Award Date

5-15-2025

Degree Type

Doctoral Project

Degree Name

Doctor of Physical Therapy (DPT)

Department

Physical Therapy

First Committee Member

Kai-Yu Ho

Second Committee Member

Daniel Young

Third Committee Member

Kai-Yu Ho

Number of Pages

39

Abstract

Purpose/Hypothesis: Individuals with patellofemoral pain (PFP) often present with knee valgus during weight-bearing activities. Weakness in the gluteal muscles is thought to contribute to this condition, but recent studies suggest that hip weakness might be a secondary problem in this population. Central nervous system adaptations have been noted in persons with PFP, which can lead to altered muscle function, faulty movement patterns, and poor function. Experimentally, central activation can be quantified by a central activation ratio (CAR) via superimposed burst (SIB) during a maximum voluntary isometric contraction (MVIC) where the ratio of volitionally activated motor units to total motor units of a single muscle can be determined. This study aims to compare the CAR of the gluteus medius (GMed) and gluteus maximus (GMax) between individuals with and without PFP and to assess the association between CAR of the gluteal musculature and the frontal plane projection angle (FPPA) of the trunk and lower extremity during weight-bearing activities using 2D motion analysis and functional assessment. We hypothesize that individuals with PFP would have a lower CAR of the GMed and GMax compared to controls, and this lower CAR would be associated with altered FPPA and diminished function.

Participants: 12 participants without PFP (4M/8F, age=24.2±1.8 yrs, BMI=24.0±4.2) and 10 participants with PFP (4M/6F, age=22.4±2.8 yrs, BMI=23.5±3.9).

Materials and Methods: Participants performed a single-leg squat, single-leg hop, single-leg landing, forward step down, and lateral step down, analyzed using an iPhone 13 Pro Max. Frontal plane kinematics (lateral trunk lean (LTL), hip FPPA, knee FPPA, and dynamic valgus index (DVI)) were measured. CAR of the GMax and GMed was tested using the SIB protocol. CAR was calculated as the ratio of maximal torque output prior to and during SIB. PFP participants also completed the Anterior Knee Pain Scale (AKPS). Independent t-tests compared CAR between groups, and Pearson correlation coefficients evaluated the associations between CAR, frontal plane kinematics, and AKPS.

Results: There was no significant difference in CAR of the GMed and GMax between groups (p≥0.067). However, significant correlations were found between CAR of the GMax and AKPS (R=0.790, p=0.003), CAR of the GMed and AKPS (R=0.584, p=0.038), and CAR of the GMax and LTL during single-limb landing (R=0.533, p=0.006).

Conclusions: While no significant group differences were found, there was a trend towards lower GMax CAR in PFP participants (PFP 0.91; control=0.93; p ≥0.067). Higher CAR was associated with better function in participants with PFP. Lower GMax CAR may relate to ipsilateral trunk lean during single-limb weight-bearing, a strategy used to reduce the external hip torque.

Clinical Relevance: Lower central activation of gluteal muscles may be linked to poorer function and altered kinematics in patients with PFP. Future larger-scale studies should identify PFP subgroups with diminished gluteal central activation.

Keywords

Gluteal Muscles; Central Activation; Frontal Plane Kinematics; Patellofemoral Pain; Physiology; Superimposed Burst Technique; Physical Therapy; Rehabilitation

Disciplines

Orthopedics | Physical Therapy | Rehabilitation and Therapy | Sports Medicine

File Format

pdf

File Size

953 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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