Traumatic Knee injuries in Females: ACL Injury Prevention
One question I often get as a physiotherapist is whether or not injuries are seasonal? My answer usually goes like this: “In the spring and summer, I see an increase in niggling running injuries such as tendinopathies as people return to outdoor running. 
The winter brings fractures and dislocations as skiing and hockey injuries tend to produce more forceful tissue damage. Lastly, the fall season brings about more traumatic knee injuries created by ballistic, running and cutting sports such as soccer, field hockey, basketball and ultimate.” Although this generalization is fairly accurate, there are many other factors that come into play with respect to how injuries occur. This article will focus on the traumatic knee injury. More specifically, the very unique characteristics within adolescent females that affect their ability to perform cutting and twisting activities effectively and make them more prone to traumatic knee injuries.
Injury Mechanism
Most traumatic knee injuries involve an inward rotation of the upper leg on a planted and bent knee. When the lower leg cannot accept such a force, the femur (thigh bone) and tibia (shin bone) shear apart. Just imagine planting your right foot down while quickly moving your body to the left. The two major resultant injuries are the anterior cruciate ligament (ACL) tear and the patellar dislocation. Both are quite severe, painful and entail lengthy recovery processes. Functional anatomy tells us that the ankle and hip joints are designed to accept and distribute multidirectional forces in the leg. The knee joint can accept compressive and shearing forces but only minor rotatory stresses. When we produce rotational movements in the body, the hips and ankles must be able to withstand and accommodate for the severity of the stresses. If not, the structures in the knee joint then become susceptible and consequently injuries occur.
Risk Factors
Numerous studies have demonstrated different factors that have been linked to having an increased risk of ACL injury amongst women. They exist at the cellular, hormonal, neuromuscular, structural and biomechanical level. This article will focus on a few of the structural and biomechanical properties within the female athlete. To better illustrate some of these factors, I will use a couple of patient case studies. They are both sixteen year old females. One plays both competitive soccer and field hockey, while the other plays volleyball and swims at an elite level. At first glance, both have appropriate muscle development and are above average in height. The first major factor that I notice is their ‘Q angle’. The ‘Q angle’ (see Fig. 1) is the orientation of the tibia relative to the femur. 
It is based on a number of factors such as shape of their pelvic bones, orientation of their hip joint as well as the shape of their femur. For these reasons, females will tend to have larger Q angles then males. This increased angulation requires that forces being transferred down the leg have to endure more medial to lateral (side to side) stresses to finish its intended job of transferring the forces through the foot to move the body. This wouldn’t be such a big deal if our rotational hip and ankles muscles were big and strong. But, they are not! Further assessment of these two female athletes goes on to find increased mobility within the hip joint as well as weakness of their medial and lateral hip muscles. Their knee joints are within normal but exhibit tight/overactive hamstring muscles and iliotibial bands. Overactive muscles usually demonstrate an inability somewhere else along the chain. Their ankle joints have increased mobility from side to side and also demonstrate weakness of the medial and lateral stabilizers in the ankle. The second major factor is that females do not absorb compressive weight through their spine, pelvis, hips and knees as well as their male counterparts. Therefore, motions such as squatting, landing and jumping have greater impact to the knee joint. When you add this all up, it means that the female knees are more prone to accepting impact in the joint and also collapsing inwards.
Prevention
Prevention begins with understanding the risk factors. The two major biomechanical factors are: poor control of hip and ankle rotation and the lack of hip and knee flexion with compressive loads. Fortunately, these factors can definitely be improved upon. Below are small videos of movement drills to improve rotational control and compressive loading. In video 1, you are trying to rotate the body without allowing the opposite knee to collapse inward.
[youtube]http://www.youtube.com/watch?v=b6x9d-NG13o[/youtube]
The exercises in video 2 show that we are working on the compressive ability of the body. It is necessary to begin the motion by reaching downward with the arms, this begins the sequence of spine, hip then knee flexion that are needed to move the body’s centre of mass towards the ground.
[youtube]http://www.youtube.com/watch?v=-J7EHKG_pmE[/youtube]
For these exercises try to ensure that the ankle, knee and hip are all in line. In video 3, the athlete gets to work on both single leg balance as well as hamstring and butt strength. These are also factors but were not discussed.
[youtube]http://www.youtube.com/watch?v=j24t6ynktl0[/youtube]
These exercises should be used during lower body strengthening training days. As you become more comfortable, you can perform the motion more quickly and then with weight or resistance. With all exercises, speed and difficulty can be increased as control of movement is achieved. A good goal would be between 30 – 50 reps of each exercise. As well, these exercises should be used as warm up drills before practices and games. Performing 30 seconds of each drill along with your other sport specific drills will help the body get ready for cutting and twisting activities. These are only a few specific exercises geared towards the factors that I feel are the most inadequate in female athletes. It does not negate other strengthening, balance or plyometric training programs. Other appropriate ACL injury prevention programs include; “FIFA – the 11 program” and the Santa Monica ‘PEP’ program. Lastly, previous ankle and knee injuries make one more susceptible to future injuries. Trying to rehabilitate on your own usually only gets you back to 80%. It is imperative to consult a reputable health practitioner to challenge and guide your body’s ability back to 110%.
