Medicine:Patellofemoral pain syndrome

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Patellofemoral pain syndrome
Other namesPatellar overload syndrome, runner's knee,[1] retropatellar pain syndrome[1]
PFPS.png
Diagram of the bones of the lower extremity. Rough distribution of areas affected by PFPS highlighted in red: patella and distal femur.
SpecialtyOrthopedics, sports medicine
SymptomsPain in the front of the knee[1]
Usual onsetGradual[2]
CausesUnclear[1]
Risk factorsTrauma, increased training, weak quadriceps muscle[1]
Diagnostic methodBased on symptoms and examination[3]
Differential diagnosisPatellar tendinopathy, infrapatellar bursitis, infrapatellar fat pad syndrome, chondromalacia patellae[2]
TreatmentRest, physical therapy[3]
PrognosisMay last for years[3]
FrequencyRelatively common[2]

Patellofemoral pain syndrome (PFPS; not to be confused with jumper's knee) is knee pain as a result of problems between the kneecap and the femur.[4] The pain is generally in the front of the knee and comes on gradually.[2][4] Pain may worsen with sitting, excessive use, or climbing and descending stairs.[1]

While the exact cause is unclear, it is believed to be due to overuse.[1][2] Risk factors include trauma, increased training, and a weak quadriceps muscle.[1] It is particularly common among runners.[3] The diagnosis is generally based on the symptoms and examination.[3] If pushing the kneecap into the femur increases the pain, the diagnosis is more likely.[1][3]

Treatment typically involves rest and rehabilitation with a physical therapist.[5] Runners may need to switch to activities such as cycling or swimming.[3] Insoles may help some people.[3] Symptoms may last for years despite treatment.[3] Patellofemoral pain syndrome is the most common cause of knee pain, affecting more than 20% of young adults.[1][2] It occurs about 2.5 times more often in females than males.[2]

Signs and symptoms

The onset of the condition is usually gradual,[4] although some cases may appear suddenly following trauma.[3] The most common symptom is diffuse vague pain around the kneecap (peripatellar) and localized pain focused behind the kneecap (retropatellar). Affected individuals typically have difficulty describing the location of the pain. They may place their hands over the anterior patella or describe a circle around the patella. This is often called the "circle sign".[3] Pain is usually initiated when weight is put on the knee extensor mechanism, such as when ascending or descending stairs or slopes, squatting, kneeling, cycling, or running.[6][7][8] Pain during prolonged sitting is sometimes termed the "movie sign" or "theatre sign" because individuals might experience pain while sitting to watch a film or similar activity.[6] The pain is typically aching and occasionally sharp. Pain may be exacerbated by activities.[3][9] The knee joint may exhibit noises such as clicking.[6] However, this has no relation to pain and function.[10][11] Giving-way of the knee may be reported.[6] Reduced knee flexion may be experienced during activities.[12]

Causes

In most patients with PFPS an examination of their history will highlight a precipitating event that caused the injury. Changes in activity patterns such as excessive increases in running mileage, repetitions such as running up steps and the addition of strength exercises that affect the patellofemoral joint are commonly associated with symptom onset. Excessively worn or poorly fitted footwear may be a contributing factor. To prevent recurrence the causal behaviour should be identified and managed correctly.[3]

The medical cause of PFPS is thought to be increased pressure on the patellofemoral joint.[6] There are several theorized mechanisms relating to how this increased pressure occurs:

  • Increased levels of physical activity[6]
  • Malalignment of the patella as it moves through the femoral groove[6]
  • Quadriceps muscle imbalance[6][13][14]
  • Tight anatomical structures, e.g. retinaculum or iliotibial band.[6]

Causes can also be a result of excessive genu valgum and the above-mentioned repetitive motions leading to abnormal lateral patellar tracking. Individuals with genu valgum have larger than normal Q-angles causing the weight-bearing line to fall lateral to the centre of the knee causing overstretching of the MCL and stressing the lateral meniscus and cartilages.[citation needed]

The cause of pain and dysfunction often results from either abnormal forces (e.g. increased pull of the lateral quadriceps retinaculum with acute or chronic lateral PF subluxation/dislocation) or prolonged repetitive compressive or shearing forces (running or jumping) on the PF joint. The result is synovial irritation and inflammation and subchondral bony changes in the distal femur or patella known as "bone bruises". Secondary causes of PF Syndrome are fractures, internal knee derangement, osteoarthritis of the knee and bony tumors in or around the knee.[15][self-published source?]

Diagnosis

Examination

People can be observed standing and walking to determine patellar alignment.[16] The Q-angle, lateral hypermobility, and J-sign are commonly used determined to determine patellar maltracking.[17] The patellofemoral glide, tilt, and grind tests (Clarke's sign), when performed, can provide strong evidence for PFPS.[3][18] Lastly, lateral instability can be assessed via the patellar apprehension test, which is deemed positive when there is pain or discomfort associated with lateral translation of the patella.[3][16] Various clinical tests have been investigated for diagnostic accuracy. The Active Instability Test, knee pain during stair climbing, Clarke's test, pain with prolonged sitting, patellar inferior pole tilt, and pain during squatting have demonstrated the best accuracy.[19] However, careful consideration is still needed when using these tests to make a differential diagnosis of PFPS.[19] Individuals with PFP may be exhibit higher pain level and lower function.[20]

Magnetic resonance imaging rarely can give useful information for managing patellofemoral pain syndrome and treatment should focus on an appropriate rehabilitation program including correcting strength and flexibility concerns.[21] In the uncommon cases where a patient has mechanical symptoms like a locked knee, knee effusion, or failure to improve following physical therapy, then an MRI may give more insight into diagnosis and treatment.[21]

Classification

PFPS is one of a handful of conditions sometimes referred to as runner's knee;[3] the other conditions being chondromalacia patellae, iliotibial band syndrome, and plica syndrome.

Chondromalacia patellae is a term sometimes used synonymously with PFPS.[6] However, there is general consensus that PFPS applies only to individuals without cartilage damage,[6] thereby distinguishing it from chondromalacia patellae, a condition with softening of the patellar articular cartilage.[3] Despite this distinction, the diagnosis of PFPS is typically made based only on the history and physical examination rather than on the results of any medical imaging. Therefore, it is unknown whether most persons with a diagnosis of PFPS have cartilage damage or not, making the difference between PFPS and chondromalacia theoretical rather than practical.[6] It is thought that only some individuals with anterior knee pain will have true chondromalacia patellae.[3]

Differential diagnosis

Main page: Medicine:Knee pain

The diagnosis of patellofemoral pain syndrome is made by ruling out patellar tendinitis, prepatellar bursitis, plica syndrome, Sinding-Larsen and Johansson syndrome, and Osgood–Schlatter disease.[22] Currently, there is not a gold standard assessment to diagnose PFPS.[19]

Treatment

A variety of treatments for patellofemoral pain syndrome are available.[23] Most people respond well to conservative therapy.[23][24][13]

Exercises

Vastus medialis

Patellofemoral pain syndrome may also result from overuse or overload of the PF joint. For this reason, knee activity should be reduced until the pain is resolved.[25][26]

There is consistent but low quality evidence that exercise therapy for PFPS reduces pain, improves function and aids long-term recovery.[27] However, there is insufficient evidence to compare the effectiveness of different types of exercises with each other, and exercises with other forms of treatment.[27]

Exercise therapy is the recommended first line treatment of PFPS.[3] Various exercises have been studied and recommended.[28] Exercises are described according to 3 parameters:[7]

  • Type of muscle activity (concentric, eccentric or isometric)
  • Type of joint movement (dynamic, isometric or static)
  • Reaction forces (closed or open kinetic chain)

The majority of exercise programs intended to treat PFPS are designed to strengthen the quadriceps muscles,[7] because their weakness and quadriceps muscle imbalance may contribute to abnormal patellar tracking. [23] If the strength of the vastus medialis muscle is inadequate, the usually larger and stronger vastus lateralis muscle will pull sideways (laterally) on the kneecap. Strengthening the vastus medialis to prevent or counter the lateral force of the vastus lateralis is one way of relieving PFPS, however it is hard to isolate and strengthen only one muscle of quadriceps.

