What are collateral ligament injuries?
The collateral ligaments are found on the sides of your knee, unlike the cruciate ligaments found within the middle of the knee joint. The medial collateral ligament (MCL) is a fan-shaped structure found on the inner side connecting the thigh bone (femur) and the shin bone (tibia). The lateral collateral ligament (LCL) is a cord-like structure on the outer side connecting the femur to the smaller bone in the lower leg (fibula). The LCL is part of a complex group of structures in that region. The collateral ligaments prevent excessive sideways movement and angulation at the knee.
Collateral ligament damage usually results from direct contact injuries that push the knee sideways. Direct blows to the outside of your knee that pushes the knee inwards towards the other knee injures the MCL. MCL injuries are the most common knee ligament injury. The LCL is injured when the knee is forced outwards. Isolated LCL injuries are rare and are usually associated with other nearby structures or cruciate ligament injuries.
What are the symptoms of collateral ligament injuries?
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.
How are they diagnosed?
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.
How are they treated?
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.