Knee Ligament Injuries: Causes, Symptoms and Treatment Options

Written and medically reviewed by
Dr Dinesh Sirisena
Consultant in Sports, Exercise & Musculoskeletal Medicine
Triaxis Sports & Joint Clinic

Knee ligament injuries happen when one or more of the ligaments that stabilise the knee are stretched or torn. The ACL, PCL, MCL and LCL can all be affected. Many of these injuries improve with non-surgical care such as rehabilitation, activity modification and, where appropriate, injection treatments including PRP, prolotherapy, steroid or hyaluronic acid. Treatment depends on the ligament involved, its severity, your activity level and any associated knee injuries.

 

What is a knee ligament injury?

A knee ligament injury occurs when one of the strong bands of tissue that stabilise the knee overstretched or torn. The four main ligaments are the ACL, PCL, MCL and LCL. Injuries can range from a mild sprain to a complete rupture and may involve more than one ligament.

Ligaments connect one bone to another and help control excessive movement.

The knee contains four main stabilising ligaments:

• Anterior cruciate ligament (ACL)
• Posterior cruciate ligament (PCL)
• Medial collateral ligament (MCL)
• Lateral collateral ligament (LCL)

The MCL and LCL mainly help control side-to-side movement, while the ACL and PCL help control forward and backward movement of the shin bone relative to the thigh bone.

A ligament injury may occur on its own or together with damage to the meniscus, cartilage or another ligament.

What do knee ligament injuries feel like?

Symptoms vary depending on the ligament involved and severity of the injury. Common signs include pain, swelling, stiffness, difficulty bearing weight and a feeling that the knee unstable or giving way. Some people also describe a pop or tearing sensation at the time of injury.

Symptoms may include:

• Sudden knee pain
• Swelling
• Reduced range of movement
• Difficulty walking
• Instability or giving way
• Tenderness along the inside or outside of the knee
• A popping sensation during injury
• Difficulty changing direction

The pattern of symptoms can provide clues, but examination needed to identify the ligament involved.

Where is pain felt with different knee ligament injuries?

The location of pain can vary according to the injured ligament. MCL injuries commonly cause pain along the inner knee, while LCL injuries may cause pain on the outer side. ACL and PCL injuries often cause deeper pain, swelling and instability rather than pain at one precise surface location.

Typical patterns include:

ACL injury
Pain and swelling may develop inside the knee, often with instability during pivoting or changing direction.

PCL injury
Symptoms may include pain deeper in the knee, swelling and difficulty with certain weight-bearing activities.

MCL injury
Tenderness commonly felt along the inner side of the knee.

LCL injury
Pain and tenderness are more commonly felt on the outer side.

Pain location alone cannot confirm the diagnosis because other structures such as the meniscus can produce similar symptoms.

What are the ACL, PCL, MCL and LCL?

The ACL, PCL, MCL and LCL are the four main ligaments that stabilise the knee. The ACL and PCL cross inside the joint, while the MCL and LCL sit on the inner and outer sides. Together, they control forward, backward and sideways movement and help keep the knee stable during daily activity and sport.

The knee joint formed mainly by the:

• Femur, or thigh bone
• Tibia, or shin bone
• Patella, or kneecap

Other important structures include:

Menisci
Two cartilage structures that distribute load and contribute to knee stability.

Quadriceps and hamstring muscles
Help control the knee during walking, running, jumping and landing.

Quadriceps and patellar tendons
Connect muscles and bones around the front of the knee.

Nerves and blood vessels
Pass around the knee and lower limb and may be relevant in more complex injuries.

Ligaments do not work alone. Muscle strength, coordination and joint control also contribute to knee stability.

What causes knee ligament injuries?

Knee ligament injuries commonly occur when the knee exposed to sudden twisting, excessive bending, a direct blow or a force that pushes it beyond its normal range. Sports injuries are common, but ligament damage can also occur during falls, collisions or other accidents.

ACL injuries often occur during:

• Sudden stopping
• Cutting or pivoting
• Rapid change of direction
• Awkward landing
• Direct collision

MCL injuries often follow a force to the outside of the knee that pushes the knee inward.

LCL injuries may result from a force to the inside of the knee that pushes it outward.

PCL injuries can occur when the shin pushed backwards relative to the thigh, such as during certain collisions or direct trauma.

Which sports are commonly associated with knee ligament injuries?

Sports involving pivoting, jumping, cutting, rapid acceleration or physical contact place greater demands on the knee ligaments. Football, basketball, netball, rugby, badminton and skiing are commonly associated with ligament injuries, although they can occur in almost any sport.

Sports that may involve higher ligament loads include:

• Football
• Futsal
• Basketball
• Netball
• Rugby
• Badminton
• Tennis
• Skiing
• Martial arts
• Running involving rapid directional changes
• Weightlifting where the knee loaded under poor control

ACL injuries are particularly associated with rapid changes in direction and landing mechanics.

However, simply participating in a sport does not mean a ligament injury will occur.

Who’s more likely to develop a knee ligament injury?

Risk depends on the sport, movement demands, previous injury, knee anatomy, strength, coordination and other individual factors. People who participate in pivoting or contact sports may have higher exposure to ligament injury, while a previous knee injury may also affect future stability and movement patterns.

Factors can include:

• Participation in pivoting or contact sports
• Previous knee ligament injury
• Poor landing or cutting control
• Reduced lower-limb strength
• High training exposure
• Environmental factors such as playing surface
• Individual anatomy

Risk factors do not predict with certainty who will be injured.

How are knee ligament injuries diagnosed?

Diagnosis usually begins with a detailed history and physical examination. The clinician considers how the injury happened, swelling, range of movement, tenderness and knee stability. Specific examination tests can assess the ACL, PCL, MCL and LCL. Imaging may then be considered if it’s likely to clarify the injury or identify associated damage.

During assessment, the clinician may ask:

• Did the knee twist?
• Was there a direct impact?
• Was there a pop?
• How quickly did swelling develop?
• Can you bear weight?
• Does the knee give way?
• Can you fully straighten and bend it?

For ACL injury, evidence supports using history and physical examination as an important part of diagnosis.

The clinician may also assess the meniscus, cartilage and other ligaments because combined injuries can occur.

Do I need an X-ray, MRI or ultrasound?

Not every knee ligament injury requires every type of scan. X-rays are useful when fracture or dislocation a concern. Musculoskeletal ultrasound valuable for the many knee injuries that involve structures other than the deep cruciate ligaments, including the collateral ligaments, the tendons and other superficial soft tissues, and it can also examine the knee while it moves and guide injections accurately. For the deeper ACL and PCL inside the joint, MRI provides the most detailed assessment of the ligaments, menisci and cartilage.

X-ray
May be considered after trauma when fracture, dislocation or bone injury suspected.

MRI
Can help confirm ligament injuries and identify associated meniscus, cartilage or other ligament damage.

Musculoskeletal ultrasound
A versatile, radiation-free scan that particularly useful for the collateral ligaments (MCL and LCL), the patellar and quadriceps tendons and other superficial soft tissues. It allows the knee to be assessed dynamically as it moves, compared with the other side, and used to guide injections precisely. For the deep cruciate ligaments inside the joint, MRI remains the more detailed test.

Imaging should be chosen according to the clinical question rather than ordered routinely.

Can knee ligament injuries heal without surgery?

Yes. Some knee ligament injuries can be managed without surgery, particularly partial injuries or knees that remain functionally stable. The likelihood of non-surgical management being appropriate depends on which ligament injured, the degree of instability, other knee damage, activity level and the individual’s goals.

Non-surgical management may include:

• Education
• Short-term activity modification
• Bracing where appropriate
• Gradual restoration of movement
• Strengthening
• Balance and coordination work
• Progressive return to activity

Some people with ACL injuries can function well without reconstruction, particularly when activity demands are lower and the knee remains stable.

Collateral ligament injuries such as many MCL sprains may also recover with rehabilitation.

What does rehabilitation involve after a knee ligament injury?

Rehabilitation aims to restore knee movement, strength, stability and confidence before a return to normal activity or sport. The programme depends on the ligament injured and whether surgery has been performed. Progressive strengthening, balance exercises, movement retraining and sport-specific drills are commonly introduced as recovery progresses.

