Growing Pains around the Hip & Pelvis: Apophysitis and Avulsion Fracture

What are growing pains, apophysitis and avulsion fractures?

The term ‘growing pains’ is a general term used for pain associated with growth in children and adolescents. In younger children, the pain is thought to be associated primarily with muscles and is most commonly experienced in the thighs and calves. In adolescence, growth-related pain is most likely to be due to traction of muscles pulling on bony growth centres, called apophyses, which are where the muscles attach to the bone. Pain or inflammation of an apophysis is diagnosed as apophysitis. Occasionally, a rapid large muscle force may even disrupt the growth centre, with the muscle pulling away a small piece of bone from the main part of the bone (see the dotted red lines in Figure 1 for where this can occur around the hip and pelvis). This is known as an avulsion f

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Figure 1: The bones of the hip and pelvis, viewed from the front. Growth centres (apophyses) are delineated by the dotted red lines. These are the sites of apophysitis and avulsion fracture where a small piece of bone may dislodge with the muscle that attaches there. Most common sites are depicted on the right and less common sites on the left of the picture. ASIS: Anterior Superior Iliac Spine; AIIS: Anterior Inferior Iliac Spine.

Possible sites of apophysitis or avulsion fracture around the hip & pelvis (Figure 1), from most common to least common include:

The hamstring muscle insertion onto the ischial tuberosity (sitting bone), accounting for over 50% of cases of pelvic apophysitis¹
The rectus femoris muscle insertion onto the front of the pelvis (AIIS), accounting for just over 20%¹
The sartorius muscle insertion onto the front of the pelvis (ASIS), accounting for almost 20% of cases¹and much less commonly^2,3:
The iliopsoas muscle (hip flexor) insertion onto the lesser trochanter of the femur (thigh bone)
The hip abductor (gluteus medius and minimus) muscle insertion onto the greater trochanter of the femur (Figure 1)
The abdominal muscle insertion onto the top of the pelvis (Iliac crest)

What are the usual symptoms?

Apophysitis

The pain of apophysitis is generally experienced locally at the area of muscle attachment but can radiate around the area as well.
There is also often tenderness at the muscle attachment for most sites. The iliopsoas (hip flexor) muscle insertion onto the lesser trochanter of the femur (Figure 1) is located deep beneath the inner thigh muscles and is therefore not easy to touch.
Pain is usually worse following activity and eases with rest.

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Avulsion fracture

Young athletes presenting with an avulsion fracture commonly report an episode of sharp, sudden pain during a forceful movement and sometimes an accompanying sound, like a ‘pop’.
Swelling and bruising and tenderness may develop over the area
There is usually an immediate loss of muscle power related to pain or more significant bony disruption. This may result in a limp and difficulty lifting the knee up in front (rectus femoris, sartorius or iliopsoas muscle attachments) or the heel up behind (hamstring muscle attachment).

What causes apophysitis or avulsion fracture around the hip and pelvis?

Apophysitis

Apophysitis is due to long bones such as the femur (thigh bone) growing more quickly than the muscles of the thigh or hip. This is why it is sometimes referred to as “growing pains.” The relatively tight muscles then tug on the growth zones in the immature pelvis and femur, which is why the condition is often referred to as ‘traction apophysitis’.

Factors related to the development of apophysitis include:

Muscle tightness – for example, shortened hamstring muscles in the back of the thigh will place greater loads on the apophysis at the ischial tuberosity (sitting bone).
Rapid growth spurts – this problem often comes and goes during adolescence, with symptoms recurring during or just after a growth spurt. This is a period where the muscles are relatively short compared to the newly lengthened bones.
Being male – apophysitis is more common in males, generally because males tend to grow in more rapid spurts.
High activity levels – being very active places repetitive loads on the growth plates, which if combined with the other factors above, may contribute to the development of pain.
Type of activity – sports that involve rapid acceleration and deceleration, and large ranges of hip movement, such as soccer and gymnastics, place greater load across the hip and pelvic growth centres⁴.

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Figure 2: A position of hip flexion (thigh towards chest) and knee extension (knee straight). This position places the hamstring muscles on high stretch and places high loads on the bony growth centre at the muscle attachment to the ischial tuberosity (sitting bone).

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Figure 3: A position of hip extension (thigh moving backwards) and knee flexion (knee bent). This position places the hip flexor muscles, and particularly the rectus femoris, on high stretch. High loads are placed on the bony growth centres at the muscle attachments to the front of the pelvis and the lesser trochanter of the femur (thigh bone).

Avulsion Fracture

An avulsion fracture almost always occurs in response to a large, rapid force where the muscle is in a position of stretch and contracting very hard, pulling on the growth centre.

An avulsion fracture of the ischial apophysis (the growth centre at the ischial tuberosity) occur typically as a result of a large force exerted by the hamstring muscles in the back of the thigh, with the muscle on stretch. A position of stretch for the hamstrings is one in which the hip is flexed (knee towards the chest) and the knee is straight or close to straight (Figure 2). This might occur in ‘pike’ type positions, front splits (front leg) or in a high kick to the front.

An avulsion fracture of the rectus femoris, sartorius or iliopsoas muscle attachments (see Figure 1) typically occurs with a large force where the thigh is moving backwards (hip extension). For a rectus femoris avulsion, the most common type, the combination of the thigh moving backwards with the knee bent, (hip extension and knee flexion) creates highest stretch and greatest force on the growth centre at the front of the pelvis. This may occur during a rapid backflip (Figure 3), a forceful backwards kick or a wind up for a soccer kick.

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Getting Help. What is the treatment for apophysitis and avulsion fracture?

Apophysitis is generally managed well with good education around temporary activity modification, icing after activity and an exercise program. Taping to support the muscle-bone interface may sometimes be successful in providing some pain relief.

An exercise program aims to:

optimise trunk and pelvic control to avoid unnecessary stresses and strains across the pelvic region
gradually restore muscle strength and length as pain settles
restore full sporting function as pain allows

Avulsion fracture

Non-surgical care

Adolescents with a minimal displacement of the bony fragment are generally treated non-surgically. Most will require a period of protected weightbearing, where crutches as used during walking to allow the pain to settle and the fracture to heal. Icing in the acute period can assist with pain relief. There is some evidence that non-steroidal anti-inflammatory medications should be avoided or limited where a bony injury is involved, due to the possibility that these medications may interfere with the bony healing process².

Rehabilitation is initiated at an early stage to prevent unnecessary levels of muscle weakening and reduced mobility. An exercise program will have similar aims as for apophysitis, but the progress and recovery will be slower.

Return to sport requires:

bony healing
restoration of range of motion and muscle strength
restoration of agility and sport specific skills
restoration of confidence to return to sport (sport readiness)

Surgical care

Surgical intervention to reattach the fragment is rare in the immediate post-injury phase. This is generally reserved for athletes who sustain an avulsion fracture of the ischial apophysis (hamstring insertion at the sitting bone), where the bony fragment has been displaced more than 2cm.

Later stage surgery may be considered in those with: