Associated with Patellofemoral Pain Syndrome; A Systematic Review

Lankhorst NE, Bierma-Zeinstra SM, van Middelkoop M. Br J Sports Med. 2012 Jul 19. [Epub ahead of print]

pain syndrome (PFPS) is a very common diagnosis, making up about 25% of all
running injuries. It can also be a very frustrating diagnosis for both patients
and clinicians. Whereas short-term treatments can be successful in alleviating
symptoms, long-term results are variable, and there is no definitive operative
management for PFPS. Several studies have examined risk factors for the
development of PFPS with the goal of directing treatments at modifiable
factors. The purpose of this comprehensive, systematic review was to summarize
which risk factors have been associated with PFPS. The authors used several
online research databases to identify case-control
or cross-sectional
studies including a minimum of 20 patients with PFPS that examined at least 1
possible risk factor for PFPS. The search yielded 4,664 potentially relevant
articles, of which a meta-analysis was performed on 47 studies, which examined
523 variables. The authors were able to combine data from multiple studies for
8 factors – which is one benefit of performing a meta-analysis. Six of the
eight factors were associated with PFPS. Three anatomic risk factors were
associated with PFPS including a larger Q-angle, a larger sulcus
, and a larger patellar
tilt angle
. In addition, there were three muscle imbalances which were
associated with PFPS including less hip abduction strength, lower knee
extension peak torque, and less hip external rotation strength in PFPS patients
compared with controls. The authors also evaluated foot arch height index and patellar congruence
but these were not associated with PFPS after the meta-analysis.

study is important because it uses the strength of a meta-analysis to examine
factors associated with PFPS. However, it is important to note that, because of
the case-control and cross-sectional nature of the studies included, conclusions
cannot be made about whether the risk factors are causative. Biomechanical risk
factors, as the authors’ point out, are subject to measurement error. In
particular, there is an ongoing debate regarding how Q-angle should be measured.
And, although biomechanical factors are thought to be associated with PFPS,
surgical correction with patellofemoral realignment techniques has not been
found to reliably treat PFPS symptoms. Several physical therapy techniques have
been focused on the muscle imbalances which are associated with PFPS and are
the cornerstone of current PFPS treatment. A good therapy program focused on
increasing vastus medialis (VMO) strength and addressing hip abductor and
external rotator weakness may help treat PFPS. However, more research is needed
to determine if the muscle weakness is a cause or effect of PFPS. The authors
suggest that since females are more commonly affected by PFPS, then this might
explain the findings of decreased muscle strength in general depending on how
the studies were completed. In addition, if patients with PFPS stop exercising
secondary to the PFPS symptoms, then this may also explain decreased strength
compared with controls. Another potential limitation of this study is that PFPS
does not have clear diagnostic criteria and there may be subtle differences in
factors associated with PFPS compared with interchangeable diagnoses that may
have been included in the studies such as patellar chondromalacia, patellar
tendonosis, and quadriceps tendonosis. Despite these important limitations, the
data from this study may be used to further our understanding of PFPS and
identifies some modifiable factors which may improve treatment. What has your
experience with PFPS been? Do you find PFPS affects a certain “type” of
patient? Have you found effective treatments?

By: Hallie Labrador, MD MS
by: Jeffrey Driban


Lankhorst NE, Bierma-Zeinstra SM, & van Middelkoop M (2012). Factors associated with patellofemoral pain syndrome: a systematic review. British Journal of Sports Medicine PMID: 22815424