We explored the construct validity and test-retest reliability of the passive motion component of the Cyriax soft tissue diagnosis system. We compared the hypothesized and actual patterns of restriction, end-feel, and pain/resistance sequence (P/RS) of 79 subjects with osteoarthritis (OA) of the knee and examined associations among these indicators of dysfunction and related constructs of joint motion, pain intensity, and chronicity.
Subjects had a mean age of 68.5 years (SD = 13.3, range = 28-95), knee stiffness for an average of 83.6 months (SD = 122.4, range = 1-612), knee pain averaging 5.6 cm (SD = 3.1, range = 0-10) on a 10-cm visual analogue scale, and at least a 10-degree limitation in passive range of motion (ROM) of the knee.
Passive ROM (goniometry, n = 79), end-feel (n = 79), and P/RS during end-feel testing (n = 62) were assessed for extension and flexion on three occasions by one of four experienced physical therapists. Test-retest reliability was estimated for the 2-month period between the last two occasions.
Consistent with hypotheses based on Cyriax's assertions about patients with OA, most subjects had capsular end-feels for extension; subjects with tissue approximation end-feels for flexion had more flexion ROM than did subjects with capsular end-feels, and the P/RS was significantly correlated with pain intensity (rho = .35, extension; rho = .30, flexion). Contrary to hypotheses based on Cyriax's assertions, most subjects had noncapsular patterns, tissue approximation end-feels for flexion, and what Cyriax called pain synchronous with resistance for both motions. Pain intensity did not differ depending on end-feel. The P/RS was not correlated with chronicity (rho = .03, extension; rho = .01, flexion). Reliability, as analyzed by intraclass correlation coefficients (ICC[3,1]) and Cohen's kappa coefficients, was acceptable (> or = .80) or nearly acceptable for ROM (ICC = .71-.86, extension; ICC = .95-.99, flexion) but not for end-feel (kappa = .17, extension; kappa = .48, flexion) and P/RS (kappa = .36, extension; kappa = .34, flexion).
The use of a quantitative definition of the capsular pattern, end-feels, and P/RS as indicators of knee OA should be reexamined. The validity of the P/RS as representing chronicity and the reliability of end-feel and the P/RS are questionable. More study of the soft tissue diagnosis system is indicated.