Background/Purpose: Patellofemoral (PF) osteoarthritis (OA) is prevalent in middle-aged adults. Aberrant lower extremity (LE) biomechanics is one etiology of knee OA. Reduced peak knee flexion angles and increased peak tibial abduction angles were reported during sit-to-stand (STS) in persons with general knee OA and with PF OA, respectively. Additionally, reduced strength of the hip abductor, hip extensor, and knee extensor muscles was reported in PF OA, which may impact LE biomechanics. Studies have reported improved knee and hip biomechanics in persons with PF pain when treated with proximal LE strengthening. It is unknown if a proximal LE strengthening program with pelvic/abdominal stabilization training will alter LE kinematics, improve symptoms, and improve function in persons with PF OA. This study examined the impact of a 6-week hip and trunk muscle strengthening and stabilization program on knee and hip kinematics during STS and a step-down (StDn) task and self-reported symptoms and function in persons with PF OA.

Methods: Six female subjects with PF OA and anterior knee pain, median age (interquartile range [IQR]): 52 years (48-56 years) participated in the study. Subjects attended a biomechanical evaluation, 10 supervised exercise treatment sessions, and a reevaluation. Biomechanics of the most painful LE were examined during STS from a stool and StDn on a 3-step staircase. Subjects were treated with hip and abdominal/trunk strengthening exercises. In addition, subjects were instructed in proper LE position and pelvic stability. Outcome measures included triplanar knee and hip joint peak angles and the Knee Injury and Osteoarthritis Outcome Score (KOOS). Data analysis included group medians (IQR) and Wilcoxon Signed Rank tests.

Results: Peak knee flexion angle during STS increased: Initial: 76º (67, 86), Final: 93º (87, 97), p=.03. Peak knee extension angle during STS decreased: Initial: 2º (0.4, 9), Final: -7º (-11, -4), p=.03. Peak knee extension angle during StDn decreased: Initial: -0.2º (-5, 0.5), Final: -11º (-16, -6), p=.03. KOOS-Symptoms score improved: Initial: 62 (54, 68), Final: 75 (68, 89), p=.03. KOOS-Function score improved: Initial: 69 (47, 76), Final: 84 (79, 85), p=.03.

Conclusion: A hip and trunk strengthening program with education in proper LE alignment and pelvic stability resulted in increased knee flexion angles and reduced knee extension angles during two tasks that increase PF joint stress. In addition, subjects reported significant improvement in symptoms and function.  The intervention may have improved subjects’ ability to tolerate loading the PF compartment in activities requiring knee flexion. This may be one method to improve symptoms and function in persons with PF OA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/changes-in-knee-kinematics-from-a-6-week-hip-and-trunk-strengthening-program-for-persons-with-patellofemoral-osteoarthritis/