Knee PCL – Posterior Cruciate Ligament Injury and Treatments
We will often get an email from someone who tells us that their doctors are in debate whether or not that they, the person with the injury, has a PCL tear or not. This debate will come after a few MRIs that were inconclusive. Later in this article we will explore the controversies over PCL ligament tear diagnosis and treatment.
The posterior cruciate ligament (PCL) is one of four ligaments of the knee which function to keep the knee stable. The primary purpose of the PCL is to hold the shin bone in its proper alignment to the knee.
The PCL is a strong ligament, it would take a lot of impact to injure it. Therefore it is usually not injured in isolation, it is usually injured when the knee has taken a significant impact blow and other ligaments are torn such as the more famous ACL, and there is damage to the meniscus.
So, it is unlikely that the knee pain and stability problems you are having is solely a problem of a PCL sprain or tear.
The PCL in relation to the other knee ligaments – whole knee damage needs whole knee treatment
The anterior cruciate ligament sits in front of the PCL and together the ACL and PCL keep the tibia (shin bone) from sliding too far forward and the tibia in position below the femur (thigh bone). The PCL is the knee’s basic stabilizer and almost twice as strong as the ACL.
Posterior cruciate ligament (PCL) injuries make up between 3 and 20 percent of all knee ligament injuries. However, PCL injuries are often left undiagnosed. Why it is left undiagnosed and untreated is because the PCL is not well understood. Listen to this research:
Research: Doctors do not understand the PCL, this is why your knee may be unstable
- Doctors in Switzerland published a detailed analysis of what the PCL does and how what it does stabilizes the knee.
- This is important information for people, especially athletes and workers with physically demanding jobs to understand.
- This research appeared in the science journal Public Library of Science one.(1)
The research opens with: “The posterior cruciate ligament PCL is the strongest ligament of the knee, serving as one of the major passive stabilizers of the tibio-femoral joint. However, despite a number of experimental and modeling approaches to understand the kinematics and kinetics of the ligament (how it moves and stabilizes), the normal loading conditions of the PCL and its functional bundles are still controversially discussed.”
Controversy in medicine simply means no one is quite sure how to diagnose or to treat. There are theories and there are understandings but there is no consensus. So it is possible you can have a knee problem and go to three doctors and hear three different things:
- You have a problem with your PCL
- The PCL is probably not a problem
- I really can’t tell – we need an MRI. Unfortunately, after the MRI you may not be able to tell either. Have you had confusing or contradictory MRI readings? Please see our article: Is my MRI accurate?
Isolating a PCL problem by the activity causing you pain
The Swiss researchers made these observations when it came to understand that the PCL can be the problem:
- Passive flexion of the knee – if it hurts when you do this PCL can be involved.
- If you sit on a table or chair with your feet dangling off the floor. You cross your ankles with the “good knee” on top and then slowly move your ankles backward. If it hurts the “bad knee,” it is possible a PCL is involved. An examination with an experienced health care provider can reveal more clues.
- FORWARD LUNGE and SQUATS. The odd behavior of the PCL is seen in these exercises. Research has shown that the PCL carries the weight load through various knee angles in these exercises and distributes the load to the other structures of the knee at other angles. This means during these exercises the whole knee comes into play with the PCL being a supportive stabilizer.
We stop here because while these elements may isolate on a PCL problem, in our office, we do not treat the PCL as an island unto itself. We treat the whole knee. The research that we examined above relates to a “healthy,” knee. Now we will look at compromised knees.
The ACL and the PCL. The PCL is often ignored
This type of understanding or admitting lack of understanding of the PCL’s place in the knee was alluded to by researchers in Germany who suggest that “Posterior cruciate ligament injuries are still often overlooked and treatment of a ruptured PCL is inherently different in comparison to anterior cruciate ligaments. Conservative treatment is the first-line therapy for acute isolated PCL injuries leading to good clinical and biomechanical results.”(2)
In our opinion, this could be a problem trying to isolate the PCL as the problem without addressing the impact a PCL injury can have on the whole knee. Simply, if part of the knee is damaged, it has a cause and effect on the whole knee.
Isolated PCL injuries are already under scrutiny. Untreated knee instability from an undiagnosed PCL tear can lead to meniscal tears and osteochondral injuries which are relatively prevalent in isolated acute PCL injury of the knee.
