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Clinically Relevant Anatomy
The knee is stabilized by four main ligaments: 2 collateral ligaments (medial and lateral) and 2 cruciate ligaments both anterior (front) and posterior (back). The cruciate ligaments attach to the femur (thigh bone) and travel within the knee joint to the upper surface of the tibia (shin bone). The ligaments pass each other in the middle of the joint forming a cross shape, hence the name ‘cruciate’.
posterior cruciate ligament (PCL) functions mainly in preventing the tibia from traveling backwards on the femur, known as posterior drawer. It also helps to prevent the tibia from twisting outwards. Injury to the ligament leads to knee instability with the shin bone having a tendency to ‘sag’ backwards when the knee is bent at 90 degrees.
Mechanism of injury.
The incidence of injuries of the PCL is less than that of the anterior cruciate ligament. This is mainly due to the greater thickness and strength of the PCL. Nevertheless, the most common way in which the PCL is injured is by direct impact to the front of the tibia itself, usually when the knee is bent. This may occur in a front-on tackle or collision or when falling with the knee bent. The injury is commonly associated with injuries to other structures in the rear compartment of the knee joint such as lateral meniscus tears. In addition the articular cartilage may also be damaged.
PCL tears are graded I- III with III being the most severe. These gradings are classified depending on the amount of backward tibial displacement observed when the knee is bent at 90 degrees. In extreme cases the ligament may become avulsed, or pulled off the bone completely.
- Pain at the time of impact which, over time, may also be felt in the calf region.
- Swelling, although this may be minimal.
- Pain when the posterior cruciate ligament is stressed (see assessment).
- Positive sign on the ‘Posterior draw test’.
- Pain and laxity when a ‘reverse Lachman’s test’ is performed.
- Instability of the joint, perhaps associated with the feeling of the knee ‘giving way.
General Advice for a patient:
- Apply Relative rest, compression and elevation.
- See a sports injury professional immediately.
Health professional and Physiotherapy management:
- A sports injury professional will firstly aim to correctly diagnose the injury. This may be achieved by performing specific tests such as the ‘posterior drawer test’ or ‘reverse Lachman’s’.
- Referral for an MRI scan and/or X-ray to assess the extent of the damage. Operate – surgery for posterior cruciate ligament.
1. Conservative Treatment
This is indicated in most PCL injuries and may consist of:
- Ice and heat treatment.
- Electrotherapy e.g. TENS and Ultrasound
- Manual therapy treatments
- Advise on a specific rehabilitative exercise program which may include: quadriceps and hamstring strengthening, gait reeducation and balance training using wobble boards.
- A knee support or brace can be used in the early to mid stages.
2. Surgical Treatment
A lesser proportion of PCl injuries require surgical intervention. However in more serious cases, in particular those in which other structures within the knee joint have been injured, surgery may be recommended. Surgery may also be indicated if the conservative management has not aided the stability of the knee sufficiently over a period of time.
In general, those who have sustained a PCL injury normally have good recovery rates, with most being able to return to sporting activities at the same level as before the injury. However, full recovery from cruciate ligament damage is highly dependant on the ability to adhere to a strict rehabilitation program.