The posterior cruciate ligament (PCL) is an intra-articular extrasynovial ligament of the knee. The PCL is paired with the anterior cruciate ligament (ACL), and is one of the four main ligaments that stabilize the knee joint. The PCL tracks posteriorly and inferiorly and provides posterior stability of the tibia on the femur.1
Injury to the PCL may be the result of direct trauma, from a motor vehicle collision (MVC) or acute sports injury. The PCL functions to prevent the femur from continuing to move anteriorly on the tibia and prevent the tibia from moving posteriorly on the femur.2 Thus, PCL injuries tend to occur with a sudden posterior tibial translation mechanism. The PCL also functions to limit external rotation of the tibia. PCL tears that result from an MVC are typically due to the knee striking the dashboard-knee bar.3 In sports activities, injury to the PCL usually occurs when the knee strikes the ground in a hyperflexed position. In contact or combat sports, the PCL may be injured with a posteriorly directed blow to the proximal tibia when the foot is flexed on the ground. Knee injuries associated with rotation and a concomitant varus or valgus force may also injure the PCL.4
Epidemiology including risk factors and primary prevention
PCL injuries occur less commonly than ACL injuries; PCL injuries occur in only about 3% of all knee injuries.5
PCL injuries are most commonly seen in men between the ages of 18 and 44 years old.3 The type of injury that occurs to the PCL appears to be patient- and activity-dependent. Universally, a high velocity activity or trauma is more likely to result in injury to the PCL than at a lower velocity.1
There is some evidence that PCL injury can be prevented with proper warm-up and stretching. Proper aerobic and weight training, with proprioceptive training, can assist in avoiding these types of injuries.6
The PCL attaches to the anterolateral aspect of the medial femoral condyle and the posterior tibial surface. The PCL is composed of anterolateral and posteromedial components. The anterolateral component is the larger and stronger of the two and is taut when the knee is in flexion.7 Conversely, the posteromedial component is taut in knee extension. The vascular supply for the PCL is provided by the middle genicular artery, a branch of the popliteal artery. Secondary blood supply is derived from the inferior medial and lateral genicular arteries.8 Innervation is provided by the posterior articular nerve, which is a branch of the tibial nerve.9
The PCL functions to resist posterior displacement of the tibia in relation to the femur, prevent hyperextension, and limit varus/valgus rotation. The PCL also resists external rotation of the tibia on the femur.1 This combination of support by the PCL accounts for 85% to 100% of the restraint of tibial translation of the knee in flexion.10
PCL injuries can occur in isolation but are more often a component of multi-ligament knee injuries.11 PCL injuries are associated with ACL injuries in 46% of cases, medial collateral ligament injuries in 31% of cases, and injuries to the posterolateral corner in 62% of cases.12 The posterolateral corner of the knee is made up of the popliteus muscle, the posterior capsule fibers, the lateral meniscus, lateral cruciate ligament, and iliotibial band.1,13
Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time)
In most cases of PCL injury, trauma is the cause. The patient may describe an event such as an MVC or sports contact injury to the knee that leads to a physical examination and/or imaging of the joint.12
In some cases, a PCL injury may go undiagnosed. A patient may present months after an injury with mild symptoms of pain and knee instability.12,14
Specific secondary or associated conditions and complications
When an isolated PCL tear diagnosis is missed, a chronic PCL tear may persist and result in secondary problems in the knee joint. Symptoms include ongoing pain and instability in the joint, as well as an alteration in gait pattern. The natural history of a chronic PCL tear is increased pain, arthrosis in the medial and patellofemoral compartments, and meniscal breakdown.13
When the PCL injury is more complex, other structures in the knee may also be damaged. This commonly involves the PCL and the posterolateral corner of the knee.1 This is more common in a high velocity trauma to the knee. Often, with PCL tears and trauma, a contusion of the proximal anterior tibial surface will be seen on magnetic resonance imaging (MRI). Other structures of the posterolateral corner that may be involved include the lateral meniscus, articular cartilage surfaces on the tibia and femur, lateral cruciate ligament, and iliotibial band.15
2. ESSENTIALS OF ASSESSMENT
In an acute injury, it is important to focus on the mechanism of action of the injury and the type of trauma to the knee. In the case of trauma, such as a MVC, knowing that the knee bar was struck can help. In sports-related injuries, the act is often witnessed and thus the mechanism can often be described.
Patients may describe an audible pop at the time of injury. Complaints will often include instability of the knee, swelling, and throbbing pain, and may even include weakness, numbness, and tingling. Pain with standing, ranging the knee, and/or sitting at rest with the knee in extension or flexion may also be described. Antalgic gait is frequently present, with significant guarding of the knee with ambulation.1,2
In the patient with a chronic PCL tear, complaints of pain and aching in the knee joint are common. In some cases, patients may describe a feeling of give-way or instability.1
On inspection, look for clues of trauma, such as contusions or lacerations. This should be followed by palpation of the joint, evaluation of range of motion, neurovascular testing, and special tests.
