Knee sprain and anterior cruciate ligament (ACL) tear

Knee sprains affect thousands of Quebecers every year, whether on a soccer field, while skiing, or simply by walking on uneven ground. The anterior cruciate ligament (ACL) is the knee ligament most often affected in pivoting sports.¹ If you 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 helps you understand your injury, treatment options, and how to optimize your recovery. Physiotherapy is the recommended first-line intervention for treating knee sprains. To understand how this discipline can help you, consult our complete guide to physiotherapy for knee pain.

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

A knee sprain is a stretch or tear 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 shin bone (tibia) from sliding forward relative to the thigh bone (femur). It also controls knee rotation. This is the most commonly injured ligament 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 shin bone (tibia) from sliding backward. PCL injuries are less common and often occur from a direct impact to a bent knee. The medial collateral ligament (MCL). Located on the inside of the knee, it stabilizes the knee against forces that push inward. It is the most frequently injured ligament in the knee.² The lateral collateral ligament (LCL). Located on the outside of the knee, it protects against forces that push outward. Isolated LCL injuries are rare.

Knee sprains can affect a single ligament or multiple ligaments at once. The most common combinations are ACL + MCL (the "unhappy triad") and ACL + meniscus. Approximately 50% of ACL tears are accompanied by injuries to other knee structures.³

What causes a knee sprain?

A knee sprain always occurs due to trauma or an accident. There must be a clear and identifiable event. If your knee pain appeared slowly and gradually without an accident, it is not a sprain. It is likely another condition that we describe in our guide on knee pain.

Most frequent injury mechanisms

Pivoting with the foot planted. This is the classic mechanism for an ACL tear. Your foot remains planted while your body suddenly twists. This often happens in soccer, basketball, or skiing during a rapid change of direction.⁴ Uncontrolled landing. Landing from a jump with your knee in a poor position can stretch or tear the ACL. This mechanism is particularly common among female athletes, who have a 2 to 8 times higher risk of ACL injury than men in the same sports.⁵ Direct blow to the knee. An impact to the outside of the knee (like a tackle in football) can force the knee inward and injure the MCL. A blow to the front of a bent knee can damage the PCL. Falling on the knee. Falling directly onto a 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 the risk

Certain factors make knee ligament injuries more likely:

• Weakness of thigh muscles (quadriceps and hamstrings)
• Lack of neuromuscular control during jumps and changes of direction
• Muscle fatigue at the end of a game or training
• History of knee sprain (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 affected ligaments. Generally, the more severe the sprain, the more pronounced the symptoms. Here's what you might experience.

Immediate symptoms (at the time of injury)

An audible "pop". Approximately 50 to 70% of people who tear their ACL hear or feel a "pop" in their knee at the time of injury.⁶ This characteristic sound is often the first indication of a serious injury. Sudden intense pain. The pain is usually sharp at the time of the injury. Its intensity varies depending on how severe the injury is. 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 into the joint (hemarthrosis), which is common with an ACL tear.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 might be unable to walk normally or feel pain when putting weight on your knee. Stiffness and loss of movement. Swelling and pain often limit your ability to fully bend or straighten your knee.

Persistent symptoms

Feeling of instability. This is the characteristic symptom of a significant ligament injury. You might feel like your knee is "giving way" or not holding up well, especially when pivoting or changing direction. Episodes where the knee gives way. Your knee might actually give way or buckle under you, especially during activities that stress the injured ligament. Pain during certain movements. Pain increases when you make movements that put tension on the ligament.

How is a knee sprain diagnosed?

Diagnosing a knee sprain primarily relies on your injury history and a physical examination. A qualified healthcare professional can often determine which ligament is affected and the severity of the injury without the need for imaging.

Clinical evaluation

Injury history. How did the accident happen? Did you hear a "pop"? Were you able to keep walking? Did swelling appear quickly? This information helps identify which ligament is likely affected. Physical examination. Your physiotherapist or doctor will perform specific tests to assess each ligament. The Lachman test and the anterior drawer test evaluate the ACL. The posterior drawer test evaluates the PCL. Valgus and varus stress tests evaluate the collateral ligaments.⁸

The reliability of clinical tests for diagnosing an ACL injury is high when performed by an experienced professional. The Lachman test has a sensitivity of 85 to 95% for detecting an ACL tear.⁹

Imaging

X-ray. It doesn't show ligaments but can reveal fractures associated with the sprain. It's often requested to rule out a fracture, especially if you cannot put weight on your leg. MRI (Magnetic Resonance Imaging). This is the standard imaging test to visualize ligaments and confirm a tear. MRI shows the extent of the injury and can detect associated damage (menisci, other ligaments, cartilage).

Here's an important point to understand. MRI is not always necessary. In the majority of knee sprains, a clinical examination is sufficient to make a diagnosis and establish a treatment plan.¹⁰ MRI is primarily useful when a complete ACL tear is suspected and a surgical decision needs to be made.

When should you seek help for a knee sprain?

You should consult a physiotherapist or a doctor if you experience the symptoms described above following a knee injury. You do not need a doctor's referral to see a physiotherapist. If your condition requires further investigation or medical advice, your physiotherapist will be able to guide you.

