Kyle O'Flaherty used to be stoked by his weekly workout routine, a heavy rotation of cycling, boxing, jiu-jitsu, and running. But even at age 20, his hips started to ache, and not just during exercise. He's not unusual. "I've seen a tremendous spike in young, active men with hip pain in my practice in the past five to 10 years," says orthopedic surgeon Benjamin Domb, M.D. In fact, more 45- to 54-year-olds are opting for hip replacement, according to a National Hospital Discharge Survey. Follow our guide to stay out of the OR and keep your hips pain-free.

How your hips go haywire

Each thighbone attaches to a socket in your pelvis. A cartilage coating allows for smooth movement. Ligaments, tendons, and muscles provide stability and range of motion. But things can go awry. Watch for these common problems.

1. Muscle Strain

This happens when your muscle fibers stretch or rip, often during a sudden turn or jump--common movements in soccer or hockey. The typical remedy is rest and alternating ice and heat therapy to relieve the pain as it heals.

2. Tendinopathy

Muscle weakness or overuse can damage the tendons that link your glutes to your hip bones. You might feel sore when walking, climbing stairs, or lying on the affected side. Train your hip abductor muscles--see the next page.

3. Bursitis

Bursae are like mini pillows that cushion your hips; the average hip has six of them. Bursitis occurs when these sacs become irritated. Your risk goes up if you run on hard surfaces, so go with a track or grass.

4. Torn Labrum

The labrum is the gasket-like ring of cartilage that lines each hip joint. Squats and lunges, which require deep bending, can wear it down until it tears. This may require surgical repair. If these moves cause hip pain during your workout, avoid them.

5. Arthritis

The cartilage in your joints can deteriorate over time from wear and tear, injuries, deformities, and too much body weight. To stay active, try Nordic walking, that kooky style of striding with poles. It can help you strengthen arthritic hips without irritating them, Scandinavian research suggests.

6. Genetic Issues

Exercise can cause pain in people who have an underlying hip abnormality. Dysplasia is when a hip is slightly dislocated because the socket is too shallow. Doctors try to detect this in babies, but it's often missed and lingers into adulthood. Impingement is when extra bone in a hip makes the thighbone crush the socket. Surgery may be needed.

7. Stress Fracture

If you do the same motion too often, a hip bone can crack. Training for a marathon, for example, may cause a stress fracture. Your risk spikes if you suddenly amp up the intensity, so follow a gradual training plan. Pick one from Runner's World magazine: rw.runnersworld.com/ training-plan-finder.

Diagnose trouble with our quick self-test hip check

Do your hips seem stiff? Try this at-home test: Lie on your back and bring your right knee up toward your left shoulder as far as comfortably possible. Then repeat on the other side. If you feel pain in your groin during these motions, then you may have impingement (see #6 above). See a physical therapist for targeted exercises. Even adjusting your favorite activities could make a big difference. Running could be okay as long as you avoid hills or take shorter strides, for example.

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The hip wreckers

Healthy guys can get achy hips too. Here are four possible causes.

1. All those two-a-days you did back in school

Serious sports training for kids who haven't finished growing may change the shape of their hip bones, leading to problems that could show up in adulthood. Boys who play ice hockey, basketball, or soccer three or more times a week in adolescence have an increased risk of hip trouble, a recent study review revealed.

2. Your job

The average guy spends nearly eight hours a day on his keister. All that sitting weakens your hip flexors, IT bands, and other important hip-supporting structures. Gentle exercises that stretch and strengthen the muscles can help you counteract this.

3. Your extra poundage

Obesity is tough on hips. Each pound of weight adds 6 pounds of force on each side.

4. Your overtraining habit

People nowadays know that they need to be active in their spare time, says Rafael Sierra, M.D., a professor of orthopedics at the Mayo Clinic. Exercise is healthy, but many signature moves of CrossFit-type programs (squats, lunges, box jumps) can be pretty stressful on hips. O'Flaherty, an avid exerciser, had underlying bone deformities and then tore his hip cartilage. He needed surgery and physical therapy.

How bad hips hurt your body

The muscles and joints in your hips form a bridge between your upper and lower body, so when they're messed up, your whole body pays the price.

Stiff Hips: Back pain

You may overcompensate for stiffness by rotating from your lower back instead of your hips, says Joe Eischen, P.T., of the Mayo Clinic. This can lead to back pain.

Impingement: Torn ACL

People with limited internal hip rotation may have a greater risk of tearing an ACL. When you have trouble twisting from your hips, your legs take some of the work.

Hip Pain: Achy feet

Hip pain can make you walk funny, which inflames the tissue that supports your soles. Treating the hip problem often helps the foot problem, says Dr. Domb.

Labrum Tear: Groin pain

Impingement and labrum tears can show up as groin pain, especially if your workouts are intense or require cutting or jumping, as with basketball and tennis.

The hip pain prevention plan

To keep your hips strong and supple, do these moves by David Reavy, D.P.T.. Hold each for 3 seconds; repeat 20 times.

Kneeling hip thrust

Place a resistance band just below your butt. Anchor the other end to something secure in front of you. Kneel and push your hips forward as you tighten your glutes.

Kneeling hip thrust (Part 2)

Loop the band around your hips. Anchor the other end to something secure behind you. Kneel and push your hips forward as you tighten your glutes.

Hip fold

Place the band around one thigh; anchor it on the same side. Kneel and drop that hip inward, toward the opposite knee.

Hip slide

Lie on your back. Wrap the band around one leg, by your groin. Anchor it to something secure on the same side. Raise your leg and pull the band across your body.