Is there a relationship between tracking ability, joint position sense, and functional level in patellofemoral pain syndrome?

This prospective cohort study investigated proprioception and motor control changes in patients with patellofemoral pain syndrome (PFPS), and how these changes related to knee function, pain, muscle strength and muscle endurance. The study included 43 women diagnosed with unilateral patellofemoral pain syndrome. Thirty-one healthy women were recruited as control group. Peak quadriceps femoris and hamstring muscle isokinetic torques were recorded at 60 and 180A degrees/s. Joint position sense was tested by active reproduction of joint position during horizontal squat performance. Muscle coordination and motor control ability were tested by a multi-joint lower limb tracking-trajectory test. Muscle endurance was tested using a computerized functional squat system. Severity of pain in during stair ascent/descent, squatting, and prolonged sitting with knees 90A degrees flexed were measured using a 10 category modified visual analogue scale. Functional levels of patients were determined using Kujala patellofemoral scores. Active reproduction of joint position did not differ between PFPS and control groups. However, tracking-trajectory error was significantly higher in PFPS group than control subjects. Hamstring and quadriceps peak isokinetic torque and muscle endurance scores were significantly lower in the PFPS group. Kujala patellofemoral score displayed significant relationships with peak isokinetic quadriceps torque, knee pain, and joint position sense scores. Pain during stair descent, sitting, and quadriceps torque at 180A degrees/s explained 57.7 % of the variation in Kujala patellofemoral score. Although lower extremity joint position sense did not differ between groups, the PFPS group displayed a target-trajectory muscular coordination deficit, decreased muscular endurance, and decreased muscular strength compared to control group subjects. Pain level directly related to motor control performance while joint position sense scores did not. Knee pain and impaired strength related more to functional performance impairment than joint position sense scores in patients with PFPS. Prospective case-control study, Level III.