Idiopathic anterior knee pain has been described by various other terms (Table 27-1). It refers to nonspecific, vague, mostly activity-related anterior knee pain and is the most common cause of knee pain in adolescents. Anterior knee pain has been reported in half of adolescent athletes at some time.
Many factors have been postulated to contribute to the development of anterior knee pain in adolescents (Table 27-2).1–4 Intense physical activity overloading the patellofemoral mechanism (Figure 27-1) appears to be the most consistent factor leading to the development of anterior knee pain. The patellofemoral unit provides the mechanism for knee extension and deceleration. The stability of the patella in the femoral groove is provided by the surrounding soft tissue attachments and the bony supporting structures (Figure 27-2). Malalignment and abnormal tracking of the patella have been postulated to contribute to anterior knee pain. Vastus medialis obliquus plays an important role in stabilizing the patella in the femoral groove and its proper tracking. A chondromalacia patella is a pathologic diagnosis indicating softening and erosion of the cartilage of the patellofemoral joint; in some athletes, it is a cause of severe anterior knee pain.2
Overuse |
Patella alta |
Patellar maltracking |
Abnormal Q angle |
Knee extensor and flexor muscle strength imbalance |
Knee and patellar ligamentous laxity |
Exaggerated lumbar lordosis |
Genu varus |
Genu valgus |
Hyperpronated feet |
Tight Achilles |
Patellar chondromalacia |
The young active athlete presents with either acute or gradual onset anterior knee pain affecting one or both knees, usually seen following a recent increase in physical activity. The pain is increased after prolonged sitting (theater sign), ascending or descending stairs, and repeated squatting exercises. Usually, the pain has been present for few weeks with intermittent activity-related exacerbations and improvement with a period of rest. Deterioration of sports performance because of increased frequency and worsening of the pain, leads the athlete to seek medical attention. The athlete may give a history of the knee catching, pseudolocking, or giving away.
On examination, look for abnormal gait, increased lumbar lordosis, and any asymmetry of hips or lower extremities; also observe for atrophy and weakness of the quadriceps muscles by comparing it to the normal side. A decrease in flexibility of the hamstrings and quadriceps is a common finding (Figure 27-3). Isometric quadriceps contraction with the leg extended, may reveal a subtle lateral patellar deviation. This can be assessed by placing a row of three dots in a straight line while the knee is relaxed (one several inches above the knee in the midline, one several inches below, and one at midpatellar point); then look for lateral displacement of the patellar dot on isometric quadriceps contraction (Figure 27-4). Knee effusion or soft tissue swelling is an uncommon finding. A full range of motion is maintained. In some athletes, tenderness may be elicited by palpating and exerting pressure on the articular margins of the patella while displacing it medially or laterally. A crepitus may be felt in some athletes. Pain is elicited with patellar inhibition or compression test (Figure 27-5).
Figure 27-3
Test for hamstring flexibility. With the athlete supine on the table first flex the hip and knee (A). This is followed by bringing the hip to 90-degree flexion and gently extending the knee (B). Normally the knee should extend close to 180 degrees (C). Lack of extension is a measure of hamstring tightness.
Figure 27-4
Test for patellar tracking. Isometric quadriceps contraction with the leg extended may reveal a subtle lateral patellar deviation. This can be assessed by placing a row of three dots in a straight line while the knee is relaxed (A). One dot is placed several inches above the knee in the midline, one several inches below, and one at mid patellar point. Look for lateral displacement of the patellar dot on isometric quadriceps contraction (B). No significant lateral deviation of the patella is noted here.
Figure 27-5
Patellofemoral compression test. With the athlete supine and knee in extension, have the athlete contract the quadriceps to assess if pain is elicited because of patellar compression. This can be further exacerbated by placing a hand just proximal to patella and not allowing it to glide upward with quadriceps contraction.