Also, there is growing evidence that shows proximal factors play a much larger role than vastus medialis (VMO) strength deficits or quadriceps imbalance.[29] Hip abductor, extensor, and external rotator strengthening may help.[30] Emphasis during exercise may be placed on coordinated contraction of the medial and lateral parts of the quadriceps as well as of the hip adductor, hip abductor and gluteal muscles.[7] Many exercise programs include stretches designed to improve lower limb flexibility.[7]

Electromyographic biofeedback allows visualization of specific muscle contractions and may help individuals performing the exercises to target the intended muscles during the exercise.[7] Neuromuscular electrical stimulation to strengthen quadracep muscles is sometimes suggested, however the effectiveness of this treatment is not certain.[31]

Inflexibility has often been cited as a source of patellofemoral pain syndrome. Stretching of the lateral knee has been suggested to help.[32]

Knee and lumbar joint mobilization are not recommended as primary interventions for PFPS. It can be used as combination intervention, but as we continue to promote use of active and physical interventions for PFPS, passive interventions such as joint mobilizations are not recommended.[33]

Manual therapy

Manual therapy in addition to exercises helps in reducing pain, improving function, and knee range of motion in patients with PFPS. Manual therapy such as patellar joint mobilization, manipulation and soft tissue mobilization along with physical therapy exercises is found to be effective in treating PFPS. However, there is not enough evidence that supports lumbopelvic spine manipulation has any effect on the quadriceps muscle activation to improve function & reduce pain.[34]

Medication

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used to treat PFPS; however, there is only very limited evidence that they are effective.[6] NSAIDs may reduce pain in the short term; overall, however, after three months pain is not improved.[35] There is no evidence that one type of NSAID is superior to another in PFPS, and therefore some authors have recommended that the NSAID with fewest side effects and which is cheapest should be used.[6]

Glycosaminoglycan polysulfate (GAGPS) inhibits proteolytic enzymes and increases synthesis and degree of polymerization of hyaluronic acid in synovial fluid.[6] There is contradictory evidence that it is effective in PFPS.[6]

Braces and taping

There is no difference in pain symptoms between taping and non-taping in individuals with PFPS.[35] Although taping alone is not shown to reduce pain, studies show that taping in conjunction with therapeutic exercise can have a significant effect on pain reduction.[36]

Knee braces are ineffective in treating PFPS.[35] The technique of McConnell taping involves pulling the patella medially with tape (medial glide). Findings from some studies suggest that there is limited benefit with patella taping or bracing when compared to quadriceps exercises alone.[23] There is a lack of evidence to show that knee braces, sleeves, or straps are effective.[37]

Insoles

Low arches can cause overpronation or the feet to roll inward too much increasing load on the patellofemoral joint. Poor lower extremity biomechanics may cause stress on the knees and can be related to the development of patellofemoral pain syndrome, although the exact mechanism linking joint loading to the development of the condition is not clear. Foot orthoses can help to improve lower extremity biomechanics and may be used as a component of overall treatment.[38][39] Foot orthoses may be useful for reducing knee pain in the short term,[40] and may be combined with exercise programs or physical therapy. However, there is no evidence supporting use of combined exercise with foot orthoses as intervention beyond 12 months for adults. Evidence for long term use of foot orthoses for adolescents is uncertain. No evidence supports use of custom made foot orthoses.[33]

Surgery

The scientific consensus is that surgery should be avoided except in very severe cases in which conservative treatments fail.[6] The majority of individuals with PFPS receive nonsurgical treatment.[7]

Alternative medicine

The use of electrophysical agents and therapeutic modalities are not recommended as passive treatments should not be the focus of the plan of care.[41] There is no evidence to support the use of acupuncture or low-level laser therapy.[42] Most studies claiming benefits of alternative therapies for PFPS were conducted with flawed experimental design, and therefore did not produce reliable results.[43]

Prognosis

Patellarfemoral pain syndrome can become a chronic injury, with an estimated 50% of people reporting persistent patellar-femoral pain after a year.[31] Risk factors for a prolonged recovery (or persistent condition) include age (older athletes), females, increased body weight, a reduction in muscle strength, time to seek care, and in those who experience symptoms for more than two months.[31]

Epidemiology

Patellofemoral pain syndrome is the most common cause of anterior knee pain in the outpatient.[3][44] Specific populations at high risk of primary PFPS include runners, bicyclists, basketball players, young athletes and females.[45]

BMI did not significantly increase risk of developing PFPS in adolescents. However, adults with PFPS have higher BMI than those without. It is suggested that higher BMI is associated with limited physical activity in people with PFPS as physical activity levels decrease as a result of pain associated with the condition. However, no longitudinal studies are able to show that BMI can be a predictor of development or progression of the condition.[46]

