To assist you in your preparation for this year's fantasy baseball season, we have created a primer for you on some of the key injuries you will encounter in baseball. Hitters and pitchers are completely different creatures, and, for the most part, so are their injuries. To that end, the injuries listed below have been separated into which group they tend to impact the most.

It is important to remember that these groupings represent trends, not absolutes. Just like Rick Ankiel crossed over from the mound to the outfield, injuries often associated with one group can pop up in the other group without warning. For instance, the oblique abdominal strain that has plagued pitchers for years (and is included in their section), recently seems to be on the rise amongst hitters. Injuries respect no boundaries.

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Muscle strains | Meniscus tears | Hand/Wrist injuries | Elbow tendinitis | Rotator cuff tendinitis

Labral tears | Dead arm | Ulnar collateral ligament (Tommy John) | Oblique strains

HITTERS

Injuries that affect hitters tend to run the gamut. Anything is possible because most are unpredictable, such as the result of an odd collision (Brewers' ace Yovani Gallardo tore his right ACL when he ran into the Cubs' Reed Johnson). Nonetheless, outside of these unusual occurrences there are a few consistent ailments that tend to crop up with hitters, either as a result of base running, fielding, sliding or batting.

Muscle strain

Also referred to as a "pull," "tweak," "twinge" or "tear," the oft-reported muscle strain is the ultimate definition of boring when it comes to injury in baseball, but it is so commonplace that we would be remiss if we did not address it. The most commonly strained muscles tend to be the hamstrings (large muscles on the back of the thigh) and the quadriceps (large muscles on the front of the thigh) because these are the power muscles used during explosive running. Baseball is a game of frequent stops and starts, rapid acceleration and deceleration, which demands power from these muscle groups. Other muscles hitters tend to strain are the calf (lower leg) and oblique abdominals. The calf muscles aid in push-off and deceleration and typically get injured while running, while the obliques are most often injured during power swings as these muscles help rotate the trunk.

Strains are assigned a grade of I (mild), II (moderate) or III (severe) and a strict timetable for return to play with any grade is impossible to guarantee. Teams rarely reveal the extent of a muscle injury to an athlete, which often cannot be precisely determined anyway (except in the case of a complete tear) but there are some guidelines to follow. A mild strain is often not even overtly noted as a formal injury, but may be as simple as a player feeling the leg "tighten up" during practice. A Grade I strain suggests that there is no or minimally visible damage to the muscle fibers, but there is microtrauma which results in pain and inflammation. The athlete may miss up to two weeks, or he may not miss any time at all. A Grade II strain suggests definitive damage to the muscle itself and because of its variability, it results in the widest range of deficit and time lost. A Grade III strain reflects a complete tear of the muscle (there may be a few fibers that remain intact, but for all intents and purposes the muscle has been disrupted). This severe injury typically results in surgical repair for a major muscle group like the quads or hamstrings, although depending upon where the tear is located, some with severe injuries opt for the rehab route. The above definitions reflect the acute or sudden muscle strain, but there are also those muscle injuries that repeat over time and become chronic. Chronic strains can be extremely debilitating and potentially career threatening; just ask Diamondbacks' outfielder Eric Byrnes, who was forced to end the 2008 season early because of recurring hamstring injuries in both legs.

There are many theories as to why athletes suffer muscle strains, often pointing to multiple variables as opposed to just one. There are a few things to consider for your fantasy draft though: Is a player you are considering prone to repetitive muscle strains? Or has he experienced a recent string of multiple muscle strains, even in different body regions (like the A's Eric Chavez), which might suggest that he is wearing down physically, especially if his baseball age is climbing? How fit is the athlete? Better conditioning appears to be one factor in maintaining better overall health. Treatment primarily consists of rest, with the key being adequate time to allow proper healing. Modalities such as ultrasound, light therapy and electric stimulation can all be used to help influence tissue healing and exercise is used to help restore the muscle's strength and flexibility as healing permits. Even when a fantasy owner is dying to get a player back in his lineup, it is important to keep in mind that the risk of returning an athlete too soon after a muscle strain is re-injury, which may ultimately result in a worse outlook than the one associated with the original injury.

