What are the signs you have a MCL injury?

Several. Mcl injury is a planting, cutting injury. Most people experience a "pop" pain swelling and gradual stiffness over the next several hours. Mcl injuries can be associated with injury to the meniscus and other ligament injuries. Ice, elevate and maintain motion the best you can. A mild injury should loosen up in a few days to weeks. More severe injuries take longer and rarely surgery. Get it checked.