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 Ferri, Fred F. (2016) (in en). Ferri's Clinical Advisor 2017 E-Book: 5 Books in 1. Elsevier Health Sciences. p. 936.e6. ISBN 9780323448383. https://books.google.com/books?id=rRhCDAAAQBAJ&pg=PA936-IA6. 
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Dutton, RA; Khadavi, MJ; Fredericson, M (February 2016). "Patellofemoral Pain.". Physical Medicine and Rehabilitation Clinics of North America 27 (1): 31–52. doi:10.1016/j.pmr.2015.08.002. PMID 26616176. 
  3. 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 "Management of patellofemoral pain syndrome". American Family Physician 75 (2): 194–202. January 2007. PMID 17263214. http://www.aafp.org/afp/2007/0115/p194.html. 
  4. 4.0 4.1 4.2 "Patellar taping for patellofemoral pain syndrome in adults". The Cochrane Database of Systematic Reviews 4 (4): CD006717. April 2012. doi:10.1002/14651858.CD006717.pub2. PMID 22513943. 
  5. "Patellofemoral pain syndrome - Diagnosis and treatment - Mayo Clinic". https://www.mayoclinic.org/diseases-conditions/patellofemoral-pain-syndrome/diagnosis-treatment/drc-20350797. 
  6. 6.00 6.01 6.02 6.03 6.04 6.05 6.06 6.07 6.08 6.09 6.10 6.11 6.12 6.13 6.14 6.15 6.16 "Pharmacotherapy for patellofemoral pain syndrome". The Cochrane Database of Systematic Reviews 2008 (3): CD003470. 2004. doi:10.1002/14651858.CD003470.pub2. PMID 15266488. 
  7. 7.0 7.1 7.2 7.3 7.4 7.5 7.6 "Exercise for treating patellofemoral pain syndrome (Protocol)". Cochrane Database of Systematic Reviews 2: CD010387. 2013. doi:10.1002/14651858.CD010387. 
  8. "Knee orthoses for treating patellofemoral pain syndrome (Protocol)". Cochrane Database of Systematic Reviews 5: CD010513. 2013. doi:10.1002/14651858.CD010513. 
  9. "Female Adults with Patellofemoral Pain Are Characterized by Widespread Hyperalgesia, Which Is Not Affected Immediately by Patellofemoral Joint Loading". Pain Medicine 17 (10): 1953–1961. October 2016. doi:10.1093/pm/pnw068. PMID 27113220. 
  10. "Knee crepitus is prevalent in women with patellofemoral pain, but is not related with function, physical activity and pain". Physical Therapy in Sport 33: 7–11. September 2018. doi:10.1016/j.ptsp.2018.06.002. PMID 29890402. 
  11. "Implications of knee crepitus to the overall clinical presentation of women with and without patellofemoral pain". Physical Therapy in Sport 33: 89–95. September 2018. doi:10.1016/j.ptsp.2018.07.007. PMID 30059950. 
  12. "Reduced knee flexion is a possible cause of increased loading rates in individuals with patellofemoral pain". Clinical Biomechanics 30 (9): 971–5. November 2015. doi:10.1016/j.clinbiomech.2015.06.021. PMID 26169602. 
  13. 13.0 13.1 "Quadriceps neuromuscular function in women with patellofemoral pain: Influences of the type of the task and the level of pain". PLOS ONE 13 (10): e0205553. 2018. doi:10.1371/journal.pone.0205553. PMID 30304030. Bibcode2018PLoSO..1305553B. 
  14. "Patellofemoral Pain: Clinical Practice Guidelines Linked to the International Classification of Functioning, Disability and Health From the Academy of Orthopaedic Physical Therapy of the American Physical Therapy Association". Journal of Orthopaedic & Sports Physical Therapy 49 (9): CPG1–CPG95. 2019. doi:10.2519/jospt.2019.0302. PMID 31475628. 
  15. Plamondon, Tom (12 Aug 2009). "Special tests in the clinical examination of patellofemoral syndrome". Doctors Lounge 09 (8): 287. http://www.doctorslounge.com/index.php/articles/page/287. Retrieved 2012-08-20. 
  16. 16.0 16.1 Sarwark, John F (2010). Essentials of musculoskeletal care. Rosemont, Ill.: American Academy of Orthopaedic Surgeons. ISBN 9780892035793. OCLC 706805938. 
