Knee
Knee Ligament Sprain (MCL / ACL)
Overstretched or torn knee ligaments after a twist, tackle or awkward landing. MCL sprains usually settle with rehab; ACL tears need careful assessment.
Common symptoms
- Pain on the inner side of the knee after a sideways force (MCL)
- A 'pop' felt or heard at the moment of injury (ACL)
- Rapid swelling within a few hours
- Knee feels unstable, wobbly or gives way when turning
- Difficulty fully straightening the knee
- Pain and apprehension when the knee is pushed inward
- Bruising on the inner knee a few days later
Overview
Ligaments are strong bands of tissue that hold the knee together. The two most commonly injured are the medial collateral ligament (MCL) on the inner side, and the anterior cruciate ligament (ACL) inside the joint. Ligament injuries are graded from 1 (overstretched) to 3 (complete tear).
MCL sprains typically happen when a force pushes the knee inward — a tackle from the side, a ski that catches an edge, or an awkward landing. They cause pain on the inner knee, and the majority recover well with rehabilitation because the MCL has a good blood supply.
ACL injuries usually involve a sudden pivot or landing with the foot planted. Many people hear or feel a "pop", the knee swells quickly, and it later feels unstable or gives way when turning. Because the ACL does not repair itself, treatment decisions depend on your age, sport and how the knee behaves after rehabilitation. Some people do well with structured rehab alone; others, especially those returning to pivoting sports, may be referred for a surgical opinion.
Causes and risk factors
- Contact sports — football, rugby, basketball — and skiing
- Landing from a jump with the knee collapsing inward
- Sudden change of direction with the foot planted on the ground
- Weak hip and hamstring muscles that fail to control the knee
- Previous knee ligament injury
- Being female (ACL injury rates are higher in women's sport)
- Fatigue late in a game or training session
How we may be able to help
A careful assessment is the priority. We check each ligament with specific tests, assess the meniscus and the amount of swelling, and look for signs that need medical imaging. For suspected ACL tears or multi-ligament injuries, we can arrange an online private GP consultation for MRI and an orthopaedic opinion so that decisions are made with full information.
Physiotherapy is the core of treatment for both MCL and ACL injuries, whether or not surgery is eventually chosen. Early goals are to settle swelling, restore full straightening and bending, and get the thigh muscles firing. From there, rehabilitation exercise progresses through strength, balance and control work into hopping, cutting and sport-specific drills. For ACL injuries, strong evidence supports a period of rehabilitation before any surgical decision, and good "prehab" improves outcomes if surgery goes ahead.
Interferential therapy may help with pain and swelling early on. Kinesiology taping can support the inner knee during the recovery phase of an MCL sprain. If your foot posture or alignment increases inward knee collapse, a 3D foot scan and orthotics may be considered.
What you can do at home
- For the first 72 hours: relative rest, elevation and a wrapped ice pack for 15 minutes several times a day
- Keep the knee moving gently — bend and straighten within comfort, several times daily
- Tense the thigh muscle with the leg straight (quad sets) to prevent wasting
- Avoid twisting, pivoting and sports until assessed
- Use crutches briefly if walking is painful, but aim to walk with a normal pattern as soon as you can
- Do not ignore a knee that gives way — get it checked
When to seek urgent help
If you have any of the following, call us straight away for an urgent same-day appointment — we can examine you and arrange fast-track X-ray or MRI through our imaging partner. If you cannot reach us, go to A&E. For loss of bladder or bowel control, numbness around the groin, chest pain, a sudden severe headache or rapidly worsening weakness, call 999 or go to A&E immediately:
- Knee visibly deformed or kneecap out of place — go to A&E
- Numbness, coldness or colour change in the foot after injury (possible nerve or blood-vessel damage) — call 999 or go to A&E
- Unable to put any weight through the leg
- Massive swelling within an hour, especially with a feeling of the knee 'coming apart'
- Hot, red, swollen knee with fever
Frequently asked questions
How do I know if it's my ACL or my MCL?
MCL injuries cause pain on the inner knee and usually follow a sideways force. ACL injuries often involve a pop, fast swelling and later instability. Only a proper examination — and sometimes MRI — can tell for sure, so get assessed rather than guessing.
Does an ACL tear always need surgery?
No. Research shows that a structured rehabilitation programme allows many people to return to daily life and even some sport without reconstruction. Surgery is more likely to be recommended for younger people returning to pivoting sports or if the knee keeps giving way after rehab. We can help you reach a decision with an orthopaedic opinion.
Should I wear a knee brace?
A hinged brace may be helpful for some higher-grade MCL sprains in the early weeks. For most grade 1–2 sprains and for ACL rehab, strengthening is more useful than bracing. We advise based on your assessment.
How long until I can play again?
Grade 1 MCL sprains often settle in a few weeks; higher grades take longer. ACL recovery, with or without surgery, is measured in months. Return to sport is based on passing strength and hop tests, not on a calendar date.
This page is general information, not a diagnosis. A clinician will assess you before recommending any treatment. Outcomes vary from person to person. Written with reference to NHS and other peer-reviewed guidance.
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