Introduction
Anterior knee pain can result from many pathological conditions involving not only the knee, but also the hip. Most are related to overuse injuries. The exception is referred pain from a condition like Legg-Calv-Perthes disease or a slipped capital femoral epiphysis. Patients with anterior knee pain are normally more active and athletic than the child without comparable complaints.
A thorough history and physical examination is necessary from any child being evaluated for anterior knee pain. The patient and his or her parents should be asked about the quality and severity of the pain, in addition to when the pain was first manifested. It is important to note what makes the pain worse and what produces symptomatic relief.
The examiner must determine the range of motion of all joints in the lower extremity. The hip must be examined for evidence of Legg-Calv-Perthes disease or a slipped capital femoral epiphysis. Any swelling, warmth or erythema in the knee should be noted. The examiner should look for evidence of an effusion. The patella is examined for evidence of maltracking. Tenderness over the lateral anterior femoral condyle or the lateral patellar facet should be noted. A thorough ligamentous examination is also performed, in addition to looking for evidence of meniscal pathology.
Radiographs of the knee should include an anterior-posterior (AP), lateral and sunrise projection. A notch view will also provide additional information in some patients. Magnetic resonance imaging (MRI) can provide excellent anatomical detail of the soft tissue in and around the knee (ligaments, menisci, etc.)
Patella Femoral Stress Syndrome
Patella femoral stress syndrome is the clinical manifestation of chondromalacia patella, an anatomic/histological term that describes the pathological softening and fragmentation of the articular cartilage of the patella. The term "chondromalacia patella" was first used by Konig in 1922. Outerbridge described four stages of chondromalacia patella in 1961:
I. Softening and swelling of the articular cartilage
II. Presence of deep fissures extending into subchondral bone
III. Fibrillation of the articular surface giving the cartilage a "crab meat" appearance
IV. Thinning of the articular surface with exposure of the subchondral bone
The clinical findings associated with patella femoral stress syndrome include activity-related retro-patellar pain, a catching sensation with motion and pain that is worse when a direct pressure is applied to the patella or with stair climbing. Patients have patellar crepitus, tenderness over the lateral facet of the patella and the anterior aspect of the lateral femoral condyle. Children and adolescents usually do not have evidence of an effusion.
Lateral patellar compression syndrome is a subset of patella femoral stress syndrome. These patients have anterior knee pain localized to the patella femoral joint and an associated tight lateral retinaculum. There is no evidence of subluxation or dislocation of the patella. Children and adolescents with lateral patellar compression syndrome have radiographic evidence of a lateral patellar tilt with narrowing of the lateral patella and femoral articular surfaces on the sunrise radiograph.
Patients with recurrent patellar subluxation or dislocation often have the same symptoms as patients with patella femoral stress syndrome in-between acute episodes of lateral patellar displacement. The etiology of recurrent patellar subluxation and dislocation includes abnormal patellar anatomy, hypoplasia of the lateral femoral condyle, patella alta, a tight lateral retinaculum, genu valgum, genu recurvatum, external tibial torsion and medial femoral torsion. Children with recurrent patellar subluxation and dislocation will have a hypermobile patella and a positive apprehension test with lateral displacement of the patella. They may have a positive Sage test, (knee flexed to approximately 20°, the patella is pushed medially. The patella should move at least one-fourth of its width; if less, this indicates a tight lateral retinaculum). Children with recurrent patellar subluxation and dislocation may have tenderness at the insertion of the vastus medialis on the medial patellar facet, in addition to atrophy of the vastus medialis obliquus. They also have lateral patellar facet and lateral femoral condylar pain.
Plain radiographs will often show a widened femoral condylar sulcus angle (normal 116°-151°) in the sunrise view. There may also be an abnormal congruence angle. The nonoperative management of patella femoral articulation disorders is compartmentalized into three stages.
- Stage I is physician-directed care. This includes strengthening exercises for the quadriceps, stretching of the hamstrings, quadriceps, gastrocs and iliotibial band, the use of a knee sleeve in patients with patellar subluxation and dislocation, nonsteroidal anti-inflammatory drugs (NSAIDs) and ice applied to the knee after each exercise session and when symptomatic.
