By Elena Voropay

Ever had trouble opening or closing a tight door while hearing a squeaking noise? Pretty annoying, isn't it. This is the way your knee feels when it is injured. When your knees are healthy and strong, you don't even think about them. But when these hurt, you can prepare yourself for putting your life on hold. Knee injuries can interfere with every single activity of daily living, from simply getting up from a chair and walking, to losing muscle mass and function of your legs.

If you've ever injured your knee, you're not alone. Knee injuries have actually become pretty common, especially among women. One of the main reasons is that we use knees more than most other joints in everyday activities. If you participate in sports or any kind of fitness endeavour, you are more likely to overuse your knees. And if the joints are not properly supported by muscles, tendons and ligaments, this can lead to a number of injuries.

Knee injuries can occur as the result of a direct blow or sudden movements that strain the knee beyond its normal range of motion. Sometimes knees are injured slowly over time from normal wear and tear, just like the treads on a tire get worn out when you drive a lot. If you have other problems with different joints, such as the hips or feet, these may change your walking patterns and  alignment of the knees. Ultimately, all these factors may lead to damage of any knee tissues. And ACL (Anterior Cruciate Ligament) injury is not uncommon.

To understand all knee injuries, first you have to understand the knee.

The structure of the knee joint resembles that of a door – your upper leg bone, femur, is the solid wall, your lower leg bone, tibia, is the moving door, and the hinge keeping these two together is your knee known as patella. The weight-bearing surface of the knee is covered by a layer of articular cartilage. On either side of the joint, between the cartilage surfaces of the femur and tibia, are the medial and lateral meniscus. These team up with cartilage and act as shock absorbers reducing the impact you put on your leg bones with every step you take. between the tibia and the femur.

The hinged knee joint is held together by the four “screws” - medial collateral ligament (MCL), lateral collateral ligament (LCL), anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL). The word 'cruciate' in this key ligament's name means 'cross-shaped' or 'marked with a cross', a seemingly odd designation for a straight strap of connective tissue, which is roughly the size of your little finger.

The ACL is one of the four main ligaments within the knee which connects the upper and lower leg bones, femur to the tibia. But unlike the medial and lateral connecting tissues which go straight down, ACL runs over the front of and is roughly perpendicular to another key supporting structure called the posterior cruciate ligament (PCL), creating a 'cross' of connective tissue cords within the knee. An easy way to picture this is to cross your index finger under your middle finger; the middle finger represents the ACL and the index finger is the PCL.

All cruciates provide support for the knee and guide all rotational movements at the knee joint. The significance of ACL is that it prevents hyper-extension of the knee, limits excessive forward movement of the lower leg and gives the knee rotational stability.

When an ACL injury occurs, the knee becomes less stable, and that is a big problem for any type of movement involving the leg. Not only that, having a hurt knee increases your chances of getting other ailments, such as poor walking technique, bad posture, back and neck problems, and serve as a good foundation for arthritis of the knee, meniscus and cartilage tears. Note that half of ACL injuries occur in combination with damage to the meniscus, articular cartilage, or other ligaments.

Are you ready to retire from your walking, biking, running, cross training or yoga? Maybe you are just getting started, so it is the best time to make your training healthy and enjoyable for many years to come.

Women complain more about knee-related injuries, especially knee pain for some very valid reasons, both anatomical and physiological. Comparing within the same sports, females are five times more likely to suffer an ACL tear than a male of the same level. Not only that, the injuries are usually more serious in female players. How serious can these get? Surgery serious.

• Body Alignment

Thanks to women's in-born gift of the expected child-bearing, women's pelvis and leg alignment is naturally different than that in men. The average angle of the pelvis for females is 15 degrees and only 10 degrees for males. The wider female pelvis tends to exaggerate the angle made at the knee between the bones of the upper and lower leg, or femur and tibia, when the foot is planted on the ground. Even though it is just five degrees difference, the inward pressure on the knee and external rotation of the tibia places excessive stress on the knee every time the foot touches the surface.

Picture this – when the leg sets on the ground, the upper leg bone, the femur, has to go in slightly to balance the wider pelvis in order go give body a stable point. This inward rotation from hip to knee forces additional internal rotation of the knee joint. A large pelvic angle women have also results in a more pronated or inverted foot when the foot's arch is decreased which further stresses the knee.

