PCL Reconstruction

Posterior Cruciate Ligament

Anatomy (Function)

The posterior cruciate ligament (PCL) is located in the knee joint, and functions to provide stability to the tibia on the femur (1). The PCL’s origin is the anterolateral aspect of the medial femoral condyle, and inserts on the posterior aspect of the tibial plateau. It is made up of a large anterolateral bundle (ALB) and a small posteromedial bundle (PMB), which both function together in load-sharing (2). The PCL’s main function is in restricting posterior translation of the tibia, with the ALB functioning more significantly in flexion, while the PMB functions more significantly in extension, as well as in resisting internal rotation during flexion (2). The PCL receives assistance in resisting posterior translation by the medial collateral ligament and the posterior oblique ligament (1). The PCL also plays a role in resisting varus, valgus, and external rotation (1). Blood supply to the PCL is from the medial geniculate artery off of the popliteal artery, and it is innervated by the tibial nerve off of the sciatic nerve.

Injuries

The PCL is less frequently injured compared to the ACL as most knee injuries occur in knee flexion (1). Additionally, the PCL is 1.3 to 2 times thicker than the ACL, and is 2 times as strong. When the PCL is injured, it is more likely from damage to the ALB in a flexed position rather than the PMB. It is most commonly injured during car accidents secondary to impact with the dashboard, motorcycle accidents, and soccer injuries, and presents with a 2:1 male to female ratio.

Injuries are evaluated on a graded scale with various treatments and rehabilitations indicated depending on the severity. Grade I PCL injuries constitute partial tears between 1 and 5mm of posterior translation. Grade II PCL injuries constitute a complete isolated tear between 6 and 10 mm of posterior translation, with the anterior tibia moving in line with the medial and lateral femoral condyles. Grade III PCL injuries indicate a complete tear with combined capsular or ligamentous injury, above 10 mm of posterior translation, and the tibia moving behind the femoral condyles.

Physical Examination

A comprehensive knee examination is performed in order to assess limb function in the setting of a possible PCL injury. Examination should include inspection, palpation, strength testing, and range of motion testing. Joint effusion is often visualized on inspection and palpation, and swelling is generally less significant in a PCL injury compared to an ACL injury (1). The joint lines should be inspected for tenderness on palpation which can indicate meniscal tear. Strength should not be significantly impacted however there may be weakness with extension and flexion of the knee, and range of motion can be restricted.

More specific examinations should be utilized to assess a combined or isolated PCL injury. The posterior drawer test is the gold standard for evaluating PCL stability. While the patient is in a supine position, the hip and knee are flexed at 45 degrees and 90 degrees, respectively. The femur is in a fixed position and a posterior force is exerted on to the proximal tibia. If the PCL is compromised, then the tibia will be posteriorly translated as a result of testing. To assess for a complete PCL tear, a quadriceps active test is useful. In supine position and flexion of the knee at 90 degrees, while fixing the foot, the patient will extend the knee, contracting the quadriceps muscle, resulting in posterior translation of the tibia in the setting of a complete PCL tear. A dial/external rotation test as well as a varus/valgus stress test is useful in evaluating a combined PCL injury.

Imaging

A stress radiograph is commonly used in evaluation of a ligamentous knee injury, via a varus, valgus, and posterior stress technique. (3). In a possible PCL injury, the patient is evaluated in a kneeling position with knee flexion at 90 degrees, and obtaining images of both knees for the sake of comparison. Typically, posterior translation observed on stress radiographs above 7mm is considered abnormal (4). An MRI is also critical in the evaluation of a PCL injury. An intact PCL will have a low signal on T1- and T2- imaging. An acutely injured PCL will have a high signal on T2- imaging. A chronic rupture of the PCL may be missed on MRI, as intact fibers on imaging does not always conclude that the PCL is intact, in contrast to the ACL.