- Stage II consists of treatments that are directed by both physician and physical therapist. These included protected range of motion activities, patellar mobilization with retinacular stretching, theraband PRE, patellar taping, high-speed isokinetic movements to low resistance, anti-sheer isokinetic work and neuromuscular stimulation. A transcutaneous electrical nerve stimulation (TENS) unit can be applied for pain relief in resistant cases. The patient may need to stop strenuous activities or begin alternate activities such as cycling and swimming.
- Stage III consists of pain clinic care and occasionally involves saphenous nerve blocks. The majority of children and adolescents with patella femoral stress syndrome will not need surgical intervention. Many children with an acute patellar subluxation or dislocation can be successfully rehabilitated without surgery as well. Surgical options for patients with resistant patella femoral articulation disorders include a lateral retinacular release, a medial retinacular advancement with vastus medialis plication, lateral patellar tendon medial transfer and transfer of the semitendinosis tendon to the patella. Osteotomies of the proximal tibia (medial transfers and elevations) should not be performed until the patient is skeletally mature.
Patellar Tendinitis ("Jumper's Knee")/Sindig-Larsen Johannson Disease
Patellar tendinitis is an inflammatory condition of the patellar tendon and the adjacent soft tissue. This is often secondary to overuse and occurs in active children between the ages of seven and ten years. This results from an extensor overload associated with increased activity. Occasionally, it can result from a direct trauma. Physical examination reveals tenderness over the patellar tendon. This area may be warm to touch and edematous. The quadriceps may also be contracted. Radiographs of the knee are unremarkable in the majority of children with patellar tendinitis. Sindig-Larsen Johannson disease represents an advanced form of patellar tendinitis. It occurs in children older than those with traditional patellar tendinitis.These children have tenderness at the inferior pole of the patella accompanied by radiographic evidence of fragmentation. This condition is related to activity and extensor overload.
The treatment of jumper's knee and Sindig-Larsen Johannson disease begins with activity modification (rest). Ice can be used for acute symptoms as well as NSAIDs. It is important to keep the hamstrings and quadriceps muscles supple and stretched. Most children respond to conservative care. Surgery is rarely indicated.
Osgood-Schlatter's Disease
In 1903, Carl Schlatter (Zurich) and Robert Bailey Osgood (Boston) independently described a disorder involving the anterior proximal portion of the tibia in adolescents. Children with Osgood-Schlatter's disease complain of pain in the tibial tubercle. This condition normally occurs in males between the ages of eleven and fifteen years. It is often bilateral.The pain increases with activity and improves with rest. The tibial tubercle is tender to palpation. It is also prominent. Patients seldom have a joint effusion. They may have decreased flexion. The pain in the tibial tubercle is accentuated with extremes of knee flexion and with resistance to knee extension. Radiographs may show evidence of soft tissue swelling. They may also demonstrate fragmentation of the tibial tubercle. Woolfrey described three radiographic stages of tibial tubercle involvement:
I: Prominent and irregular tibial tubercle
II: Irregular tibial tubercle with small bony fragments anterior to body of tubercle
III: Free bony tubercle ossicles in a skeletally mature patient, anterior and superior to the tubercle.
Treatment of Osgood-Schlatter's disease centers around activity modification. Rest normally helps the symptoms. Occasionally, a cast is necessary in severe acute cases. A neoprene sleeve can be worn during sporting activities after rehabilitation.The neoprene sleeve cushions the knee, decreases patellar mobility and forces on the tibial tubercle and provides increased proprioception to the athlete. Recently, tibial tubercle straps have also been used with good results. Most patients return to normal activity without any long-term sequelae. There have been some reports suggesting an increased risk of tibial tubercle fractures in patients with Osgood-Schlatters' disease. Some mature patients will also have an inflammatory response in the area of the ossicles after skeletal maturation has occurred. These patients may need to be treated with an excision of the ossicle in the patellar tendon.