When a Sprint Pulls on Growing Bone: Pelvic Avulsion Injuries in Teenagers

A teenager suddenly accelerates during a football match, swings a leg to kick the ball and immediately feels a sharp pain near the front of the hip. Another young athlete pushes out of the starting blocks and hears a faint crack around the pelvis. A gymnast lands from a jump and can no longer walk without limping.

These incidents are often assumed to be pulled muscles. In some cases, however, the injury is actually a pelvic avulsion fracture—a small piece of growing bone that has been pulled away from the pelvis by a forcefully contracting muscle.

Pelvic avulsion injuries occur mainly in physically active teenagers because their muscles and tendons may be stronger than the areas of developing bone to which they attach. Most of these injuries heal well without surgery, but recognising the warning signs matters. A delayed or incorrect diagnosis can lead to prolonged pain, weakness, abnormal bone healing and difficulty returning to sport. ^[1]

A pelvic avulsion injury happens when a tendon pulls so forcefully on its attachment point that it separates a small fragment of bone from the pelvis.

The injury generally occurs at an apophysis, which is a developing area of bone where a major muscle or tendon attaches. These growth-related attachment points have not yet fully fused with the main pelvic bone during adolescence.

In an adult, an explosive movement may be more likely to strain or tear the muscle or tendon. In a teenager whose skeleton is still developing, the same force may cause the relatively vulnerable apophysis to separate instead.

This is why a pelvic avulsion injury is technically a fracture, even though it does not usually result from a fall from height, road accident or direct blow to the pelvis. It is commonly produced by the teenager’s own muscle contraction during sport. ^[1]

During a growth spurt, the bones, muscles and tendons do not always develop at the same rate. Muscles can become tight as the long bones lengthen, while the pelvic attachment sites remain incompletely fused.

At the same time, adolescent athletes may be training harder, competing more frequently and developing greater muscular power. A strong muscle contracting against an immature attachment point creates the ideal circumstances for an avulsion injury.

The vulnerable period is relatively narrow and is closely connected to skeletal maturation. In a large study of 719 pelvic and hip avulsion fractures, the average patient was 14.6 years old. Most injuries occurred during sport, and 78 per cent were identified in male patients. However, girls can certainly develop pelvic avulsion fractures, particularly when participating in sprinting, football, dance, gymnastics and other explosive activities. ^[2]

The immediate cause is usually a sudden, powerful muscle contraction or rapid stretching of a contracted muscle. The tendon remains attached to the muscle, but the force transmitted through it pulls on the growing bone.

Common movements associated with pelvic avulsion injuries include:

• Accelerating suddenly during a sprint
• Kicking a football forcefully
• Jumping or taking off from one leg
• Performing the splits or an extreme stretch
• Changing direction at speed
• Hurdling
• Landing awkwardly
• Sliding into a base
• Performing explosive gymnastics or dance movements

Running and kicking are among the most frequently reported mechanisms. In the study of 719 fractures, running accounted for approximately 28 per cent of the injuries and kicking for nearly 27 per cent. Football was the most commonly associated sport in that patient group. ^[2]

The injury does not always come completely out of nowhere. Some teenagers experience aching or intermittent pain around the hip, groin or buttock before the acute event. This may indicate irritation of the developing attachment point, known as apophysitis. Continuing to sprint, kick or jump through this pain may leave the area more vulnerable to an acute avulsion. ^[1]

The location of the pain depends on which muscle has pulled on its pelvic attachment.

The anterior superior iliac spine is the prominent bony area near the front and side of the waist. The sartorius muscle attaches here and is active during hip flexion and movements involving the leg.

An injury in this location may occur during sprinting, jumping or a rapid change of direction. Pain is usually felt at the front or outer edge of the pelvis.

The anterior inferior iliac spine lies slightly lower and deeper than the anterior superior iliac spine. Part of the rectus femoris muscle, one of the major thigh muscles, attaches here.

Avulsion injuries at this site are often associated with kicking, sprinting or forcefully straightening the knee while moving the hip. The teenager may describe pain at the front of the hip or deep in the groin.

The ischial tuberosity is the bone beneath the buttock that bears weight while sitting. The hamstring muscles originate from this area.