Causes of anterior knee pain are listed in Table 27-3.1,5–7 Knee pain can be referred pain from the hip or lumbar spine pathology. Hip conditions to be considered include slipped capital femoral epiphysis, Legg-Calve-Perthes disease, and femoral neck stress fracture, whereas spine conditions to be considered include tumors of the spine or the cord, herniated disk, or spinal stenosis. Pain around the knee joint can also occur in osteosarcoma, Ewing sarcoma, synovial tumors, or osteoid osteoma. Systemic causes of knee pain include chronic juvenile arthritis, sickle cell arthropathy, and leukemia.
Quadriceps tendonitis |
Prepatellar bursitis |
Patellar stress fracture |
Osteochondritis dissecans of the patella |
Multipartite patella |
Infrapatellar bursitis |
Sinding-Larsen-Johansson syndrome |
Patellar tendonitis |
Hoffa syndrome |
Osgood-Schlatter disease |
Idiopathic anterior knee pain |
Plain x-ray films may help rule out other conditions causing anterior knee pain such as osteochondritis dissecans of the patella or knee, or stress fracture of the patella. Radiographs are not indicated routinely. Abnormal tilt of the patella may indicate maltracking, best seen on a tangential view at 45 degrees of flexion of the knee (Figure 27-6).
In adolescent athletes, the prognosis for resolution of pain and continued sports participation is excellent with conservative treatment. It is a benign, self-limited condition with gradual resolution over a period of few weeks; rarely in some athletes, it may take up to 2 years for complete resolution of symptoms.
Conservative treatment consists of relative rest with modification of activities, local ice, and a short-term use of anti-inflammatory medications (Appendix D) to help control the pain. Complete rest and cessation of all activities are generally not necessary, and the athlete should be allowed to continue all activities as tolerated. Prolonged sitting, squatting, climbing up or going downstairs, and full arc knee extension exercises should be avoided. Alternative activities such as cycling with a proper fit, swimming, and walking are encouraged as tolerated. The effectiveness of different kinds of taping techniques and knee braces varies considerably; their use should be individualized.
Rehabilitation exercises focus on increasing the flexibility, strength, endurance, and neuromuscular retraining of the quadriceps, hamstrings, gastrocnemius, and soleus muscles (Appendix C).8 Closed kinetic chain exercises are found to be most effective. Knee immobilization is not recommended, except in rare instances when pain is severely affecting daily activities.
Osgood-Schlatter disease is an overuse injury, a traction apophysitis, affecting the tibial tubercle apophysis. Osgood-Schlatter disease is commonly seen during Tanner stage 2 or 3. It is more common in adolescent boys. The incidence is higher in athletes compared to nonathletes, 21% in athletes compared to 4.5% in nonathletes in one study.
Rapid growth and increased physical activity predisposes to the development of this condition during early adolescence. The immature patellar tendon-tibial tubercle junction is highly susceptible to submaximal, repetitive tensile stress resulting from high-intensity sport activity. The underlying pathology is suggestive of minor avulsions at the site and subsequent inflammatory reaction.
Osgood-Schlatter disease is most commonly seen between 11 and 13 years of age in girls and between 12 and 15 years in boys. Adolescent presents with pain over the tibial tubercle just below the knee. The pain is bilateral in 20% to 30% of patients. The pain is aggravated by sports involving jumping, squatting, and kneeling, and is relieved by a period of rest. Localized tenderness and sometimes swelling over the tibial tubercle are noted on examination.
X-ray may show fragmentation of tibial tubercle and sometimes an ossicle in the patellar tendon (Figure 27-7).
Treatment is conservative. Decreased activity and rest will result in significant improvement in pain. In some athletes, it is not uncommon for recurrent pain to last up to 2 years before complete resolution. Osgood-Schlatter disease is a benign, self-limited condition and overtreatment should be avoided. The adolescent should be allowed to participate in all sports as tolerated. Hamstrings and quadriceps stretches should be done on a regular basis to improve and maintain flexibility. The most common complication is a persistent localized swelling, which may only be of cosmetic concern.
Ossicle formation in the patellar tendon may be a source of chronic pain in some athletes and removal of such an ossicle may be indicated. Presence of Osgood-Schlatter disease does not necessarily predispose the athlete for complete avulsion of the patellar tendon from the tibial tuberosity. This is only a potential concern during rapid growth phase just prior to fusion of the tublercle to tibia.
