First things first, ligaments are very different to tendons. Ligaments connect bone to bone; tendons connect muscle to bone. If you injure a ligament, your joint will be destablized; if you injure a tendon, the muscle it attaches to will no longer be able to usefully pull on anything.

In response to your question, it wasn't until Avicenna, a thousand years ago, that tendon repair was well documented and recommended. Galen describes one instance of tendon repair on an injured gladiator but generally recommended against it. The vast majority of the world population even in Avicenna's time did not have access to Avicenna or the surgeons he trained, so the answer to your question is... live as best they could.

ACL repair as a modern surgery is only about 100 years old. You can function reasonably well with a torn knee ligament by the way -- you'll certainly have trouble doing anything athletic, and your knee may buckle frequently, but you should be able to walk.

Further reading: Insights into Avicenna’s knowledge of the science of orthopedics. Behnam Dalfardi et al. World journal of orthopedics 5 (1), 67, 2014