Rehabilitation may include:

• Reducing swelling
• Restoring knee extension and flexion
• Quadriceps strengthening
• Hamstring strengthening
• Hip and calf strengthening
• Balance exercises
• Single-leg control
• Running progression
• Jumping and landing drills
• Cutting and change-of-direction work

Rehabilitation following ACL reconstruction commonly progresses according to pain, motion, strength and functional recovery rather than time alone.

Return to sport should therefore be based on function as well as healing time.

How can injections and regenerative treatments help knee ligament injuries?

Many knee ligament injuries improve with non-surgical care, and targeted injections can support that recovery alongside rehabilitation. Platelet-rich plasma (PRP) and prolotherapy may help ligaments heal and are used for collateral ligament injuries and, in selected cases, even partial ACL injuries.

Steroid injections can settle acute pain and inflammation, while hyaluronic acid can ease joint-related symptoms.

The most suitable option depends on the ligament involved, the stage of injury and your goals.

Delivering these injections under ultrasound guidance allows the treatment to be placed precisely at the injured structure. Because many knee ligaments and the tissues around them lie close to the surface, ultrasound particularly well suited to guiding them accurately.

PRP (platelet-rich plasma)
This uses a small sample of your own blood, concentrated to increase the platelets that release growth factors, which is then injected around or into the injured ligament under ultrasound guidance. It’s used to support healing in collateral ligament injuries and increasingly considered for selected partial ACL injuries where the knee remains stable. Improvement in pain and function usually gradual over the weeks that follow.

Prolotherapy
This involves injecting a mild irritant solution, often dextrose, close to the injured ligament to prompt a local healing response and improve ligament strength and stability. It can be helpful for chronic ligament strains or ongoing looseness that has not settled with rehabilitation alone.

Steroid injections
A corticosteroid injection can be useful for calming significant acute pain and inflammation, making it easier to move and to take part in rehabilitation. It’s used selectively, for the situations where settling inflammation the main priority.

Hyaluronic acid
Injected into the knee joint itself, hyaluronic acid can ease joint-related symptoms such as stiffness and discomfort, particularly where there associated cartilage wear or irritation of the joint lining after injury. It works by improving lubrication and cushioning within the joint.

These treatments work best as part of a broader plan that includes accurate diagnosis and rehabilitation. Where a ligament completely torn and the knee remains unstable, it’s still important to assess the knee fully before deciding on the best approach.

What activities can make a knee ligament injury worse?

Activities that involve twisting, pivoting, sudden direction changes or high-impact loading may aggravate symptoms when the knee unstable or still recovering. Early return to sport before strength and movement control are restored may also increase the risk of further injury.

Activities that may be difficult initially include:

• Running
• Jumping
• Cutting
• Pivoting
• Deep squatting
• Sudden acceleration
• Contact sport

However, complete rest not always required.

The goal usually to modify activities temporarily while maintaining safe movement and gradually rebuilding knee capacity.

A rehabilitation programme should guide when more demanding activities are reintroduced.

How long does a knee ligament injury take to recover?

Recovery time varies widely depending on the ligament injured, whether the tear partial or complete, associated injuries and whether surgery required. Mild ligament sprains may recover over weeks, while major ACL reconstruction or multiligament injuries often require many months of rehabilitation before return to demanding sport.

Recovery influenced by:

• Injury severity
• Number of structures involved
• Swelling and range of movement
• Strength
• Rehabilitation progress
• Surgical or non-surgical management
• Sport and work demands

A fixed return-to-sport date therefore not appropriate.

Instead, clinicians may assess strength, balance, movement quality, running tolerance, jumping ability and confidence before progressing activity.

When should I seek medical assessment after a knee injury?

Seek assessment when a knee injury causes marked swelling, difficulty bearing weight, instability, loss of movement or persistent pain. Prompt review also appropriate after a major collision, suspected fracture or dislocation, or when the knee repeatedly gives way after an injury.

Consider assessment if you notice:

• A loud pop or tearing sensation
• Rapid swelling
• Significant difficulty walking
• Inability to fully straighten the knee
• Repeated giving way
• Locking or catching
• Significant bruising
• Persistent pain after trauma

Associated injuries to the meniscus or cartilage may also contribute to these symptoms.