A case study was reported in the American journal of physical medicine & rehabilitation in April 2020. (7) Here the doctors described a 24-yr-old male soccer player with a seven year history of left posterior knee “looseness.” Evaluation seven years ago, at the time of initial injury, revealed atraumatic anterior and posterior cruciate ligament sprains.
Seven years later at a new consultation the patient described the pain as a constant, dull ache, a 3 out of ten pain. His biggest complaint however was this feeling of “instability” and looseness where his knee would “buckle” 3-4 times a week.
Physical examination was positive for grade 1 posterior drawer and grade 1 posterior sag signs (signs of a partial tear). Sonographic evaluation confirmed magnetic resonance imaging findings of posterior cruciate ligament laxity and buckling and a small cystic lesion pressing against the posterior cruciate ligament. After a trial of physical therapy, the patient elected to undergo experimental injection of dextrose hyperosmolar (Prolotherapy) solution. This resulted in resolution of the cyst and the patient’s subjective feeling of looseness and instability resolved by seven weeks.
Getting back to your PCL injury
PCL injuries frequently involve a blow to the knee when the knee is bent. Most athletic PCL injuries occur during a fall on the flexed knee with the toes pointing down and the top of the foot in line with the front of the leg. The shin, or tibia, hits the ground first and is pushed backward. During a motor vehicle accident, the dashboard may drive the shin backward on the flexed knee.
PCL injuries are commonly seen with severe trauma and may occur in conjunction with injuries to other ligaments of the knee, such as an anterior cruciate ligament (ACL) injury, a medial collateral ligament (MCL) injury or a lateral collateral ligament (LCL) injury. These types of injuries stress the PCL, and if the force is high enough, a PCL tear can be the result.
Hyperflexion of the knee without a direct blow to the tibia can also cause an isolated PCL injury, one in which no other ligaments are damaged.
PCL injury diagnosis
It is important for the physician to know how the injury occurred in order to make a diagnosis. For instance, was the knee bent or straight. A common test called the posterior drawer test is very helpful in making the diagnosis. With the knee bent, the doctor presses the tibia backward to stress the PCL. Abnormal movement can suggest an injury to the PCL. The doctor will also look for an abnormal gait.
X-rays may be ordered to detect pieces of bone that may have broken loose from the injury. MRIs may be ordered to verify the injury, detect the location of a tear and visualize whether there is damage to any other structures in the knee.
An injury to the PCL can cause mild to severe damage and is graded by the severity of injury: grade I through IV. The extent of laxity measured during the examination determines the grade. The classification is as follows:
- Grade I: The PCL has a partial tear.
- Grade II: The PCL is partially torn and is looser than in Grade I.
- Grade III: The PCL is completely torn and the knee is unstable.
- Grade IV: The PCL is damaged along with another ligament in the knee.
Initial treatment of the pain and swelling consists of the use of crutches, ice, and elevation. This treatment may temporarily relieve the symptoms of the injury, but they do not treat the ligament, which is the source of the injury. Immobilization, ice, and elevation are all designed to decrease inflammation; however, the injured ligament needs the blood supply and healing factors that occur with inflammation. The injured ligament also needs motion for healing.
Treatment may also include anti-inflammatory medications or cortisone injections. Once again, these medications may provide some pain relief, but they both have been shown to inhibit healing and contribute to the degenerative process.
Physical therapy is commonly recommended to improve knee motion and strength. Although a great treatment modality, physical therapy is unable to heal the injured ligament.
As unsatisfactory as these treatments may be to the athlete, a new study comparing these treatments to PCL surgery found more satisfactory and consistent stability in the reconstructive treatment group. However, more complications and the small differences in stability between groups should be also considered.5 In other words, there was not much difference between the two groups except the surgical group had more complications.
PCL Surgery and Controversial Results
Many people have had successful knee surgery. Others have continue pain after surgery. They may have a story that goes like this: I had PCL reconstruction surgery and meniscus repair. However, the slight buckling of the operated on knee is still occurring as it was pre-surgical intervention. I have been doing physical therapy for about 2 months with little results.
