involvement is infrapatellar at or near the infrapatellar pole, but it may also be suprapatellar.
Depending on the duration of symptoms, jumper's knee can be classified into 1 of 4 stages, as follows:
- Stage 1 – Pain only after activity, without functional impairment
- Stage 2 – Pain during and after activity, although the patient is still able to perform satisfactorily in his or her sport
- Stage 3 – Prolonged pain during and after activity, with increasing difficulty in performing at a satisfactory level
- Stage 4 – Complete tendon tear requiring surgical repair
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Quadriceps Tendon Rupture
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Specialty Site Surgery
Physical
Physical examination may reveal the following findings:
- Point tenderness at the inferior patellar pole, superior patellar pole, or tibial tuberosity
- Hamstring and quadriceps tightness
- Normal ligamentous stability of the knee during testing
- Normal knee range of motion
- Normal neurovascular examination
- Normal hip and ankle examination
- Intra-articular effusion of the knee (rare)
Causes
The cause of jumper's knee remains unclear.
Histologic specimens are devoid of inflammatory cells; therefore, the disease process probably rarely involves a true tendinitis. Histologic studies have found increased numbers of mast cells associated with vascular hyperplasia, as well as an increased number of apoptotic cells.14
Biomechanical research has shown that a greater tensile load is borne by the anterior fibers.3 This observation contradicts the theory that jumper's knee is caused by repetitive tensile loading, given that the proximal posterior patellar tendon is routinely affected.
The degenerative "tendinosis" rather than inflammatory "tendinitis" model has prevailed since the 1970s. Hamilton and Purdam have proposed an adaptive model, whereby compressive rather than tensile loads occur at the proximal posterior aspect of the tendon, resulting in structural changes from altered biomechanical forces.15 This model is said to account for the presence of the routinely found asymptomatic lesions, and perhaps the absence of inflammatory cells in histologic specimens.
Almekinders et al suggested that stress shielding by the anterior fibers may lead to degenerative change or tendon wear of the posterior ones due to compressive forces.2 They also proposed that such stress shielding and/or compressive forces, rather than repetitive tensile loads, may be more important etiologic factors in insertional tendinopathy.
More on Jumper's Knee |
 Overview: Jumper's Knee |
| Differential Diagnoses & Workup: Jumper's Knee |
| Treatment & Medication: Jumper's Knee |
| Follow-up: Jumper's Knee |
| Multimedia: Jumper's Knee |
| References |
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References
Blazina ME, Kerlan RK, Jobe FW, Carter VS, Carlson GJ. Jumper's knee. Orthop Clin North Am. Jul 1973;4(3):665-78. [Medline].
Almekinders LC, Vellema JH, Weinhold PS. Strain patterns in the patellar tendon and the implications for patellar tendinopathy. Knee Surg Sports Traumatol Arthrosc. Jan 2002;10(1):2-5. [Medline].
Basso O, Amis AA, Race A, Johnson DP. Patellar tendon fiber strains: their differential responses to quadriceps tension. Clin Orthop Relat Res. Jul 2002;400:246-53. [Medline].
Cook JL, Kiss ZS, Khan KM, Purdam CR, Webster KE. Anthropometry, physical performance, and ultrasound patellar tendon abnormality in elite junior basketball players: a cross-sectional study. Br J Sports Med. Apr 2004;38(2):206-9. [Medline]. [Full Text].
Cook JL, Khan KM, Kiss ZS, Purdam CR, Griffiths L. Reproducibility and clinical utility of tendon palpation to detect patellar tendinopathy in young basketball players. Victorian Institute of Sport tendon study group. Br J Sports Med. Feb 2001;35(1):65-9. [Medline]. [Full Text].
Cook JL, Khan KM, Kiss ZS, Purdam CR, Griffiths L. Prospective imaging study of asymptomatic patellar tendinopathy in elite junior basketball players. J Ultrasound Med. Jul 2000;19(7):473-9. [Medline].
Busch MT. Sports medicine in children and adolescents. In: Morrissy RT, ed. Lovell and Winter's Pediatric Orthopaedics. Philadelphia, Pa: Lippincott-Raven; 1990:1091-1128.
Ferretti A, Ippolito E, Mariani P, Puddu G. Jumper's knee. Am J Sports Med. Mar-Apr 1983;11(2):58-62. [Medline].
Lian Ø, Refsnes PE, Engebretsen L, Bahr R. Performance characteristics of volleyball players with patellar tendinopathy. Am J Sports Med. May-Jun 2003;31(3):408-13. [Medline].
Ferretti A. Epidemiology of jumper's knee. Sports Med. Jul-Aug 1986;3(4):289-95. [Medline].
Kujala UM, Osterman K, Kvist M, Aalto T, Friberg O. Factors predisposing to patellar chondropathy and patellar apicitis in athletes. Int Orthop. 1986;10(3):195-200. [Medline].
Witvrouw E, Bellemans J, Lysens R, Danneels L, Cambier D. Intrinsic risk factors for the development of patellar tendinitis in an athletic population. A two-year prospective study. Am J Sports Med. Mar-Apr 2001;29(2):190-5. [Medline].
