Functional pain measure in knee osteoarthitis - a proof of concept study on a novel method of assessing pain during function

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s / Osteoarthritis and Cartilage 20 (2012) S54–S296 S162 stresses is reduced due to tissue removed. Impaired knee function, such as poor self-reported outcomes, muscle weakness and reduced functional performance is other suggested factors that may contribute to progression of knee OA. This study aimed to examine pre-operative knee function in middle-aged female and male patients with degenerative meniscus tears eligible for arthroscopic surgery, compared to a healthy population and the respective patient non-injured leg. Methods: 70 patients (36% females, age (mean SD) 49 6, BMI 27 3) with an MRI verified degenerative meniscal tear considered eligible for surgery were included. Outcomemeasures were the Knee injury and Osteoarthritis Outcome Score (KOOS), isokinetic knee extension and flexion muscle strength tests and three lower extremity performance tests; maximum number of kneebendings in 30s, the one leg hop for distance and the 6meter timed hop test. The performance tests are in addition to muscle strength also dependent on the ability to switch between concentric and eccentric muscle contraction, balance and functional stability, and for the hop tests confidence in the knee. Results: KOOS mean subscale scores ranged from 43 to 76. Mean score differences between the patients and an age matched population based reference group ranged from 13 to 38 (p1⁄4<0.000), Figure 1. There were no significant differences in KOOS scores between genders. The index leg was significantly weaker in isokinetic knee extension and flexion strength compared to the contralateral leg (155Nm 53 and 84Nm 27 vs. 179Nm 51 and 87Nm 24, p 0.03). Mean differences in peak torque and total work quadriceps muscle strength compared with the contralateral leg was 15% and 14% for the females and 13% and 9% for the males, respectively. For all three lower extremity performance tests the results of the index leg were significantly worse than for the contralateral leg (number of kneebendings 26 10 vs. 28 10, p1⁄4<0.001, one leg hop 82 35 vs. 92 31 cm p1⁄4<0.001, 6-meter timed hop test 3.0 1.4 vs. 2.5 0.8 s, p1⁄4<0.001). Mean differences in the three tests compared with the contralateral leg ranged from 12% to 14% for the females and 5% to 12% for the males. Conclusions: Patients with a degenerative meniscus tear considered eligible for surgery reported severely impaired pain, other symptoms, function in daily living and sports, and knee related quality of life compared to an age matched population based reference group. Muscle function in the index leg was significantly worse with up to 15% lower muscle function compared to the contralateral leg. These results suggest that risk factors for OA onset, other than intraarticular damage, are present in patients with a degenerative meniscus tear.