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Vårbakken K1, Lorås H1, Nilsson KG2, Engdal M3, Stensdotter A-K1
1Norwegian University of Science and Technology, Department of Neuromedicine and Movement Science, Trondheim, Norway, 2Umea University, Surgical and Perioperative Sciences, Umea, Sweden, 3Trondheim University Hospital, Orthopedic Department, Orthopedic Research Center, Trondheim, Norway
Background: Patients with knee osteoarthritis (KOA) commonly present with quadriceps weakness and respond moderately well to strength training. However, previous case-control studies have mainly compared strength in knee extension. There is a lack of knowledge regarding strength across the entire kinetic chain of both lower limbs in patients with KOA compared to healthy controls (HC).
Purpose: Our main objective was to compare peak strength across the ankle, the knee, and the hip joint in all main directions for both lower limbs, between patients with KOA and matched healthy volunteers.
Methods: In an explorative cross-sectional case-control study, we recruited patients aged 45 to 70 years, referred by physician to physiotherapists or osteoarthritis-school at the orthopedic department at the hospital, with knee pain > 1 year, and radiographic osteoarthritis (OA). Further, we recruited age- and gender-matched healthy controls. All were measured on peak strength for the main muscles of both lower limbs. We applied a Biodex Dynamometer linked protocol (1-5) and a hand held dynamometer protocol (6). The protocols were:
1) knee extension/flexion,
2) hip internal/external rotation,
3) ankle dorsal/plantar flexion,
4) ankle eversion/inversion,
5) hip flexion/extension, and
6) hip ab/adduction.
Specifically, protocol 1-5 had five maximum repetitions in isokinetic concentric mode at a speed of 60 degrees/second, whereas protocol 6 had three maximum isometric repetitions. We divided the best repetition by body mass. Then, strength comparisons between groups (KOA - HC) were performed by t-tests. Moreover, effect sizes were calculated as standardized mean difference (SMD) with 95% confidence intervals (CI). [SMD = Cohen's d]. Finally, we interpreted SMD as > 0.2 = small, > 0.5 = moderate, and > 0.8 = large. Pain was measured using the Numeric rating scale (0-10, best to worst).
Results: We included 28 patients diagnosed with KOA by primary care physicians (64% females, mean age 62, BMI 28) and 31 HCs (54% females, mean age 55, BMI 27). Three patients were referred to physiotherapy and 25 to OA-school participation. Most had light to moderate radiographic OA. Average pain during the last week was 4 and 0 in the KOA-and HC-group (mean, median). For peak strength, there were significant large strength differences in the KOA-group for ankle eversion and hip external and internal rotation on the involved side compared to the HC-group. (I.e., SMD [95% CI] -0.96 [-1.49, -0.42], -0.93 [-1.46, -0.39], -0.91 [-1.41, -0.38], respectively.) Additionally, there was significant moderate lower peak strength for nine other joint-directions, including knee flexion and extension and ankle inversion in the involved leg and four joint-directions in the uninvolved leg. However, there were no significant differences for the remaining 50% of the strength measurements.
Conclusion(s): This comprehensive study of muscle strength in patients with KOA indicates large weaknesses in ankle and hip muscles used for coordination in the frontal and transverse planes. Future work should evaluate the stability and replicability of these findings, and their clinical relevance for physiotherapy.
Implications: For patients with KOA physiotherapists may pay particular attention to the strength of these three muscle groups as possible supplement to existing recommended strength training protocols.
Keywords: Muscle Strength Dynamometer, Osteoarthritis, Knee, Case-Control Studies
Funding acknowledgements: This project has internal funds for a PhD-student position offered by the former Sor-Trondelag University College, Trondheim, Norway.
Purpose: Our main objective was to compare peak strength across the ankle, the knee, and the hip joint in all main directions for both lower limbs, between patients with KOA and matched healthy volunteers.
Methods: In an explorative cross-sectional case-control study, we recruited patients aged 45 to 70 years, referred by physician to physiotherapists or osteoarthritis-school at the orthopedic department at the hospital, with knee pain > 1 year, and radiographic osteoarthritis (OA). Further, we recruited age- and gender-matched healthy controls. All were measured on peak strength for the main muscles of both lower limbs. We applied a Biodex Dynamometer linked protocol (1-5) and a hand held dynamometer protocol (6). The protocols were:
1) knee extension/flexion,
2) hip internal/external rotation,
3) ankle dorsal/plantar flexion,
4) ankle eversion/inversion,
5) hip flexion/extension, and
6) hip ab/adduction.
Specifically, protocol 1-5 had five maximum repetitions in isokinetic concentric mode at a speed of 60 degrees/second, whereas protocol 6 had three maximum isometric repetitions. We divided the best repetition by body mass. Then, strength comparisons between groups (KOA - HC) were performed by t-tests. Moreover, effect sizes were calculated as standardized mean difference (SMD) with 95% confidence intervals (CI). [SMD = Cohen's d]. Finally, we interpreted SMD as > 0.2 = small, > 0.5 = moderate, and > 0.8 = large. Pain was measured using the Numeric rating scale (0-10, best to worst).
Results: We included 28 patients diagnosed with KOA by primary care physicians (64% females, mean age 62, BMI 28) and 31 HCs (54% females, mean age 55, BMI 27). Three patients were referred to physiotherapy and 25 to OA-school participation. Most had light to moderate radiographic OA. Average pain during the last week was 4 and 0 in the KOA-and HC-group (mean, median). For peak strength, there were significant large strength differences in the KOA-group for ankle eversion and hip external and internal rotation on the involved side compared to the HC-group. (I.e., SMD [95% CI] -0.96 [-1.49, -0.42], -0.93 [-1.46, -0.39], -0.91 [-1.41, -0.38], respectively.) Additionally, there was significant moderate lower peak strength for nine other joint-directions, including knee flexion and extension and ankle inversion in the involved leg and four joint-directions in the uninvolved leg. However, there were no significant differences for the remaining 50% of the strength measurements.
Conclusion(s): This comprehensive study of muscle strength in patients with KOA indicates large weaknesses in ankle and hip muscles used for coordination in the frontal and transverse planes. Future work should evaluate the stability and replicability of these findings, and their clinical relevance for physiotherapy.
Implications: For patients with KOA physiotherapists may pay particular attention to the strength of these three muscle groups as possible supplement to existing recommended strength training protocols.
Keywords: Muscle Strength Dynamometer, Osteoarthritis, Knee, Case-Control Studies
Funding acknowledgements: This project has internal funds for a PhD-student position offered by the former Sor-Trondelag University College, Trondheim, Norway.
Topic: Musculoskeletal: lower limb; Orthopaedics; Rheumatology
Ethics approval required: Yes
Institution: The Norwegian Ministry of Education and Research
Ethics committee: The Regional Committees for Medical and Health Research Ethics, REK-nord
Ethics number: 2016/984
All authors, affiliations and abstracts have been published as submitted.
