Patellofemoral Pain Syndrome: A Quick Reference
What Is It?
Patellofemoral Pain Syndrome (PFPS; also referred to as just Patellofemoral Pain or PFP) is a common condition in which one experiences “diffuse retropatellar and peripatellar pain that is aggravated with squatting, prolonged sitting, and stair activities” (Kooiker et al. 2014). It is a diagnosis that is not dependent upon the presence of tissue injury.
Who Gets It and Why?
The cause of PFPS is multifactorial and can include a combination of pathomechanical and psychosocial factors. There is inconsistent evidence to suggest the association of PFPS and:
- Increased patellofemoral joint stress during walking and squatting
- Decreased contact area of patellofemoral joint (at lower degrees of knee flexion), potentially due to patellar maltracking or malalignment
- Quadriceps weakness and delayed activation of vastus medialis compared to vastus lateralis
- Altered sagittal, frontal, and transverse hip and knee kinematics
- Tighter and thicker IT band
- Lower PF joint reaction forces during walking, running, and stair ambulation (possibly as compensatory mechanism)
- Increased and delayed rearfoot eversion during walking and running
- Decreased hip extension, abduction, and external rotation strength [6,7]
It’s important to note that all of these factors are not predictive of developing PFPS. In fact, in some cases, the exact opposite has been found (e.g., increased hip abduction and external rotation strength and less pronation in those who ended up developing PFPS). Additionally, PFPS can be associated with elements of central sensitization and neuropathic pain, as well as increased catastrophization and kinesiophobia. 
Females tend to develop PFPS more than males. In adolescents, it has a prevalence of 7-28% and incidence of 9.2%.  Other than in military populations, there is little to no other research on incidence and prevalence in other populations.
Other conditions that should be ruled out when determining if someone has PFPS include
- Patellar tendinopathy
- Chondral defects
- Patellar instability (can sometimes be considered a subset of PFPS)
- Patellofemoral Osteoarthritis
- Fat pad impingement
- Osgood-Schlatter Disease (age dependent)
- Sinding-Larsen-Johansson Syndrome (age dependent)
There is no definitive clinical or special test to aid in diagnosis of PFPS. The two tests found to have the strongest diagnostic accuracy are:
- The Patellar Tilt Test (Positive Likelihood Ratio of 5.4; Negative Likelihood Ratio of 0.6)
- Pain with Squatting (Positive Likelihood Ratio of 1.8; Negative Likelihood Ratio of 0.2) 
Other tests with less clinical utility include Clarke’s Test, palpation of patellar edges, and the patellar apprehension test. 
Given the lack of a gold standard clinical test or accurate cluster of tests, diagnosis of PFPS should likely rely more heavily on clinical presentation and exclusion of other diagnoses (consideration of these factors should be important for any diagnosis, but particularly so with PFPS). As always, a thorough examination that includes assessment of strength, range of motion, and joint mobility, of the knee, as well as the joints above and below, are important.
The strongest evidence for treatment of PFPS is exercise (go figure!). The combination of hip and knee muscle strengthening tends to be more effective in reduction of pain in the short, medium, and long term and increase in function in the medium and long term compared to isolated hip or knee muscle strengthening. Evidence is conflicting as to whether open or closed kinetic chain strengthening is more effective. Regardless of contribution from pathomechanics and psychosocial/pain factors, it would be logical to avoid choosing exercises that exacerbate symptoms early in the course of treatment with a gradual progression towards being able to perform them. [1,3,4,6,7]
In addition to exercise, foot orthoses may be effective for short term pain relief in a subset of patients who have:
- Greater midfoot mobility
- Decreased ankle dorsiflexion ROM
- Immediate reduction in pain with single leg squatting with use of orthoses
Interventions with less convincing evidence at this time include patellar taping and dry needling/acupuncture.
There is no supporting evidence for the use of patellar and knee joint mobilizations for patients with PFPS. However, it is always important to examine each patient to determine their individual impairments to fully determine an appropriate plan of care. 
For more information about the anatomy/pathology, examination, and treatment related to PFPS, I encourage you to check out the references listed below (many of which are open access). As always, feel free to leave a comment or question!
- Barton CJ, Lack S, Hemmings S, Tufail S, Morrissey D. The 'Best Practice Guide to Conservative Management of Patellofemoral Pain': incorporating level 1 evidence with expert clinical reasoning. Br J Sports Med. 2015;49(14):923-34.
- Crossley KM, Stefanik JJ, Selfe J, et al. 2016 Patellofemoral pain consensus statement from the 4th International Patellofemoral Pain Research Retreat, Manchester. Part 1: Terminology, definitions, clinical examination, natural history, patellofemoral osteoarthritis and patient-reported outcome measures. Br J Sports Med. 2016;50(14):839-43.
- Crossley KM, Van middelkoop M, Callaghan MJ, Collins NJ, Rathleff MS, Barton CJ. 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. 2016;50(14):844-52.
- Kooiker L, Van de port IG, Weir A, Moen MH. Effects of physical therapist-guided quadriceps-strengthening exercises for the treatment of patellofemoral pain syndrome: a systematic review. J Orthop Sports Phys Ther. 2014;44(6):391-B1.
- Nunes GS, Stapait EL, Kirsten MH, De noronha M, Santos GM. Clinical test for diagnosis of patellofemoral pain syndrome: Systematic review with meta-analysis. Phys Ther Sport. 2013;14(1):54-9.
- Powers CM, Witvrouw E, Davis IS, Crossley KM. Evidence-based framework for a pathomechanical model of patellofemoral pain: 2017 patellofemoral pain consensus statement from the 4th International Patellofemoral Pain Research Retreat, Manchester, UK: part 3. Br J Sports Med. 2017;51(24):1713-1723.
- Witvrouw E, Callaghan MJ, Stefanik JJ, et al. Patellofemoral pain: consensus statement from the 3rd International Patellofemoral Pain Research Retreat held in Vancouver, September 2013. Br J Sports Med. 2014;48(6):411-4.