In the world of sports, injuries are an unfortunate reality that athletes often face. One of the most common and perhaps most devastating are Anterior Cruciate Ligament (ACL) tears.

ACL tears involve a long road to recovery which significantly affects an athlete’s entire season and maybe career. The rehab is intensive and focuses not only on the physical injury but also on the psychological impacts to the athlete.

With the high prevalence of ACL injuries many of our clients have asked us if there is a way to prevent these injuries from happening in the first place.

While ACL injuries are commonly associated with direct trauma (contact) or sudden changes in direction (non contact), recent research suggests that the risk of ACL injury may also be influenced by factors beyond the knee joint itself.

One intriguing aspect that has gained attention is the connection between hip stiffness and the likelihood of sustaining an ACL injury. In this blog post, we'll explore this relationship and discuss how addressing hip stiffness could potentially reduce the risk of ACL injuries.

Understanding the ACL

Before delving into the connection with hip stiffness, let's briefly understand the role of the Anterior Cruciate Ligament.

The ACL is a crucial ligament that stabilizes the knee joint, preventing excessive forward movement of the tibia (shinbone) relative to the femur (thighbone). Injuries to the ACL can occur during activities that involve sudden stops, changes in direction, or direct impact to the knee.

How Do ACL Injuries Occur?

As mentioned, ACL injuries occur either through contact or non contact mechanisms. Contact injuries occur when there is a direct impact to the knee such as when athletes are involved in knee on knee collisions or when someone lands on an athlete’s knee.

Non contact injuries occur when there is excessive force on the knee such as when an athlete is cutting, landing or decelerating. Non contact mechanisms are about 80% more likely to cause an ACL injury.

The Hip-Knee Connection

While ACL injuries are traditionally associated with the knee joint, researchers have started to examine the biomechanics of the entire lower limb to identify potential risk factors.

The forces acting on the knee will be impacted by the function and behaviour of the hip and ankle.

The hip joint, in particular, plays a significant role in controlling movements such as deceleration, cutting and landing which have all been identified as mechanisms for ACL injuries.

So hip stiffness/tightness, characterized by reduced range of motion and decreased flexibility in the hip joint, may disrupt the overall biomechanics of the lower limb, potentially influencing ACL injury risk.

How Hip Stiffness Affects ACL Injury Risk

Altered Biomechanics:

Reduced hip mobility can lead to compensatory movements in the lower limb, affecting the way forces are distributed during activities. From a rehab and injury prevention standpoint decreased hip internal rotation is our main concern.

Limited hip internal rotation will cause an athlete to shift their weight laterally when jumping and landing placing additional stress on the knee joint and increasing the risk of ACL injury.

Impaired Neuromuscular Control:

Hip stiffness can negatively impact neuromuscular control, affecting the body's ability to respond quickly and efficiently to changes in movement. This lack of control may contribute to improper landing mechanics and increased load on the knee, a known risk factor for ACL injuries.

Increased Loading on the Knee:

Restricted hip mobility may result in increased loading on the knee joint during dynamic movements. This heightened stress on the knee can contribute to the vulnerability of the ACL, especially during activities that involve cutting, pivoting, or jumping.

If one joint in the system is compromised (stiff) more force will be distributed to the other joints involved in that particular movement. For example, one of the most common mechanisms to ACL injury is the cutting motion in football.

When the athlete plants their foot into the turf and starts to change direction they need mobility in their hip (particularly internal rotation) to do this. If the hip does not have the necessary internal rotation eventually the body will have to “steal” range of motion from somewhere else in order to do the cutting motion correctly. The joint that the body steals this range from is the knee. Too much excessive motion in the knee eventually can lead to the ACL rupturing.

Test Yourself

Wondering if you’re at risk for an ACL injury? Here are 2 tests you can do to find out.

Test 1: 90/90 Hip Rotations

Sit down on the ground with your knees bent and heels touching the ground.
Next, drop both knees down towards the ground to the right.
Swing your knee towards the ground in the other direction.

If one knee drops further than the other it means that one hip joint is tighter. Sometimes you may even feel a pinching feeling deep in your hip as you’re dropping your knees to one side.

Test 2: Single Leg Step Downs

Another quick test you can do to see if you’re at risk for ACL injury is the single leg step down.

Stand in front of a mirror on a block or any raised surface on one leg.
Step down from the block touching your heel to the ground with your opposite foot.
Look to see if the knee of the leg making contact with the block move inwards towards the opposite knee.

If you see your knee collapsing inwards towards the other knee this is called excessive knee valgus and this can contribute to knee instability and put you at risk for and ACL injury.

Prevention and Rehabilitation Strategies

Addressing hip stiffness is crucial for athletes looking to minimize their risk of ACL injuries. Sports injury clinics play a vital role in providing comprehensive assessments and targeted interventions to improve hip mobility and reduce the risk of injury. Some strategies that may be employed include:

Manual Therapy: Address your hip stiffness by getting a therapist to get that hip joint moving. This involves manually mobilizing the hip joint and also loosening surrounding muscles that are tight.

Hip Mobility Exercises: Incorporating specific exercises to enhance hip flexibility and range of motion can be beneficial in preventing hip stiffness. Ensure you have a targeted mobility program you can incorporate into your training routine 2-3 times per week.

Strength Training: Targeted strength training exercises for the hip muscles can improve stability and control, reducing the likelihood of compensatory movements that may contribute to ACL injuries.

Functional Movement Training: Implementing sport-specific drills that mimic the demands of the athlete's activity can enhance neuromuscular control and improve overall movement patterns.

Conclusion

While ACL injuries are multifactorial, considering the role of hip stiffness in the overall biomechanics of the lower limb is a promising avenue for injury prevention.

Athletes, coaches, and sports injury clinics can collaborate to develop personalized strategies that address hip mobility, ultimately reducing the risk of ACL injuries and promoting long-term athletic success.

By understanding and addressing the hip-knee connection, we take a significant step toward a more comprehensive approach to sports injury prevention.

Move well, move often,

Michal Dabrowski
Elevate Rehabilitation and Performance