Meniscus tears

The meniscus is a fibrocartilage disc, of which there are two, inside the knee joint. One sits on the inner aspect (medial) and one is on the outer portion (lateral). The discs help provide some cushion between the two bones, tibia and femur, that form the joint, and actually serve to increase joint stability. When a meniscus develops even a minor tear it can behave like a hangnail, "catching" in the joint as the knee tries to go through various motions. This catching can cause the knee to lock up, preventing normal range of motion, and it can be painful, making it virtually impossible to pivot (when swinging a bat at the plate), run or slide, all of which, incidentally, can be the same things that can lead to a tear in the first place.

Many minor meniscal tears are addressed via arthroscopic surgery, in which the offending flap is removed. Once the flap is removed, the athlete can return to sport, usually within four to six weeks, but there may be future consequences, depending on the size and location of the tear. Larger tears are more problematic because the knee loses a bigger piece of its cushion. If the location of the tear is at a point where there is extensive joint pressure, the absence of a portion of the meniscus results in bone on bone contact, which ultimately can lead to wearing of the protective cartilage and associated inflammation (arthritis). Occasionally a meniscus tear will be repaired via stitches if that seems like a viable option, but the rehab period for a repair is much longer (several months) than for a removal. The repair advantage? The athlete keeps the protective cushion inside the knee joint. So why isn't that done every time? Because the meniscus itself does not have a great blood supply, which means tears don't tend to heal well, hence the reluctance to repair it.

Players will typically have this type of injury surgically addressed, and most often it will be a partial removal (meniscectomy) instead of a repair. Depending on the timing of the injury and the degree of disability, however, they may opt to defer the procedure until the season ends. So what can you expect from an athlete who is playing with a meniscal injury? As a fantasy owner you can expect the athlete to be up and down with it, and you will have to contend with unpredictability. The injury can affect a hitter's swing (because it limits his ability to pivot), his speed (especially rounding corners) and it will impact his base-stealing ability (hurts speed and ability to slide, especially feet first).

Hand/wrist injuries

There are too many possible variations in this category to elaborate on all of them, but suffice it to say that typically these injuries are the result of the hand making contact with something it shouldn't. An errant pitch, contact with another player, a dive to the ground -- all can result in a finger or wrist sprain (ligament injury), a fracture (broken bone) or dislocation (a bone slips out of the joint). The severity of the injury will determine whether treatment is as simple as "buddy taping" two fingers together or as complicated as surgery. Time missed can range from as little as a few days for a sprain to months if bone, ligament or tendon is badly damaged. A primary concern for hitters after such an injury is their ability to grip the bat. Can they bend the finger or hand enough to control the bat? Can they maintain their grip throughout the range of their swing (which dictates power)?

Broken bones in the wrist affect hitters similarly. We are hearing more about hamate fractures in hitters, often in the non-dominant hand. The hamate bone has a hook-like projection that sits very near the surface of the palm and it can develop a crack as a result of contact with the bat or shearing of the tendons that pass over it. Athletes often don't recognize an initial specific injury, but begin to complain of pain and swelling in the area at which point imaging, usually a CT scan, uncovers the problem. Treatment may be surgery to remove the broken piece and it typically takes a couple of months to recover. Once fully healed, the good news is this should not be a recurring problem. Other wrist and forearm fractures vary in terms of severity, depending on the location and the complexity of the fracture. Most simple fractures take roughly six weeks to heal, however, so if a member of your fantasy team succumbs to one, you can count on at least that window of time.

PITCHERS

The injuries that affect throwers tend to be much more similar, and anyone who is a fan of baseball can probably rattle off a list of common pitching ailments, much like the standard lunch menu at the company cafeteria. Rotator cuff tendinitis, elbow tendinitis and medial elbow ligament disruption requiring the dreaded "Tommy John" reconstruction are a few of the most familiar. And, as with hitters, pitchers can suffer a random injury due to the occasional misstep (Yankees' pitcher Chien-Ming Wang suffered a Lisfranc injury to his right foot while running the bases in June). You'll note that we include oblique injuries here too, as they have tended to primarily affect pitchers in the past, although that trend may be changing to some degree. Nonetheless, although back, hip and knee injuries can and do occur, the primary nemesis for a thrower is any injury that compromises the million- (or multimillion-) dollar arm.