Special tests that can be done to assist with PCL evaluations include the following:
- Posterior Drawer Test: The patient lies supine with hips flexed to 45 degrees and knees flexed to 90 degrees. A posterior force is applied to the proximal tibia, while stabilizing the foot. When the PCL is torn, laxity will be apparent as compared to the contralateral knee.
- Posterior Sag Sign: The patient lies supine with hips flexed to 45 degrees and knees flexed to 90 degrees. Sagging of the tibia compared to the contralateral side suggests a PCL tear.
- Quadriceps Active Test: The patient lies supine with hips flexed to 45 degrees and knees flexed to 90 degrees. The foot and thigh are stabilized, and the patient is asked to contract the quadriceps muscles. With a PCL tear, anterior tibial translation may be seen.
- Dial test: The patient lies prone. The relative degree of external rotation is compared side-to-side with the knees flexed to 30 and subsequently to 90 degrees. An increase in more than 10 degrees of external rotation at both positions suggests a possible posterolateral corner injury which may be associated with a PCL injury.
After completion of the physical examination, if there is suspicion of a PCL tear, or bony fracture, x-rays with weightbearing A/P, lateral, sunrise, and tunnel views should be obtained.16 More recently, stress radiography of the joint has been incorporated to evaluate for knee instability; with PCL laxity, posterior tibial subluxation may be demonstrated on stress views. The bony anatomy and alignment of the tibia, femur, and patella can be evaluated with x-ray. More detail about the soft tissues, ligaments, and menisci can be obtained from an MRI of the knee. MRI has a high sensitivity and specificity for diagnosing acute PCL tears17; however, it should be cautioned that 28% of chronic PCL tears may appear nearly normal on MRI.18
Supplemental assessment tools
PCL tears can be graded based on the type and quality of tear:
- Grade I – sprain with preservation of knee stability
- Grade II – partial tear with laxity on examination
- Grade III – complete tear with knee instability
- Grade IV – complete tear of PCL combined with other ligamentous damage and knee instability
An injury to the PCL is commonly associated with a trauma or sports activity. Many times in the case of trauma, an MVC is the cause, with the result of contact to the knee bar.
As for patients who are involved in sporting activities, those who participate in contact sports are more likely to sustain an injury to the PCL. High velocity activities with contact place a higher risk on PCL injury.
Return-to-play will be the first question from most patients, followed by treatment options, and how much time is required for rehabilitation. It may be necessary for the physician to manage player, coach, therapist, and trainer.
3. REHABILITATION MANAGEMENT AND TREATMENTS
Available or current treatment guidelines
Because the PCL requires a prolonged time for healing, as compared with the ACL, appropriate and timely rehabilitation is crucial for successful recovery.
With grade I and II PCL tears, physical therapy and rehabilitation programs focus on proprioception and quadriceps and hamstring strengthening. Eccentric quadriceps muscle contractions with lunges and squats can be initiated28,29. A core strengthening program should be started, and assessment of the kinetic chain should be completed. Knee braces, which provide anterior and posterior support, may be utilized.19,20
The rehabilitative course for a non-operative approach to PCL tears has three phases.
Phase I (initial 6 weeks post-injury): consists of early immobilization, partial weight bearing, and hamstring, quadriceps, and gastrocnemius stretching.
Phase II (6-12 weeks post-injury): emphasizes quadriceps strengthening, range of motion, and proprioceptive training.
Phase III (13-18 weeks post-injury: the patient eases into running and sport-specific training.
In the final phase, the patient usually will return to sport about 4 to 8 months after the initial injury, marked by full quadriceps strength.21
For grade II, III and IV tears of the PCL, surgical options should be considered in the active high-functioning patient and athlete.1,2,19
A PCL tear is more likely to be treated surgically when it is a component of a multi-ligament knee injury, though repair versus reconstruction and optimal timing of surgery remain unclear.22
PCL tears with avulsions from either the femoral or tibial surface should be repaired with a pinning surgical process.1,2
In post-surgical PCL repair, the purpose of the rehabilitation course is to establish a return to full range of motion of the knee. Initially the knee is immobilized for 3 to 6 weeks to allow for limited stress on the new ligament; this is then followed by passive range of motion and partial weight bearing during weeks 6 to 10, and finally full weight bearing beyond 10 weeks. Following that, active and passive full range of motion of the knee is established over the next 6 to 9 months.12 The patient should focus on quadriceps strengthening with open kinetic chain exercises and gradual progression to closed kinetic chain exercises. Gradually, running and sports-specific activities should be introduced. One functional marker that is used to establish return to full function is quadriceps strength. Once quadriceps muscle strength is greater than 90% of the contralateral side, full level activity may be initiated.14
Patient & family education
When discussing treatment options, whether conservative or surgical, the risks and benefits should be explained to the patient. Patient education regarding the injury and process of injury is important. This will allow the patient to develop goals and motivation for the rehabilitative process, whether surgical correction is needed or not. Discussing the biomechanics of the PCL and knee joint with the patient, family, trainers, etc., may also help to prevent future injury. Stressing the importance of a rehabilitation program for the patient is key. Developing a home exercise program and routine to strengthen the knee will also play a key role.
