What's the reason why i may need a cast on my knee? is there any point of having one for a meniscus tear and possible ligament laxity

Knee immobilizer: A removable hinged knee brace is more commonly used to help protect the unstable knee, especially for the first 6 weeks after reconstructive surgery. Meniscal repairs do not routinely require bracing, although limited weight bearing (crutches) along with limits of range of motion (0-90 degrees) are commonly recommended for about 6 weeks