Treatments

Proper treatment of a PCL injury must be considered in the context of acute vs chronic injury, and isolated vs combined injury. A non-operative treatment is designated in acute, isolated grade I and II injuries where posterior translation is between 8 mm and 12 mm, as well as grade III injuries in which the patient is not exhibiting severe symptoms or participating in strenuous activities (1). This is secondary to the PCL’s innate capability of healing (1). RICE techniques (rest, ice, compression, elevation) are appropriate with the use of a knee brace, as well as crutches for quadricep recovery. An operative treatment is designated in acute PCL injuries with posterior translation over 12 mm in severity with combined meniscal or capsuloligamentous injury, as well as chronic PCL injuries with posterior translation over 8 mm. A single-bundle technique is typically practiced in PCL repair, however there are an abundant procedures that are appropriately utilized, including double-bundle technique, graft fixation (transtibial tunnel, tibial-inlay), and high tibial osteotomy (HTO).

Rehabilitation

Non-operative treatments involve bracing and immobilization as well as physical therapy to restore regular tibiofemoral configuration and function (pierce 5). A three-phase program is recommended for maximal rehabilitation of injury. In phase I (0 to 4 weeks), the knee is secured in flexion in a brace between 0 and 60 degrees, with partial weight-bearing restrictions, focusing on hamstring stretching and quadriceps strengthening. In phase II (7 to 12 weeks), full weight-bearing and range of motion protocol is utilized, still focusing on quadriceps and hamstring strengthening. Phase III (5 to 6 months) allows for the patient to return to regular sport activity, with a jogging regiment and utilization of proprioceptive exercises. Physical therapy should focus on knee range of motion solely in the prone position for the first weeks after injury treatment, limited to 90 degrees in the first 2 weeks, and minimized stress on the PCL during knee flexion between 40 and 90 degrees.

In operative treatments, the focus is shifted towards rebuilding full range of motion and recovering quadriceps strength, and depends on the technique utilized for surgical repair. A more conservative protocol is taken for double bundle, with the knee immobilized in extension after surgery, and avoidance of exercises involving posterior translation. In the event of a single-bundle repair, a program involving the use of a knee brace locked in extension, quadriceps and hamstring strengthening, and improving weight-bearing is utilized, with expected milestones at 45 and 90 days. Crutches are utilized for 45 days with advancement in weight-bearing after 10 days. Passive flexion is continually increased from 60 degrees to 95 degrees by day 45, and to 120 by day 90. Half-squat and horizontal leg press between 0 and 60 degrees are started on day 45 for quadriceps and gastrocnemius strengthening, with graduation from double-leg to single-leg exercises on day 90. Return to sports activity is allowed 8 months after the repair.

A five-phase program is recommended for maximal rehabilitation of injury after double-bundle repair. In phase I (0 to 4 weeks), the knee is locked in extension, flexion not allowed past 90 degrees, with the aim of improving joint effusion and quadriceps strength. The use of crutches is indicated for ambulation with advancement to a long leg knee brace during phase I. Phase II (4 to 8 weeks) increases active range of motion of knee flexion from 0 to 130 degrees, and increased weight-bearing. Phase III (8 to 12 weeks) specifies the patient should complete single-leg exercises (squat and hop testing) and demonstrate symmetrical active knee range of motion. Phase IV (12 to 16 weeks) returns the patient to running and agility exercises, and phase V (16 to 20 weeks) replicates sports movements with attention to the injured PCL.

References

1. https://www.ncbi.nlm.nih.gov/books/NBK430726/
2. https://www.arthroscopyjournal.org/article/S0749-8063(19)31205-8/fulltext
3. https://pubmed.ncbi.nlm.nih.gov/33384079/
4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6100662/
5. https://link-springer-com.unr.idm.oclc.org/article/10.1007/s00167-012-1970-1

If you would like to have additional information on knee treatments or would like to learn more about PCL reconstruction surgery, please contact Dr. Gilmer, serving the communities of Reno, NV.