Quadriceps Strengthening At Different Angles in Patellofemoral Pain

Introduction: Patellofemoral pain (PFP) is characterized by anterior, retropatellar and/or peripatellar pain during activities such as running, squatting, kneeling, or prolonged sitting. This condition affects approximately 25% of the general population. Given its complex and multifactorial etiology, PFP presents a significant treatment challenge. All clinical practice guidelines recommend strengthening the quadriceps femoris muscle as a key component in the management of PFP. However, exercises aimed at strengthening the quadriceps place considerable stress on the patellofemoral joint and are often poorly tolerated by patients. Clinicians commonly employ a conservative strategy that restricts open kinetic chain knee extension exercises to a limited range of 90° to 45° of knee flexion and closed kinetic chain exercises to 0° to 45°. Yet, restricting the range of motion may result in suboptimal outcomes for patients with higher load tolerance and may foster beliefs regarding knee joint fragility. Objective: We aim to compare the effects of quadriceps femoris strengthening within a limited range to a patient-guided range of motion on pain, function, knee confidence, and kinesiophobia in individuals with PFP. Methods: A randomized clinical trial will be conducted with two parallel groups, using a balanced 1:1 allocation and a double-blind design. The study population will include men and women aged 18 to 35 years, diagnosed with PFP. Participants will be randomly assigned to either the limited range group or the patient-guided range of motion group. They will participate in a supervised therapeutic protocol, with sessions averaging 40 minutes, twice a week, for six consecutive weeks. The primary outcome will be pain, assessed using the numerical pain rating scale (0-10), and kinesiophobia, assessed by the Tampa Scale . Secondary outcomes will include pain, self-reported function, measured by the Anterior Knee Pain Scale (AKPS), perceived improvement by the Global Rating of Change Scale, quadriceps strength, kinesiophobia and analgesic consumption.