Anterior cruciate ligament – ACL

Date: 22/06/2021

Hours: 2

Total hours: 185

Anatomy:

The knee joint is made up of the tibia, fibula, femur with the patella bone also found anterior to this. The muscles surrounding this joint are responsible for the movements of the knee. The quadriceps, which insert at the patella tendon, are known as rectus femoris, vastus lateralis, vastus intermedius and vastus medialis. These muscles are responsible for knee extension. The hamstring muscles on the posterior side of the knee are responsible for knee flexion and are made up of 3 muscles known as bicep femoris, semitendinosus and semimembranosus.

Within the knee there are many other structures such as burae and the meniscus, which acts as a shock absorber within the knee and is located on the top of the tibia bone and can be palpated at the joint line. Other structures in the knee are the knee ligaments known collectively as the collateral ligaments which are as follows:

ACL -anterior cruciate ligament

PCL – posterior cruciate ligament

LCL- lateral collateral ligament

MCL – medial collateral ligament

Mechanism of injury:

In ACL injuries, one of the most common causes of noncontact injury mechanisms in football are due to change of direction. These changes of direction are usually due to movements such as cutting, landing or deceleration (Shultz et al, 2007). Associated with this mechanism is excessive loading of the knee joint where movements within the sagittal plane, such as movements in knee flexion and knee valgus with a planted foot, can cause excessive loading through the ACL (Yu & Garrett, 2007).

Gender has been suggested to have an impact on injury mechanism. Hewett et al (2010) identified how there was a difference in the biomechanics between male and females during landing, with the position of the female lower limb were slightly more exaggerated upon landing due to weight distribution of the ankles forcing the knee into a valgus position and the trunk being tilted laterally, with the centre of mass being at the outside of the foot. The mechanism was similar in men however the positioning was found to be much greater in women. This research is also supported by the epidemiology of women having a higher injury occurrence compared to men (Walden et al, 2011). Other factors which may affect this are quadricep dominance and leg dominance which will affect knee extensor/flexor strength and coordination (Myer et al, 2011).

Although the most common mechanism of injury is through noncontact forces, the occurrence of contact mechanisms can still cause damage to the ACL. An example of this is in sports such as football where most of these types of injuries occurring during the attacking phase of play with defenders and strikers being most effected by this during a tackling movement (Waldén et al, 2015). It has also been suggested that contact mechanisms may occur more often during adolescence which may be due to not having the required skills set, with incidences of collision being approximately 46.15% of reported injury which was identified by Emery et al (2005). Contact injury at the ACL from a young age may influence the onset of osteoarthritis at a later stage. There may be a difference in noncontact ACL injuries dependant on the type of playing surface which is used and the effect this can have on player biomechanics. The properties of the surface, shoe characteristics and weather conditions can impact the mechanism of an ACL injury.

Hamstring grafts:

The most common type of graft for an ACLR is used from a hamstring tendon, most typically from the semitendinosus or Gracilis tendons (Geib et al, 2009). It has been suggested that there are commonly hamstring strength and functional deficits after an ACLR (Buckthorpe et al, 2020). This means that the hamstrings must be incorporated within any ACL rehabilitation programme to help restore function at the knee (McEwen et al, 2020). These exercises can include isometric hamstring exercises, towel stretches and heel slides. Movements such as running in different directions or speeds and landing exercises in plyometric training can help assist in building hamstring strength, early ROM restoration, improve knee function and balance (Saka et al, 2014).

Rehabilitation and return to play:

The rehabilitation after an ACLR surgery is important and early intervention is essential for the best recovery. The main aims for rehabilitation for post ACLR surgery are to reduce inflammation, increase ROM, introduce quadricep and hamstring strengthening and improve mobility (Davies et al, 2020). The use of early knee extension and early weight baring exercises are essential in the progression of knee rehabilitation, this has also been shown to reduce the risk of quadricep atrophy and restore quadricep function more quickly post ACLR (Lepley et al, 2015).

Within the first phases of rehabilitation the focus of gait should be to encourage partial weight baring and full weight baring activity. This can be completed through using 1 crutch or using something stable to hold onto. Normal gait patterns can be encouraged with the use of an anti-gravity treadmill. This can encourage a normal running or walking gait while the athlete is at 50% of their own bodyweight (Hansen et al, 2017). In later stages, this can be used as a form of interval training to ensure cardiovascular fitness before return to play and reduce reinjury risk by correcting abnormalities within the gait pattern (de Heer et al, 2020). Towards the later stages at approximately 6-12 weeks, normal gait patterns should be encouraged to ensure no neuromuscular asymmetries (Gardinier et al, 2012).

After surgery, the athletes balance abilities can become impaired as some fears of reinjury may begin to occur. This is where appropriate balance and proprioception training should be included within the rehabilitation of an athlete returning to football (Silva et al, 2012). The use of proprioception training can increase balance ability and awareness of movement. Kaya et al (2019) found that joint position sense was better in those who completed neuromuscular exercises. Proprioceptive exercises can include single leg balance which can be progressed with the use of a balance board. Backwards running has also been proven to help improve knee proprioception (Shen et al, 2019).

Eccentric exercise, which is known as the lengthening of the muscle during exercise, has been commonly used during rehabilitation programmes to help increase strength (LaStayo et al, 2014). The use of eccentric exercise at the quadriceps was most effective in the recovery phase of ACL rehabilitation due to the exercise promoting greater neuromuscular activation and muscle hypertrophy (LaStayo et al, 2003). The use of eccentric exercise when implemented progressively has shown to have improvements with gluteus maximus and quadricep strength, improved quadricep torque and improved knee ROM during gait. Some examples of early eccentric exercises involve active knee flexion and extension which can be completed as a non-weight baring exercise or with an increased resistance dependant of the athlete’s tolerance at the stage (Biscarini et al, 2016). These exercises can include hamstring/calf stretches, straight leg raises, half squats or static lunges for early-stage rehabilitation of the ACL around 1-4 weeks (Millett et al, 2010).