HACKENSACK, N.J. — Hit by line drives, high sticks and 200-pound tacklers, more young athletes are ending up in hospital emergency rooms.

Some casualties arrive by ambulance; others are escorted by coaches or parents: A 15-year-old shortstop whose nose was bashed by a bad throw. A teen whose spleen was ruptured by a hockey stick. A girls' volleyball player who was elbowed going after a spike. An elementary-school boxer with a broken thumb.

"There are tons of organized sports injuries," said Dr. Peter Lee, director of the pediatric emergency department at The Valley Hospital in Ridgewood, N.J.

Injuries are rising because adolescent and teen athletes are playing more aggressively now at younger ages, emergency room doctors said. With travel teams and clinics running year-round, young athletes have more opportunity to injure themselves — and less downtime to heal.

About five to 10 injured young athletes a day — more on the weekends, when there are more games — come to Englewood Hospital and Medical Center, said Dr. Barbara Schreibman, acting director of the emergency department.

Many have suffered sprains, strains and contusions "from getting hit with an errant lacrosse stick," she said. Others arrive with nose and eye socket injuries as well as rib fractures.

"I definitely find it increasing," said Schreibman, who has been at Englewood for 15 years. "We're seeing more of a volume, certainly at this time of year."

More than 3.5 million children ages 14 and younger are treated for sports injuries each year in the United States. High school athletes suffer 2 million injuries — requiring 500,000 doctor visits and 30,000 hospitalizations annually, according to federal health data.

Some of those injuries are serious, like the heart-stopping, near-fatal line drive to the chest, which felled a 13-year-old Wayne, N.J., boy last year. A few athletes here have suffered brain injuries from multiple concussions.

Dr. Joseph Testa, chairman of emergency medical services at St. Joseph's Wayne Hospital, is concerned about the athletes who shrug off their injuries and never get checked out by a doctor.

"For every injury that warrants a child coming to the ER, there are probably at least a dozen other injuries" that need treatment, Testa said.

Each season arrives with its own brand of injuries and athletes in different uniforms limping into the ER. The fall brings football players with concussions and broken knees, as well as soccer players with ankle sprains and head injuries from colliding with other players.

Winter arrives with basketball, which is tough on the ankles. Sprained or dislocated fingers are the bane of the spring baseball and softball season, said Dr. Richard Schwab, director of emergency medicine at Holy Name Hospital in Teaneck, N.J.

"We've seen plenty of minor concussions," Schwab said. "The worst are kids tearing ligaments, blowing out their knees" in football.

Not just the boys

Girls as well as boys are suffering injuries.

"If you think girls are not aggressive on the athletic field, hang out in my emergency department," said Dr. Michael Gerardi, director of pediatric emergency services at Morristown Memorial Hospital. "These girls go at it hard."

Many young athletes are simply playing too much, said Dr. Jack Kripsak of the New Jersey State Interscholastic Athletic Association.

"A lot of adolescent athletes tend to play school team sports, then play on recreation teams, and also on travel teams," Kripsak said. "That leads to a lot of overuse" of growing muscle, bone and tissue.

That's why some young athletes are developing bursitis, tendonitis and other repetitive stress injuries in elbows and other joints from overuse, doctors said.

"One thing that's hard to impress on parents is they're just kids. They need time to rest," Kripsak said.

But try telling that to a kid who is playing in a showcase game for baseball scouts. In a culture that teaches athletes to shake off a hit, athletes often get back into the game before their bodies are ready — which leads to even more injuries.

"The pressure is on to do well, to perform well," Kripsak said. "So there's a greater risk for injuries."

Coaches and athletic trainers are especially concerned that players who suffer concussions aren't taking enough time off to heal. Research shows teen athletes are far more vulnerable to concussions than adults. Even minor concussions — the "dings" and "bell ringers" athletes shrug off — cause changes in the brain that last for days. Repeat concussions can lead to serious brain problems, even death.

Although most coaches are trained in giving first aid, "they should have a short fuse for calling 911," said Holy Name's Schwab, whose son and daughter are active in sports. "Because the police get there quickly, and an ambulance follows."

At Hackensack University Medical Center, Dr. Ruth Borgen recently treated a teenager whose spleen was lacerated by a hockey stick. The youngest athlete she's treated was a 12-year-old boxer with a fractured thumb.

The boy arrived still wearing his glittery green warm-up jacket, said Borgen, medical director of the pediatric emergency department. "I splinted the fracture. He was totally cool," she said. "His mother was so proud of him."

Some parents want a doctor's note to keep their injured child from playing for a while. Others want the student to get right back in the game.

"It's very competitive out there for college sports scholarships," Borgen said.