Patellofemoral pain syndrome (PFPS) is characterized by pain in/around the patella and caused by complex causes such as increased Q-angle in weight bearing position, genu valgum, patella malalignment, weakness of gluteus medius and gluteus maximus, degenerative changes in the patellofemoral joint in older adults and overactivity and acceleration of activity in young athletes and military person (Earl and Hoch, 2011; Rothermich et al., 2015). Patients with PFPS describe escalation of symptoms when going up/down stairs, running, jumping, or squatting, as these functional activities increase the compressive forces at the patellofemoral joint (Rothermich et al., 2015).
Valgus collapse of the knee during forward-step-down (FSD) test is related to diminished strength of hip abductor and external rotator, and is implicated in anterior cruciate ligament injury and patellofemoral joint dysfunction (Herman et al., 2016; Loudon et al., 2002). FSD test shows moderate to high intra-rater reliability (intraclass correlation coefficient [ICC] = 0.94) when recording the number of FSD repetitions during 30 seconds and fair to good inter-rater reliability (ICC = 0.61) when scoring the movement deviation of pelvis, hip and knee during performing FSD in individuals with PFPS (Herman et al., 2016; Loudon et al., 2002). Although three-dimensional motion analysis system has been used to measure the center of mass during FSD as objective test postural stability (Lopes Ferreira et al., 2019), scoring system of FSD performance test is easy to measure the postural stability as inexpensive and time-saving test in clinics (Herman et al., 2016). FSD is also used as neuromuscular training, such as tactile feedback to the lateral knee or visual feedback using mirror to keep the knee over second toe and level pelvis during FSD for preventing hip adduction and contralateral pelvic drop in individuals with PFPS (Wouters et al., 2012).
Non-operative management for PFPS, including hip-focused and knee-focused exercises combined with taping/bracing, manual therapy, and pharmacology, has been considered the mainstay for first-line management (Collins et al., 2018). Among non-operative management, taping and bracing are easy to use, noninvasive and less time-consuming and decreased burden associated with treating knee pain by self-brace and self-tape than other methods, and it has immediate effects in reducing knee pain (Warden et al., 2008; Wilson et al., 2003). When comparing the brace, taping techniques have advantage that was the possibility of adjusting the tape in accordance to the individual's anatomy and symptoms (Podolsky and Kalichman, 2015). Patella medial glide taping is often used because traditional management of PFPS has focused on correcting patellar lateral tracking (Cowan et al., 2002). However, a poor correlation was demonstrated between patellar lateralization and radiographic signs in patients with PFPS (Wilson et al., 2003). Additionally, patella medial glide taping is less effective for reducing pain than patellar taping techniques using neutral and lateral gliding, which indicates that the mechanism of pain relief in patients with PFPS does not involve medialization of the patella (Wilson et al., 2003).
Excessive tibiofemoral rotation in weight-bearing position may be associated with pain of PFPS rather than only patellar lateralization because excessive tibiofemoral rotation, especially from 20[degrees] to 30[degrees] of medial femoral rotation relative to tibia, results in an increase in patellofemoral contact pressure on the lateral facets of the patella (Lee et al., 2003). Previous studies demonstrated the effects of femoral rotational taping on reduction of knee pain and tibiofemoral rotation during single-leg squat and the star excursion balance test in individuals with PFPS, resulting in successful pain reduction and a change in patellar kinematics, but failed to alter tibiofemoral rotation (Song et al., 2015; 2017). Another literature suggested that "posterior X taping" method is effective for correcting the reduction of hip adduction and tibiofemoral rotation in weight bearing position, thus leading to pain relief (Sahrmann, 2011). A strip of posterior X taping was applied in a spiral fashion, starting from the proximal lateral thigh and ending at the distal medial tibia to assist in reducing tibiofemoral rotation and hip adduction. Another strip of posterior X taping was applied symmetry, starting from the proximal medial thigh and ending at the distal lateral tibia to prevent knee hyperextension (Sahrmann, 2011). A recent study demonstrated the posterior X taping in patients with knee osteoarthritis on the improvements in self-reported pain (11 point-numerical rating scale, 2.5 reduction), self-reported difficulty (5-point Likert scale, 1 reduction), and self-reported stability (5-point Likert scale, 2 reduction) during stair down test (Park and Kim, 2018). Previous study suggested the possible causes of knee pain reduction with posterior X taping might be decreased tibiofemoral rotation internally and externally and varus/valgus movement, and deceased fear and avoidance of weight-bearing activities, although kinematic changes in hip and knee joints were not assessed (Park and Kim, 2018).
No study has been investigated the effects of posterior X taping on the reduction of hip adduction and tibiofemoral rotation using three-dimensional (3D) assessments, leading to reduction of knee pain intensity in patients with PFPS. Hence, we investigated the effects of posterior X taping on the 3D angles of the lower limb (hip adduction and tibiofemoral rotation in particular), FSD performance test scores, and intensity of knee pain during FSD in patients with PFPS. We hypothesized that posterior X taping may reduce maximal excursion of hip adduction and tibiofemoral rotation in 3D assessments, improve the FSD performance test scores, and decrease the knee pain intensity during FSD.
A one-group pre-post test design was conducted in laboratory setting. We conducted an a priori power analysis using G-Power 3.0.1 software, and the sample size calculations were based on a clinical minimal difference of 20 mm on a 100 mm VAS (Crossley et al., 2004). Assuming a standard deviation of 20 mm, a power of 0.80, two tailed [alpha] value of 0.05, and effect size of 1.58, we required 10 subjects.
Sixteen participants with PFPS were included in the study from the university if they had experienced knee pain during at least two of the following activities: prolonged sitting, climbing up and down stairs, squatting, running, kneeling, jumping, deep knee flexion, and isometric contraction of quadriceps muscle (Song et al., 2017). Additional inclusion criteria were gradual onset of symptoms unrelated to a traumatic accident, a pain score of at least 30 on a 100 mm visual analog scale (VAS) during the previous week, and pain lasting for >2 months.
Participants were excluded from the study if they had a history of knee osteoarthritis by radiographic features and clinical symptomology; a history of dislocation or subluxation of the knee joint; history of surgery for repair of the meniscus, knee ligament, and knee joint; physiotherapy of the knee within the previous 6 months; steroid injection or oral medication within the previous 6 months; any neurological deficit; or allergy to tape. Before entry into the study, participants were informed about its objectives as well as the experimental and safety procedures. Each participant provided written informed consent. This study was approved by the Institutional Review Board of Jeonju University.
Posterior X taping
Non-elastic tape of 3.75 cm width (Leukotape; BSN Medical, Hamburg, Germany) was applied to participant's leg by an experienced physical therapist. Knee stiffness was lowest at 20[degrees] of knee flexion than 0[degrees] and 65[degrees] of knee flexion, and 20[degrees] of knee flexion was used for valgus-varus stress testing as loose-packed position according to the international knee documentation...