At the time of injury, there is pain at the relevant side of the knee. There is often swelling and bruising over the side of the knee and leg. Swelling within the knee itself is less common. Your knee can feel unstable and may give way. Sometimes the symptoms are quite subtle, particularly with partial tears. If there are associated injuries such as an ACL rupture, these symptoms may predominate.

The symptoms and a careful examination will usually suggest the diagnosis. An x-ray can be useful to look for associated fractures, but an MRI scan is the investigation of choice.

Fortunately, MCL and isolated LCL injuries rarely require surgery. Injuries heal well with ice therapy, bracing to protect the knee from sidewise forces, and a rehabilitation programme to strengthen the muscles around the knee. Initially, you may be advised to limit the amount of weight put on the leg with the use of crutches. 

Even complete tears of the collaterals can heal without surgery. Surgery may be recommended for certain tear configurations that don’t heal well or when there are associated knee ligament injuries. Persistent instability after non-operative treatment is also an indication for surgery. 

Recent MCL tears can often be repaired but are often augmented with synthetic material (“internal bracing”). Long-standing injuries with persistent instability usually require reconstruction with a tissue graft. This can be taken from another part of your knee or leg (autograft) or from a human cadaver donor (allograft). Repair of LCL injuries is less successful and usually require additional reconstruction with a tissue graft. 

Physiotherapy and rehabilitation play a crucial role in returning to sport and activity, whether you have surgery or not. A knee brace may be recommended during sports activities to add additional stability and prevent re-injury.