  17. "Q-angle and J-sign: indicative of maltracking subgroups in patellofemoral pain". Clinical Orthopaedics and Related Research 468 (1): 266–75. January 2010. doi:10.1007/s11999-009-0880-0. PMID 19430854. 
  18. Malanga, Gerard; Nadler, Scott (2006). Musculoskeletal physical examination : an evidence-based approach. Philadelphia, Penns.: Elsevier Mosby. pp. 302–304. ISBN 9781560535911. https://books.google.com/books?id=bCN_Ux5Nj4UC&pg=PA304. 
  19. 19.0 19.1 19.2 "Best tests/clinical findings for screening and diagnosis of patellofemoral pain syndrome: a systematic review". Physiotherapy 98 (2): 93–100. June 2012. doi:10.1016/j.physio.2011.09.001. PMID 22507358. 
  20. "Differences in pain and function between adolescent athletes and physically active non-athletes with patellofemoral pain". Physical Therapy in Sport 33: 70–75. 2018. doi:10.1016/j.ptsp.2018.07.005. PMID 30025378. 
  21. 21.0 21.1 American Medical Society for Sports Medicine (24 April 2014), "Five Things Physicians and Patients Should Question", Choosing Wisely: an initiative of the ABIM Foundation (American Medical Society for Sports Medicine), http://www.choosingwisely.org/doctor-patient-lists/american-medical-society-for-sports-medicine/, retrieved 29 July 2014 , which cites
  22. "Females with patellofemoral pain syndrome have weak hip muscles: a systematic review". The Australian Journal of Physiotherapy 55 (1): 9–15. 2009. doi:10.1016/S0004-9514(09)70055-8. PMID 19226237. 
  23. 23.0 23.1 23.2 23.3 "An update for the conservative management of patellofemoral pain syndrome: a systematic review of the literature from 2000 to 2010". International Journal of Sports Physical Therapy 6 (2): 112–25. June 2011. PMID 21713229. 
  24. "Patellofemoral pain". Physical Medicine and Rehabilitation Clinics of North America 18 (3): 439–58, viii. August 2007. doi:10.1016/j.pmr.2007.05.004. PMID 17678761. 
  25. "Patellofemoral pain syndrome in young women. I. A clinical analysis of alignment, pain parameters, common symptoms and functional activity level". Scandinavian Journal of Medicine & Science in Sports 5 (4): 237–44. August 1995. doi:10.1111/j.1600-0838.1995.tb00040.x. PMID 7552769. 
  26. "Conservative care for patellofemoral pain". The Orthopedic Clinics of North America 23 (4): 545–54. October 1992. doi:10.1016/S0030-5898(20)31770-3. PMID 1408039. 
  27. 27.0 27.1 "Exercise for treating patellofemoral pain syndrome". The Cochrane Database of Systematic Reviews 1: CD010387. January 2015. doi:10.1002/14651858.CD010387.pub2. PMID 25603546. 
  28. van der Heijden, Rianne A; Lankhorst, Nienke E; van Linschoten, Robbart; Bierma-Zeinstra, Sita MA; van Middelkoop, Marienke; van Middelkoop, Marienke (2013). Van Middelkoop, Marienke. ed. "Exercise for treating patellofemoral pain syndrome". Reviews. doi:10.1002/14651858.CD010387. 
  29. "Proximal mechanics during stair ascent are more discriminate of females with patellofemoral pain than distal mechanics". Clinical Biomechanics 35: 56–61. June 2016. doi:10.1016/j.clinbiomech.2016.04.009. PMID 27128766. 
  30. Powers, CM (February 2010). "The influence of abnormal hip mechanics on knee injury: a biomechanical perspective.". The Journal of Orthopaedic and Sports Physical Therapy 40 (2): 42–51. doi:10.2519/jospt.2010.3337. PMID 20118526. 
  31. 31.0 31.1 31.2 Martimbianco, Ana Luiza C.; Torloni, Maria Regina; Andriolo, Brenda Ng; Porfírio, Gustavo Jm; Riera, Rachel (2017-12-12). "Neuromuscular electrical stimulation (NMES) for patellofemoral pain syndrome". The Cochrane Database of Systematic Reviews 2017 (12): CD011289. doi:10.1002/14651858.CD011289.pub2. ISSN 1469-493X. PMID 29231243. 
