KNEE LIGAMENT INJURIES
POSTERIOR CRUCIATE LIGAMENT TEAR
The posterior cruciate ligament lies at the back of the knee. It is the primary restraint to posterior (backwards) motion or translation of the tibia (lower bone) on the femur. It also prevents hyperextension (the knee bends backwards beyond its normal position)
The posterior cruciate ligament is much less commonly torn than the anterior cruciate ligament. Surgical reconstruction is required less often in all grades of PCL injury.
This simply a strain of the fibres and there is no complete disruption or significant lengthening of the posterior cruciate ligament. On examination, there is less than 0.5cm of increased posterior instability.
Effectively the posterior cruciate ligament is stretched with between 0.5cm and 1.5cm of increased posterior instability.
A complete disruption of the posterior cruciate ligament fibres with gross instability and greater than 1.5cm of posterior instability.
Grade I and II tears, especially in isolation, are typically treated conservatively. This requires no surgical intervention. A straight leg knee brace is used with a posterior support behind the calf to prevent the lower leg shifting (subluxing) posteriorly. This is worn for 8 weeks with no active hamstring contraction allowed for the same period.
A Grade III anterior cruciate ligament tear can also be treated conservatively especially when isolated. When this is in conjunction with other ligamentous instabilities, or conservative treatment still results in an unstable symptomatic knee, a posterior cruciate ligament reconstruction can be undertaken.
I do an arthroscopic reconstruction of the posterior cruciate ligament via keyhole surgery from the front of the knee.
A graft is needed to reconstruct the posterior cruciate and this is typically a hamstring graft from the patient. Other options are quadriceps and patellar tendon graft from the patient. Once can also use tissue donor graft such as tibialis tendon and Achilles tendon.
Postoperative rehab after a posterior cruciate ligament reconstruction requires a posterior cruciate ligament straight leg brace with a posterior support to protect the ligament repair and prevent stretching. This brace is worn for 8 weeks with no active hamstring contractions allowed during this period. After 8 weeks the patient can have the brace removed or be converted to a hinged knee brace depending on the associated injury.
The typical return to sport after a posterior cruciate ligament tear is 4 to 9 months depending on the grade of tear and the treatment required.