To investigate the correlation of lower-limb muscle function with clinical status, balance, and quality of life in individuals with Parkinson disease (PD). Methods: Twenty-five participants were included. Outcome measures were assessed through scales and questionnaires. Quadriceps muscle function was assessed through a maximal isometric voluntary contraction. Spearman's correlation coefficient (ρ) analysis was performed. Results: Quadriceps peak force was negatively correlated with scores of the Unified Parkinson's Disease Rating Scale (UPDRS) part III (ρ = 0.610) but positively correlated with scores of the Mini-BESTest (ρ = 0.484) and the Timed Up and Go test (ρ = 0.528). The rate of force development was negatively correlated with scores of the UPDRS II (ρ = −0.437) and III (ρ = −0.577). Force variability was positively correlated with the quality of life (Parkinson's Disease Questionnaire 39; ρ = 0.455). Conclusion: Better quadriceps muscle function is associated with better clinical status, balance, and quality of life in people with PD.