  32. Zaffagnini, Stefano; Dejour, David; Arendt, Elizabeth A. (2010). Patellofemoral pain, instability, and arthritis clinical presentation, imaging, and treatment. Berlin: Springer. p. 134. ISBN 9783642054242. https://books.google.com/books?id=ktGTBxRxbpEC&pg=PA134. 
  33. 33.0 33.1 "2018 Consensus statement on exercise therapy and physical interventions (orthoses, taping and manual therapy) to treat patellofemoral pain: recommendations from the 5th International Patellofemoral Pain Research Retreat, Gold Coast, Australia, 2017". British Journal of Sports Medicine 52 (18): 1170–1178. September 2018. doi:10.1136/bjsports-2018-099397. PMID 29925502. 
  34. Espí-López, Gemma Victoria; Arnal-Gómez, Anna; Balasch-Bernat, Mercè; Inglés, Marta (June 2017). "Effectiveness of Manual Therapy Combined With Physical Therapy in Treatment of Patellofemoral Pain Syndrome: Systematic Review". Journal of Chiropractic Medicine 16 (2): 139–146. doi:10.1016/j.jcm.2016.10.003. ISSN 1556-3707. PMID 28559754. 
  35. 35.0 35.1 35.2 "Evidence Based Conservative Management of Patello-femoral Syndrome". The Archives of Bone and Joint Surgery 2 (1): 4–6. March 2014. PMID 25207305. 
  36. "Systematic Review of the Effect of Taping Techniques on Patellofemoral Pain Syndrome". Sports Health 9 (5): 456–461. September 2017. doi:10.1177/1941738117710938. PMID 28617653. 
  37. "Knee orthoses for treating patellofemoral pain syndrome". The Cochrane Database of Systematic Reviews 2015 (12): CD010513. December 2015. doi:10.1002/14651858.CD010513.pub2. PMID 26645724. PMC 8763348. https://ueaeprints.uea.ac.uk/56085/1/Smith_et_al_The_Cochrane_Library.pdf. 
  38. "Effectiveness of orthotic shoe inserts in the long-distance runner". The American Journal of Sports Medicine 19 (4): 409–12. 1991. doi:10.1177/036354659101900416. PMID 1897659. 
  39. "Evaluation of soft foot orthotics in the treatment of patellofemoral pain syndrome". Physical Therapy 73 (2): 62–8; discussion 68–70. February 1993. doi:10.1093/ptj/73.2.62. PMID 8421719. 
  40. "Foot orthoses for patellofemoral pain in adults". The Cochrane Database of Systematic Reviews (1): CD008402. January 2011. doi:10.1002/14651858.CD008402.pub2. PMID 21249707. 
  41. "2018 Consensus statement on exercise therapy and physical interventions (orthoses, taping and manual therapy) to treat patellofemoral pain: recommendations from the 5th International Patellofemoral Pain Research Retreat, Gold Coast, Australia, 2017". British Journal of Sports Medicine 52 (18): 1170–1178. September 2018. doi:10.1136/bjsports-2018-099397. PMID 29925502. 
  42. "A systematic review of physical interventions for patellofemoral pain syndrome". Clinical Journal of Sport Medicine 11 (2): 103–10. April 2001. doi:10.1097/00042752-200104000-00007. PMID 11403109. 
  43. "Systematic review of the quality of randomized controlled trials for patellofemoral pain syndrome". The Journal of Orthopaedic and Sports Physical Therapy 33 (1): 4–20. January 2003. doi:10.2519/jospt.2003.33.7.F4. PMID 12570282. 
  44. "How to manage patellofemoral pain - Understanding the multifactorial nature and treatment options". Physical Therapy in Sport 32: 155–166. July 2018. doi:10.1016/j.ptsp.2018.04.010. PMID 29793124. 
  45. "Injuries and chronic conditions of the knee in young athletes". Pediatrics in Review 30 (11): 419–28; quiz 429–30. November 2009. doi:10.1542/pir.30-11-419. PMID 19884282. 
  46. "Is body mass index associated with patellofemoral pain and patellofemoral osteoarthritis? A systematic review and meta-regression and analysis". British Journal of Sports Medicine 51 (10): 781–790. May 2017. doi:10.1136/bjsports-2016-096768. PMID 27927675. 

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