Knee ligament injury

What is a knee ligament injury?

A knee ligament injury happens when one of the bands of tissue that hold your knee joint together is overstretched, partially torn, or completely torn. There are four main ligaments around the knee, and any of them can be affected, usually after a sudden twist, direct blow, or awkward landing.

Symptoms of a knee ligament injury

Symptoms can appear straight away or build up over a few hours, and may include:

• pain in or around the knee, often worse on the sides or at the back, depending on which ligament is affected
• sudden swelling
• a popping or snapping sound or sensation at the time of injury
• your knee feeling loose, unstable, or like it might give way or buckle
• difficulty fully bending or straightening your knee
• being unable to put weight on your leg

You might also notice bruising, tenderness or warmth around the knee. Locking or clicking in the joint can be a sign that the cartilage has been damaged alongside the ligament.

Causes of knee ligament injury and who is at risk

Ligament injuries happen when the knee is forced to move further than its natural range, such as through:

• sudden twisting of the knee
• the knee being bent or straightened too far
• a direct blow to the knee
• landing awkwardly from a jump

You're more likely to injure a knee ligament if you play sports that involve sudden stops, twists or changes of direction, such as football, basketball, rugby, skiing, hockey or netball. Your risk is also higher if you suddenly increase your training intensity, start a new sport without the right equipment or technique, or play a demanding sport all year round without time to rest and recover.

Are there different types of knee ligament injury?

Yes, in two ways. Ligament injuries are named after the ligament involved:

• the anterior cruciate ligament (ACL), at the front of the knee; this is the ligament most often completely torn, often in football, netball or skiing
• the posterior cruciate ligament (PCL), at the back of the knee, the largest and strongest knee ligament
• the medial collateral ligament (MCL), on the inner side of the knee; this is the most commonly sprained knee ligament, often from twisting injuries or tackles
• the lateral collateral ligament (LCL), on the outer side of the knee

Injuries are also graded by severity. Grade 1 (mild stretching with little or no tearing), grade 2 (a partial tear) and grade 3 (a complete tear, also called a ligament rupture). More than one ligament can be injured at the same time, especially in high-impact injuries.

How a knee ligament injury is diagnosed

Your doctor or physiotherapist will examine your knee, checking your range of movement and often comparing it with your other knee. They'll ask when your symptoms started, what caused the injury and may carry out specific movement tests to check the ligaments.

You may also need imaging, such as an X-ray, ultrasound or MRI scan, to assess the extent of the damage and check for injuries to other structures, such as the cartilage.

How a knee ligament injury is treated

Non-surgical treatment

Most knee ligament injuries, including many complete tears of the MCL or an isolated PCL, heal well without surgery. Initial treatment follows the RICE method:

• rest, avoiding weight on the knee for at least 48 hours, using crutches if needed
• ice, applied for 15–20 minutes at a time, wrapped in a cloth rather than placed directly on the skin
• compression, using an elastic bandage, removed before sleep
• elevation, keeping your knee raised above the level of your heart

Over-the-counter painkillers, such as ibuprofen or paracetamol, can help with pain and swelling; check with your doctor before taking them for more than 10 days. Once the initial swelling settles, a graded exercise programme or physiotherapy will help restore movement and strengthen the muscles around your knee. More significant injuries may need a supportive brace while they heal.

Surgical treatment

Surgery is more likely to be needed for a complete ACL tear, especially in younger or active patients, or if your knee keeps giving way. It's also more likely if you've injured more than one ligament at the same time, since combined injuries tend to cause more serious instability.

Surgical treatment usually involves keyhole surgery (arthroscopy) to reconstruct the ligament using a tissue graft, followed by a course of physiotherapy. Multiple ligament reconstructions are a bigger undertaking than a single ACL repair, and usually involve a short hospital stay, a supportive brace afterwards, and a slower, more cautious rehabilitation programme.

When to see a doctor

See a GP or go to a minor injuries unit if your knee pain doesn't improve within a few weeks.

Get urgent advice from NHS 111 if your knee:

• is very painful, or you can't move it or put any weight on it
• is badly swollen or has changed shape
• locks, gives way, or clicks painfully
• is hot, red and very swollen alongside a high temperature, which can be a sign of infection

Go to A&E if you have severe pain, worsening swelling, or you can't move your knee or leg at all, particularly after a fall or direct blow to the knee.