Patellofemoral pain syndrome (PFPS) is a chronic condition of the musculoskeletal system characterized by retropatellar and/or peripatellar pain usually worsening during weight-bearing activities (Collins et al., 2018). In the general population annual prevalence rates for patellofemoral pain of approximately 25% have been reported (Smith et al., 2018). Most patients with PFPS report a feeling of stiffness, especially with knee flexion (Petersen et al., 2017). Functional activities such as walking, running, jumping, stair climbing and prolonged sitting and kneeling usually increase symptoms (Crossley et al., 2016).
Although not entirely understood, the aetiology of PFPS has been considered multifactorial (Petersen et al., 2014). Laxity of the knee joint, decreased knee extensor strength, malalignment of the lower extremity and poor coordination between vastus lateralis and vastus medialis obliquus muscle activation have been identified as local risk factors (Van Tiggelen et al., 2009; Davis and Powers, 2010; Lankhorst et al., 2013). Proximal risk factors such as dysfunction of the lumbosacral region and sacroiliac joint (SIJ), and decreased hip range of motion have also been associated to PFPS (Iverson et al., 2008; Suter et al., 2000; Hillermann et al., 2006; Grindstaff et al., 2012).
The use of exercise therapy has recently been reconfirmed as the intervention of choice in the management of patellofemoral pain (Collins et al., 2018). Combined knee and hip targeted exercises have been shown effective in reducing pain and improving function in the short, medium and long term. However, PFPS has also been shown recalcitrant to local exercise therapy and may persist for many years (Rathleff et al., 2016). About half of the patients with PFPS continue to experience pain and dysfunction at mid and long term (Collins et al., 2013; Lankhorst et al., 2016). Due to its persistent nature the absence of full recovery may result in psychological disorders such as a higher mental distress, kinesiophobia, anxiety, catastrophizing and depression (Domenech et al., 2013; Maclachlan et al., 2017). Since patellofemoral pain usually precedes knee osteoarthritis (Crossley et al., 2016) failure of an effective conservative management strategy for PFPS may potentially lead to invasive medical procedures later in life.
Although isolated lumbar mobilisations or manipulations have been reported to be inappropriate in the treatment of patellofemoral pain in the short and medium terms (Behranggrad et al., 2017), combined exercise and manipulative therapy interventions have been recommended (Espi-Lopez et al., 2017; Collins et al., 2018). Spinal manual therapy may include hands-on mobilisations and/or manipulations of the thoracolumbar region and/or SIJ. The immediate positive effects of spinal and lumbopelvic manipulations have been demonstrated in patients with PFPS (Motealleh et al., 2016; Hillermann et al., 2006; Connell, 2008; Brantingham et al., 2012, 2009; Iverson et al., 2008; Suter et al., 1999; Crowell and Wofford, 2012). It has been suggested that SIJ manipulation may increase activation and strength of the quadriceps in patients with PFPS (Suter et al., 1999; Hillermann et al., 2006). It has been shown that SIJ (L1 to S2) and quadriceps muscle (L2 to L4) share overlap in segmental innervation (Murata et al., 2001). Therefore, it has been suggested that altered mechanoreceptor afferent activity in the ventral part of the SIJ may contribute to a decrease in quadriceps muscle inhibition. Although a clinical prediction rule for patients with PFPS based on lumbopelvic manipulation was developed in 2008 by Iverson and colleagues, Crowell and Watford (2012) were not able to replicate these earlier findings. To the knowledge of the authors, the clinical effectiveness of spinal manual manipulations on pain, function and strength has not been investigated in the medium term. Therefore, the aim of this study was to compare the effectiveness of local exercise therapy versus spinal manual therapy in patients with PFPS after 6 weeks of intervention and at 6 weeks of follow-up.