Posterior Cruciate Ligament Injuries
Over the past two weeks we have covered the ligaments on the inside (MCL) and outside (LCL) of the knee. Over the next two weeks we are going to discuss the ligaments in the centre of the joint the Anterior and Posterior cruciate ligaments.
One of the major injuries that can occur at the knee is damage to the posterior cruciate ligament (PCL). The PCL is one of the four major ligaments found in the knee and crucial to its internal stability. Although common, it is the least common ligament to get injured out of the four major knee ligaments because it is larger and stronger than the other three. It is estimated that approximately 10-20% of all knee injuries involve the PCL.
The PCL originates from the medial aspect of the thigh bone (femur) and branches into two bundles (posteromedial and anterolateral) before inserting into the posterior aspect of the shin bone (tibia).
The other main ligament inside the knee, the ACL, connects from the opposite sides and they both form an X shape (cruciate) of support inside the knee to provide translatory and rotary stability.
The PCL is made of tough fibrous material that is about the width of a person’s little finger and functions to control excessive motion by limiting joint mobility. In particular, it resists hyperextension, posterior (backward) tibial displacement and provides a rotational axis of stability. It also prevents excessive tibial external rotation.
PCL tears are caused by an increase in the tensile load of the ligament beyond its normal length and therefore results in partial or complete tearing of the structure.
Forces that cause this increase in load include incidents such as direct trauma to the front of the tibia causing a posterior translation of the tibia on the femur, such as falling onto your knees or hitting the knee against the dashboard during a motor vehicle accident.
Sporting injuries are also a very common cause where landing with a rotational component or hyperextending the knee causes the PCL to tear. In these such types of injury especially where rotation is involved other knee injuries are highly correlated such as ACL, MCL, LCL and meniscus tears.
There are 4 main grades involved when diagnosing a PCL tear
Grade 1: The ligament is mildly damaged; it has been slightly stretched, but is still able to help keep the knee joint stable.
Grade 2: The ligament has been stretched to the point where it tears and becomes loose. This is often referred to as a partial tear of the ligament, where up to 80% of the ligament has torn.
Grade 3: This type of sprain is referred to as a complete tear of the ligament. The ligament has been split into two pieces, and the knee joint becomes unstable.
Grade 4: A complete tear of the ACL with inclusion of a complete tear of another ligament
in the knee.
Symptoms of a PCL tear can vary depending on the severity of the tear however the most common symptoms seen are:
· Pain and swelling that occurs steadily and quickly after the injury
· Swelling that makes the knee stiff and may cause a limp
· Difficulty walking or bearing weight on the knee
· The knee feels unstable, like it may "give way", especially when turning.
· An obvious step deformity at the front of the knee after a collision injury
Isolated PCL injuries usually heal quite well on their own, without the need for surgery, and therefore conservative physical therapy is usually recommended as a first base of treatment.
Your physiotherapist or chiropractor will conservatively manage your injury by first reducing the swelling, inflammation and pain. This may include a period of non-weight bearing immobilisation in a brace and using crutches to prevent further aggravation of the injury.
Other modalities such as ice, gentle compression and soft tissue release will also assist to reduce inflammation in the area. Once the initial pain and inflammation has subsided a comprehensive rehabilitation program should be started which will first work to return function to the knee by increasing the range of motion in the joint and later by increasing the strength of the surrounding muscles that support the knee.
These exercises will particularly focus on the strength of the quadriceps muscles which have been shown to be a major factor for successful recovery. If there are combined injuries to surrounding ligaments or the meniscus or if conservative treatment fails, surgery may be needed to restore the function to the PCL. This will usually involve a graft taken from elsewhere in the body or from and external source to replace the ligament.
Knee ligament injuries are very hard to predict due to the velocity and unpredictable environment in which they occur, however 3 tips to help minimise the risk of injuring your PCL include:
1. Increase the strength of your knee with regular quadriceps, hamstring and calf exercises and modify them to resemble activities or sports that you participate in.
2. Warm up and stretch your legs thoroughly before and after activities to improve muscle activation, and the active stability around the knee.
3. If you engage in contact sports, especially those that promote front-on contact with the lower leg (rugby, Aussie rule ruck contests) then consider appropriate bracing or preventative equipment.
So that’s a brief overview of how PCL injuries occur, If you have questions or comments feel free to e-mail us at firstname.lastname@example.org and we will be happy to answer them for you or call us on (08) 9486 8653 and our therapists will be happy to talk with you.