Translation into practice: practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills
Patients with PCL injury most often will present with a history of trauma. Whether they undergo conservative or surgical treatment, they need to complete a rehabilitation program to re-establish strength and range of motion.
A focus on the kinetic chain and core strengthening should also be discussed and established. Working on the core muscles, incorporating plyometics, and understanding the concept of kinetic chain theory can help advance a patient’s rehabilitation.
Patients with previous PCL injury are prone to knee problems such as meniscal breakdown, patellofemoral syndrome, and arthrosis. Being aware of these problems, and educating patients may help prevent such complications.
Chronic PCL injuries can result in complications such as residual laxity and loss of range of motion, most notable with knee flexion.22
4. CUTTING EDGE/EMERGING AND UNIQUE CONCEPTS AND PRACTICE
Cutting edge concepts and practice
At present, repair of the PCL can be done with an autograft or allograft. The Achilles tendon is the most commonly used allograft.11 Autograft is typically harvested from the patellar tendon or hamstrings.11 Controversy exists regarding taking an autograft, when harvested from the patellar tendon, as harvesting from the patellar tendon may weaken the quadriceps muscle group and inhibit rehabilitation.14 Bone-patellar tendon-bone autografts are also being used, but it is unclear if there is any benefit to use of remnant-bone technique as compared to conventional techniques.
Techniques for surgical replacement of the PCL are debatable. Four techniques are currently used: trans-tibial, tibial inlay, single bundle, and double bundle approaches. The single bundle technique is considered the “classic” approach to the PCL reconstruction. One prospective study comparing single bundle and double bundle techniques revealed statistically significant improvements in posterior stability with the double bundle technique when compared to single bundle; however, the remainder of the data did not clearly establish superiority of the double bundle technique over the single bundle technique.24 Further studies are needed to evaluate differences in outcomes amongst the techniques used for PCL reconstruction.
5. GAPS IN THE EVIDENCE-BASED KNOWLEDGE
Additional research is needed to compare outcomes of surgical versus conservative management of PCL injuries, particularly with respect to different populations based on age and activity levels. Studies have demonstrated that degenerative wear after PCL reconstruction occurs regardless of posterior knee stability25; given these outcomes and both the risk of limb-length imbalance after reconstruction in immature populations26 and the possible need of revision procedures27, surgical interventions should be rigorously compared to non-operative approaches.
- Dowd GS. Reconstruction of the posterior cruciate ligament. Indications and results. J Bone Joint Surg Br. 2004;86(4):480-491.
- Margheritini F, Mariani PF, Mariani PP. Current concepts in diagnosis and treatment of posterior cruciate ligament injury. Acta Orthop Belg. 2000;66(3):217-228.
- Bergfeld JA, Graham SM, Parker RD, Valdevit AD, Kambic HE. A biomechanical comparison of posterior cruciate ligament reconstructions using single- and double-bundle tibial inlay techniques. Am J Sports Med. 2005;33(7):976-981.
- Rosenthal MD, Rainey CE, Tognoni A, Worms R. Evaluation and management of posterior cruciate ligament injuries. Phys Ther Sport. 2012;13(4):196-208.
- Naraghi A, White LM. MR imaging of cruciate ligaments. Magn Reson Imaging Clin N Am. 2014;22(4):557-580.
- Cross MJ, Powell JF. Long-term followup of posterior cruciate ligament rupture: a study of 116 cases. Am J Sports Med. 1984;12(4):292-297.
- Harner CD, Xerogeanes JW, Livesay GA, et al. The human posterior cruciate ligament complex: an interdisciplinary study. Ligament morphology and biomechanical evaluation. Am J Sports Med. 1995;23(6):736-745.
- Arnoczky SP. Blood supply to the anterior cruciate ligament and supporting structures. Orthop Clin North Am. 1985;16(1):15-28.
- Kennedy JC, Weinberg HW, Wilson AS. The anatomy and function of the anterior cruciate ligament. As determined by clinical and morphological studies. J Bone Joint Surg Am. 1974;56(2):223-235.