An ischial tuberosity avulsion may occur during sprinting, hurdling, kicking, gymnastics or a sudden forward bend with the knee straight. Pain may be felt deep in the buttock or at the top of the back of the thigh.

This injury is particularly likely to be mistaken for a hamstring strain. Misdiagnosis can delay appropriate treatment, especially when the bone fragment has moved significantly. ^[3]

The iliac crest forms the curved upper border of the pelvis. Avulsion injuries in this region may cause pain along the side of the waist or upper hip, particularly during running, twisting or side-bending movements.

The lesser trochanter is located on the upper part of the thigh bone near the hip. The iliopsoas muscle attaches there and helps lift the thigh.

An avulsion at this site can cause deep groin pain, pain while raising the knee and difficulty climbing stairs.

The anterior inferior iliac spine, anterior superior iliac spine and ischial tuberosity are the most frequently affected locations. Together, they accounted for more than 80 per cent of fractures in a large adolescent case series. ^[2]

A pelvic avulsion injury often has a recognisable pattern. The most important warning sign is sudden, localised pain during an explosive movement.

A teenager may report:

• A sharp or tearing pain in the hip, groin, buttock or upper thigh
• A popping, cracking or snapping sensation
• Immediate difficulty continuing the activity
• Pain while walking or putting weight on the affected leg
• A noticeable limp
• Tenderness over one specific bony area
• Swelling or bruising
• Weakness while kicking, running or lifting the knee
• Pain when the involved muscle is stretched
• Pain when the teenager tries to contract the involved muscle

Pain produced both by actively using the muscle and by stretching it is an important clinical clue. For example, an avulsion near a hamstring attachment may hurt when the teenager bends the knee against resistance and when the hamstring is stretched. ^[1]

Some teenagers can still walk after the injury, especially when the fragment is minimally displaced. Being able to walk does not rule out a fracture.

Not every pelvic avulsion begins with a dramatic crack. The developing bone attachment may first become irritated through repeated pulling.

Earlier warning signs can include:

• Pain that appears during training and settles with rest
• Recurrent groin, hip or buttock discomfort after sport
• Pain when sprinting at maximum speed
• Pain during powerful kicking
• Tenderness over a pelvic attachment point
• Tightness that repeatedly returns despite stretching
• Gradual loss of speed or kicking power
• A change in running technique or stride length
• Limping after training
• Pain while sitting, particularly with an irritated hamstring attachment

These symptoms may indicate pelvic apophysitis rather than a complete avulsion fracture. The distinction requires clinical assessment, but both conditions deserve attention. Continuing full-intensity activity through persistent growth-related pelvic pain can prolong symptoms and may increase stress on the attachment site. ^[1]

A teenager should be medically assessed after sudden pelvic, hip, groin or buttock pain if the pain occurred during sprinting, jumping, kicking or another forceful movement.

Prompt evaluation is particularly important when the teenager:

• Heard or felt a crack or pop
• Cannot walk normally
• Cannot put full weight on the leg
• Has severe or highly localised pain
• Develops swelling or bruising
• Cannot raise the leg, kick or bend the knee normally
• Has pain directly over a pelvic bone
• Continues to limp after the initial pain settles
• Was previously experiencing pain in the same area
• Has symptoms that are not improving with rest

The teenager should stop the activity immediately. Trying to “run it off,” repeatedly testing the leg or aggressively stretching the painful area could worsen discomfort and potentially increase displacement of the bone fragment.

Pelvic avulsion fractures and muscle strains can occur during the same movements and produce pain in similar locations. Both may cause tenderness, weakness, bruising and difficulty walking.

A teenager with pain near the buttock may be diagnosed with a hamstring pull. Front-of-hip pain may be attributed to a hip flexor strain, while groin pain may be assumed to involve the adductor muscles.

The teenager’s age and the exact mechanism provide important clues. Sudden pain during an explosive contraction, especially with a crack or pop and tenderness over a specific bony attachment point, should raise suspicion of an avulsion fracture.

Research has documented cases of ischial tuberosity fractures initially diagnosed as hamstring injuries. Delayed recognition may allow the fragment to heal in an abnormal position or fail to unite properly, potentially making treatment more complicated. ^[3]

The clinician will ask how the injury happened, where the pain began and whether the teenager experienced a crack, pop or previous episodes of activity-related pain.