How are knee ligament injuries assessed at Triaxis Sports & Joint Clinic?

At Triaxis Sports & Joint Clinic, knee ligament injuries are assessed within a Sports Medicine and Musculoskeletal Medicine framework. The aim to identify the likely ligament involved, evaluate knee stability and function, consider imaging where appropriate and develop an individual management and rehabilitation plan.

Assessment may include:

• Mechanism of injury
• Knee swelling and range of movement
• Ligament stability testing
• Strength and functional assessment
• Review of sporting or work demands
• Sports ultrasound where appropriate
• Review or recommendation of imaging when clinically indicated
• Rehabilitation planning
• Patient education
• Shared decision-making

Where a more significant ligament tear or multiligament injury suspected, further imaging or surgical assessment may be discussed.

The focus remains on understanding the injury and choosing management according to the individual’s clinical needs rather than promoting a particular intervention.

This approach also consistent with Singapore healthcare advertising requirements. MOH states that healthcare advertising content should be accurate and truthful and should not create exaggerated expectations or induce unnecessary consumption of healthcare services.

Frequently Asked Questions About Knee Ligament Injuries

Can I walk with a torn knee ligament?

Some people can still walk after a knee ligament tear, particularly when the injury partial or swelling limited. However, being able to walk does not rule out a significant injury. ACL and other ligament injuries can still cause instability, swelling or giving way despite reasonable walking ability. Assessment appropriate when symptoms persist or the knee feels unstable.

How can I tell whether I injured my ACL or MCL?

ACL injuries commonly follow pivoting, sudden stopping or awkward landing and may cause a pop, rapid swelling and instability. MCL injuries more commonly cause pain and tenderness along the inner side of the knee, often following a sideways force. However, symptoms can overlap, so physical examination and imaging where necessary provide a more reliable diagnosis.

Does an ACL tear always need surgery?

No. Treatment depends on knee stability, activity level, associated injuries and individual goals. Some people with lower activity demands and a functionally stable knee can manage an ACL injury without reconstruction. However, active people who experience recurrent instability or need to return to high-demand pivoting sport may be more likely to consider reconstruction.

Can an MCL tear heal without surgery?

Many isolated MCL injuries can be managed without surgery because the ligament has the potential to heal with appropriate protection and rehabilitation. Management may include temporary bracing, activity modification and progressive strengthening. More complex injuries involving several ligaments or persistent instability may require further assessment.

What happens if a knee ligament injury is left untreated?

The effect depends on the ligament and severity. A mild sprain may recover without major problems, while a knee that remains unstable may repeatedly give way and limit sport or daily activity. Associated meniscus or cartilage injuries may also influence long-term function. Persistent instability should therefore be assessed rather than simply tolerated.

Can ultrasound diagnose an ACL tear?

Musculoskeletal ultrasound can evaluate many structures around the knee but has a limited role for directly assessing the ACL because the ACL lies deep inside the joint. MRI is generally more useful when detailed assessment of the ACL, PCL, menisci and other internal structures required. Ultrasound, however, very useful for many other knee injuries, including the collateral ligaments, the tendons and superficial soft tissues, and for guiding injections accurately.

How do I know when I can return to sport?

Return to sport should be based on more than time since injury. Clinicians may assess knee movement, strength, single-leg control, running tolerance, jumping, landing, change-of-direction ability and confidence. The requirements differ between sports, so a runner may progress differently from a football or badminton player.

Can a torn knee ligament heal completely?

The answer depends on which ligament injured and the type of tear. Some collateral ligament injuries have good healing potential, while a complete ACL rupture has less ability to heal in a way that reliably restores normal stability. Even when a ligament heals structurally, rehabilitation needed to restore strength, movement and confidence.

About the Author

Dr Dinesh Sirisena a Consultant in Sports, Exercise & Musculoskeletal Medicine. His clinical work includes the assessment and management of sports injuries and musculoskeletal conditions affecting the knee, joints, muscles, tendons and ligaments.

Medical Disclaimer

This page provides general educational information and does not replace individual medical advice. Knee ligament injuries vary considerably in severity. Decisions about imaging, rehabilitation, surgery or other procedures should be based on the individual’s symptoms, examination findings, medical history, activity goals and clinical assessment.