Knee valgus angle during single leg squat and landing in patellofemoral pain patients and controls Lee Herrington ⁎ Allerton Building, University of Salford, Manchester M6 6PU, United Kingdom abstract article info Article history: Received 25 March 2013 Received in revised form 23 October 2013 Accepted 13 November 2013 Keywords: Limb load Alignment Pain Background: Patellofemoral pain (PFP) is a commonly presenting disorder of the lower limb, frequently effecting young physically active individuals particularly females. The condition has been associated with poor control of limb alignment while undertaking unilateral limb loading tasks. This poor alignment of the limb is believed to alter loading stress within the patellofemoral joint. This study aims to investigate the degree of knee valgus, assessed as 2D frontal plane projection angle (FPPA) during single leg squatting (SLS) and hop landing (SLL) tasks in patients with PFP and compare their performance to controls and the uninjured limb. Method: Twelve female subjects with unilateral PFP formed the patient group and thirty asymptomatic females formed the control group. They had their 2D frontal plane projection angle (FPPA) assessed during single leg squatting (SLS) and hop landing (SLL) tasks. Results: In the asymptomatic control group the mean FPPA for SLS was 8.4±5.1° and SLL had a mean FPPA of 13.5±5.7°. In the PFP group the mean FPPA for SLS was 16.8±5.4° and SLL had a mean FPPA of 21.7+/-3.6°, these differences were significant (p b 0.01) for both tasks. Conclusion: Patients with PFP have a greater degree of knee valgus on unilateral limb loading task than either their contralateral asymptomatic limb or an asymptomatic control group. If not corrected this may lead to further PFJ stress and ongoing morbidity. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Patellofemoral pain (PFP) is one of the most common disorders of the lower limb, often specifically affecting young physically active fe- male athletes [1]. The presence of PFP often limits participation in recre- ational and sporting activities [2] and, has been linked to the development of patellofemoral osteoarthritis [1,3]. Although the under- lying mechanisms are still poorly understood, faulty lower extremity biomechanics and the development of increased knee valgus on limb loading are believed to play a role in the development of PFP [4]. The abnormal lower extremity mechanics are thought to negatively influence alignment of the patella as it passes through the trochlear groove [5]. Noehren et al. [6] showed a significant correlation between knee abduction and external rotation and lateral patella translation when asymptomatic subjects squatted with knees aligned in a valgus or neutral orientation. Wilson et al. [5] found that PFP patients had in- creased lateral patellar translation and tilt during squatting with the knee aligned in a neutral position. When the load-bearing surface areas are altered, with altered patellar tracking, abnormal distribution of the stresses on the patellofemoral joint will occur [7]. This abnormal distri- bution of stresses is considered to have a strong correlation with patellar disorders, such as chondromalacia and subsequent osteoarthritis [8], with Tanamas et al. [9] reporting increased lateral patellar tilt being asso- ciated with both decreased medial and lateral patella facet cartilage volumes, further adding to increased stress on loading. Poor limb alignment, specifically an increased knee valgus during single leg squat [10], running [11] and bilateral landing tasks [12] has been associated with PFP. None of the above studies investigated if dif- ferent movement patterns occurred between different single leg move- ment tasks and how that relate to the presence of PFP. Therefore, the objective of this study was to assess the knee valgus angle (as defined by the 2D frontal plane projection angle) of female PFP patients and asymptomatic controls while undertaking both a single leg squat and single leg landing tasks. The aim of the study being to establish if female PFP patients single leg land and squat with greater knee valgus than controls and if the nature of the task changes the magnitude of knee val- gus. The hypothesis of the study being that the symptomatic knee of the PFP patients would present with a significantly greater knee valgus angle during the unilateral limb loading tasks, which would increase from single leg squat to single leg landing. 2. Materials and method 2.1. Subjects Thirty asymptomatic female subjects participated in the testing (mean age 20.4±1.4 year, range 18–26 years, height mean 1.66 m The Knee 21 (2014) 514–517 ⁎ Tel.: +44 1612952326; fax: +44 1612952395. E-mail address: L.C.Herrington@Salford.ac.uk. 0968-0160/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.knee.2013.11.011 Contents lists available at ScienceDirect The Knee