There is another very specific factor for women to consider. The place where the ACL passes through the knee joint, the intercondylar notch at the bottom of the upper leg bone, is smaller in females than in males. The ACL moves within this notch and provides stability to the knee by preventing the bone of the lower leg from sliding forward and rotating inward. Since the notch is more narrow in women, ACL movement is restricted and the femoral condyles can easily pinch the ACL within the joint, especially during twisting, jumping, cutting or any other hyper-extended movements – a sure way to tear or rupture ACL.

• Muscular Imbalances

The balance of muscle power and the recruitment patterns between the front and back leg muscles, or quadriceps and hamstrings, is crucial to knee stability. Research shows that female athletes tend to use their quadriceps strength dominates, whereas men have a better balance around the upper leg.

Training the inside of your thighs is good not just for trimming your thighs, but for keeping your knees in place. Not surprisingly, women's vastus medialis muscles located on the inside of the thighs are not as strong and dense as men's which directly translates into weakness in the knees.

• Hormones

Differences in sex hormones also play a role in females’ susceptibility to ACL injuries. There are specific receptors for the female hormones estrogen, progesterone and relaxin on the surfaces of cells in the ligament. These hormones increase tissue laxity and decrease its strength. This is especially pronounced during the ovulatory phase (days 5 through 12) of women's menstrual cycle. What's more, with aging, hormonal changes associated with menopause may be involved.

• Muscle Failure and Fatigue

Muscle failure and fatigue have a profound impact on the efficiency of performance. Long workouts and races squeeze and drain all your physical and emotional juices. Your body tissues run out of their energy reserves and this influences bodies' protective mechanisms. At these times when you are most likely to get injured. This is especially important when it comes to knees.

Interestingly, women's legs usually fatigue faster than men's given the same fitness level. As soon as fatigue kicks in, women tend to stand up straighter than men lowering knee flexion angle, and putting their ACL at a greater risk.

Your ACL is thin, but quite strong – it can support a force of 1700 N (Newton's) before complete failure. But when the injury sets in, there is no force. If you tear, over-stretch or rupture ACL, the symptoms are all alike. All of these cause pain, inflammation, instability and may precede the development of other unwanted ailments.

When an Anterior Cruciate Ligament gets damaged, you may:

Hear a pop from the inside of the knee
Feel the knee snap out and back into place
Observe inflammation almost immediately or within a few hours after the injury and the knee may turn into a small balloon
Feel pain, unless you take painkillers on a regular basis

As with all injuries, the best way to handle ACLs is not to hurt them. If you follow common sense, write down the following tips and stick them on your fridge and into your training dairy, then put the protection of your joints on top of all workout priorities, your healthy knees are guaranteed.

1.Before exercising or participating in sports, warm up by walking or riding a stationary bicycle, then do stretches. The warm up before stretching is very important and will help improve range of motion, reduce stiffness and muscle soreness, improve overall mobility and performance.

2.Stretching will keep the muscles and tendons flexible, so they can absorb shock better. Stretching the muscles in the front of the thigh (quadriceps) and back of the thigh (hamstrings) reduces tension on the tendons and relieves pressure on the knee during activity. Remember the magic six stretches for legs: Calves, Hamstrings, Quadriceps, Hip Flexors, Adductors and Abductors (or inner and outer thighs).

3.Wear shoes that both fit properly and are in good condition to maintain balance and leg alignment at all times, whether you walk, run, squat or simply stand in place. If you feet are flat or over-pronated that roll inward, you increase your risk of all sorts of knee injuries. You may help reduce some of these problems by wearing special shoe inserts (orthotics) and ensure good fitting.

4.Strengthen the leg muscles by walking up stairs or hills, riding a bicycle, and incorporating walking lunges, hamstring curls, leg extensions, and toe raises into every leg workout. One thing of caution – when you do squats and leg presses, watch your form and check the entire body and knee alignment.

5.Avoid sudden changes in the intensity of exercise. Increase the force or duration of activity gradually. Improving leg strength is a sure way for a more stable knee joint. Technique is everything; close attention must be paid to the performance of these exercises in order to avoid injury.

6.Plyometric exercises are excellent for your knees, but only if these joints are healthy and strong to begin with. Squat-jumps, Scissor-jumps, Single-leg hops, Lateral hops and Forward-backward jumping lunges will help you to build power, strength and speed. The most important element during plyometrics is the soft landing on the balls of your feet and slow rolling back to the heel. Remember to keep knees bent and hips straight.

7.Add the following joint-supporting supplements to your regular mountain of pills and powders: Glucosamine, Chondroitin Sulphate, MSM (Methyl Sulfonyl Methane), Hydrolyzed Collagen Protein (Gelatin), and Omega-3 fatty acids.