Knee sprain and anterior cruciate ligament (ACL) tear

Knee sprains affect thousands of Quebecers every year, whether on the soccer field, while skiing, or simply walking on uneven ground. The anterior cruciate ligament (ACL) is the knee ligament most often affected in pivoting sports.¹ If you've felt a "pop" in your knee followed by rapid swelling, you're probably wondering what happened and what you should do. Here's the good news: even a significant ACL injury can heal well with the right care. This guide will help you understand your injury, treatment options, and how to optimize your recovery. Physical therapy is the recommended first-line treatment for knee sprains. To understand how this discipline can help you, check out our comprehensive guide to physical therapy for knee pain.

What is a knee sprain and which ligaments can be affected?

A knee sprain is a stretching or tearing of one or more ligaments in the joint. A ligament is a band of fibrous tissue that connects one bone to another to stabilize the joint. Without ligaments, your knee would be unable to support your weight or control your movements.

The knee has four main ligaments that work together to ensure its stability:

The anterior cruciate ligament (ACL). Located in the center of the knee, it prevents the tibia from sliding forward relative to the femur. It also controls the rotation of the knee. It is the ligament most often injured in pivoting sports such as soccer, basketball, and skiing. The posterior cruciate ligament (PCL). It crosses the ACL to form an "X" in the center of the knee. It prevents the tibia from sliding backward. PCL injuries are less common and often occur during a direct impact to the bent knee. The medial collateral ligament (MCL). Located on the inner side of the knee, it stabilizes the knee against forces pushing inward. It is the most commonly injured ligament in the knee.² The lateral collateral ligament (LCL). Located on the outer side of the knee, it protects against outward forces. Isolated injuries to the LCL are rare.

Knee sprains can affect a single ligament or several ligaments at once. The most common combinations are ACL + MCL (the "unfortunate triad") and ACL + meniscus. Approximately 50% of ACL tears are accompanied by injuries to other structures in the knee^.

What causes a knee sprain?

A knee sprain always occurs as a result of trauma or an accident. There must be a clear and identifiable event. If your knee pain developed slowly and gradually without any accident, it is not a sprain. It is probably another condition that we describe in our guide to knee pain.

Most common injury mechanisms

Swiveling with foot fixed to the floor. This is the classic mechanism for tearing the ACL. Your foot remains planted while your body turns abruptly. This often happens in soccer, basketball, or skiing when changing direction quickly.⁴ The poorly controlled landing. Landing awkwardly from a jump with the knee in the wrong position can stretch or tear the ACL. This mechanism is particularly common among female athletes, who are 2 to 8 times more likely to suffer ACL injuries than men in the same sports.⁵ A direct blow to the knee. An impact to the outside of the knee (such as a tackle in football) can force the knee inward and injure the MCL. A blow to the front of the bent knee can damage the PCL. Falling on your knee. Falling directly onto one knee can cause different types of injuries depending on the angle and force of the impact. Hyperextension. When the knee bends too far backward, the ACL can be stretched or torn.

Factors that increase risk

Certain factors make knee ligament injuries more likely:

- Weakness in the thigh muscles (quadriceps and hamstrings) - Lack of neuromuscular control when jumping and changing direction - Muscle fatigue at the end of a game or training session - History of knee sprains (the risk of recurrence is significantly higher) - Inadequate playing surface or inappropriate footwear

What are the symptoms of a knee sprain?

Symptoms vary depending on the severity of the sprain and the ligaments affected. In general, the more severe the sprain, the more pronounced the symptoms. Here is what you may experience.

Immediate symptoms (at the time of injury)

An audible "pop." Approximately 50 to 70 percent of people who tear their ACL hear or feel a "pop" in their knee at the moment of injury.⁶ This characteristic sound is often the first sign of a serious injury. Sudden intense pain. The pain is usually sharp at the time of the accident. Its intensity varies depending on the severity of the injury. Inability to continue the activity. Most people with a significant tear cannot resume their sport or activity immediately after the injury.

Symptoms in the following hours

Rapid swelling. Swelling that appears within 2 to 4 hours after the injury suggests bleeding in the joint (hemarthrosis), which is common with ACL tears.⁷ Slower swelling, which takes 24 to 48 hours to appear, is typical of a less severe sprain. Difficulty putting weight on the leg. Depending on the severity, you may be unable to walk normally or feel pain when putting weight on your knee. Stiffness and loss of movement. Swelling and pain often limit the ability to fully bend or straighten the knee.

Symptoms that persist

Feeling of instability. This is a characteristic symptom of a significant ligament injury. You feel as though your knee is "giving way" or not holding properly, especially when pivoting or changing direction. Episodes where the knee gives way. The knee may actually give way or buckle beneath you, particularly during activities that put strain on the injured ligament. Pain during certain movements. The pain increases when you make movements that put tension on the ligament.

How is a knee sprain diagnosed?

The diagnosis of a knee sprain is based primarily on the history of the injury and physical examination. A qualified healthcare professional can often determine which ligament is affected and the severity of the injury without imaging.

