How Stretching Can Help Prevent ACL Injuries

woman doing kneeling hip flexor stretch

Verywell / Ben Goldstein

The knee is a complicated structure that has lots of moving parts held together by four main ligaments, a type of connective tissue that attaches muscles to bones. One of the most vulnerable ligaments in the knee is the anterior cruciate ligament (ACL).

Sprains and tears of the ACL are common, especially among athletes. Basketball players, football players, and soccer players are particularly vulnerable to ACL injuries, which sometimes are severe enough to require surgery. Even if you aren't a high-level athlete, it's smart to do all you can to protect your ACL joint. Of course, you can't change the structure of ligaments in a joint, or the bones that make up the joint either, for that matter. But there's a lot you can do to help stabilize and protect them. One important way to prevent ACL injuries is by keeping the muscles that support the knee flexible with stretches.

What's in a Knee?

Three bones come together to form the knee joint: The bottom of the thigh bone (femur), the top of the shin bone (tibia), and the kneecap (patella). The muscles that connect this trio of structures are the quadriceps (the large muscles that make up the front of the thigh that often are referred to as the quads); the hamstrings (equally large muscles in the back of the upper leg); and the calf muscles of the lower leg. There's also an important length of connective tissue called the iliotibial (IT) band that connects the hip bone to the knee.

Exercises that focus on building up the muscles surrounding the knee are important for keeping it strong enough to safely take on a person's body weight. Stretching those muscles is equally important. They need to be pliable enough to allow the joint to move through a full range of motion. Image what would happen if, say, you tried to straighten your knee to kick a ball and your muscles wouldn't allow your leg to extend all the way? The ligaments could snap like a stiff rubber band.

Easy Stretches for the ACL

Calf Stretch

  • Stand with both feet on the ground, toes pointing straight ahead, feet hip-distance apart.
  • From your hips, bend forward and reach your hands toward the ground.
  • At the same time, bend your right knee, but keep your left leg straight.
  • Keep reaching toward the ground until you feel a stretch in the back of your calf. If your lower back is tight or injured, rest your hands on your thighs, just above your knees.
  • Hold for 30 seconds without bouncing or forcing the stretch; breathe normally.
  • Switch legs and repeat. Do this stretch twice on both sides. 

Quadriceps Stretch

  • Stand next to a sturdy chair or recruit a friend to help you. Place your left hand on the chair or your partner's shoulder. 
  • Bend your right knee behind you to bring your heel toward your right buttock. Reach back with your right hand and grab the front of your right ankle.
  • Keeping your right knee pointed downward and next to your left knee, gently pull your heel closer to your butt until you feel gentle tension along the front of your thigh from knee to pelvis.
  • Hold for 30 seconds, breathing normally, then lower your foot to the ground and switch sides. Do both sides two times. 

Hamstring Stretch 

Hamstring Stretch
Verywell / Ben Goldstein
  • Sit on the ground with your right leg extended in front of you.
  • Bend your left knee and rest the bottom of your foot against the inside of your right thigh.
  • Keeping a slight curve in your lower back, reach your chest toward your knee. Go only as far as you can without hunching over.
  • If this is far enough to feel a stretch along the back of your leg, stop here. If you have the flexibility to reach forward and grab the toes of your right foot with both hands without losing the curve in your back, that will give your hamstring a little extra stretch.
  • Breathing normally, hold the stretch for 30 seconds, then repeat with the other leg.

Inner Thigh Stretch (20 seconds x 3 reps)

Inner Thigh Stretch
Verywell / Ben Goldstein
  • While still seated on the ground, extend both legs in front of you, then widen then as far apart as comfortable. 
  • Keeping the slight curve in your low back, reach both hands in front of you toward the ground between your legs. 
  • Go just far enough to feel a stretch in your inner thigh.
  • Hold the stretch for 20 seconds and repeat three times.

Hip Flexor Stretch (20 seconds x 2 reps)

Hip Flexor Stretch
Verywell / Ben Goldstein
  • From standing, step far forward with your right leg and drop your left knee to the ground.
  • Drop your left knee down to the ground.
  • Place both hands on top of your right thigh and lean forward, keeping your hips square with your shoulders.
  • If you can do this while staying balanced, reach behind you with your left hand and grab your left ankle to pull your foot closer to your buttocks.
  • Hold for 20 seconds and repeat on the other side.
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Article Sources

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  • American Council on Exercise "What Exercises Are Best to Strengthen My Knee?", by Adam Bordes, Nov 16, 2011.