BACKGROUND: Post-traumatic knee osteoarthritis affects an estimated one in two people within a decade of traumatic knee injury. While altered biomechanics in older adults are associated with the onset and progression of insidious-onset knee osteoarthritis, the relationship between biomechanics and post-traumatic osteoarthritis is less clear. OBJECTIVE: We aimed to evaluate associations between knee biomechanics and future structural and symptomatic outcomes post-surgery for traumatic knee injuries. METHODS: We systematically searched MEDLINE, EMBASE, Scopus, CINAHL, and SPORTDiscus from inception until May 2025. The eligibility criteria were studies that: (1) included participants post-surgery for traumatic knee injuries; (2) assessed knee biomechanics (kinetics, kinematics) during dynamic tasks (e.g. walking, hopping); and (3) reported longitudinal associations between early knee biomechanics and future post-traumatic osteoarthritis outcomes, including joint structure (imaging) or symptoms (patient-reported outcomes). Meta-analyses were completed where possible, with the remaining studies synthesised narratively due to heterogeneity precluding meta-analysis. RESULTS: We included 18 studies (structure = 12, symptoms = 6); 17 following anterior cruciate ligament reconstruction and one post-meniscectomy. Meta-analysis of three studies examined the association between patellofemoral contact force up to 1-year post-anterior cruciate ligament reconstruction and future cartilage structure at 1-5 years, assessed via T2 relaxation times and progression of cartilage defects on magnetic resonance imaging. Lower patellofemoral contact force was associated with worse future trochlear cartilage structure (r = - 0.48, 95% confidence interval - 0.63, - 0.31; I = 0%), but the association with patellar cartilage was not significant (r = - 0.09, 95% confidence interval - 0.30, 0.12; I = 0%). A meta-analysis of three studies found no relationship between joint kinetics (e.g. knee flexion moment or knee adduction moment) and future structural outcomes in the tibiofemoral compartment, including T1 rho relaxation times, cartilage defects on magnetic resonance imaging and radiographic osteoarthritis. Narrative synthesis of other studies found that lower kinetic measures (e.g. knee flexion moment, knee adduction moment) were associated with worse future trochlear cartilage, but relationships with patellar cartilage and tibiofemoral joint structure were inconsistent. For symptoms, although time post-surgery appears to influence associations with mechanical loading, lower measures of frontal plane kinetics (e.g. knee adduction moment, medial ground reaction force) were associated with better future symptoms regardless of the timepoint. CONCLUSIONS: Underloading of the patellofemoral joint within the first year post-anterior cruciate ligament reconstruction is associated with worse patellofemoral cartilage, a pattern not observed in the tibiofemoral joint. Clinicians should consider optimising loading interventions and addressing modifiable biomechanical alterations post-surgery to preserve cartilage health and reduce symptoms. PROTOCOL REGISTRATION: PROSPERO: CRD42024504099.