Abstract
PURPOSE: Patients with cerebral palsy commonly exhibit flexed knee gait. Hamstring lengthening is a common intervention, and the popliteal angle test (PAT) is widely used to assess hamstring tightness and guide surgical planning. This systematic review evaluated the role of the popliteal angle test in relation to surgical hamstring lengthening. METHODS: PubMed, Scopus, Web of Science, Embase, and Cochrane Library were searched from inception to January 29, 2025 for articles involving cerebral palsy, popliteal angle test, and hamstring lengthening. RESULTS: Thirty-one articles met the inclusion criteria. Outcomes were reported per patient or per limb, with Gross Motor Function Classification System level specified in 19 studies. Nineteen studies (61.3%) incorporated the popliteal angle test in preoperative assessments, 6 (19.4%) used it as the sole surgical determinant, and 4 (12.9%) applied it intraoperatively to guide additional hamstring lengthening. Twenty-seven studies reported pre- and postoperative popliteal angle test values; among the 21 providing statistical analyses, all showed significant postoperative improvement, although repeat procedures and longer follow-up failed to demonstrate sustained benefit. Kinematic data were reported in 20 studies, but analyses were mostly limited to sagittal knee flexion/extension during stance. Follow-up was reported in 24 studies, but durations rarely exceeded 2 years. CONCLUSIONS: The popliteal angle test remains widely used in the surgical assessment of flexed knee gait in cerebral palsy, but methodological heterogeneity limits comparability across studies. While postoperative improvements are common, they cannot be reliably correlated with gait outcomes. The main limitation lies in its use as the sole surgical or intraoperative determinant. Standardized protocols, integration with gait analysis, and long-term follow-up are needed to clarify its prognostic value.