Seek prompt medical attention if you have

• Significant and rapid swelling (within the first few hours)
• An inability to put weight on your leg
• A distinct feeling that your knee is 'giving way' or buckling
• Visible knee deformity
• Knee locking (inability to fully bend or straighten it)

Go to the emergency room if you have

• Significant knee deformity
• Numbness or loss of sensation in your foot or leg
• Paleness or coldness in your foot (a sign of vascular damage)
• Extreme pain that does not lessen

How does physiotherapy treat a knee sprain?

Physiotherapy is the first-line treatment for the vast majority of knee sprains, even after an ACL tear.¹¹ The body has a remarkable natural healing capacity. The role of physiotherapy 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 clear debris and rebuild tissues. This process takes time and cannot be magically sped up.

Think of healing a sprain like caring for a plant. You can't make a plant grow faster by pulling on it. However, you can ensure it gets enough water, sunlight, and fertilizer. The goal is to create the optimal environment for healing. This is exactly what physiotherapy does.

What Your Physiotherapist Assesses

During the initial assessment, your physiotherapist will examine several aspects:

• Your knee's range of motion
• The strength of your muscles (quadriceps, hamstrings, calves, hips)
• The quality of your movements and your neuromuscular control
• The stability of your knee
• Your walking pattern

Physiotherapy Interventions

Education and advice. Understanding your injury reduces anxiety and promotes healing. Your physiotherapist will explain what's happening in your knee, what to expect, and how to manage your activities. Strengthening exercises. Muscle strengthening 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 your knee's mobility and reduce pain. Functional progression. As you heal, exercises become more complex to prepare you for returning to your normal and sports activities.

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 method and incorporates current knowledge on tissue healing.¹³

PEACE (first few days)

• Protection: Avoid movements that worsen pain
• Elevation: Elevate your knee above your heart to reduce swelling
• Avoidance: Avoid anti-inflammatory medications and excessive ice, which can hinder 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 weight-bearing on the leg
• Optimism: Maintain a positive attitude, as it promotes healing
• Vascularization: Engage in light cardiovascular activities to stimulate circulation
• Exercise: Perform your exercises to restore mobility, strength, and proprioception

What is the recovery time for a knee sprain?

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

Returning to pivoting sports after an ACL tear without surgery depends on achieving functional stability. Some individuals manage this, while others eventually choose surgery.

Factors influencing recovery

Several factors affect your healing time:

• Your age and general health. Tissues generally heal faster in younger, healthier individuals.
• The severity of the injury. A complete tear takes longer to heal than a minor strain.
• Associated injuries. If menisci or other ligaments are also affected, recovery will take longer.
• Your adherence to the rehabilitation program. Regularly doing your exercises speeds up recovery.
• Your target activity level. Returning to competitive pivoting sports takes longer than simply resuming walking.

Is surgery necessary for an ACL tear?

The decision to have surgery for an ACL tear is not automatic. It depends on several factors and should be made on an individual basis after discussing 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

• Less active individuals or those who are willing to modify their activities
• Sports activities that do not involve sudden pivoting (cycling, swimming, straight-line jogging)
• Good functional stability achieved through rehabilitation
• Older individuals with moderate activity expectations

What the research says

Recent studies show that conservative treatment can be as effective as surgery for some people.¹⁴ An increasingly popular approach is to start with intensive physiotherapy rehabilitation, then decide on surgery based on the results. Approximately 50% of people who follow this approach ultimately do not need surgery.¹⁵

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

What exercises can be done at home for a knee sprain?

Your physiotherapist will provide you with a personalized exercise program. Here are some general principles and examples of exercises that can help, depending on your stage of recovery.

Acute Phase (first few days)

• Quadriceps Isometric Contractions. While sitting or lying down, press the back of your knee into the floor by tightening 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. Perform 10-15 repetitions, 2-3 sets.
• Mini-Squats. Standing, lower yourself slightly by bending your knees (30 to 45 degrees), then return to the starting position. 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 Activities 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.
• Sport-Specific Exercises. Your physiotherapist 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 ligament healing takes time, even when the pain is gone. Follow your physiotherapist's recommendations to avoid recurrence.

How to Prevent Knee Sprains?

Prevention is especially important if you have previously had a knee sprain, as the risk of recurrence is significant. Here are some proven strategies.

Injury prevention programs

Structured prevention programs like FIFA 11+ have demonstrated a 30 to 50% reduction in knee injuries among athletes.¹⁶ These programs include:

• Leg and Core Strengthening Exercises
• Balance and proprioception exercises
• Jump and Landing Training
• Movement Technique Education

Muscle strengthening

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

• To the quadriceps (front of the thigh)
• To the hamstrings (back of the thigh)
• To the hip muscles (glutes, abductors)
• To the core (abdominal and back muscles)

Neuromuscular training

Teach your body to properly control your movements:

• Practice changing direction with proper technique
• Controlled jumping and landing exercises
• Single-leg balance exercises

Proper warm-up

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

• Light cardiovascular activity (5-10 minutes)
• Dynamic stretches (avoid static stretches before activity)
• Sport-specific movements

Frequently Asked Questions about Knee Sprains

Can I walk with a sprained knee?

