Athletes who run, jump, kick, and slide are likely to strain some muscles around their hip. In fact, strains and contusions are the most common injuries experienced in young athletes. That being said, one should not assume that a child or adolescent athlete complaining of hip, thigh, or knee pain has “just a groin pull” or “a hip flexor strain” unless a careful history and physical exam exclude other injuries. Until skeletal maturity, younger athletes have various cartilaginous growth centers in the hip and pelvis that predispose them to injuries that do not occur in adults. The physes are the growth centers of long bones, such as at the ends of the femur; whereas, the apophyses are the outgrowths of bones developing from separate ossification centers, such as those about the pelvis and trochanters of the femur. A better understanding of this anatomy, and the ability to perform some simple physical exam maneuvers can help physicians, trainers, and coaches identify injuries and protect young athletes.
Pain around the hip can be very localized; however, some hip conditions may present with subtle limp, vague symptoms, or referred pain extending down the thigh or even to the knee. Unlike our fingers, which were designed for fine two-point discrimination, the nerve supply around our hip is a somewhat less specific. In particular, the obturator nerve exits the pelvis medial to the hip through the obturator foramen. It innervates the adductor muscles and provides sensation to the medial (and some anterior) thigh and knee. Due to this sensory distribution, patients with hip problems may actually complain of knee pain rather than hip pain. For this reason, any patient complaining of anterior or medial knee pain should have his or her hip carefully examined. Failure to do so can result in over-treating the knee or under-treating important hip pathology.
The proximal femoral growth plate (physis) is one anatomical site that, if injured, can lead to devastating results, especially if not treated appropriately. A slipped capital femoral epiphysis (SCFE) occurs when the femoral neck slips with respect to the top (caput) of the femur. In a child, the femoral head is referred to as the epiphysis, hence the name SCFE (pronounces “skiffy”). Affecting approximately 10/100,000 children in the United States between the ages of 9-16 years, the incidence of SCFEs may be affected by biology (males > females; hormonal balance of growth hormone, estrogen, testosterone, and thyroid hormone affects growth plates), race (Black/Hispanic > White), geography (Northeast and West > Midwest and South), and mechanics (weight/body mass increases risk). SCFEs are graded as either “stable” or “unstable” and are defined by the patient’s ability to bear weight on the affected extremity. Unstable SCFEs typically occur as acute events, and, due to the patient’s pain and inability to bear weight, are rarely missed. These injuries require emergent surgical treatment. Failure to stabilize the slip and decompress the blood from within the hip joint can result in avascular necrosis, or death of the femoral head. The stable slips have presentations that may be subtle and therefore misdiagnosed. Patients may go days, weeks, or even months with a stable slip and the symptoms can range from mild to severe. The problem here is that a stable slip can suddenly convert to an unstable slip at any time, similar to ice cream starting to slide off of an ice cream cone and then suddenly falling completely off. It is for this reason that once identified, a stable slip should be surgically fixed to avoid the potential for catastrophic results. The key is identifying the patient before it’s too late.
The common complaints for patients with stable SCFEs are vague hip or knee pain. Obviously, many athletes will have such complaints, so it is important to know what to look for. Patients may limp or walk with a slightly externally rotated foot. This is because the femoral neck typically moves into a more external and extended position with respect to the femoral head. Attempts to flex the patient’s hip will result in “obligate external rotation” (Figure 1) and attempts to internally rotate the hip cause pain. One of the best ways to assess for lack of internal rotation is to place the patient in the prone position and gently rotate the shin outward so that the femoral head is rotating inward with respect to the hip socket, or acetabulum (Figure 2). This maneuver can be done on the field, in a training room, or a medical office. Any reported pain or asymmetric hip rotation with this maneuver warrants immediate removal from any athletic participation. Ideally, the patient should be made non-weight bearing on the affected side with crutches, a walker, or a stretcher until anterior-posterior (AP) and frog lateral X-rays of the pelvis can be obtained (Figure 3 A&B). Failure to protect the player can result in further progression of the slip or, worse, conversion of a stable slip to an unstable slip. Most SCFEs will be revealed on simple radiographs. Occasionally, an MRI is required to rule out a pre-slip that occurs prior to any actual migration of the femoral neck with respect to the head. Stable or mildly displaced slips are typically treated with a minimally invasive percutaneously placed screw technique (Figure 4); whereas, unstable or severely displaced SCFEs often require open reconstructive procedures.
