"The effects [of a chronic knee injury] are vague and nonspecific, and if you don't understand the causes, you're not going to be able to adequately treat them," said Dr. Anderson of the University of Washington, Seattle. An evaluation of chronic knee pain should include extrinsic factors (training and equipment) and intrinsic factors (muscle flexibility and alignment).
Inflexibility looms large as a cause of chronic knee pain in both children and adults, Dr. Anderson said. Possible pain generators in the knee include the subchondral bone, synovium, tendon, bursa, ligament, and apophysis. Tumors, infections, and rheumatologic problems should always be in the differential diagnosis of knee pain that presents without an obvious injury--athletes aren't immune to medical problems that are unrelated to sports.
Some common overuse knee injuries:
* Osgood-Schlatter disease. This condition is most common in boys aged 13-15 years. There's some debate about whether rapid growth makes muscles tight, but the majority of kids with Osgood-Schlatter have tight hamstrings and the condition occurs during times of rapid growth. Running with tight muscles creates additional tension on the tibial tubercle and is tantamount to driving with the brakes on," Dr. Anderson said.
Children with this problem will have history of pain and infrapatellar swelling as well as a tender and swollen tibial tubercle. Treatment means limiting activity to a pain-free level, controlling inflammation with ice, and stretching the hamstrings, quadriceps, calf muscles, and hip flexors. This should be followed by a gradual resumption of activity as symptoms allow.
* Patellar tendinitis. Also known as "jumper's knee," the pain gets worse with jumping, lunging, or going downstairs. The tenderness can be appreciated by palpating the proximal portion of the patellar tendon at its attachment site on the inferior patellar pole, Dr. Anderson said. If the patella moves around or tracks abnormally, a patellar stability brace or corrective shoe may be helpful.
* Plica syndrome. This is more common in adolescents than adults. When the knee develops, it starts as three bursal compartments. At the end of the fourth embryologic month, the walls of these compartments melt away so one compartment for the knee remains, but remnants of these walls remain as synovial folds or plicas.
There are three plicas: one above the kneecap, one over the anterior cruciate ligament, and one in the medial portion of the knee. These can become inflamed and thickened, which can cause snapping and popping. Inflamed plicas can cause anterior knee pain and can mimic a torn meniscus.
Plica syndrome is best treated with soft-tissue mobilization, ultrasound, or a knee sleeve with side support. If conservative measures fail, surgical resection is an option.
RELATED ARTICLE: Knee Assessment Cheat Sheet
Children with chronic knee pain may have one of these risk factors, or possibly more than one of them:
Anatomic Risk Factors for Patellofemoral Pain:
* Increased Q angle (15 degrees in a normal knee).
* Unusually high or low patella.
* Hypermobile patella.
* Knee bent outward or inward (bowlegged or knock-kneed).
* Twisting of thigh or lower leg (femoral anteversion or internal tibial torsion).
* Hyperpronated subtalar joint.
* Muscle insufficiency in quadriceps or hamstrings.
* Muscle tightness in quadriceps or hamstrings.
External Risk Factors for Patellofemoral Pain:
* Inappropriate exercise surfaces (too hard, too hilly too uneven).
* Inappropriate training such as excess speed, distance, or general overload.
* Improper shoes or poorly fitting equipment (bicycle seat too low).