Elbow tendinitis

The injury label can be as generic as elbow tendinitis, which simply means inflammation of some tendon around the elbow. For throwers, the most commonly affected tendons are those located on the medial or inner aspect of the elbow. It is here that the tendons of the wrist flexors (which bend the wrist down toward the ground) and the forearm pronators (which rotate the forearm from a palm-up to a palm-down position) attach, hence the term flexor-pronator group. The flexor-pronator muscles provide protection to the elbow joint by countering the torque produced during pitching, so lingering problems here can put the elbow at risk. Treatment begins with rest, while addressing pain and swelling, followed by soft tissue work and strengthening. Time lost will depend on the severity of the episode, but you can usually count on a couple of weeks at the minimum. If managed well, this can be a "one and done" type of scenario. As an example of just that, in 2008, Rays ace Scott Kazmir had inflammation in his throwing elbow in spring training, but was available to pitch a month into the regular season, and held up well through the remainder of campaign.

Rotator cuff tendinitis

The terms "tendinitis," "inflammation" and "strain" are often used in combination with the words "rotator cuff" to describe any problem affecting this muscle group or the tendons that anchor them to the arm bone (humerus). The rotator cuff is a group of four muscles (supraspinatus, infraspinatus, subscapularis and teres minor) that combine strength and finesse to coordinate motion about the shoulder. This muscle group represents the pitcher's bread and butter as its most significant functions are to help stabilize the arm in the socket and decelerate the arm from the violent motion of pitching. The forces are so great on the shoulder when throwing that the rotator cuff must work extremely hard during every pitch. The effectiveness of the rotator cuff muscles is further dependent on the muscles that control movement of the scapula, or shoulder blade, and these muscles are often surprisingly weak in throwers.

When throwers develop rotator cuff problems, and almost all of them certainly will at some point in their career, initial treatment usually begins with a period of "shutting down," meaning no throwing so that the shoulder can completely rest. The time period varies depending on the seriousness of the injury and other treatment to help decrease pain and inflammation happens concurrently. As the shoulder improves, strengthening exercises are initiated, not only for the rotator cuff but also for the scapular muscles. If that goes well, the athlete is progressed to a staged return to throwing program. If the athlete successfully completes each stage of the throwing program, then he moves on to bullpens, simulated games and rehab starts, until the team, in conjunction with the medical staff, determines that he is ready to resume game situation pitching. After offseason rest, this condition often settles enough for the athlete to return in spring without a hitch. The fantasy owner who sees this crop up midseason, however, has a sense of dread, and deservedly so, as it can become a recurring theme throughout the season (read: multiple trips to the DL), and the timetable for return has a wide variability, ranging from weeks to months to not again this season. In the worst case scenario, there may be a tear in the rotator cuff that ultimately requires surgery. Return after rotator cuff repair is not a sure thing, so a fantasy owner should hope for an athlete's recovery after conservative treatment. Any pitcher coming off rotator cuff repair is a risk in a fantasy draft, and although it can turn out well (former New York Mets ace Pedro Martinez showed us that in 2007), the risk likely outweighs the reward in the early stages of the athlete's return.

Labral tears

Injury to the labrum of the shoulder in a thrower is not something a fantasy owner wants to hear. But guess what? You will hear it frequently. Labral tears are just part of the territory for a major league pitcher; it's just a question of degree and disability. In other words, if you were to look through a surgical scope at the inside of a thrower's shoulder, including those that had no reported symptoms, you would find damage to the labrum more often than not. The fascinating thing is that some pitchers manage to throw and throw well despite the presence of significant tissue damage. Other pitchers have relatively minor injuries, but are completely incapacitated. The reason for this is unclear. It is not necessarily a question of pain tolerance; rather it appears to be a much more complicated mechanical picture.

