Table 3. Prevalence.
| Study | Quality score | Study population | Sample Size | Case definition | Response rate | Results |
|---|---|---|---|---|---|---|
| Military | ||||||
| Boling (2010) [13] | 3/3 | United States Naval Academy (USNA) (39.8% female; mean age unknown, range 18–25*). | 1,525 | Retropatellar pain of any duration with two of the following activities: ascending/descending stairs, hopping/jogging, prolonged sitting with flexed knees, kneeling, and squatting. Plus one of the following: pain on palpation of medial or lateral patellar facets, or pain on palpation of the anterior portion of the medial or lateral femoral condyles. | 1,525/1,525 (100%) | Point prevalence of PFPS was 13.5% (95% confidence interval (CI): 11.7%, 15.3%]. For females and males it was 15.3% (95% CI: 13.7%, 16.9%) and 12.3% (95% CI: 11.1%, 13.4%), respectively. |
| General Adult Population | ||||||
| Dey (2016) [83] | 3/3 | Community within the UK. Convenience sample of attendance at a University science fair (53% female; mean age 30). | 111 | Anterior knee or retropatellar pain, often bilateral, of insidious onset present for at least a month and associated with pain or difficulty with prolonged sitting or activities which load the patellofemoral joint, e.g., ascending or descending stairs, running and squatting. Positive diagnosis identified through a self-report questionnaire (SNAPPS- Survey instrument for Natural history, Aetiology and Prevalence of Patellofemoral pain Studies) | 110/111 (99%) | Annual prevalence 25/110 (22.7%). Females 67%; males 33%. |
| Roush (2012) [5] | 3/3 | 18–35 year old females, general population*, USA (mean age 24.7) | 769 | Anterior Knee Pain Scale score < 83 | 724/769 (94.1%) | Point prevalence was 12–13%*. |
| Weiss (1985) [24] | 3/3 | Amateur multi-day cyclist in USA (69% male; mean age 41.4). | 132 | Self-reported complaint of patella pain during a cycling event. Tenderness of posterior aspect of patella during flexion and extension. | 113/132 (86%) | Point prevalence was 35%. |
| General Adolescents Population | ||||||
| Fairbank (1984) [27] | 1/3 | 13–17 year-old students, randomly selected from a comprehensive school in the United Kingdom (49% female, mean age 14.7) | 446 | 11 point questionnaire, including: Do you like playing sport? Have you had painful knees in the last year? Do your knees hurt climbing stairs? Do your knees hurt coming downstairs? Where do you feel the pain in your knees? Does your knee hurt after sitting for a long time? Does your knee hurt only after a lot of exercise? | 446/1850 (24.1%) | Annual prevalence 129/446 (28.9%). |
| Hall (2015) [29] | 2/3 | Female adolescent athletes in middle and high school, USA (mean age 14.0). | 546* | Assessment included the Anterior Knee Pain Scale (AKPS), International Knee Documentation Committee (IKDC) form, standardized history and physician-administered physical examination. | 546/546* | Point prevalence 151/546* (28%). |
| Molgaard (2011) [9] | 3/3 | 16–18 year-old students at one local high school in Denmark (mixed sex; mean age 16.9) | 299 | Anterior knee pain during physical activity for at least 1 month and pain in at least two of the following four tests: isometric contraction of quads, concentric extension against resistance, palpation of joint line, and compression of the patella. | 227/299 (76%) | Point prevalence 13/227 (5.7%). Females 69%; males 31%. |
| Myer (2010) [16] | 2/3 | Female adolescent athletes in middle and high school, USA (mean age 13.4 years). | 240 | Anterior Knee Pain Scale score < 100; knee pain with or shortly following activity and also if anterior knee tenderness was recent. | 240/240 (100%) | Point prevalence was 39/240 (16.3%). |
| Rathleff (2014) [84] | 3/3 | Population-based cohort of students from secondary schools, Denmark, aged 15–19 years (64.9% female; mean age 17.2). | 2,200 | Insidious onset of anterior knee or retropatellar pain for at least the past 6 weeks; pain provoked by at least 2 of the following activities: prolonged sitting or kneeling, squatting, running, hopping, or stair walking and tenderness on palpation of the patella. | 2,220/2846* (77.3%) | Point prevalence 153/2,062 (7.4%)*. |
| Steinberg (2012) [31] | 1/3 | Non-professional female dancers, aged 8–20, Israel (mean age 13.7 years*). | 1,359 | Pain reproduced during clinical examination; knee swelling was evident, or a positive grinding sign and/or a positive Patellar Inhibition Test (PIT) was obtained when the knee and especially the patella were palpated, contracted and stretched. | 1,359/1,359 (100%) | Point prevalence 321/1,359 (23.6%). |
| Elite Athletes | ||||||
| Clarsen (2010) [12] | 2/3 | Professional cycling; 7 training camps (100% male*; mean age 26) | 109 | Cyclist reported complaint of anterior knee pain in the last 12 months, of any duration. Cyclist reported complaint of anterior knee pain in the last 12 months, >30 days | 109/109 (100%) | Annual prevalence 39/109 (35.8%). Annual prevalence 7/109 (6.4%). |
| Nejati (2010) [11] | 1/3 | Female athletes participating in 3rd Iranian Sports Olympiad (mean age 21.6, range 15–35). | 418 | Non traumatic anterior knee pain of at least 3 months duration that was felt retropatellar or peripatellar and was aggravated by descending or ascending stairs, squatting or prolonged sitting. | 418/unknown | Point prevalence was 70/418 (16.7%). |
| Winslow (1995) [85] | 1/3 | University female ballet dancers, USA (mean age unknown) | 41 | Pain in front of or under the knee cap with 3 out of 5: associated with kneeling; squatting; during stair climbing; sensations of cracking/grinding or with incidents of joint locking or "catching." | 41/unknown | Point prevalence was 12/41 (29.3%). |
*Information not within publication, authors contacted for clarification.