If the outside of your knee hits something while your leg is bearing your weight, you might well injure your medial collateral ligament. It can also be injured if you fall over and your knee falls inwards.
You will feel pain on the inside of the joint, and there may well be swelling and bruising. The knee joint itself might swell, and the whole area will become very tender. Although you’ll probably be able to bear weight on your leg, it will be painful if you try and bend the knee inwards.
Your knee specialist will talk to you about the injury you experienced, and will examine your knee. They may also take an x-ray. If the knee doesn’t bend sideways too much, then it is considered stable and your doctor won’t need to investigate any further. However, if it does bend or the doctor thinks there is another injury, then they may carry out an MRI scan.
If the injury is just a sprain, then you can probably alleviate the symptoms with the RICE technique – Rest, Ice, Compression and Elevation – followed with some physiotherapy. However, more serious injuries may require a knee brace or surgery.
In severe cases, the anterior cruciate ligament (ACL) may also be injured, and you will need to wear a brace for a few weeks. Your specialist will refer you to a physiotherapist who will give you a series of exercises to do once the swelling has gone down. If the ligament is badly torn, you may need surgery.