An ACL injury is normally describing a tear of the anterior cruciate ligament, a major ligament that runs diagonally in the middle of the knee. It prevents the tibia from sliding out in front of the femur, as well as providing rotational stability to the knee.
ACL injuries most commonly occur during sports that involve sudden stops, jumping or changes in direction such as basketball, football, tennis, downhill skiing, volleyball and gymnastics.
Many people hear or feel a "pop" like sound in the knee when an ACL injury occurs. Your knee may become inflamed, feel unstable and become too painful to bear weight.
When the ligament is damaged, there is usually a partial or complete tear across the tissue. A mild injury may overextend the ligament but leave it intact.
Depending on the severity of your ACL injury, treatment may include rest and rehabilitation exercises to help you regain strength and stability, or surgery to replace the torn ligament followed by rehabilitation. A proper training program may help reduce the risk of an ACL injury.
Symptoms and Diagnosis
There are three categories that ACL tears are put into depending on their severity. Below are signs and symptoms of the three different grades:
- Grade I Tear:
The fibres of the ligament are stretched but there is no tear.
There is a little tenderness and swelling.
The knee does not feel unstable or give out during activity.
No increased laxity and there is a firm end feel.
- Grade II Tear:
The fibres of the ligament are partially torn or incomplete tear with bleeding.
There is a little tenderness and moderate swelling with some loss of function.
The joint may feel unstable or give out during activity.
Increased anterior translation (amount of movement between tibia and fibula) yet there is still a firm end point.
- Grade III Tear:
The fibres of the ligament are completely torn (ruptured); the ligament itself has torn completely into two parts.
There is tenderness but not a lot of pain, especially when compared to the seriousness of the injury.
There may be a little swelling or a lot of swelling.
The ligament cannot control knee movements. The knee feels unstable or gives out at certain times.
There is also rotational instability.
No end point is evident.
Haemarthrosis (bleeding into joint space) occurs within 1-2 hours.
Often the diagnosis can be made on the basis of the physical exam alone, these tests include assessing the stability of the knee, often a clinician will see whether the knee has excessive forward movement, comparing the injured and un-injured leg to see clear differences. There is a chance that you may need scans to rule out other causes and to determine the severity of the injury.
These tests may include:
- X-rays may be needed to rule out a bone fracture. However, X-rays can't visualize soft tissues, such as ligaments and tendons.
- Magnetic resonance imaging (MRI). An MRI uses radio waves and a strong magnetic field to create images of both hard and soft tissues in your body. An MRI can show the extent of an ACL injury and signs of damage to other tissues in the knee.
The diagnosis will tell you whether you have torn your ACL and if you have, what grade (severity) the injury is.
For minor grade 1 or grade 2 tears the treatment is often a combination of rest and strengthening exercises. In order to fully rest and support the knee joint a knee brace would be very useful. The body cannot heal correctly if there is continuing damage to the ligament so appropriate rest involves keeping any twisting or hyperextension to an absolute minimum.
Initial steps should be taken to reduce swelling by applying the established RICE principles (Rest, Ice, Compression, and Elevation). Early efforts should be made to regain full range of motion (extending and bending the knee as far as you can before it gets too painful). You can also do isometric exercises, this is essentially trying to extend and bend your leg against an immovable object, making the muscles tense.
Sit on a chair that is facing a wall.
Wearing shoes, put your toes against the wall but with your foot still on the floor.
Make sure that your knee is around 90 degrees.
Apply pressure against the wall with your foot, holding the position for 10 seconds and then relaxing.
Repeat 4 times.
Knee Flexion (bending)
Sit on a standard four legged chair.
With shoes on, place your heel again the front of the chair leg.
Push backwards against the chair leg, hold for 10 seconds.
Relax and repeat 4 times.
Once you are able to fully extend and bend your knee (compare your injured leg to the uninjured, if they have the same end points then you have full range of motion) you will be able to start introducing more advanced strengthening exercises. You should find these exercises challenging and it is normal to feel uncomfortable but if you feel pain, you must stop that exercise and wait a few more days.
Hip adduction and abduction
Use a section of resistance tubing, attach to something stable and around the ankle.
For adduction, stand on one leg whilst pulling the other leg across the body, keeping the knee straight.
For abduction, turn around (keeping the tubing on the same leg) and take the leg away from the body against resistance, again keeping the knee straight.
Repeat 10 reps and 3 sets of each direction.
Leg Extension Lifts
Lay flat, tummy down on floor with you arms and legs straight.
Lift your leg backwards off the ground. Aim to lift the leg around 15-20cm off the floor and hold it there for 15 seconds.
Relax back to the ground and repeat 6 times on each leg.
Hamstring curls with band
Lay on your front with a resistance band tied to an object that won't move and also your ankle.
Start with your leg straight and then bring your heel to your bum, against the resistance of the band.
Do 10 reps and 3 sets on each leg.
If you are starting to find these exercises too easy, and continue to feel no pain, you can continue to the next stage of exercises.
Standing one leg in front of the other.
Bend the front leg to lean forwards and return to standing.
Aim for 3 sets of 10 to 20 repetitions.
Increase intensity by adding weight.
Ensure stomach muscles are kept firm when performing this exercise.
Lay on the floor on your back.
Bend your knees and place your feet flat on the floor, halfway towards your buttocks.
Lift the hips and thighs off the floor to form a straight line between your knees and shoulders.
Hold for 30 seconds and relax
Repeat 4 times.
Stand straight with feet hip-width apart.
Tighten your stomach muscles.
Lower down your body, as if you were sitting down on a chair. Don’t allow your knees to go too far forward. You don’t want them to stick out past your toes.
Straighten your legs. Repeat the movement.
Firstly squat down to about a quarter of the way down and return to the starting position.
Aim for 3 sets of 10 to 20 repetitions.
Progress this by going down to half way and then full squats (so you go down to where your upper legs are horizontal). Increase the intensity by adding weight.
It is also important to add some proprioception exercises. These exercises are used to re-teach the muscles to react accordingly when put in certain situations, better proprioception normally equals better body control.
Box Jumps - Numerous exercises can be created using a box or step to jump over.
Jump sideways over the box, moving rapidly from one foot on one side, to the other foot on the other side. This may also be performed front to back.
A further progression is high jumps over the box, firstly landing on two feet and progressing to one.
Hopping exercises - Again there are many variations on hopping exercises that can be used.
Start with a small hop on the spot and gradually increase the height jumped.
Try hopping to the front, to the side and backwards.
Try hopping from one leg and landing on the other.
Equipment such as hoops, agility ladders and minim hurdles can all be used to add further challenge.
Grade three tears tend to need surgery, after the surgery is done and at least a week has past, you may be able to start the rehabilitation as stated above.
It is important that you are finding all of these exercises easy and painless before you consider yourself to be back to full fitness. It is also recommended that you carry on some of the later stage rehabilitation exercises as this is a great way of preventing similar injury in the future.