Hi welcome to HCM I have gone thru your query regarding exercises for torn ACL in knee . Congrats for maintaining your activity level inspite of torn ACL in one knee (40 yrs ago - no surgery or rehab) and torn cartilage in the other , without any any surgery or medication for such long time till this age . Maintaining activity level is very essential to keep your body get going . Knee Mobility and strengthening exercises can begin any time . ! . After injury it is common for the patient to have difficulty straightening the leg. Gently bend and straighten the knee to keep it mobile and try to improve range of motion. You can do this in sitting, standing or lying, however you are most comfortable. Don t push it into pain, only do what you can comfortably achieve. Repeat 10 to 20 times. Repeat the set 3 times a day until full mobility is restored. 2. Lie on your back and bend the knee ensuring the foot stays in contact with the floor. Repeat 10 to 20 times. Slight discomfort may be felt but not pain. This exercise can also be done by using a towel or similar to assist in pulling the leg in. 3. Stretche the adductor muscles on the inside of the thigh. Sit on the floor with both legs out straight, as far apart as you comfortably can. Lean forwards from the hips until you feel a gentle stretch in the groin area. Hold for 20-30 seconds. . 4 .Sit on a chair .Spread your legs , parllel to your seat . stretch your legs as much as you can . Knees should not bend , stay for 20 - 30 seconds .Relax and keep feet on ground . 5. While sitting on chair , raise one foot up and keep your heel onthe brink of chair . Hold your foot from centre with fingers of both the hand and stretchyour leg in front . knee should not fold .stay befor you get stressed Relax .Keep the foot down , Repeat the same with the other foot . These exercises increase Mobility and strength & should be performed on a daily basis . Each patient and injury will be different so always take the advice of your medical professional or surgeon . Hope this helps solves your query .Take care .All the best .Get well soon Don t hesitate to come back in case of any further query . .