Muscle strains are injuries that come with overuse of a muscle. In baseball, hitters generally get strains in their quadriceps or hamstrings due to the explosive movements involved in both batting and running. Commonly these injuries arise due to lack of stretching or a player's awkward movements. Pitchers and position players also can get a leg muscle strain while landing during their throwing motion or fielding a ball. Lastly, players can strain their arms while throwing and hitting as well.
Most commonly, baseball players get tendonitis around the area of the elbow or rotator cuff. This injury arises due to players constantly throwing the ball, day-in and day-out. When the throwing muscles in the wrist, hand, and shoulder are constantly under stress, they can lead to inflammation. This inflammation causes stiffness as well as pain around the joints like the elbow. Pitchers are especially susceptible to tendonitis as their arms make the most stressful throws in the game. Tendonitis generally will go away with rest, stretching, and muscle work. However, it is a nagging injury which will not go away if the muscles are not properly rested. Baseball teams usually shutdown a pitcher's arm, then after a week or longer will begin to stretch, until finally allowing the pitcher to pitch in simulated games.
Pitchers are almost always the victims of torn labrums. The labrum is a ring of cartilage in the shoulder that can be damaged during the extremes of the throwing motion. Since pitchers repeat this motion over and over throughout the game, they are likely to tear the labrum. Many times surgery is necessary and recovery time is lengthy. Additionally, it is hard for pitchers to regain their form after the injury and it may take a long time to get back to their pre-injury self. After the surgery, the path back to full recovery is full of slow reestablishment of strength and form.
The UCL (unilateral collateral ligament) is a ligament on the inside of the elbow. When it is severely damaged it requires the famous "Tommy John surgery" to reconstruct the arm. It was first done on baseball pitcher Tommy John in 1974 and since has become one of the most common surgeries in baseball. Famous MLB stars who have recovered from the surgery are players Stephen Strausburg, Jacob deGrom, and Adam Wainwright. These are all pitchers and once again this injury is prevalent in pitchers, but many position players also need it. After the surgery, baseball players need to take off about a year in order to learn to throw and strengthen both their elbow and shoulder.
"Dead Arm" is essentially an extremely fatigued arm that has been overthrown. This arises in all players as well as many pitchers. It generally occurs when people have taken time off (such as during the offseason) and have begun to get back into a full throwing schedule. It also occurs in young players or people who continually make throws beyond their arm's capabilities. All this injury needs is rest for a full recovery.
In baseball, ankle sprains are commonly sustained on the basepath. They can occur when a base runner hits the bag awkwardly while either running or sliding. While the major leagues have well groomed fields, at lower levels such as high school or little league, players can also sustain an ankle sprain while fielding on uneven surfaces. In all sports this is probably the most common injury, but in baseball it does not occur as often. Depending on the severity, this injury can take anywhere between a week and a month.
The meniscus is in the knee and is susceptible to injury mostly while batting in baseball. Due to the power that is used in the explosion of batter's and pitcher's front knees, the meniscus often tears in baseball. This tear makes it extremely difficult and painful to pivot. While tears can be played through, players may be less effective and will eventually need to get surgery on their knee.
The hands and wrists are also frequently hurt in baseball. One common way this occurs is during a batter's swing. With bats that weigh around 2 pounds, many times the wrist or hand can be hurt if the batter uses improper form. Likewise, the same can be said for throwing a baseball. Hands and wrists are also hurt when players are hit with the ball. These types of injuries are typically easy to recover from and return to form. At times, players can even play through these injuries with relative ease.
A bone bruise is an injury to a bone which is less severe than a fracture. It always often occurs in baseball when a player is hit with the ball. This can occur when a player is batting or when a pitcher or fielder gets hit by the ball. Generally the bruise can heal in a few weeks, but it could last up to 6 months. These injuries are moderate and are typically good news to players who fear a fracture.
One injury that is uncommon but highly dangerous is a baseball head injury. With a baseball that can be thrown around 100 miles per hour by elite pitchers or hit in the hundreds miles per hour by a hitter, if the ball hits a player in the head it can be disastrous. MLB all-star Giancarlo Stanton got hit by an 88 miles per hour pitch in the face and suffered a facial fracture. Other players, such as Aaron Rowand in 2010, have been hit by pitches and suffered concussions. Some players now put facial covers on their helmet to protect them from suffering a head injury.