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Abnormalities in quadriceps-hamstring strength. Relationships in polymyositis and dermatomyositis
M A Kroll1, J C Otis, L J Kagen
1Department of Rehabilitation, Hospital for Special Surgery affiliated with New York Hospital-Cornell University Medical College, New York 10021.
The Journal of Rheumatology
|December 1, 1988
Summary
Patients with inflammatory muscle diseases like dermatomyositis often show preferential weakness in quadriceps compared to hamstring muscles. This quadriceps-to-hamstring torque ratio is a key indicator of disease involvement.
Area of Science:
- Neurology
- Rheumatology
- Muscle Physiology
Background:
- Inflammatory myopathies, including dermatomyositis and polymyositis, cause significant muscle weakness.
- Assessing muscle strength is crucial for diagnosing and monitoring these conditions.
Purpose of the Study:
- To investigate the pattern of muscle weakness in patients with inflammatory myopathies.
- To determine if there is preferential involvement of specific muscle groups, such as quadriceps versus hamstrings.
Main Methods:
- Muscle strength was quantified as torque in patients diagnosed with dermatomyositis and polymyositis.
- The ratio of quadriceps torque to hamstring torque (Q:H) was calculated and compared between patients and healthy controls.
Main Results:
- Patients exhibited weakness in both quadriceps and hamstring muscle groups.
- The mean Q:H ratio was lower in patients (1.60) compared to controls (1.93).
- Lower Q:H ratios correlated with older age, greater weakness, and higher prednisone doses, and were observed in 56% initially and 64% over time.
Conclusions:
- Preferential involvement and weakness of the quadriceps muscle group characterize inflammatory muscle diseases.
- The Q:H ratio serves as a potential biomarker for disease activity and severity in inflammatory myopathies.