Clinical evaluation

The story of the injury. How did the injury occur? Did you hear a "pop"? Were you able to continue walking? Did the swelling appear quickly? This information helps identify the ligament that is likely to be affected. The physical examination. Your physical therapist or doctor will perform specific tests to evaluate each ligament. The Lachman test and anterior drawer test evaluate the ACL. The posterior drawer test evaluates the PCL. The valgus and varus tests evaluate the collateral ligaments.⁸

Clinical tests for diagnosing ACL injuries are highly reliable when performed by an experienced professional. The Lachman test has a sensitivity of 85 to 95% for detecting ACL tears.⁹

Imaging

X-ray. It does not show ligaments, but can reveal fractures associated with the sprain. It is often requested to rule out a fracture, especially if you cannot put weight on the leg. MRI (Magnetic Resonance Imaging). This is the standard test for visualizing ligaments and confirming a tear. An MRI scan allows the extent of the injury to be seen and any associated damage (menisci, other ligaments, cartilage) to be detected.

Here is an important point to understand. An MRI is not always necessary. In most knee sprains, a clinical examination is sufficient to make a diagnosis and establish a treatment plan^. An MRI is especially useful when a complete ACL tear is suspected and a decision about surgery must be made.

When should you seek medical attention for a knee sprain?

You should consult a physical therapist or doctor if you experience the symptoms described above following a knee injury. You do not need to see a doctor before consulting a physical therapist. If your condition requires further investigation or medical advice, your physical therapist will be able to refer you.

Check quickly if you have

- Significant and rapid swelling (in the first few hours) - Inability to put weight on the leg - A distinct feeling that the knee is "giving way" or buckling - Visible deformation of the knee - Locking of the knee (inability to bend or straighten it completely)

Go to the emergency room if you have

- Significant knee deformity - Numbness or loss of sensation in the foot or leg - Pale or cold feet (sign of vascular damage) - Extreme pain that does not subside

How does physical therapy treat knee sprains?

Physical therapy is the first line of treatment for the vast majority of knee sprains, even after an ACL tear.¹¹ The body has a remarkable natural ability to heal itself. The role of physical therapy is to optimize this healing and prevent complications.

Understanding Natural Healing

Inflammation after an injury is a normal and necessary process for proper healing. Your body sends specialized cells to clean up debris and rebuild tissue. This process takes time and cannot be magically accelerated.

Think of healing a sprain as caring for a plant. You can't make a plant grow faster by pulling on it. However, you can make sure it gets enough water, sunlight, and fertilizer. You want to create the optimal environment for healing. That's exactly what physical therapy does.

What your physical therapist evaluates

During the initial assessment, your physical therapist will examine several aspects:

- The range of motion in your knee - The strength of your muscles (quadriceps, hamstrings, calves, hips) - The quality of your movements and your neuromuscular control - The stability of your knee - The way you walk

Physiotherapy interventions

Education and advice. Understanding your injury reduces anxiety and promotes healing. Your physical therapist will explain what is happening in your knee, what you can expect, and how to pace your activities. Strengthening exercises. Strength training is the cornerstone of treatment for knee sprains. Strong muscles compensate for ligament laxity and protect the knee. Exercises specifically target the quadriceps, hamstrings, and hip muscles.¹² Neuromuscular control exercises. These exercises train your nervous system to better control knee movements. They include balance, proprioception, and coordination exercises. Joint mobilization. Gentle manual techniques can help maintain knee mobility and reduce pain. Functional progression. As you heal, the exercises become more complex to prepare you for returning to your normal activities and sports.

The PEACE and LOVE protocol

For the first few days after a knee sprain, follow the PEACE and LOVE principles. This modern protocol replaces the old RICE protocol and incorporates current knowledge about tissue healing.¹³

PEACE (early days)

- Protection: Avoid movements that aggravate the pain - Elevation: Elevate your knee above your heart to reduce swelling - Avoidance: Avoid anti-inflammatory drugs and excessive ice, which can interfere with healing - Compression: Use an elastic bandage to limit swelling - Education: Learn about your injury and trust the healing process

LOVE (following days)

- Load: Gradually resume putting weight on the leg - Optimism: Maintain a positive attitude, as this promotes healing - Vascularization: Engage in light cardiovascular activities to stimulate circulation - Exercise: Perform exercises to restore mobility, strength, and proprioception

How long does it take to recover from a knee sprain?

Healing time varies considerably depending on the severity of the sprain, the ligament affected, and the level of activity you wish to resume.

Le retour aux sports de pivotement après une déchirure du LCA sans chirurgie dépend de la stabilité fonctionnelle atteinte. Certaines personnes y arrivent, d'autres optent éventuellement pour la chirurgie.

Factors that influence recovery

Several factors affect your recovery time:

- Your age and overall health. Tissue generally heals faster in younger, healthier people. - The severity of the injury. A complete tear takes longer to heal than a mild sprain. - Associated injuries. If menisci or other ligaments are also affected, recovery takes longer. - Your adherence to the rehabilitation program. Doing your exercises regularly speeds up recovery. - Your target activity level. Returning to competitive pivot sports takes longer than simply resuming walking.

