What is an anterior cruciate ligament (ACL)
The anterior cruciate ligament (ACL) is a very strong band of dense collagenous material that is situated in the centre of the knee joint and connects the femur (thigh bone) to the tibia (shin bone). The ACL is a very important stabilizer of the knee joint and it’s main function is to prevent the tibia from moving forward in relation to the femur (provides 85% of this restraining force). It therefore plays a significant role in maintaining optimal biomechanics of knee joint movement.
ACL ruptures are a relatively common knee injury in sports which involve pivoting (e.g. soccer, netball, basketball, skiing, AFL). They are more common in females than males and tend to occur in non-contact situations. Like other ligamentous injuries, tears can range from mild (stretched fibres with some torn) to completely ruptured (all fibres torn).
What causes an anterior cruciate ligament Injury
As mentioned earlier non-contact ACL injuries are the most common and are normally associated with a cut and plant movement of the body during physical activities. This movement often occurs during rapid changes in direction and/or speed whilst the foot is planted. Other movements such as twisting, pivoting and landing from height can also cause ACL ruptures however, they are less common. There are numerous additional factors that can predispose or be involved in the cause of an ACL injury including inadequate lower limb muscle strength and conditioning, poor neuromuscular control/timing, poor balance/proprioception, poor skill execution, fatigue and lack of concentration.
Are there different grades to an anterior cruciate ligament Injury?
Yes. There are three grades which ACL tears are categorised into:
- Fibres are stretched and a small amount torn
- No feelings of knee instability
- Mild swelling and little tenderness
- End feel felt on ligamentous structural integrity tests
- Knee joint maintains functionality with no feelings of instability
- A large number of fibres are torn
- Definite feelings of knee instability
- Moderate swelling and tenderness
- End feel noted on ligamentous structural integrity tests with forward movement of the tibia on femur noted.
- Knee joint loses some functionality and may experience sensations of collapsing or giving out in weight bearing positions.
- All fibres of the ligament are torn and there are subsequently two loose ends within the knee joint
- Mild, moderate or severe swelling (may occur rapidly) with little pain considering the seriousness of the injury
- Sensations of knee instability and giving out with weight bearing activities
- No end feel is detected due to the ligament losing all structural integrity
- Haemarthrosis (bleeding into the knee joint)
A variation of ACL injury is an avulsion whereby the ligament pulls a small part of bone away from either the tibia or the femur. This injury is uncommon and usually will occur in children.
How is an anterior cruciate ligament Injury diagnosed?
A physical examination by a skilled physiotherapist can normally detect injury to the ACL. Pain commonly presents with the anterior drawer, Lachmans and the pivot shift ligament integrity tests. Local knee swelling and feelings of instability or giving way of the knee are commonly noted also. Often MRI’s are conducted to determine the extent of injury, especially if it’s difficult to determine through clinical tests alone, and to provide additional information to see if surgical intervention is required.
What is the treatment / management of an anterior cruciate ligament Injury
Treatment for ACL tears initially involves reducing the inflammatory phase that accompanies ligamentous injuries. Rest, ice, compression and elevation of the injured knee over the initial 72 hours will assist in limiting the inflammatory effect. A hinged knee brace and/or walking crutches is recommended in cases of considerable discomfort and to provide knee stability in instances where it is lacking. The above management is essential for both conservative and surgical approaches.
Conservative (non-surgical) is recommended in grade 1 and some grade 2 ACL tears. Surgical intervention for grade 2 tears is dependant on factors such as the future physical demands of the individual and age. It is important that each individual is assessed on their own merits and appropriate intervention decided accordingly. Conservative management involves a progressive exercise program aimed at addressing and improving lower limb muscular strength/endurance, neuromuscular coordination, flexibility, balance/proprioception and restrictions in knee joint range of motion.
Surgical intervention is generally recommended in some grade 2 and all grade 3 ACL tears. Once again this may be influenced by the levels of activity, age and health status of the injured individual along with the amount of forward movement of the tibia on femur (ligament laxity) and additional injured structures within the knee joint (meniscal tears and additional ligament tears). In instances of complete rupture of the ACL a graft is used in its place. The most common grafts used are the hamstring and patellar ligament. Post surgical rehabilitation follows similar protocols as conservative with special attention payed to the healing graft and avoidance of certain types of exercises (open kinetic chain) to avoid damage to the graft during the early stages of rehabilitation.
Following the correct rehabilitation protocols for an ACL tear or reconstruction is essential in order to achieve optimal ligament strength and knee function. If you suspect you may have injured your ACL or if you require assistance for conservative or post-surgical rehabilitation please contact us at Central Baldivis Physiotherapy.