Being overweight puts you at risk for a whole host of health issues, but most people don’t think about the risk posed to their knees. The anterior cruciate ligament, or ACL, is one of the major ligaments of the knee and one of the most susceptible to injury. Injury information on more than 1,600 men and women at the U.S. Naval Academy showed that those with a higher body mass index (BMI) had a greater incidence of ACL tears. A difference in BMI of only 1.2 (25.6 versus 24.4) made the difference between having and not having this kind of injury. (To learn more about BMI, read HPRC's explanation.)

Like the adage “You don’t know what you’ve got until it’s gone,” knees are something we generally take for granted. To stay on top of your game, you need your knees. An easy way to protect them is to drop the extra weight you’re asking them to carry around.

An ankle sprain involves damage to elastic structures in the body called ligaments. When a joint such as the ankle goes beyond its normal range of motion, ligaments are stretched beyond their limits and tearing of the fibers can occur. In military populations, ankle sprains are very common and affect operational readiness. In fact, ankle sprains are more common in the military than in civilian populations, and women are more likely than men to sustain this type of injury. Stretching and strengthening the muscles of the foot and ankle can help you prevent and recover from ankle sprains. WebMD has lots of ideas on how to prevent injuries, covering footwear, exercises, and more. The Foot and Ankle Conditioning Program from the American Academy of Orthopaedic Surgeons focuses on recovering from injury but includes well-illustrated exercises that are good for preventive conditioning too.

Your body is a segmented, or jointed, system designed for potentially powerful and efficient movement. Coordinated and efficient movements require a give and take between mobility and stability of the involved joints, as well as the surrounding muscles, tendons, and ligaments. These components, together with muscular fitness, are necessary to achieve functional movement, which is integral in performance and sport related skills.

According to the American Council on Exercise (ACE), joint mobility—also known as range of motion (ROM)—is the degree to which a joint is able to move before it is restricted by surrounding ligaments, muscles, and tendons. Joint stability is the ability to control or restrict joint movement through the coupled actions of surrounding tissues. Preventing injuries requires, among other things, both mobility and stability of your musculoskeletal system. Deficiencies in one or the other, due to improper or imbalanced training, may lead to injuries during movement patterns, such as walking, running, and repetitive lifting.

One example of an elite training program is the Army Ranger RAW functional fitness program. It is unique in that it focuses on whole-body mobility and stability. Exercises are typically performed using your own body weight against fixed surfaces (i.e. the floor or wall), instead of using free weights or machine weights.

For joint stability and balance, the National Academy of Sports Medicine (NASM) recommends performing one to three sets of 12-20 repetitions at a slow, controlled pace. According to American College of Sports Medicine (ACSM), there is not enough research to make definitive recommendations on the frequency and duration for this type of training. However some research has shown improvements using training frequencies of 2-3 days per week, with sessions lasting ≥20-30 minutes, for a total of ≥60 minutes per week.

The amount of joint mobility is partially determined by the flexibility of the surrounding muscles, tendons, and ligaments. For example, decreased shoulder flexibility might impact your ability to complete a full pushup. Refer to these FITT guidelines for flexibility training.

Frequency: According to ACSM, short-term improvements in flexibility may be seen after each bout of stretching. More long-term changes, however, are seen after three to four weeks of regular stretching. Flexibility exercises should be performed at least two to three days per week, but daily exercise will improve range of motion.

Intensity: ACSM also recommends that flexibility exercises should involve major muscle groups (neck shoulders, upper and lower body), stretching to the point of slight discomfort within the range of motion, but no further. You should feel slight tension in the muscle, but it should not be painful.

Type: There are several different types of stretches:

• Static stretching slowly elongates a muscle by holding the position for a period of time.

• Dynamic stretching is usually sport specific. It requires a joint to be stretched through its full range of motion, to lengthen and increase the muscles temperature.

• Ballistic stretching is a type of dynamic stretch where the muscle is forcefully elongated through a bouncing motion. There’s no evidence that ballistic stretching results in injury, but there is still question and ongoing research as to whether this technique affects muscular performance.

• Proprioceptive Neuromuscular Facilitation or PNF stretching may produce greater gains in ROM, however, it may be less practical since an experienced partner is needed to perform this type of exercise.

Time: Your stretching routine should take about ten minutes or so to complete. Static stretches should be held for 15-20 seconds, while PNF stretches should involve a six-second contraction followed by a 10- to 30-second assisted stretch.

Use caution when working on mobility and stability exercises. Done properly, these exercises should not cause pain in the joint or muscle. Never push through your threshold, have patience, and treat your joints with care.

Knee pain can be caused by myriad factors. Injury is one common cause. Another, especially if you’re a woman, is chondromalacia, which the National Institutes of Health describes as a softening of the cartilage under the kneecap. This results from improper alignment of the kneecap, muscle tightness or weakness, and extra stress on the knee joints.  Some simple suggestions offered by the American Orthopedic Society of Sports Medicine include stretching the quadriceps and hamstring muscles, strengthening the quadriceps, applying ice, and taking non-steroidal anti-inflammatory medications as directed by your physician. But most important, you should temporarily modify your training until symptoms subside. For example, if running is part of your cardiovascular routine, choose a softer surface such as a specially prepared track rather than concrete. You could also try an alternate activity such as biking, which is less stressful on the joints.