The labrum is a ring of cartilage that surrounds the glenoid or the "socket" portion of the shoulder joint and actually serves to enhance shoulder joint stability. When torn, the labrum can catch, causing the shoulder to be painful and potentially feel unstable. The biceps tendon has an attachment to the labrum, so if the biceps is involved, it can lead to problems at the labrum. The labrum undergoes great strain where it attaches to the biceps at the extremes of motion, when the shoulder is at its fully cocked position before ball delivery, and at the end of ball release (during follow through). Since a pitcher repeats that motion time and again -- not only during a game but also during warm-ups, bullpen sessions and any other episode of throwing -- the labrum is constantly subject to stress. Surgical repair may be the eventual treatment in a thrower who does not respond to a period of rest and conservative rehabilitation, and the recovery is lengthy. Pitchers do return from labral repair, but their timetable to return and their effectiveness when they do come back is variable (although early word on the Angels' Kelvim Escobar is that he is ahead of schedule and looks good following his surgery last July). Fantasy owners who draft a pitcher coming off of labral surgery in the offseason should recognize that there is a bit of a risk involved until the athlete shows that he has indeed fully regained his form.

Dead arm

We often hear about the phenomenon known as "dead arm" associated with pitchers, but what is it really? Generally speaking, this term is associated with arm fatigue from overuse. It tends to crop up during spring training when throwers resume a more intense schedule after the offseason. The other group of throwers who tend to be affected by this are young pitchers who get moved up to the majors midseason. The adjustment to the level of competition, as well as the strain of an increased workload, can take a toll on the young pitcher's arm. It is not completely understood, but the interesting feature is that the symptoms are predominantly weakness, not pain. Weakness means the pitcher simply can't deliver the ball the way he intends and as a result becomes ineffective. There is also some thought that the condition is associated with instability in the shoulder, which is not uncommon for throwers since their shoulders are inherently "looser" in order to allow them to do what they do. Combine decreased joint stability with fatigue of the muscles that help support that joint, and you have an ineffective arm. Treatment is very simple: rest. The thrower is shut down, usually for a period of at least two weeks, to let the arm recover, and is then gradually introduced to throwing again. Unlike most other injuries, the dead arm syndrome does not appear to have any long-term injury implications in and of itself, so it does not spell doomsday for fantasy owners. It may, however, signal that a thrower needs to increase his overall strength for the long-term protection of his shoulder.

Ulnar collateral ligament (UCL) reconstruction or "Tommy John" surgery

By now this procedure has become so commonplace amongst throwers, that it has come to be primarily referred to by its nickname "Tommy John," for the first major league pitcher to undergo this operation. The actual ligament that is damaged, which then needs to be reconstructed, is the ulnar (medial) collateral ligament which reinforces the inner aspect of the elbow and runs from the end of the humerus (arm bone) to attach on the ulna (inner forearm bone). When this ligament is damaged, the pitcher loses command of his pitches and typically has pain directly over the area of the ligament. Additionally, the elbow joint can be less stable, but this is not a defining feature of the condition. The surgical procedure involves taking a tendon from elsewhere in the body (most often one of the forearm tendons) and weaving it through drill holes in the two bones where the ligament normally attaches, thereby reinforcing the inner aspect of the joint. The rehabilitation process is long, running typically one year from surgery to pitching.