Another source of hip pain and limp in children is a condition known as Legg-Calvé-Perthes disease. This condition is characterized by an idiopathic avascular necrosis of the femoral head in children ages 4-12 years. Although the cause of the condition is unknown, it typically progresses through phases of pre-radiographic findings to fragmentation of the femoral head epiphysis to collapse of the femoral head to reossification to remodeling over about 2 years. The amount of collapse and resulting femoral head deformity determines outcome. The first signs of this condition are limp and asymmetric hip abduction (spread) and rotation. Just as for patients with SCFE, young patients with hip pain and physical exam findings of limited range of motion should stop sports participation and be referred for radiographic imaging (Figure 5). Treatment for Legg-Calvé-Perthes disease typically involves rest and activity modifications combined with gentle range of motion exercises for children under age 6 years. Older children may benefit more from surgical intervention, including femoral and/or pelvic osteotomies.
The apophyses of the pelvis and hip can also be sites of adolescent and childhood injuries mistaken for muscle strains. Unlike the insidious onset of some SCFEs and Legg- Calvé-Perthes disease, apophyseal avulsion fractures typically occur suddenly (Figure 6). The forceful pull of a muscle originating or inserting on a bony apophysis can result in failure of the cartilage and displacement of the apophyseal fragment. The history or mechanism of injury is very important. For example, rapid knee extension and hip flexion during a powerful kick against an object (such as a soccer ball or football) can result in the rectus femoris muscle avulsing the anterior inferior iliac spine (AIIS) or the sartorius muscle avulsing the anterior superior iliac spine (ASIS). Landing a long jump is a common mechanism for the hamstring muscles to avulse the ischial apophysis. Less commonly, the iliopsoas can pull off the lesser trochanter, abdominal obliques can avulse the iliac crest apophysis, gluteal muscles can avulse the greater trochanter, or the adductors can pull off pubic apophysis. With any of these injuries, the patient may have pain with direct palpation of the bony prominence or with active contraction or passive stretch of the offending muscle.
Most apophyseal avulsion fractures are treated non-operatively. An initial rest period of 4-6 weeks allows for early bone healing. Weight bearing is allowed when tolerated, and gentle range of motion can be started when pain subsides. Strengthening must be delayed until full pain-free motion has been re-established. X-rays of the pelvis are useful in identifying and managing these fractures. Surgery is usually reserved for those with significant displacement (> 2 centimeters) or painful nonunions. Heterotopic, or excess, bone may form at the site of such fractures, but excision of any prominent symptomatic bone masses should be delayed until the fracture callus has fully matured and remodeled (typically 6-12 months). Failure to wait increases the risk of recurrence.
Muscle strains and contusions about the hip are commonly experienced by athletes of all ages. Such injuries can usually be treated with periods of rest, ice, and a gradual return to sports. Pediatric patients, however, are susceptible to a number of conditions that aren’t encountered in skeletally mature individuals. Knowledge of these conditions will help those involved with young athletes identify those who need additional treatment and may help prevent or decrease permanent disability.
1) Aronsson DD, Loder RT, Breur GH, Weinstein SL. Slipped capital femoral epiphysis: current concepts. J Am Acad Orthop Surg. 2006 Nov;14(2):666-79.
2) Kocher MS, Tucker R. Pediatric athlete hip disorders. Clin Sports Med. 2006 Apr;25(2):241-53.
3) Kovacevic D, Mariscalco M, Goodwin RC. Injuries about the hip in adolescent athlete. Sports Med Arthrosc. 2011 Mar;19(1):64-74.
4) Lehmann CL, Arons RR, Loder RT, Vitale MG: The epidemiology of slipped capital femoral epiphysis: an update. J Pediatr Orthop. 2006 May-Jun;26(3):286-90.
5) McKinney BI, Nelson C, Carrion W. Apophyseal avulsion fractures of the hip and pelvis. Orthopedics. 2009 Jan;32(1):42.
6) Nguyen NA, Klein G, Dogbey G, McCourt JB, Mehlman CT. Operative versus nonoperative treatments for Legg-Calve-Perthes disease: a meta-analysis. J Pediatr Orthop. 2012 Oct-Nov;32(7):697-705.
7) Waters PM, Millis MB. Hip and pelvic injuries in the young athlete. Clin Sports Med. 1988 Jul;7(3):513-26.
8) Weiner D. Pathogenesis of slipped capital femoral epiphysis: current concept. J Pediatr Orthop B. 1996 Spring;5(2):67-73.
Dr. Pierz is a Pediatric Orthopaedic Surgeon at Connecticut Children’s. She treats a variety of musculoskeletal problems, and has a special interest in gait abnormalities. Dr. Pierz is an expert in treating limb deformities and the management of sports injuries such as anterior cruciate ligament (ACL) tears, osteochondritis dissecans and overuse injuries. Dr. Pierz also specializes in the treatment of cerebral palsy, child and adolescent trauma, clubfeet, developmental dysplasia of the hip, and injury prevention.