Is surgery necessary for an ACL tear?

The decision to undergo surgery for an ACL tear is not automatic. It depends on several factors and should be made on an individual basis after discussion with your healthcare team.

When surgery is often recommended

- Young athletes who want to return to high-level pivoting sports - Functional instability that persists despite rehabilitation - Combined injuries (ACL + meniscus + other ligament) - Demanding physical work that requires a stable knee

When conservative treatment may be sufficient

- People who are less active or who are willing to modify their activities - Sports activities that do not require sudden pivots (cycling, swimming, jogging in a straight line) - Good functional stability achieved through rehabilitation - Older people with moderate activity expectations

What the research says

Recent studies show that conservative treatment can be as effective as surgery for some people^. An increasingly popular approach is to start with intensive physical therapy rehabilitation and then decide on surgery based on the results. Approximately 50% of people who follow this approach ultimately do not need surgery^.

If you decide to have surgery, you should know that ACL reconstruction is a proven procedure. It involves replacing the torn ligament with a graft (usually taken from your own tendons). Post-surgical rehabilitation takes approximately 9 to 12 months.

What exercises can you do at home for a knee sprain?

Your physical therapist will give you a personalized exercise program. Here are some general principles and examples of exercises that may help, depending on the stage of your recovery.

Acute phase (first few days)

- Isometric quadriceps contractions. While sitting or lying down, push the back of your knee toward the floor by contracting your thigh muscle. Hold for 5-10 seconds, repeat 10-15 times. - Ankle pumping movements. Move your foot up and down to promote circulation and reduce swelling. - Gentle knee flexion/extension. Gently bend and straighten your knee within a pain-free range of motion.

Recovery phase

- Straight leg raises. Lying on your back with your leg straight, lift your leg to about 45 degrees. Do 10-15 reps, 2-3 sets. - Mini squats. Standing, lower yourself slightly by bending your knees (30 to 45 degrees), then rise back up. Keep your knees aligned with your toes. - Balance exercises. Stand on one leg (the injured one) for 30-60 seconds. Progress to an unstable surface when this becomes easy.

Return to work phase

- Deeper squats and lunges. Gradually increase the range of motion and add resistance. - Jumping and landing exercises. Start with small jumps in place, then progress to more complex jumps. - Exercises specific to your sport. Your physical therapist will guide you in reintroducing pivoting movements and changes of direction.

Important advice. Pain is a guide, but don't rely solely on the disappearance of pain to progress. Complete healing of ligaments takes time, even when the pain is gone. Follow your physical therapist's recommendations to avoid recurrence.

How can knee sprains be prevented?

Prevention is particularly important if you have already had a knee sprain, as the risk of recurrence is significant. Here are some strategies that have proven effective.

Injury prevention programs

Structured prevention programs such as FIFA 11+ have been shown to reduce knee injuries in athletes by 30 to 50%.¹⁶ These programs include:

- Leg and core strengthening exercises - Balance and proprioception exercises - Jumping and landing training - Education on movement technique

Muscle strengthening

Strong muscles around the knee absorb forces and protect the ligaments. Pay special attention to:

- Quadriceps (front of the thigh) - Hamstrings (back of the thigh) - Hip muscles (glutes, abductors) - Core (abdominal and back muscles)

Neuromuscular training

Teach your body to control your movements well:

- Practicing changes of direction with good technique - Controlled jumping and landing exercises - One-leg balance exercises

Proper warm-up

A good warm-up prepares your muscles and joints for exercise. It should include:

- Light cardiovascular activity (5-10 minutes) - Dynamic stretching (not static stretching before activity) - Movements specific to the sport being played

Frequently asked questions about knee sprains

Can I walk with a sprained knee?

It depends on the severity. For mild sprains, you can usually walk with some discomfort. For more severe sprains, you may need crutches at first. The general rule is to put weight on gradually, respecting the pain. If you are limping significantly, use crutches until you can walk without limping.

Should you put ice on a sprained knee?

Ice can help reduce pain in the short term, but excessive use is no longer recommended. Inflammation is a natural healing process. If you use ice, limit applications to 10-15 minutes, a few times a day, mainly for pain relief in the early days.

Do I need to wear a splint or knee brace?

A splint or compression bandage can be helpful in the early days to reduce swelling and provide a feeling of stability. For more severe injuries, your healthcare professional may recommend a specific orthotic device. However, avoid wearing a rigid splint for too long, as this can weaken your muscles.

How long before you can resume sports after an ACL sprain?

Without surgery, some people can resume sports that do not require pivoting after 3-4 months of rehabilitation. Returning to pivoting sports depends on the functional stability achieved. After reconstructive surgery, it generally takes 9-12 months before a full return to pivoting sports.

Will my knee be normal after a sprain?

Most people recover completely from mild to moderate sprains. In the case of complete ACL tears, even after surgery, the knee may not return to exactly the same condition it was in before the injury. However, with proper rehabilitation, the vast majority of people regain a level of function that allows them to do the activities they want to do.

References

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