- Fu FH, Harner CD, Johnson DL, Miller MD, Woo SL. Biomechanics of knee ligaments: basic concepts and clinical application. Instr Course Lect. 1994;43:137-148.
- Kim YM, Lee CA, Matava MJ. Clinical results of arthroscopic single-bundle transtibial posterior cruciate ligament reconstruction: a systematic review. Am J Sports Med. 2011;39(2):425-434.
- Fanelli GC, Edson CJ. Posterior cruciate ligament injuries in trauma patients: Part II. Arthroscopy. 1995;11(5):526-529.
- Cosgarea AJ, Jay PR. Posterior cruciate ligament injuries: evaluation and management. J Am Acad Orthop Surg. 2001;9(5):297-307.
- Fanelli GC, Beck JD, Edson CJ. Current concepts review: the posterior cruciate ligament. J Knee Surg. 2010;23(2):61-72.
- Ross G, Chapman AW, Newberg AR, Scheller AD. Magnetic resonance imaging for the evaluation of acute posterolateral complex injuries of the knee. Am J Sports Med. 1997;25(4):444-448.
- Colvin AC, Meislin RJ. Posterior cruciate ligament injuries in the athlete: diagnosis and treatment. Bull NYU Hosp Jt Dis. 2009;67(1):45-51.
- Laoruengthana A, Jarusriwanna A. Sensitivity and specificity of magnetic resonance imaging for knee injury and clinical application for the Naresuan University Hospital. J Med Assoc Thai. 2012;95 Suppl 10:S151-157.
- Jung YB, Jung HJ, Yang JJ, et al. Characterization of spontaneous healing of chronic posterior cruciate ligament injury: Analysis of instability and magnetic resonance imaging. J Magn Reson Imaging. 2008;27(6):1336-1340.
- Lutz GE, Palmitier RA, An KN, Chao EY. Comparison of tibiofemoral joint forces during open-kinetic-chain and closed-kinetic-chain exercises. J Bone Joint Surg Am. 1993;75(5):732-739.
- Dejour H, Walch G, Peyrot J, Eberhard P. [The natural history of rupture of the posterior cruciate ligament]. Rev Chir Orthop Reparatrice Appar Mot. 1988;74(1):35-43.
- Pierce CM, O’Brien L, Griffin LW, Laprade RF. Posterior cruciate ligament tears: functional and postoperative rehabilitation. Knee Surg Sports Traumatol Arthrosc. 2013;21(5):1071-1084.
- Zawodny SR, Miller MD. Complications of posterior cruciate ligament surgery. Sports Med Arthrosc. 2010;18(4):269-274.
- Del Buono A, Radmilovic J, Gargano G, Gatto S, Maffulli N. Augmentation or reconstruction of PCL? A quantitative review. Knee Surg Sports Traumatol Arthrosc. 2013;21(5):1050-1063.
- Yoon KH, Bae DK, Song SJ, Cho HJ, Lee JH. A prospective randomized study comparing arthroscopic single-bundle and double-bundle posterior cruciate ligament reconstructions preserving remnant fibers. Am J Sports Med. 2011;39(3):474-480.
- Agolley D, Gabr A, Benjamin-Laing H, Haddad FS. Successful return to sports in athletes following non-operative management of acute isolated posterior cruciate ligament injuries: medium-term follow-up. Bone Joint J.2017 Jun;99-B(6):774-778
- Sørensen OG, Faunø P, Christiansen SE, Lind M. Posterior cruciate ligament reconstruction in skeletal immature children. Knee Surg Sports Traumatol Arthrosc. 2017 Dec;25(12):3901-3905
- Mygind-Klavsen B, Nielsen TG, Lind MC. Outcomes After Posterior Cruciate Ligament (PCL) Reconstruction in Patients With Isolated and Combined PCL Tears. Orthop J Sports Med. 2017 Apr 10;5(4):2325967117700077
- MacLean CL, Taunton JE, Clement DB, Regan W. Eccentric and concentric isokinetic moment characteristics in the quadriceps and hamstrings of the chronic isolated posterior cruciate ligament injured knee. Br J Sports Med. 1999 Dec;33(6):405-8
- MacLean CL, Taunton JE, Clement DB, Regan WD, Stanish WD Eccentric kinetic chain exercise as a conservative means of functionally rehabilitating chronic isolated insufficiency of the posterior cruciate ligament. Clin J Sport Med. 1999 Jul;9(3):142-50
Original Version of the Topic
Steve M. Aydin, DO. Posterior cruciate ligament (PCL) injuries. 01/30/2014/.
Daniel C. Herman, MD, Ph.D
Nothing to Disclose
Sara N. Raiser, MD
Nothing to Disclose