It depends on how severe the sprain is. For mild sprains, you can usually walk, though you might feel some discomfort. For more severe sprains, you might need crutches initially. The general rule is to gradually put weight on your knee, listening to your pain. If you are limping a lot, use crutches until you can walk without a noticeable limp.

Should I put ice on a sprained knee?

Ice can help reduce pain in the short term, but using it too much is no longer recommended. Inflammation is a natural part of the healing process. If you do use ice, limit applications to 10-15 minutes, a few times a day, mainly for pain relief during the first few days.

Should I wear a knee brace or support?

A brace or compression bandage can be helpful in the first few days to reduce swelling and provide a sense of stability. For more severe injuries, your healthcare professional might recommend a specific brace. However, avoid wearing a rigid brace for too long, as it can weaken your muscles.

How long until I can return to sports after an ACL sprain?

Without surgery, some people can return to sports that don't involve pivoting after 3-4 months of rehabilitation. Returning to pivoting sports depends on how much functional stability you achieve. After reconstructive surgery, it generally takes 9-12 months before you can fully return to pivoting sports.

Will my knee be normal after a sprain?

For mild to moderate sprains, most people recover completely. For complete ACL tears, even after surgery, the knee may not return exactly to its pre-injury state. However, with proper rehabilitation, the vast majority of people regain a functional level that allows them to do the activities they want.

References

1. Majewski M, Susanne H, Klaus S. Epidemiology of athletic knee injuries: A 10-year study. Knee. 2006;13(3):184-188.
2. Phisitkul P, James SL, Wolf BR, Amendola A. MCL injuries of the knee: current concepts review. Iowa Orthop J. 2006;26:77-90.
3. Noyes FR, Mooar PA, Matthews DS, Butler DL. The symptomatic anterior cruciate-deficient knee. Part I: the long-term functional disability in athletically active individuals. J Bone Joint Surg Am. 1983;65(2):154-162.
4. Boden BP, Dean GS, Feagin JA Jr, Garrett WE Jr. Mechanisms of anterior cruciate ligament injury. Orthopedics. 2000;23(6):573-578.
5. Prodromos CC, Han Y, Rogowski J, Joyce B, Shi K. A meta-analysis of the incidence of anterior cruciate ligament tears as a function of gender, sport, and a knee injury-reduction regimen. Arthroscopy. 2007;23(12):1320-1325.
6. Kostogiannis I, Ageberg E, Neuman P, Dahlberg L, Friden T, Roos H. Activity level and subjective knee function 15 years after anterior cruciate ligament injury. Am J Sports Med. 2007;35(7):1135-1143.
7. Fithian DC, Paxton LW, Goltz DH. Fate of the anterior cruciate ligament-injured knee. Orthop Clin North Am. 2002;33(4):621-636.
8. Benjaminse A, Gokeler A, van der Schans CP. Clinical diagnosis of an anterior cruciate ligament rupture: a meta-analysis. J Orthop Sports Phys Ther. 2006;36(5):267-288.
9. van Eck CF, van den Bekerom MP, Fu FH,"; Poolman RW, Kerkhoffs GM. Methods to diagnose acute anterior cruciate ligament rupture: a meta-analysis of physical examinations with and without anaesthesia. Knee Surg Sports Traumatol Arthrosc. 2013;21(8):1895-1903.
10. Oei EH, Nikken JJ, Verstijnen AC, Ginai AZ, Myriam Hunink MG. MR imaging of the menisci and cruciate ligaments: a systematic review. Radiology. 2003;226(3):837-848.
11. Filbay SR, Grindem H. Evidence-based recommendations for the management of anterior cruciate ligament (ACL) rupture. Best Pract Res Clin Rheumatol. 2019;33(1):33-47.
12. Lim HY, Wong SH. Effects of isometric, eccentric, or heavy slow resistance exercises on pain and function in individuals with patellar tendinopathy: A systematic review. Physiother Res Int. 2018;23(4):e1721.
13. Dubois B, Esculier JF. Soft-tissue injuries simply need PEACE and LOVE. Br J Sports Med. 2020;54(2):72-73.
14. Frobell RB, Roos HP, Roos EM, Roemer FW, Ranstam J, Lohmander LS. Treatment for acute anterior cruciate ligament tear: five year outcome of randomised trial. BMJ. 2013;346:f232.
15. Grindem H, Eitzen I, Engebretsen L, Snyder-Mackler L, Risberg MA. Nonsurgical or Surgical Treatment of ACL Injuries: Knee Function, Sports Participation, and Knee Reinjury. J Bone Joint Surg Am. 2014;96(15):1233-1241.
16. Thorborg K, Krommes KK, Esteve E, Clausen MB, Bartels EM, Rathleff MS. Effect of specific exercise-based football injury prevention programmes on the overall injury rate in football: a systematic review and meta-analysis of the FIFA 11 and 11+ programmes. Br J Sports Med. 2017;51(7):562-571.