Knee pain in cerebral palsy (CP) is associated with increased patellofemoral forces present when walking with flexed knees. In typically developing children, knee pain and patellofemoral dysfunction are associated with obesity, genu valgum, femoral anteversion, and external tibial torsion. These problems are also common in CP, and may contribute to knee problems in this population. The purposes of this study were to define the prevalence of knee pain and patellofemoral dysfunction in children with CP, and to identify physical and gait characteristics (using 3-dimensional gait analysis data) that predispose them to such problems.
Retrospective review of 121 children with CP, Gross Motor Function Classification System level I to IV, who underwent computerized gait analysis testing. Demographics, range of motion, body mass index and hip, knee, and ankle kinematics were compared between subjects with and without knee pain.
Twenty-five of 121 subjects (21%) reported knee pain at the time of testing. Three of 121 subjects (2%) had a history of patellar subluxation/dislocation. Age and sex were significantly related to presence of knee pain. The likelihood of knee pain was almost 5 times higher in females (odds ratio=4.9, [95% confidence interval, 1.8-13.3], P=0.002), with a prevalence of 40% (17/42) in females versus 10% (8/79) in males. The likelihood of knee pain increased with age by approximately 13% per year (odds ratio=1.13, [95% confidence interval, 1.00-1.28], P=0.058). Malignant malalignment syndrome showed a potential relationship to more severe knee pain (P=0.05), which warrants further investigation. Body mass index, pes valgus, and degree of stance knee flexion showed no statistically significant relationships to knee pain (P>0.16).
The prevalence of knee pain in ambulatory patients with CP is approximately 21%. Patellar subluxation (2%) and dislocation are rare in these patients. Knee pain is not always related to crouch, femoral anteversion, external tibial torsion, genu valgum, or pes valgus. Knee pain in these patients is more prevalent in females, and increases with increasing age.
Level of Evidence:
Level III—case-control study.