The physical examination may assess:

• The precise location of tenderness
• Ability to walk and bear weight
• Hip and knee movement
• Pain during muscle contraction
• Pain when the muscle is stretched
• Strength compared with the opposite side
• Swelling, bruising or a palpable abnormality

A pelvic radiograph is generally the first imaging test. Additional angled views may be helpful when an injury near the front of the pelvis is suspected.

Magnetic resonance imaging is not routinely needed when the fracture is clearly visible on a radiograph. It may be considered when symptoms strongly suggest an avulsion injury but initial radiographs appear normal, particularly in a skeletally immature teenager with persistent pain. ^[1]

Most pelvic avulsion fractures in teenagers are treated without surgery. Initial management commonly includes rest, ice, pain relief and temporary restriction of weight-bearing. Crutches may be recommended until walking becomes comfortable and the injury begins to heal.

Rehabilitation usually progresses through:

• Protection of the injured area
• Gradual return to comfortable weight-bearing
• Restoration of hip and knee movement
• Gentle stretching when appropriate
• Progressive muscle strengthening
• Running and sport-specific exercises
• Controlled return to training
• Return to competition after strength and movement recover

Many teenagers return to sport in approximately eight to ten weeks, although the timeline depends on the fracture site, displacement, symptoms and demands of the sport. Returning simply because pain has decreased can be risky. The athlete should be able to walk, run, accelerate, change direction and perform sport-specific movements without pain or significant weakness.^[1]

Surgery is uncommon but may be considered when the bone fragment is substantially displaced, symptoms persist despite rehabilitation, the fracture fails to heal or the displaced fragment interferes with hip movement. Published recommendations differ regarding the amount of displacement that should prompt surgical consideration, so decisions are made individually by an orthopaedic specialist. ^[1]

Most correctly diagnosed pelvic avulsion injuries heal completely. Problems are more likely when the diagnosis is delayed, the fragment is substantially displaced or the teenager returns to sport too early.

Possible complications include:

• Persistent hip, groin or buttock pain
• Failure of the fragment to unite with the bone
• Healing in an abnormal position
• Excess bone formation around the injury
• Reduced muscle strength
• Recurrent injury
• Difficulty sprinting or kicking
• Pain while sitting after an ischial tuberosity injury
• Restricted hip flexion
• Mechanical conflict between an enlarged fragment and the hip joint

An avulsion from the anterior inferior iliac spine can occasionally heal in a way that mechanically restricts hip flexion and produces ongoing anterior groin pain. Ischial tuberosity injuries may produce chronic discomfort or hamstring-related symptoms if healing is incomplete. ^[1]

Not every injury can be prevented, especially during rapid growth. However, sensible training practices may reduce unnecessary stress on vulnerable pelvic attachment points.

Teenage athletes should:

• Increase training intensity gradually
• Avoid sudden spikes in sprinting, kicking or jumping volume
• Take persistent hip, groin or buttock pain seriously
• Include appropriate strength and mobility work
• Warm up before high-speed activity
• Allow adequate recovery between demanding sessions
• Avoid competing through a limp
• Follow rehabilitation fully after a previous injury
• Inform coaches about pain rather than hiding it
• Return to sport progressively rather than immediately resuming full competition

Stretching should not be forced through sharp pain. In a teenager with an irritated or injured apophysis, aggressive stretching can pull directly on the painful attachment site.

Pelvic avulsion injuries are distinctive fractures that mainly affect active teenagers whose pelvic growth areas have not yet fully matured. They frequently occur during sprinting, forceful kicking, jumping or gymnastics and can easily be mistaken for ordinary muscle strains.

The clearest warning signs are sudden localised pain, a cracking or popping sensation, tenderness over a pelvic bone, limping and pain when the connected muscle is either contracted or stretched. Recurrent exercise-related hip, groin or buttock pain before the acute event should not be dismissed as routine soreness.

Most teenagers recover fully with rest, protected weight-bearing and structured rehabilitation. The key is recognising the injury early, confirming the diagnosis and resisting the temptation to return to sport before the bone and surrounding muscles are ready.

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