Osteotomy for instability
The ligaments around the knee rely on the mechanics of the knee joint and leg alignment to help control knee movement. Once a ligament has been injured it may not heal due to a mechanical problem of the shape of the leg. The most common example of this is a lateral collateral/posterolateral corner injury in association with a varus (bowed) leg alignment. The constant stretching force along the line of the ligament prevents healing and puts any repaired or reconstructed ligaments at high risk of stretching out or re injury.
If a ligament injury cannot be treated by reconstruction in isolation due to mal alignment of the leg or chronicity (time since injury) then an osteotomy may be required to control the instability (wobbilyness) in the knee.
For chronic deficiency of the ACL the slope of the top of the tibia can be altered (extension osteotomy) to reduce the forward movement of the knee. If there is wear of the inside of the knee then the alignment from side to side can also be improved with a proximal tibial osteotomy.
For chronic PCL injuries the top of the tibia can be shifted in the opposite direction (flexion osteotomy) to reduce the backwards movement of the knee. Again if there is wear of the inside the knee the flexion osteotomy can be combined with a valgus tibial osteotomy.
In cases of chronic LCL injuries, especially if the leg has become bow legged then a high tibial osteotomy can be combined with reconstruction of the ligament. If the leg is significantly bowed then the osteotomy must be combined with the ligament reconstruction or it will fail.