Alterations in Center of Pressure During Single-Limb Loading in Individuals with Patellofemoral Pain.

BACKGROUND: Altered foot loading during weightbearing is suggested to play a role in the development of patellofemoral pain (PFP). This study aimed to determine foot-loading characteristics associated with PFP by assessing center of pressure (COP) during single-limb loading in individuals with PFP compared with noninjured controls. METHODS: Thirty recreationally active patients with PFP and 30 noninjured control participants had barefoot plantar pressure assessed during single-limb squats (SLSs) from which COP parameters (COP velocity and COP index) were obtained. Groups were compared using independent t tests. RESULTS: Individuals with PFP demonstrated a greater COP index (P = .042), indicating a more lateral foot-loading pattern, and exhibited increased overall COP velocity (P = .013) and anteroposterior COP velocity during SLSs compared with control participants (P = .033). CONCLUSIONS: Greater lateral foot loading and increased COP velocity during SLSs demonstrated by individuals with PFP may indicate reduced dynamic balance in this patient group, which may be implicated in the development of PFP.

Two-dimensional frontal plane projection angle can identify subgroups of patellofemoral pain patients who demonstrate dynamic knee valgus.

BACKGROUND: Identifying individuals with patellofemoral pain who demonstrate similar modifiable factors including dynamic knee valgus may be useful in establishing subgroups of patients that can undergo individualised management strategies. However, a lack of objective assessment criteria means that the findings are of limited value to clinicians aiming to distinguish between patients with and without altered frontal plane knee kinematics. Therefore, the aim of the study was to investigate dynamic knee valgus in individuals with and without patellofemoral pain by determining frontal plane knee alignment during functional activity. METHODS: Thirty recreationally active individuals with patellofemoral pain and 30 non-injured individuals had frontal plane knee alignment assessed via two-dimensional analysis of the frontal plane projection angle during single limb stance and single limb squats to 60° of knee flexion. FINDINGS: Individuals with patellofemoral pain demonstrated excessive frontal plane knee alignment (P = .003; ES = 0.68) compared to uninjured participants during single limb squats. In addition, assessing frontal plane knee alignment using two-dimensional analysis had fair specificity and sensitivity of discriminating patellofemoral pain injury. INTERPRETATION: Clinical quantification of two-dimensional frontal plane knee alignment may be utilised to subgroup patients with patellofemoral pain that display dynamic knee valgus during single limb squats. Furthermore, this may be a useful clinical tool to determine individuals that may be at risk of developing pain in the future.

Quantifying frontal plane knee motion during single limb squats: reliability and validity of 2-dimensional measures.

BACKGROUND: Clinical assessment of lower limb kinematics during dynamic tasks may identify individuals who demonstrate abnormal movement patterns that may lead to etiology of exacerbation of knee conditions such as patellofemoral joint (PFJt) pain. PURPOSE: The purpose of this study was to determine the reliability, validity and associated measurement error of a clinically appropriate two-dimensional (2-D) procedure of quantifying frontal plane knee alignment during single limb squats. METHODS: Nine female and nine male recreationally active subjects with no history of PFJt pain had frontal plane limb alignment assessed using three-dimensional (3-D) motion analysis and digital video cameras (2-D analysis) while performing single limb squats. The association between 2-D and 3-D measures was quantified using Pearson's product correlation coefficients. Intraclass correlation coefficients (ICCs) were determined for within- and between-session reliability of 2-D data and standard error of measurement (SEM) was used to establish measurement error. RESULTS: Frontal plane limb alignment assessed with 2-D analysis demonstrated good correlation compared with 3-D methods (r = 0.64 to 0.78, p < 0.001). Within-session (0.86) and between-session ICCs (0.74) demonstrated good reliability for 2-D measures and SEM scores ranged from 2° to 4°. CONCLUSION: 2-D measures have good consistency and may provide a valid measure of lower limb alignment when compared to existing 3-D methods. CLINICAL RELEVANCE: Assessment of lower limb kinematics using 2-D methods may be an accurate and clinically useful alternative to 3-D motion analysis when identifying individuals who demonstrate abnormal movement patterns associated with PFJt pain. LEVEL OF EVIDENCE: 2b.