Posterior Cruciate Ligament (PCL) Injuries
PCL injuries often occur due to an athletic or motor vehicle related trauma (1). While not being as prevalent as ACL injuries, they have a prevalence of 2-3% in the athletic population and 40% in trauma patients (1). Mechanisms of injuring the PCL:
- Hyperextension
- Posterior (backwards) force applied to top of tibia (shin-bone) while the knee is bent
- Forced hyperflexion of the knee
- Rotation combined with an medial or lateral force (in-ward or out-ward)
- Knee dislocation
Management of PCL injuries can still be a source of debate amongst researchers and clinicians. One such reason for this is that PCL injury management remains under-researched particularly regarding the long-term effects of conservative management for PCL ruptures (3). This limitation of research to draw upon is largely at fault for there being an uncertainty behind the “best” operative technique, post-operative rehabilitation and optimal conservative management (1).
What is the PCL?
The PCL is one of the four ligaments of the knee and is in fact the strongest – twice the strength of any other ligament in the knee (1). The PCL is the primary constraint for backward movement of the shin (posterior translation of the tibia) (1). However, studies have shown that the PCL only does this when the knee is bent 60 degrees or further (1).
Non-operative Management
This type of management is usually recommended when the PCL has been injured in isolation with research supporting the use of conservative measures to rehabilitate grade I, II and III tears (1). Those who suffer an acute isolated grade I or II injuries are likely to make a return to sport without the need for surgery (1). Protective weight-bearing for grade II and III tears can be of use with the focus of acute management being:
- Reduce swelling in the knee
- Restore knee movement
- Regain strength of the knee particularly the quadriceps
Grade I and II tears usually have a fast recovery (i.e back to sport in 2-4 weeks) (1). Research suggests eccentric strengthening should be included in PCL rehab for both the quadricep and hamstring muscle groups (1). Closed chain exercises should also be performed during the rehab period to increase neuro-muscular re-education for the affected limb and improve balance and coordination (1). Closed chain exercises also increase co-activation of muscles which in turn reduces shear forces on the thigh and shin bones – increasing stability and reducing ligamentous injury risk (1).
Following a period of neuromuscular, closed chain and eccentric strengthening exercises, the individual can begin agility based drills (1). However, the presence of swelling following these or any other exercises indicates that the load was perhaps too high or too soon (1).
Grade III tears are much slower to rehabilitate than the other grades (1). Grade III tears are usually immobilised for 2-4 weeks in full extension, refer to image below (1). Immobilisation reduces backward forces placed on the tibia that are caused by the hamstrings and improves healing (1).
Initial exercises for grade III tears include quadricep activation and straight leg raises (1). Quadriceps strength remains the focus with an initial avoidance of greater than 70 degrees knee flexion and isolated hamstring work (1). After 4 weeks, closed chain exercises and open eccentric quadricep work can both begin to be added to the program with functional activities such as biking, leg press and stair climbing being added as the individual progresses (1).
Return to sport for grade III tears can be after 3 months depending on the sport. However, if pain is present and/or they do not return to their previous level of function – surgical intervention is then considered (1).
Bracing
Unfortunately, there is limited evidence that evaluates the effectiveness of PCL knee brace (2). PCL knee bracing aims to improve dynamic knee stability by reducing backward movement of the shin during movement (1). One study showed an improvement of backward sag of the tibia after 4 months of wearing the PCL brace following an acute PCL injury – however, with no control group it is unknown as to whether or not the improvement was due to the brace (1).
Operative and Post-operative Management
Surgery is recommended for injuries that result in severe backward movement of the shin bone on assessment (posterior translation) on instability (1). When other ligamentous structures are involved with the injury – and increase the rotational instability of the knee joint – surgical measures are recommended within the first 2 weeks (1). Avoiding surgery in these cases can result in pain and chronic instability (1).
Rehabilitation following PCL reconstructive surgery is vital to have sufficient functional outcomes and typically takes 6-9 months (1). A brief summary of PCL reconstruction rehab guidelines is pictured below in table 1.
Outcomes of Conservative and Operative Managements
Operative outcomes across 21 studies showed a failure rate of 12% for isolated PCL reconstructions and combined PCL surgeries (1). The studies showed that isolated PCL reconstructions had a better rate of returning to sport (51-82%) compared to combined PCL with a rate of 19-68% (1).
Conservative management outcomes varied and were difficult for the research to conclude due to the subject and medical variance – however 2 large prospective studies showed 50-76% returning to their previous level of sport with a third study showing 32% returning to a lower level of function (1).
Summary
If you’ve injured your PCL – it is important to receive a thorough physical assessment and appropriate to organise an MRI. Following your scan results and physical assessment, it should be determined what grade tear of the PCL you have and whether other soft tissue injuries accompany this PCL injury or whether it is the PCL in isolation. 
Graph adaptation from research concluded from Rosenthal, et al. (2012).
It is important to note that whether an operative or non-operative approach is undertaken – the injured knee will require consistent and progressive strength and conditioning. This is vital for any individual to return to their previous level of sport or physical activity as the PCl deficient knee will be more unstable than before it was injured. By improving strength and stability of the knee, this will aid in the prevention of further injury to the PCL or to other structures of the knee and/or body.
Alec Lablache
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References
- Rosenthal, M. D., Rainey, C. E., Tognoni, A., & Worms, R. (2012). Evaluation and management of posterior cruciate ligament injuries. Physical Therapy in Sport, 13(4), 196-208. doi:10.1016/j.ptsp.2012.03.016
- Jansson, K. S., Jansson, K. S., Costello, K. E., Costello, K. E., O’Brien, L., O’Brien, L., . . . LaPrade, R. F. (2013). A historical perspective of PCL bracing. Knee Surgery, Sports Traumatology, Arthroscopy, 21(5), 1064-1070. doi:10.1007/s00167-012-2048-9
- Petersen, W., Loerch, S., Schanz, S., Raschke, M., & Zantop, T. (2008). The role of the posterior oblique ligament in controlling posterior tibial translation in the posterior cruciate ligament-deficient knee. The American Journal of Sports Medicine, 36(3), 495-501. doi:10.1177/0363546507310077
- Pain Assist. (2020). Knee Sprain [IMAGE]. Retrieved from: https://www.epainassist.com/sports-injuries/knee-injuries/knee-sprain
