Patellofemoral Pain Syndrome | Diagnosis & Treatment for Physios

Patellofemoral Pain Syndrome (PFPS) typically refers to anterior knee pain usually occurring during activities such as running, squatting, or walking up and downstairs. It should be seen as a diagnosis of exclusion though, meaning that the diagnosis is formed once all other possible conditions have been excluded such as meniscus, ligamentous or intra-articular pathologies (Crossley et al. 2016).

One hypothesis is abnormal patellofemoral joint alignment and morphology of the trochlear groove. Consequently, the patella can’t track smoothly up and down, which over time can cause irritation of the joint surfaces and triggers nociception (Crossley et al. 2016).

Secondly, muscle weakness of the quadriceps (Lankhorst et al. 2012) and glutes (Rathleff et al. 2014) have been considered potential risk factors associated with PFPS. Patients with PFPS showed 6-12 % less strength than their healthy controls. It is assumed that poor strength and function in the quadriceps will influence how the patella tracks in the trochlea and how the load is distributed across the patellofemoral joint (Willy et al. 2016).

Weak glutes on the other hand can alter the leg axis if the femur adopts a more internally rotated position with regards to the tibia again impairing smooth movement of the patella within the femoral trochlea (Willson et al. 2008, Powers 2010).

The biomechanics of PFPS have been challenged though. A systematic review of prospective predictors by Pappas et al (2012) found no significant link in many of the proposed anthropometric variables. Furthermore, Noehren (2007) found no difference in femoral internal rotation in a prospective cohort of runners who went on to develop PFPS compared to those who did not.

So while the biomechanical link may not be so clear, the above coupled with a drastic increase in load (intensity, frequency, duration) may eventually lead to symptoms.

Epidemiology

Anterior knee pain is one of the most commonly encountered problems in the primary care setting. However, no reports on the true incidence of PFPS amongst this population exist to this day (Rothermich et al. 2015). In young adolescents, studies have shown a prevalence ranging between 7-28% and an incidence of 9.2% (Rathleff et al. 2015, Hall et al. 2015). Studies on PFPS in military personnel reported an annual incidence of 3,8% in men and 6,5% in female recruits, with a prevalence of 12% in men and 15% in women (Boling et al. 2010). Typically seen in practice is a young female patient who engages in running (Glaviano et al. 2015, Smith et al. 2018).

Clinical Picture & Examination

As stated in the introduction, patients with PFPS will usually describe dull/achy pain around or behind the patella, which is aggravated by at least one weight-bearing activity such as squatting, stair ambulation, jogging/running, hopping, or jumping.

Additional, but not necessarily required are:

1. Crepitus or grinding sensation from the patellofemoral joint during knee flexion movements
2. Tenderness on patellar facet palpation
3. Small effusion
4. Pain on sitting, rising on sitting, or straightening the knee following sitting

Physical Examination
While Cook et al. (2010) describe three test clusters for PFPS, they have little diagnostic value.
These are:

• Retropatellar pain during resisted quadriceps contraction + Pain during squatting
• Retropatellar pain during resisted quadriceps contraction+ Pain during squatting + Pain during peripatellar palpation
• Retropatellar pain during resisted quadriceps contraction+ Pain during squatting + Pain during kneeling

Essentially, asking a patient whether they have anterior knee pain while squatting is the best available test to date, as PFPS will be evident in 80% of people with this finding. But PFPS has to be seen as a diagnosis of exclusion meaning the diagnosis is formed after all other possible pathologies have been excluded.

One orthopedic test that can be useful as it replicates the typical pain described during 30-60° of flexion is the decline step-down test:

To conduct the test, you will need two steppers or alternatively conduct the test on a treadmill that has an inclination feature. One step is placed on the other at an angle of 20°. You can assess this angle using your smartphone inclinometer. The lower end of the stepper was 20cm high.

The patient stands on the affected leg on the stepper so that the toes are at the lower end of the stepper. They keep the ipsilateral hand over the greater trochanter and can touch the wall with one fingertip for movement control and to prevent fear.

Then the patient is asked to simulate descending stairs by stepping down and forward with the contralateral leg which induced knee flexion at the affected knee. This should only be done in the pain-free flexion range. Instruct the patient to keep the knee in line with the foot to prevent excessive knee valgus.

A study by Selfe et al. in (2000) reported a critical angle of 61.3° during the test for healthy subjects before they lost control during the step-down. This could be used as a reference to evaluate your treatment effects with this test. Alternatively, as with other lower limb performance tests, you could use a limb symmetry index between the affected and non-affected knee.