The timing of the surgery may influence the timing of the return as well. The fact throwers have to take so much time off to allow proper healing from surgery and gradually return to throwing affords them the opportunity to address other areas of concern. Even with a primary elbow injury, many throwers have shoulder concerns as well. The lengthy rehab time allows throwers to strengthen the muscles of the shoulder, fine tune the muscles of the "core" and generally get in better baseball shape. In fact, this total body rehab may be a big reason that throwers feel they can "throw harder" after such a surgery. Their delivery may well be aided by the fact their body is in better shape, placing less demand on the arm itself. Although pitchers can come back with a solid performance in the first year, statistics seem to reflect a two-year timetable to truly return to form. This may be due to the fact a year away from throwing means the pitcher needs to rediscover the finesse portion of his game. Strength comes first, command and control come later, as evidenced by Francisco Liriano's initial struggles upon his return last year. Overall, the statistics reflect a very successful return to play for those throwers who are willing to dedicate the time and effort required to have a good outcome. The motion of throwing a baseball will continue to place unnatural demands on the shoulder and elbow, and this surgery will continue to have a place in the sport. Like the aforementioned shoulder surgeries, it is an option of last resort, in the thrower who simply cannot continue to perform because of the elbow. Pitchers will typically go through two cycles of rest and rehabilitation before ending up on the operating table, so fantasy owners should keep that in mind if one of their pitchers develops a case of disabling elbow pain. The part that is hard to predict when a pitcher goes out with elbow pain is whether it will be a single episode that he will overcome (the big question right now with Angels' ace Ervin Santana, who has a sprained ulnar collateral ligament) or whether it is the beginning of a disabling cascade (St. Louis Cardinals ace Chris Carpenter never could make it back after Opening Day 2007, eventually ending up with surgery that July, only to have continued problems and a subsequent nerve transposition in 2008. It is worth noting that he is on track to start the 2009 season). Even a single episode of serious elbow pain raises some red flags that the thrower may be headed for further elbow breakdown. Unfortunately, the timetable is so variable that breakdown could happen within a season or not until months or even years later.

Oblique strains

Oblique strains fit in the category of muscle strains, but these are so problematic for pitchers in particular that we decided to give them a paragraph of their own. In recent years the number of players going on the disabled list due to oblique injuries has remained fairly consistent at about twenty per year. Pitchers as a group have comprised about half of those, but the specificity of their injuries has been remarkably consistent.

The oblique abdominal muscles are unique because they span the entire trunk (torso) and they are so specifically oriented toward rotation, yet their function is critical for trunk on pelvis stability. Since rotation is such a critical component of pitching, as is stability of the trunk on the pelvis while weight is being transferred, oblique function is key to proper delivery. Any muscle strain can be painful and pain, in turn, inhibits muscle performance. Attempts to contract an injured oblique muscle can trigger pain that immediately inhibits the other trunk muscles from functioning normally, which explains why pitchers with this injury cannot deliver the ball.

MRI studies show that the internal oblique seems to be the most commonly injured in pitchers, and specifically at the attachment on the 11th rib, on the contralateral (opposite) side. The theory amongst those who treat these athletes is that there is a massive contraction of the internal oblique during a hard throw and the muscle tears, often pulling with it a little piece of bone (also called an avulsion fracture). There is some speculation that evolution of pitching mechanics may contribute to the hard pull that results in such an oblique contraction, and potentially leads to injury in some cases.

Once the injury has been properly diagnosed there is the matter of ensuring that it is well healed before the athlete attempts to return to the mound, which can take six to eight weeks for a moderate strain. Proper trunk function is essential in order to maximize both upper and lower extremity function. Continued attempts to push through an oblique injury lead to compensations by other, often weaker, muscle groups, which can then lead to other problems, such as with the rotator cuff. Hence it becomes critical to avoid returning a player to action too soon.

Although we put this injury in the pitcher category, it is worth noting that in the 2008 season there were more hitters than pitchers who suffered this injury, although the reason remains unknown. The time frame for recovery is essentially identical and the risks of re-injury are the same if the athlete returns too soon. Just hope that no one on your fantasy roster is unlucky enough to become an oblique statistic in 2009.

Certainly there are plenty of other injuries that will make themselves apparent over the course of a season, but these seem to be the ones we hear about over and over again. The challenge for fantasy owners is that rarely do injuries fit a neat timetable, and rarely does the same injury behave the same way in two different athletes. A little knowledge, though, can go a long way in helping the fantasy owner set a lineup or make a trade. With that in mind, we wish you the best of luck and a healthy roster in 2009. Play ball!

Stephania Bell is a physical therapist who is a Board Certified Orthopedic Clinical Specialist and a Certified Strength and Conditioning Specialist. She is a clinician, author and teacher with extensive experience in the area of orthopedic manual therapy and sports medicine.