The medial meniscus of the knee joint is injured more often than the lateral meniscus because the medial meniscus is relative -
Medial meniscus is more frequently injured than lateral meniscus because : -


The medial meniscus is securely attached around the entire periphery of the joint capsule, which makes it less mobile.
Whereas the lateral meniscus is more mobile and has no weak point between a movable and relatively fixed point.
Popliteus muscle sends few fibers into the posterior margin of the lateral meniscus. Thus muscle contraction withdraws & protects the lateral meniscus by drawing it posterolaterally during flexion of the knee and medial rotation of the tibia.
More mobile
Less mobile
Thinner
Attached lightly to femur