Lower-body strength plays a crucial role in football performance and injury prevention, and thus, monitoring of strength variables has become crucial in the training process. This study aims to (1) assess knee muscle strength performance through intra- and inter-limb asymmetries and (2) examine the relationships between knee muscle strength, body composition, and vertical jump performance (squat jump and countermovement jump). Twenty-seven semiprofessional female football players (21.5 ± 4.9 years) were evaluated for body composition, isokinetic knee muscle strength (60º/s and 180º/s), and vertical jump tasks. Peak torque (PT), peak torque/body weight (PT/BW), bilateral strength deficit, and the hamstring-to-quadriceps strength ratio (H/Q) for knee extensors (KE) and flexors (KF) in both the preferred and non-preferred legs. The H/Q ratio and the bilateral strength deficit revealed no significant intra- or inter-limb asymmetries in knee muscle strength. Strong correlations were found between vertical jump performance and KE strength at both 60º/s (p ≤ 0.01) and 180º/s (p ≤ 0.01). Additionally, a significant negative correlation was observed between vertical jump performance and body fat percentage (p ≤ 0.01). These findings highlight the critical role of knee muscle strength in explosive tasks and underline the negative impact of higher body fat on lower-body strength performance.