Medial Collateral Ligament (MCL) Injury

A medial collateral ligament (MCL) injury is a sprain or tear of the strong band on the inner side of your knee. This page explains how MCL injuries are graded, the symptoms, how they are diagnosed and treated, and when surgery is considered.

What is an MCL injury?

Your knee has four main ligaments. The two cruciate ligaments cross inside the joint, and the two collateral ligaments run down each side. The medial collateral ligament is on the inside of the knee, joining the thigh bone (femur) to the shin bone (tibia). The lateral collateral ligament is on the outside.

The MCL stops your knee from bending inwards, towards the other knee. It has a good blood supply, which is one reason it usually heals well on its own.^[1] In school sport, it was the structure involved in about a third of all knee injuries.^[2]

How are MCL injuries graded?

• Grade 1 sprain. A few fibres are stretched or torn. The knee is tender but stable.
• Grade 2 sprain. More of the ligament is torn. It is still in one piece but has become loose, and the knee opens a little when it is pushed inwards.
• Grade 3 tear. The ligament is torn right through. The knee opens further when pushed inwards and can feel unstable.

What causes an MCL injury?

Most MCL injuries happen when a force pushes the knee inwards. In a study of 130 MCL injuries in professional football, three in four were caused by contact, most often being tackled.^[3] Common causes include:

• A blow to the outside of the knee, as in football, rugby and Australian rules football
• A twisting fall with the foot planted, such as in skiing
• A sudden change of direction that forces the knee inwards.

The MCL can be injured on its own or together with other structures, most often the anterior cruciate ligament (ACL) or a meniscus. Combined ACL and MCL injuries make up about one in five ligament injuries of the knee.^[4]

What are the symptoms of an MCL injury?

• Pain on the inner side of the knee, often with a tender spot along the ligament
• Swelling, which is usually mild with grade 1 injuries
• Stiffness and difficulty bending or straightening the knee fully
• A feeling that the knee is loose or wobbles sideways, more likely with grade 2 and 3 injuries.

A grade 3 tear can hurt less than a grade 2 sprain, because the torn ligament no longer has tension on it. The amount of pain is not a reliable guide to how badly the ligament is torn.

When should you see a doctor?

See your GP or physiotherapist if your knee is painful or swollen after an injury. Seek medical advice promptly if:

• You cannot put weight on your leg
• Your knee swelled up quickly, within a few hours of the injury
• Your knee gives way or feels unstable when you walk or turn
• Your knee locks, catches or will not straighten.

Quick swelling and giving way can mean the ACL or a meniscus is also injured.

How is an MCL injury diagnosed?

The diagnosis is made mainly by examination. Your doctor gently pushes your knee inwards with the knee straight and slightly bent, and compares how far it opens with your other knee. This gives the grade. The examination also checks the other ligaments and the menisci.

An MRI scan shows where the ligament is torn and whether other structures are injured.

How is an MCL injury treated without surgery?

Grade 1 and 2 injuries, and most grade 3 tears that happen on their own, are treated without surgery.^[1] The details vary between clinics, because there are few high-quality trials of MCL rehabilitation. A 2024 review of 26 reports (1,912 people) found that bracing and exercise programs were described in very different ways.^[5]

Relative rest, ice and crutches

In the first few days, ice, elevation and avoiding painful activities help settle the pain and swelling. You can usually put weight on the leg as comfort allows. Crutches help if walking is painful.

Knee brace

A hinged knee brace protects the healing ligament from sideways force while still letting the knee bend. It is mainly used for grade 2 and 3 injuries, often for about 4 to 6 weeks. Brace use differs between clinics. In professional footballers with grade 2 injuries, those who wore a brace returned to play later than those who did not, although the more severe injuries may have been the ones braced.^[3]

Physiotherapy and exercise

Physiotherapy is the main treatment. It starts early, with exercises to regain movement, then moves on to strengthening the thigh and hip muscles, balance work, and running and sport-specific drills.

Return to sport

You can usually return to sport once your knee is stable on examination, you have full movement and strength, and you can run, hop and change direction without pain. A physiotherapist can guide you through these steps.

When is surgery considered?

Surgery for an MCL injury is uncommon.^[1] It is considered when:

• The torn end of the ligament has flipped out of place or is caught, so it cannot heal in the right position
• The ligament has pulled off a piece of bone, or the tear lies inside the joint
• A grade 3 tear is combined with injuries to other ligaments
• The knee still feels unstable on the inner side months after a full course of brace and physiotherapy.

The options are a repair, where the ligament is stitched or reattached to the bone, and a reconstruction, where a graft (a tendon taken from your own leg or from a donor) replaces a ligament that has healed too loose. A repair is usually done in the first few weeks after injury, and it is sometimes augmented (reinforced) with a synthetic tape or a donor tendon (allograft) to protect it while it heals. A reconstruction is used for long-standing looseness.^[1]

What is the outlook for an MCL injury?

The outlook is good. Most MCL tears that happen on their own, without damage to other ligaments, heal without surgery, and most people return to their previous level of activity, including sport.^[1] How long this takes depends on the grade. In young athletes, a grade 1 sprain kept people out of sport for a median of about 2 weeks, and a grade 2 or 3 injury for about 4 weeks.^[6] Recovery is usually slower when another ligament or a meniscus is also injured.

References

Show all 7 referencesHide references

1. Encinas-Ullán CA et al. 2018. Isolated medial collateral ligament tears: an update on management. EFORT Open Reviews.
2. Swenson DM et al. 2013. Epidemiology of knee injuries among US high school athletes, 2005/06–2010/11. Medicine and Science in Sports and Exercise.
3. Lundblad M et al. 2019. Medial collateral ligament injuries of the knee in male professional football players: a prospective three-season study of 130 cases from the UEFA Elite Club Injury Study. Knee Surgery, Sports Traumatology, Arthroscopy.
4. Shultz CL et al. 2023. Nonoperative management, repair, or reconstruction of the medial collateral ligament in combined anterior cruciate and medial collateral ligament injuries: which is best? A systematic review and meta-analysis. American Journal of Sports Medicine.
5. Svantesson J et al. 2024. Shedding light on the non-operative treatment of the forgotten side of the knee: rehabilitation of medial collateral ligament injuries. A systematic review. BMJ Open Sport and Exercise Medicine.
6. Roach CJ et al. 2014. The epidemiology of medial collateral ligament sprains in young athletes. American Journal of Sports Medicine.
7. Ballmer PM et al. 1988. The non operative treatment of isolated complete tears of the medial collateral ligament of the knee: a prospective randomized study. Archives of Orthopaedic and Trauma Surgery.