What is the Approach to the Adolescent With A-Traumatic/A-Septic Anterior Knee Pain?

A-traumatic anterior knee pain is a common presenting complaint of adolescents. The key elements in diagnosis and treatment include: history, focused physical examination, appropriate studies and knowledge of the common differential diagnosis.

Common causes to be included in the differential diagnosis:

• Tibial tuberosity apophysitis (Osgood-Schlatter Disease)
• Tendonitis (Jumpers Knee)
• Patello-femoral pain Syndrome
• Osteochondritis Dissecans (O.C.D)
• Referred Hip Pain (Slipped Capital Femoral Epiphysis)

What are the key elements of a complete knee oriented history?
Absence of trauma or signs of infection; sex and age of patient; degree of recent growth spurts; onset of pain (acute vs. chronic); location and quality of pain; duration and degree of symptoms; association with type and level of activity; presence or absence of swelling; locking; giving way; groin pain or other joint complaints; bruising; night waking; limp or other abnormality of gait (i.e., out-toeing); factors which alleviate or worsen the pain and the parent/guardian's perspective.

What are the key elements of the physical examination?

• Observation of gait
• Visual appearance of the knee (effusion, erythema, deformity)
• Location and type of tenderness, (focal or generalized)
• Range of motion (knee and hip)
• Ability to mechanically reproduce the patient's pain
• Observation of general muscle strength/atrophy around the knee
• Specific tests: (patellar tracking, apprehension and grind; anterior/posterior drawer; Lachman; McMurray; varus/valgus stress)

What type of imaging is typically done?

• Plain view radiography of the knee: (a/p, lateral, tunnel, sunrise); of the hip: (a/p, frog lateral) if + groin pain or abnormal hip findings are found on physical examination
• MRI of the knee can be done in selected cases based on clinical impression and radiographic findings.

Tibial Tuberosity Apophysitis  (Osgood-Schlatter Disease)
Osgood-Schlatter Disease is found more often in active teenage boys that are rapidly growing. Pain can be acute or chronic and is usually worse during periods of increased activity requiring forceful contractions of the quadriceps muscle. Pain is typically localized to the usually tender and prominent tibial tubercle. Pain is lessened with rest and non-steroidal anti inflammatory medications. The pain is reproduced with resisted active knee extension or passive hyperflexion. The remainder of the knee examination is typically benign. Lateral radiographs typically show an open tibial apophysis and occasionally ossicles are noted.  The potential for pain diminishes and usually stops at skeletal maturity.

Patellar Tendonitis (Jumpers Knee)
Jumpers Knee is more common in rapidly growing teens. Reports of vague anterior knee pain persisting for months which worsens with activities such as running or with walking down stairs. Pain is usually lessened with rest, activity modification and non-steroidal anti-inflammatory medications. The pain is reproduced with resisted knee extension. Tenderness in the patellar tendon is typically present. The remainder of the physical examination is usually benign. Radiographs are typically normal.

Patello-Femoral Pain Syndrome
Patello-Femoral Pain Syndrome, commonly referred to as anterior knee pain, typically implies a biomechanical abnormality of the joint between the patella and the trochlear groove of the distal femur. Abnormal centering or tracking of the patella within the groove can increase pressure on the underneath side of the patella causing pain. The usual presentation is that of vague, mild to moderate anterior knee pain primarily under the patella.  Pain is commonly noted after prolonged sitting with knees flexed as well as with climbing and particularly with descent. Sudden giving way may be reported. An imbalance of pull from the medial and lateral aspects of the knee can result in abnormal centering and tracking of the patella. The patella is typically pulled more laterally due to weakness of the vastus medialis obliqus. Knee flexion activities increase tension in the tight lateral structures resulting in pain. Subsequent lateral patella subluxation or dislocation can occur. A positive “J-sign”, (lateral tracking of the patella noted during knee range of motion) as well as a positive “grind test”, (painful grinding as the manually compressed patella is moved against the femur), are typically noted. Tightness of the hamstrings may also be noted. The remainder of the knee exam is typically unremarkable. Radiographs taken, specifically the sunrise view, may show asymmetric positioning of the patella within the trochlear groove of the femur. The focus of treatment is to restore the biomechanical relationship between the patella and the distal femur.  The patient is referred to physical therapy to strengthen the vastus medialis obliqus and to stretch the hamstrings. Severe cases with recurrent patella dislocation may benefit from surgical intervention.

Osteochondritis Dissecans (O.C.D.)
Osteochondritis Dissecans is an avascular lesion of bone and cartilage most commonly found in the medial femoral condyle. This can be a cause of vague, poorly localized, acute or chronic adolescent knee pain. Recurrent swelling may be noted. Mechanical symptoms of knee locking may be noted. These lesions are adjacent to the articular surface and joint damage may occur. Tenderness may be noted on palpation of the joint surface of the medial femoral condyle. An effusion and quadriceps atrophy may be present. The remainder of the examination is typically benign. Four view radiographs of the knee frequently show the radiolucent lesion on the tunnel view. A free osteochondral fragment may also be noted. MRI to confirm a suspected lesion or to characterize a lesion may be helpful. Protection of the involved area by curtailing all sports and activities involving running and jumping is necessary. Young healthy adolescents with open physes may have spontaneous healing of the lesion within four months time. Activities may be resumed if the lesion becomes asymptomatic and healing is noted on repeat x-ray or MRI. In cases that do not heal, arthroscopic drilling of the lesion may encourage vascular in growth. In cases where a free fragment is present, arthroscopic surgery to remove the fragment or to restore the joint surface is indicated.

Which patients require an examination of the hip joint?
All children, particularly adolescents who present with knee pain should have an examination of the hip joint! Knee pain can be referred from the hip. The presence of limp with external rotation of the foot of the involved side is common in knee pain of hip etiology. Radiographic documentation of an S.C.F.E. requires the imposition of immediate non weight bearing status with pinning of the slip on an emergent basis.

What is an S.C.F.E.?
An S.C.F.E. is a separation of the femoral head through the growth plate. This condition occurs in adolescence and is more common in the overweight hypogonadal body type. Limitation of internal rotation of the hip with associated hip flexion contracture is typical. The complication of avascular necrosis of the femoral head is around 30% and may result in severe impairment of the hip joint.

Which adolescent with knee pain should be evaluated by a pediatric orthopedic provider?
Any adolescent where a clear diagnosis or treatment plan is unavailable.