Knee bones & ligaments

The ACL Is Not The Only Ligament In Your Knee. Injuries To The Other Ligaments Are Common, Especially Medial Collateral Ligament (MCL) Tears or ‘Sprains’.

These injuries and the much less frequent posterior cruciate ligament (PCL) tears rarely require surgery although early diagnosis and (where necessary) bracing can avoid more serious problems later.

More uncommon but sometimes devastating injuries are those involving more than one ligament. These are often high-energy injuries and may require a combination of surgery, bracing and rehabilitation. Their long-term outcomes are less predictable.

​What Is The MCL & What Does It Do?

The medial collateral ligament (MCL) is a broad ligament which sits on the inner side of the knee, connecting the thigh bone and shin bone.

The MCL helps stabilise the bones of the knee joint. It prevents excessive movement of the shin bone, limiting outwards movement relative to the thigh bone.

MCL injury is the commonest of all knee ligament injuries. It may occur in isolation, or in combination with ACL rupture, meniscal tears, complex ligament injury, or fracture.

What Are The Symptoms Of MCL Injury?

An MCL tear occurs with a wrenching or twisting injury.

It is painful when it happens. You may feel a tearing sensation and there may be some swelling and pain on the inner aspect of the knee.

If the whole knee swells up rapidly, it is probably more than just an MCL injury.

Torn Medial Collateral Ligament diagram

How Do You Diagnose An MCL Injury?

As with many knee injuries, early diagnosis is important. The faster you seek help, the better the outcomes are likely to be.

Examination will usually show tenderness on the inner aspect of the knee at the point where the MCL is torn. It can tear in the middle, or it can pull off the bone at either end.

MCL tears are graded into three groups.

Grade 1: partial tear or sprain, when some fibres are torn but it is not really stretched. Examination will reveal pain and tenderness but no laxity.

Grade 2: partial tear with definite stretching. The MCL will feel lax when examined.

Grade 3: a complete rupture with dramatic opening up. This is more likely to have an associated ACL tear.

Grade 2 and 3 are distinguished by special examinations.


With an MCL injury, X-rays might appear normal unless a fragment of bone is pulled off.

Sometimes an excessive gap between the bones on the inner aspect will be apparent.

MRI scans will show up MCL tears, as will ultrasound scans, but they are not always necessary

X-ray of a right knee MCL Rupture

X-rays might be normal, unless a fragment of bone is pulled off. Sometimes an excessive gap between the bones on the inner aspect will be apparent.

MCL Injury - MRI scan of right knee - normal & ruptured MCL

MRI scans will show up MCL tears, as will ultrasound scans, but they are not always necessary.

ACL knee brace non-surgical treatment

How Do You Treat An MCL Tear?

Most isolated MCL tears will heal very well without the need for surgery and with no long term issues.

Grade 1 injuries are treated according to symptoms. You won’t need a brace but you may find crutches valuable early on until the knee is comfortable enough to walk without them. Rest, ice, compression, elevation and physiotherapy are all beneficial. Full recovery takes at least six weeks.

Grade 2 and grade 3 injuries are usually treated with a brace for six weeks to prevent the MCL stretching while it is trying to heal. Although it is possible to do well without bracing, most knee surgeons feel it is beneficial to the outcome. For that reason early, accurate diagnosis is important, to avoid missing the boat with bracing treatment.

Full recovery can take up to 3 months. Surgery is rarely required.

Repair might be considered urgently where there is a complex ligament injury e.g. knee dislocation.

In cases of chronic laxity, especially with other ligament tears, we may occasionally undertake reconstruction using your own hamstring tendon or an artificial graft material.

What Is A PCL Injury?

Posterior cruciate ligament (PCL) injuries occur less frequently than anterior cruciate (ACL) injuries. When they do occur, they are often the result of an impact to the front of the leg, specifically the top of the shin bone at the front.

The commonest causes are sports injuries (falling heavily onto the front of a bent knee – rugby; or collisions with goalposts – football) and car accidents where the top of the shin strikes the dashboard.

