Effect of knee pain on muscles imbalance and physical limitation in individuals with bilateral knee osteoarthritis: A comparative cross-sectional study

Objectives: When osteoarthritis (OA) affects the knee, it causes muscle imbalance and physical limitations. This study aimed to determine the impact of knee pain on quadriceps strength, hamstring length, and physical limitations in individuals with bilateral knee OA. Methods: A cross-sectional study at Khyber Teaching Hospital and Northwest General Hospital, Peshawar, included individuals aged 50-65, who met the American College of Rheumatology criteria. Subjects diagnosed with bilateral knee OA (grade II or greater on the Kellgren-Lawrence grading scale) and experiencing pain in both knees (numeric pain rating scale [NPRS] score >= 1) were selected through purposive sampling (n = 70). Data collection involved the NPRS, modified belt stabilizer hand-held dynamometer, active knee extension test, and Western Ontario and McMaster Universities Arthritis Index (WOMAC) Urdu version questionnaire. Measurements from both knees assessed quadriceps muscle strength, hamstring length, and physical limitations. Results: The median interquartile range (IQR) of quadricep strength for the more painful knee was 0.53 (0.36) Nm/kg and 1.35 (0.34) Nm/kg for the less painful knee showing a significant difference in quadriceps strength (P < 0.01). In terms of hamstring length, the more painful knee had a median (IQR) of 29.0 (2.0) degrees whereas the less painful knee recorded 11.0 (6.0) degrees indicating a significant difference (P < 0.01). Likewise, there was a significant difference in WOMAC scores between the less painful and more painful knees (P < 0.01). Conclusion: This study found that individuals experiencing more knee pain demonstrated decreased quadriceps muscle strength and increased hamstring muscle tightness. In addition, those with more painful knees exhibited greater physical limitations in bilateral knee OA.