Orthopedic surgeons do not agree about the benefit of reconstruction, especially considering the technical difficulty of the surgery due to the position of the PCL in the knee. It is difficult to place grafts in this position, and the grafts tend to stretch out and fail. Generally, surgical reconstruction is reserved for severe injuries involving several major ligaments or for those with persistent knee instability. Even then, surgery involves replacing the torn PCL with either a piece of another tendon removed from elsewhere in the body or from a cadaver. This is major surgery, not a benign treatment, and one that may leave the sufferer with continued knee pain.
In research from March 2017, doctors at Penn State College of Medicine wrote of the long list of surgical interactions that must go perfectly for successful PCL reconstruction surgery, such as:
- correctly identifying sources of knee instability,
- properly placed tunnels to as closely as possible approximate the PCL insertion sites,
- and minimization of graft bending also enhances the probability of PCL reconstruction success.
- “PCL reconstruction failure may result when any or all of these surgical principles are violated.”6
Doctors in Germany released their new findings which found that athletes need realistic expectations when it comes to PCL reconstruction.
“Patients with operatively treated PCL injuries can return to sport. However, for competitive athletes, an injury to the PCL can lead to the end of their career.
A reduction of sporting activities and a change from high-impact sports to low-impact sports can be expected (in many cases).”3
A new paper found that doctors need realistic expectations when it comes to PCL reconstruction success.
“The surgical outcome of PCL reconstruction was inferior to that of ACL reconstruction both in patient-based and conventional doctor-based assessments. An improved surgical technique for PCL is required.”4
Please see our article on the anterior cruciate ligament for the latest research on ACL reconstruction surgery.
The regenerative approach to a Posterior Cruciate Ligament injury with Prolotherapy
In the case of an overstretched or partially torn ligament, a treatment approach to strengthen and heal the injured ligament should be utilized. The treatment that stimulates ligament healing and regeneration is Prolotherapy. Prolotherapy injections directed at the injured PCL will cause a mild inflammatory reaction at the site of the weakened ligament. If other ligaments are involved, they will be treated as well. The body responds by increasing blood supply and regenerative cells to the injured site. A normal wound healing cascade is stimulated by this process. In this healing process the body also deposits collagen in the area of injury. The PCL ligament is made up of a lot of collagen, and as these new collagen cells mature, the ligament becomes stronger. Once the PCL is strong and stable, the symptoms resolve.
Motion and controlled exercise will also be recommended since the ligament needs to continue moving for proper healing.
In the event of a complete tear or if a fragment of bone has broken off, requiring surgery, Prolotherapy can also be a healing complement to surgery. Most likely, the other ligaments are at minimum stretched during surgery, and would require strengthening to stabilize the knee. Ideally, a Prolotherapist is sought as a first-line treatment for a posterior cruciate ligament injury.
1 Hosseini Nasab SH, List R, Oberhofer K, Fucentese SF, Snedeker JG, Taylor WR. Loading Patterns of the Posterior Cruciate Ligament in the Healthy Knee: A Systematic Review. PLoS One. 2016 Nov 23;11(11):e0167106. [Google Scholar]
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4 Ochiai S, Hagino T, Senga S, Yamashita T, Ando T, Haro H. Prospective analysis using a patient-based health-related scale shows lower functional scores after posterior cruciate ligament reconstructions as compared with anterior cruciate ligament reconstructions of the knee. Int Orthop. 2016 Sep;40(9):1891-8. doi: 10.1007/s00264-016-3189-0. [Pubmed]
5. Ahn S, Lee YS, Song YD, Chang CB, Kang SB, Choi YS. Does surgical reconstruction produce better stability than conservative treatment in the isolated PCL injuries? Arch Orthop Trauma Surg. 2016 Jun;136(6):811-9. doi: 10.1007/s00402-016-2454-4. Epub 2016 Apr 15. [Pubmed]
6. Fanelli GC1, Fanelli MG, Fanelli DG. Revision Posterior Cruciate Ligament Surgery. Sports Med Arthrosc. 2017 Mar;25(1):30-35. [Pubmed]
7 Schroeder A, Onishi K. Vague Posterior Knee Discomfort in a Soccer Player: A Clinical Vignette. American Journal of Physical Medicine & Rehabilitation. 2020 Apr 1;99(4):e46-9. [Google Scholar]