Background: Patellofemoral pain (PFP) syndrome is closely associated with muscle tightness. However, studies regarding the effects of stretching exercises on PFP patients with inflexible hamstrings are scarce. The aim of the study was to compare the effects between static and dynamic hamstring stretching in patients with PFP who have inflexible hamstrings.
Hypothesis: Compared with static hamstring stretching, dynamic hamstring stretching will improve the parameters of hamstring flexibility, knee muscle strength, muscle activation time, and clinical outcomes in this patient population.
Study design: Prospective randomized controlled trial.
Level of evidence: Level 2.
Methods: A total of 46 patients (25, static stretching; 21, dynamic stretching) participated. Hamstring flexibility was assessed according to the popliteal angle during active knee extension. Muscle strength and muscle activation time were measured using an isokinetic device. Clinical outcomes were evaluated using the visual analog scale (VAS) for pain and the anterior knee pain scale (AKPS).
Results: There were no differences in hamstring flexibility and knee muscle strength of the affected knees between the groups (P > 0.05). Significantly improved muscle activation time and clinical outcomes of the affected knees were observed in the dynamic stretching group compared with the static stretching group (all Ps < 0.01 for hamstring, quadriceps, VAS, and AKPS).
Conclusion: In patients with PFP who have inflexible hamstrings, dynamic hamstring stretching with strengthening exercises was superior for improving muscle activation time and clinical outcomes compared with static hamstring stretching with strengthening exercises.
Clinical relevance: Clinicians and therapists could implement dynamic hamstring stretching to improve function and reduce pain in patients with PFP who have inflexible hamstrings.
Keywords: dynamic stretching; hamstring flexibility; muscle activation time; muscle strength; static stretching.