5 UFC Fighters Who Struggle to Stay Healthy

In the world of mixed martial arts, injuries are a common occurrence.

2011 was a rough year for the UFC as several of their main events were cancelled or altered because of injuries.

The third fight between Frankie Edgar and Gray Maynard, the title fight between Mauricio "Shogun" Rua and Rashad Evans, and Jon Fitch and BJ Penn's rematch are just a few examples of fights that were cancelled due to injuries this year.

The latest fighters to be hit with the injury bug are heavyweight contender Shane Carwin and welterweight champion Georges St-Pierre.

Carwin is now faced with his second surgery in as many years and will be sidelined until the middle of next year, while GSP suffered an apparent leg injury just a couple weeks before his title fight with Carlos Condit.

Carwin joins a select few fighters who have had to deal with injury setbacks on more than one occasion.

Some of these fighters have been out of the octagon for years and it remains unclear on whether fight fans will ever see them again.

Here are just a few examples of fighters who have the most trouble when it comes to remaining healthy.

Mike Swick

After being a cast-mate on the first season of the Ultimate Fighter, Mike "Quick" Swick made a name for himself in the UFC.

Swick began his UFC career in the middleweight division and won five straight fights in spectacular fashion, with only one going to a decision.

Swick had some impressive jiu-jitsu and submission skills, which was shown with his two guillotine or as he called them "Swick-otine" choke victories.

After a loss to middleweight contender Yushin Okami, Swick dropped down to welterweight and won four straight fights, which led him to a title eliminator fight against Dan Hardy.

Swick would go on to lose against Hardy as well as Paulo Thiago at UFC 109 in February 2010.

Since then, the 32-year-old has struggled to get back into the octagon.

In September 2010, Swick was mis-diagnosed with a stomach disease that required him to go on a very restrictive diet. The diet made it impossible for Swick to build any sort of muscle mass and he was unable to compete.

Swick began treatment and was hopeful that he would return in 2011. Swick was scheduled to face David Mitchell in January, but Mitchell had to pull out of the fight due to a back injury.

Instead of finding a replacement, Swick decided to pull out as well because he did not believe that his stomach problems were entirely healed.

Swick was finally scheduled to make his return this past August at UFC 134 in Rio. However, Swick would suffer a knee injury that would once again delay his return.

Swick still has a desire to return to the octagon, but it has been one difficult uphill battle.

Sean Sherk

Back in October 2006, Sean Sherk defeated Kenny Florian to win the vacant UFC lightweight championship.

Sherk had been in and out of the organization, but he had finally made a name for himself with the victory.

His first title defense would be a successful one against Hermes Franca where he scored a unanimous decision victory.

However, after the fight, Sherk was stripped of his title because a failed post-fight drug test. Sherk tested positive for the steroid Nandralone and was fined $2,500 and was suspended for a year by the California State Athletic Commission.

Sherk would get his chance at redemption almost a year later when he took on BJ Penn, who had won the title stripped from Sherk in January 2008.

Penn kept his distance with Sherk, keeping him away with pinpoint jabs that stopped Sherk from using his wrestling. Towards the end of the third round, Penn rocked Sherk with a punch that sent him backing up towards the cage. Penn attacked and hit a flying knee and ended the fight with punches.

Since that fight three years ago, fight fans have only seen the "Muscle Shark" in the octagon three times.

After a decision loss to now-champion Frankie Edgar, Sherk was scheduled to fight Gleison Tibau at UFC 104, but Swick was forced off the card with an injury.

The injury bug would bite again in January when Sherk was supposed to fight Jim Miller at UFC 108. Sherk suffered a cut during training that required several stitches and kept the Minnesota native out of action.

Next, Sherk was scheduled to face Clay Guida in March 2010, but had to be pulled from the fight after suffering yet another injury.

Sherk's next fight would not come until September 2010, when he won a controversial split decision over Evan Dunham.

After the fight, the 38-year-old decided to rehab from his past injuries and was planning a fall 2011 return, although we have yet to see him in action.

This, unfortunately, may be the end of the line for the Muscle Shark.

Alessio Sakara

Since coming into the UFC in 2005, Italian fighter Alessio Sakara has certainly had his ups and downs.

In his first fight in the organization, Sakara was kicked in the groin by Ron Faircloth and could not continue, making the fight a no-contest.

Sakara would return and pick up his first UFC victory against Elvis Sinosic in 2006.

After that victory, he would lose three of his next four fights, none of the fights making it out of the first round.

Sakara suffered a brutal knockout loss to Houston Alexander and after the fight, decided to move his training camps to American Top Team.

Since Sakara made the move, he has gone 4-1 and was slowly beginning to climb the middleweight rankings.

In March 2010, Sakara scored a TKO victory over James Irvin and was scheduled to face Nate Marquardt next at UFC 116.

However, Sakara was dealt some bad luck as his father passed away a couple months before the fight and he was forced to withdraw.