Jonsson P, Alfredson H. Superior results with eccentric compared to concentric quadriceps training in patients with jumper's knee: a prospective randomised study. Br J Sports Med. Nov 2005;39(11):847-50. [Medline].
Scott A, Lian O, Bahr R, et al. Elevated mast cell numbers in human patellar tendinosis: correlation with symptom duration and vascular hyperplasia. Br J Sports Med. Mar 4 2008;epub ahead of print. [Medline]. [Full Text].
Hamilton B, Purdam C. Patellar tendinosis as an adaptive process: a new hypothesis. Br J Sports Med. Dec 2004;38(6):758-61. [Medline]. [Full Text].
[Best Evidence] Warden SJ, Kiss ZS, Malara FA, et al. Comparative accuracy of magnetic resonance imaging and ultrasonography in confirming clinically diagnosed patellar tendinopathy. Am J Sports Med. Mar 2007;35(3):427-36. [Medline].
Alfredson H, Ohberg L. Neovascularisation in chronic painful patellar tendinosis--promising results after sclerosing neovessels outside the tendon challenge the need for surgery. Knee Surg Sports Traumatol Arthrosc. Mar 2005;13(2):74-80. [Medline].
Gisslén K, Alfredson H. Neovascularisation and pain in jumper's knee: a prospective clinical and sonographic study in elite junior volleyball players. Br J Sports Med. Jul 2005;39(7):423-8; discussion 423-8. [Medline]. [Full Text].
Johnson DP, Wakeley CJ, Watt I. Magnetic resonance imaging of patellar tendonitis. J Bone Joint Surg Br. May 1996;78(3):452-7. [Medline]. [Full Text].
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. Sep 1996;200(3):821-7. [Medline]. [Full Text].
[Best Evidence] Hoksrud A, Ohberg L, Alfredson H, Bahr R. Ultrasound-guided sclerosis of neovessels in painful chronic patellar tendinopathy: a randomized controlled trial. Am J Sports Med. Nov 2006;34(11):1738-46. [Medline].
Kongsgaard M, Aagaard P, Roikjaer S, et al. Decline eccentric squats increases patellar tendon loading compared to standard eccentric squats. Clin Biomech (Bristol, Avon). Aug 2006;21(7):748-54. [Medline].
Purdam CR, Jonsson P, Alfredson H, et al. A pilot study of the eccentric decline squat in the management of painful chronic patellar tendinopathy. Br J Sports Med. Aug 2004;38(4):395-7. [Medline]. [Full Text].
[Best Evidence] Bahr R, Fossan B, Løken S, Engebretsen L. Surgical treatment compared with eccentric training for patellar tendinopathy (jumper's knee). A randomized, controlled trial. J Bone Joint Surg Am. Aug 2006;88(8):1689-98. [Medline].
Fredberg U, Bolvig L, Pfeiffer-Jensen M, et al. Ultrasonography as a tool for diagnosis, guidance of local steroid injection and, together with pressure algometry, monitoring of the treatment of athletes with chronic jumper's knee and Achilles tendinitis: a randomized, double-blind, placebo-controlled study. In: Scand J Rheumatol. 2004:33(2):94-101.
James SL, Ali K, Pocock C, et al. Ultrasound guided dry needling and autologous blood injection for patellar tendinosis. Br J Sports Med. Aug 2007;41(8):518-21; discussion 522. [Medline].
Peers KH, Lysens RJ, Brys P, Bellemans J. Cross-sectional outcome analysis of athletes with chronic patellar tendinopathy treated surgically and by extracorporeal shock wave therapy. Clin J Sport Med. Mar 2003;13(2):79-83. [Medline].
Al-Duri ZA, Aichroth PM. Surgical aspects of patellar tendonitis: technique and results. Am J Knee Surg. Winter 2001;14(1):43-50. [Medline].
Cook JL, Khan KM, Harcourt PR, et al. A cross sectional study of 100 athletes with jumper's knee managed conservatively and surgically. The Victorian Institute of Sport Tendon Study Group. Br J Sports Med. Dec 1997;31(4):332-6. [Medline]. [Full Text].
Lian Ø, Scott A, Engebretsen L, et al. Excessive apoptosis in patellar tendinopathy in athletes. Am J Sports Med. Apr 2007;35(4):605-11. [Medline].
Matheson GO. Long-term prognosis for jumper's knee. Clin J Sport Med. May 2003;13(3):196. [Medline].
Medlar RC, Lyne ED. Sinding-Larsen-Johansson disease. Its etiology and natural history. J Bone Joint Surg Am. Dec 1978;60(8):1113-6. [Medline]. [Full Text].
Ogden JA, Southwick WO. Osgood-Schlatter's disease and tibial tuberosity development. Clin Orthop Relat Res. May 1976;116:180-9. [Medline].
Roels J, Martens M, Mulier JC, Burssens A. Patellar tendinitis (jumper's knee). Am J Sports Med. Nov-Dec 1978;6(6):362-8. [Medline].
Further Reading
Keywords
jumper's knee, knee tendinitis, patellar tendinopathy, knee pain, knee tendonitis, patellar tendinitis, patellar tendonitis, patellar tendinosis, patellar apicitis, quadriceps tendinitis, quadriceps tendonitis, infrapatellar tendinopathy, knee injury
