- Adolescent knee pain carries a poor prognosis, with many youth athletes playing through symptoms for years.
- Adolescent knee pain is most common in female youth athletes.
- The anterior knee pain provocation test offers a novel means of quantifying symptom severity and monitoring improvement.
BACKGROUND & OBJECTIVE
Patellofemoral pain (PFP) is one of the most common forms of knee pain. PFP typically develops gradually, fluctuates, and is aggravated by activities that involve knee bending and loading. The incidence of PFP is 29% during adolescence and 23% in the general population (1). PFP is seen with increased frequency in adolescent athletes as compared to non-athletes, and in females as compared to males (1,2). Although a variety of interventions have shown efficacy to improve PFP, the long-term outcomes following adolescent PFP are disappointing, with up to 40% still experiencing varying levels of symptoms for over five years (3,4).
Adolescent knee pain is so common that it was once regarded to be normal, self-limiting, and something that would just disappear over time. To the contrary, research has shown that young athletes will play through quality of life altering knee pain for years, and it has the potential to impact them into adulthood (5,6). Although diagnosing knee pain is straightforward, there is a paucity of functional tests to quantify PFP severity and measure change over time.
The aim of this study was to investigate a simple and time efficient pain provocation test for adolescents with PFP.
The AKPP test is a tool clinicians can use to engage and motivate patients, set shared goals, and monitor progress together.
The authors recruited 151 participants with PFP and 50 for the pain-free control group (age = 10-14). The anterior knee pain provocation (AKPP) test was administered in both groups at baseline, and in the intervention group at 4 and 12-weeks. The AKPP test is a 45 second unilateral squat isometric hold with the knee flexed to 60 degrees. Participants rate their pain intensity using a numeric pain rating scale (NPRS) immediately following the isometric hold. See the video for a demonstration of this test.
The 12-week intervention began with 4 weeks of activity reduction, followed by 8 weeks of progressive resistance exercise and return to sport guidance. There were 4 in-person instructional sessions attended by both the adolescent and a parent. Current best practice guidelines were used to diagnose PFP. Participants were excluded if they had concomitant injuries to the low back, hip or knee, suspected patellar instability, knee joint effusion, or a 1-year history of previous surgery, physiotherapy, or weekly anti-inflammatory use for knee pain.
The AKPP test was shown to be moderately associated with self-reported pain and sport function. At baseline, median pain after the AKPP test was 5 in the intervention group and 0 in the control group. A worse AKPP test was shown to be associated with worse KOOS-Sport/Rec and KOOS-Pain scores.
A repeated measures ANOVA showed a significant effect of time on the AKPP test, indicating its utility in measuring and objectifying a change in symptoms over time. The AKPP test rarely produces pain in adolescents without knee pain, and consistently reproduces pain when symptoms are related to loading the knee joint.
The AKPP test is not a diagnostic tool. Best practice guidelines should be used to diagnose PFP and identify appropriate patients for the AKPP test:
- Insidious onset of anterior knee or retro-patellar pain of more than 6 weeks
- Pain provoked by at least 2 of the following situations: prolonged sitting or kneeling, squatting, running, hopping, or stair walking
- Tenderness on palpation of the patella or pain when stepping down or double leg squatting
- Pain during the previous week of at least 3/10 on the NPRS
Test-retest reliability of pain ratings was not examined, as pain scale testing has been shown to be reliable in young adults.
Participants in the intervention group were 76% female, indicating the results may be less applicable to male adolescents experiencing PFP.
There are other measures of pain and sporting function that could be evaluated alongside the AKPP test to further investigate and affirm construct validity and its utility in adolescents.
The intervention utilized in this study was described in greater detail in a previously published paper from 2019 (7). Participants were given a 2-page handout with activity modification and home exercise instruction. An activity ladder was used to guide participants on re-integrating sport activity, and a digestible graphical explanation provided instruction on making progress and adjusting exercise dosage based on symptoms.