Since then, Sakara has barely been able to get inside the octagon as he has suffered several different injuries.

The 30-year-old was scheduled to face Jorge Rivera in August 2010, but was forced off the card due to an ailment.

The fight between these two was later rescheduled for November at UFC 122 and both fighters made it through their camps healthy.

However, Sakara arrived in Germany suffering from flu-like symptoms, but planned to still fight. In the end, the UFC scrapped the card the day of because of Sakara vomiting backstage.

Sakara's first fight in almost a year was against Chris Weidman at UFC Live and Sakara was dominated for three straight rounds.

The UFC finally thought they would get the fight between Sakara and Rivera done at UFC 133. However, Sakara would once again be pulled off the card as he suffered a torn ACL while training.

Sakara's journey through the UFC has been a tough one, and if he can't stay healthy, it could be over quickly.

Brock Lesnar

After successfully defending his heavyweight championship and getting his revenge against Frank Mir, Brock Lesnar was on top of the world.

The former pro wrestler had made a successful transition and was the UFC's top draw.

In his next defense, he would go up against undefeated Shane Carwin in November 2009. Carwin at the time was undefeated and was thought of as Lesnar's toughest matchup yet.

However, a few days before the fight was supposed to happen, Lesnar had to pull out of the fight because of an illness.

Lesnar had been sick for weeks and he had not felt this bad in his entire life, forcing the UFC to move the fight back to January of the following year.

In November, however, the fight was once again postponed as it was confirmed that Lesnar was suffering from mononucleosis.

UFC President Dana White stated in at the UFC 105 post-fight press conference that Lesnar was very sick and he was not getting any better.

Doctors would later discover that Lesnar was suffering from diverticulitis, an internal disorder. The 34-year-old required surgery to close up a hole in his intestine that had caused fecal matter to leak into his abdomen, causing him to contract mono.

It was questioned whether Lesnar would ever be able to fight again.

However, Lesnar announced in 2010 that he would return and successfully defended his title against Shane Carwin after taking an incredible beating in the first round. Lesnar didn't quit and would later pick up the submission victory.

In his next title defense, Lesnar was set to take on undefeated Cain Velasquez. The young Latino fighter dominated Lesnar as he won the fight in the first round and ended Lesnar's reign as champion.

In an effort to bounce back, Lesnar decided to coach against fellow heavyweight contender Junior dos Santos, which would have the two coaches fight for the No. 1 contender spot at the end of the show.

However, Lesnar's stint with diverticulitis was not over as he had to yet again battle the disorder, causing him to withdraw from the contest against dos Santos.

Lesnar has a successful surgery in May of this year, where a 12-inch piece of his colon was removed and repaired.

Now Lesnar is ready to return to the octagon and is set to take on former Strikeforce heavyweight champion Alistair Overeem.

It is unknown whether or not the disorder is past Lesnar or if he will ever be 100 percent healthy again. The former wrestler is not getting any younger and another run with it could cause a major setback.

Shane Carwin

In 2008, undefeated Shane Carwin made his debut in the UFC and took the organization by storm.

The Colorado native won four straight fights and did so in dominating fashion.

Not only did he win all of those fights by way of KO or technical knockout, but none of the fights made it past the first round.

It seemed that no fighter could get past Carwin's heavy hands and knockout power, including former heavyweight champion Frank Mir.

Carwin's impressive streak earned him a title shot against then-champion Brock Lesnar. Carwin was the first fighter that matched up with Lesnar physically, as 36-year-old weighed in at 254 pounds, compared to Lesnar's 265.

At the beginning of the fight, it seemed like Carwin had the title in the bag as he dropped Lesnar early and was raining down the punches on the champion. Referee Josh Rosenthal did not see it necessary to stop the fight as Lesnar was defending himself and he made it out of the round.

It was clear that Carwin was winded after trying to finish the fight and Lesnar took advantage of it, taking the challenger down and sinking in an arm-triangle choke for the submission victory.

Carwin looked to rebound from the loss against Ultimate Fighter winner Roy Nelson at the beginning of 2011.

However, the engineer was forced to pull out of the fight due to neck pain, that required surgery.

After a successful surgery, Carwin stated in January that he was ready to return to the octagon and get back into the title picture.

When Brock Lesnar was forced out of his No. 1 contender matchup against Junior dos Santos, Carwin stepped in to take on the Brazilian.

The fight stayed on the feet as dos Santos dominated Carwin throughout with his precise and accurate strikes. The damage to Carwin's face showed how powerful and dangerous "Cigano" really is.

After the fight, Carwin stated that he was 100% healthy and planned to return towards the end of 2011.

However, as previously mentioned, it was announced this week that Carwin would require yet another surgery, this time on his back, which will sideline him until mid-2012.

Carwin is eager to get back into the octagon to show that he can still compete with the best, but his injuries have halted that goal momentarily, possibly permanently.