The knee may swell and you may feel initial pain and a sense of the knee being unstable but these injuries rarely cause true instability unless they are combined with damage to another ligament.


PCL Injuries -PCL MRI scan of a normal & PCL tear injury

How Do You Treat PCL Injuries?

Where the PCL is the only injury physiotherapy will usually be sufficient. If the diagnosis is made within a week or so, a special brace (PCL brace) might be used to hold the tibia forwards while some healing occurs. Surgery is not usually required.

The prognosis following these injuries is good but some patients do develop pain behind the knee cap over many years, because of increased load on that joint. Nevertheless, many people with this injury return to full activities including high-level sport.

PCL injuries combined with other ligament damage, however, usually produce instability problems which typically require surgical reconstruction.

ACL torn Anterior Cruciate Ligament

What Are Complex Ligament Injuries?

A complex ligament (or multi-ligament) injury of the knee implies that more than one of the major knee ligaments have been damaged.

The major knee ligaments are the anterior cruciate ligament (ACL), the posterior cruciate ligament (PCL), the medial collateral ligament (MCL) and the lateral collateral ligament (LCL).

The LCL has important associated structures grouped together, which are referred to as the postero-lateral corner.

In order to sustain a complex ligament injury of the knee the patient will usually have experienced a major accident or high-energy twisting injury. In such cases both the treatment and rehabilitation can be difficult and prolonged.

What Are The Symptoms Of A Complex Knee Ligament Injury?

In order to damage more than one ligament the knee will have dislocated at the moment of injury. Even if it immediately pops back into place the ligament damage can remain.

This means that injuries can present as obviously dislocated knees requiring immediate manipulation to simply restore the shape of the leg (and reduce pressure on important blood vessels). Alternatively, the injury may first appear to be minor but with increased pain and/or swelling. Sometimes it can take time for a patient to seek help, usually when they realise their knee feels unstable (as though it will give way).

Pain is usually more severe than with simple injuries and sometimes the injury can involve the blood vessels supplying the lower leg (an emergency) or a vital nerve (‘common peroneal’) leading to temporary or permanent ‘foot drop’.

Complex Knee Ligament Injury Knee Dislocation
Complex Knee Ligament Injuries - MRI scan of a normal LCK & an LCL tear

How Do You Diagnose Complex Knee Ligament Damage?

Urgent assessment by a knee specialist is critical for these injuries as surgery is usually required.

For some injuries this should ideally take place within 2-3 weeks (except combined ACL/MCL injuries– see below).

A clinical examination will be combined with imaging (x-rays, MRI and sometimes additional blood vessel investigations) in order to plan treatment.

How Do You Treat Complex Knee Ligament Injuries?

Complex ligament injuries of the knee are quite rare and treatment is, by definition, more difficult. It usually involves multiple ligament reconstruction and a long period of rehabilitation.

Where early surgery is required this often takes place after swelling has reduced and is normally followed by a period of time with the knee in a brace, and using crutches.

ACL/MCL injuries are probably the most common combination and are usually best treated by allowing the MCL to heal with the knee protected in a hinged knee brace for a few weeks followed later by ACL reconstruction.

Sometimes, if there is severe stretching of the outer ligaments of the knee, where patients seek help some time after the injury, an osteotomy may be required to try and improve the alignment of the knee.

Results of surgery for complex knee ligament injury depend on the specific injury pattern and are much less predictable than for simple ACL reconstruction.

When these injuries are combined with nerve and/or blood vessel damage the chances of returning to active sport is substantially reduced – but the faster you seek help, the greater the likelihood of a positive outcome.

For Swift, Expert Diagnosis Of Your Injury

You May Also Be Interested In

Treatment FAQs, your questions answered

Treatment FAQs

Here are some of our knee specialists’ most frequently asked questions for some of our most common procedures

Specialist knee surgeons will help you to speed up your recovery

Sports Injuries

Early diagnosis, collaboration & understanding to speed your recovery

Watch the Is My Knee Injury Serious video

Yorkshire Knee Clinic Videos

It’s much easier to understand what’s really happening inside the knee when you can see it for yourself

Internet Explorer is no longer supported.