Other orthopedic tests to assess patellofemoral pain are:

• Patellofemoral Pain Cluster (of Cook)
• Clarke’s Sign

Treatment

Several treatment approaches have been proposed for the management of PFPS. The 2018 consensus statement again states that exercise therapy is the treatment of choice (Collins et al. 2018). Uncertainty remains around adjunct therapies such as acupuncture or manual soft tissue therapies. In the early to intermediate term, patellar taping may allow the patient to perform strengthening exercises pain-free though the mechanism through which pain inhibition occurs is rather non-biomechanical  (Barton et al (2015).

Here are two different taping techniques that might help your patient to relieve pain on short-term:

We have since filmed three different proposed exercise programs that target the hip, knee, or a combination of the two. Choosing which exercises to incorporate remains subjective and should be tailored to the patient’s demands and needs. Starting with the activity or movement that causes pain, try to modify it and see if it influences the knee pain and incorporate proximal muscle strengthening (Lack et al. 2015).

Treatment of PFPS has to be seen as multimodal and this is supported most consistently by multiple high-quality reviews. Barton et al. (2015) emphasize that a combination of education, and active over passive interventions showed the most consistent short and long-term results. Education plays a key role in the treatment of the condition. Recommendations are:

Ensure the patient understands potential contributing factors to their condition and treatment optionsAdvise of appropriate activity modificationManage the patient’s expectations regarding rehabilitationEncourage and emphasize the importance of participation in active rehabilitationAs with all overuse injuries, load management in a biopsychosocial framework is key to rehab success. So while you may address strength deficits with a targeted exercise program, improve running mechanics, and reduce other factors such as high levels of stress, poor sleep quality, fear-avoidance beliefs, or thoughts that pain equals damage should not be forgotten as they play a key role in the pain experience.

References

Barton, C. J., Lack, S., Hemmings, S., Tufail, S., & Morrissey, D. (2015). The ‘Best Practice Guide to Conservative Management of Patellofemoral Pain’: incorporating level 1 evidence with expert clinical reasoning. British journal of sports medicine, 49(14), 923-934.

Ophey, M. J., Bosch, K., Khalfallah, F. Z., Wijnands, A. M., van den Berg, R. B., Bernards, N. T., … & Tak, I. J. (2019). The decline step-down test measuring the maximum pain-free flexion angle: A reliable and valid performance test in patients with patellofemoral pain. Physical Therapy in Sport, 36, 43-50.

Boling, M., et al. “Gender differences in the incidence and prevalence of patellofemoral pain syndrome.” Scandinavian journal of medicine & science in sports 20.5 (2010): 725-730.

Chiu JK, Wong YM, Yung PS, Ng GY. The effects of quadriceps strengthening on pain, function, and patellofemoral joint contact area in persons with patellofemoral pain. American journal of physical medicine & rehabilitation. 2012 Feb 1;91(2):98-106.

Cook, Chad, et al. “Diagnostic accuracy and association to disability of clinical test findings associated with patellofemoral pain syndrome.” Physiotherapy Canada 62.1 (2010): 17-24.

Crossley, Kay M., et al. “2016 Patellofemoral pain consensus statement from the 4th International Patellofemoral Pain Research Retreat, Manchester. Part 2: recommended physical interventions (exercise, taping, bracing, foot orthoses and combined interventions).” Br J Sports Med 50.14 (2016): 844-852.

Esculier JF, Bouyer LJ, Dubois B, Fremont P, Moore L, McFadyen B, Roy JS. Is combining gait retraining or an exercise programme with education better than education alone in treating runners with patellofemoral pain? A randomised clinical trial. Br J Sports Med. 2018 May 1;52(10):659-66.

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Nakagawa, Theresa H., et al. “Trunk, pelvis, hip, and knee kinematics, hip strength, and gluteal muscle activation during a single-leg squat in males and females with and without patellofemoral pain syndrome.” journal of orthopaedic & sports physical therapy 42.6 (2012): 491-501.

Noehren, Brian, and Irene Davis. “Prospective study of the biomechanical factors associated with patellofemoral pain syndrome.” American Society of Biomechanics Annual Meeting. Palo Alto, CA. 2007.

Pappas, Evangelos, and Wing M. Wong-Tom. “Prospective predictors of patellofemoral pain syndrome: a systematic review with meta-analysis.” Sports Health 4.2 (2012): 115-120.

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Willy, Richard W., and Erik P. Meira. “Current concepts in biomechanical interventions for patellofemoral pain.” International journal of sports physical therapy 11.6 (2016): 877.

Willson, John D., and Irene S. Davis. “Lower extremity mechanics of females with and without patellofemoral pain across activities with progressively greater task demands.” Clinical biomechanics 23.2 (2008): 203-211.