Exercises started with isometric knee extension and supine bridges, progressing to side-lying hip strengthening, open chain knee extension, and eventually standing unilateral hip exercises, band terminal knee extension, and bodyweight lunges and squats. The results were promising, with 68% returning to sport at 3-months and 78% by 4-months. Hip and knee torque increased significantly, and pain and quality of life were improved. Although the exercises were bodyweight only and lacked plyometrics, they represent a safe, realistic, and low-cost program adolescents can easily follow at home with the support of their parents.
The authors of this paper were successful in conceiving a tool to efficiently measure progress in adolescents with PFP. The AKPP test is not a special test and is not meant to discriminate between PFP or other common adolescent knee pathologies. In practice, the AKPP test can be used to chart patients’ improvement over time, inform clinicians on making treatment adjustments, and objectify progress toward a goal. Moreover, the AKPP test is a tool clinicians can use to engage and motivate patients, set shared goals, and monitor progress together.
The AKPP test was devised specifically to assess symptom severity, whereas most functional knee tests are intended to identify performance deficits. Anecdotally, in adolescent patients it can be particularly challenging to assess symptom severity at times due to communication challenges. In cases where performance is not hindered, readiness for sport is not called into question and there is only pain with activity, the AKPP test offers a relevant tool to provoke, discriminate, quantify, and monitor symptoms in adolescents.
Rathleff M, Holden S, Krommes K, Winiarski L, Hölmich P, Salim T & Thorborg K (2022) The 45-second anterior knee pain provocation test: A quick test of knee pain and sporting function in 10-14-year-old adolescents with patellofemoral pain. Physical Therapy in Sport.
- Smith, B. E., Selfe, J., Thacker, D., Hendrick, P., Bateman, M., Moffatt, F., … Logan, P. (2018). Incidence and prevalence of patellofemoral pain: A systematic review and meta-analysis. PLOS ONE.
- Ferreira, A. S., de Oliveira Silva, D., Priore, L., Garcia, C., Ducatti, M., Botta, A., Waiteman, M. C., & de Azevedo, F. M. (2018). Differences in pain and function between adolescent athletes and physically active non-athletes with patellofemoral pain. Physical Therapy in Sport.
- Rathleff, M. S., Holden, S., Straszek, C. L., Olesen, J. L., Jensen, M. B., & Roos, E. M. (2019). Five-year prognosis and impact of adolescent knee pain: a prospective population-based cohort study of 504 adolescents in Denmark. BMJ open.
- Hamstra-Wright, K. L., Aydemir, B., Earl-Boehm, J., Bolgla, L., Emery, C., & Ferber, R. (2017). Lasting Improvement of Patient-Reported Outcomes 6 Months After Patellofemoral Pain Rehabilitation. Journal of sport rehabilitation.
- Rathleff, M. S., Rathleff, C. R., Olesen, J. L., Rasmussen, S., & Roos, E. M. (2016). Is Knee Pain During Adolescence a Self-limiting Condition? AJSM.
- Coburn, S. L., Barton, C. J., Filbay, S. R., Hart, H. F., Rathleff, M. S., & Crossley, K. M. (2018). Quality of life in individuals with patellofemoral pain: A systematic review including meta-analysis. Physical Therapy in Sport.
- Rathleff, M. S., Graven-Nielsen, T., Hölmich, P., Winiarski, L., Krommes, K., Holden, S., & Thorborg, K. (2019). Activity Modification and Load Management of Adolescents With Patellofemoral Pain: A Prospective Intervention Study Including 151 Adolescents. The American journal of sports medicine.
- Rathleff, M. S., Winiarski, L., Krommes, K., Graven-Nielsen, T., Hölmich, P., Olesen, J. L., … Thorborg, K. (2020). Pain, Sports Participation, and Physical Function in 10-14 Year Olds With Patellofemoral Pain and Osgood Schlatter: A Matched Cross-Sectional Study of 252 Adolescents. JOSPT.
- Ferber, R., Bolgla, L., Earl-Boehm, J. E., Emery, C., & Hamstra-Wright, K. (2015). Strengthening of the hip and core versus knee muscles for the treatment of patellofemoral pain: a multicenter randomized controlled trial. Journal of athletic training.