Assessment of muscle strength and thigh girth

The participant sat on a testing table with his back resting firmly on the back rest, and the knees flexed over the edge of the testing table. The cable tensiometer was attached to the padded ankle of participant’s leg via its cable with the knee angle at 60 degrees of flexion (Adegoke BOA: Comparative efficacy of open and closed kinetic chain exercises in the treatment of osteoarthritic knee. PhD Thesis. Department of Physiotherapy, University of Ibadan; 2003, unpublished, [27]). After three trial tests, participants were instructed to hold the side of the testing table, look straight ahead, and try to straighten their knee with maximum effort without jerking (Adegoke BOA: Comparative efficacy of open and closed kinetic chain exercises in the treatment of osteoarthritic knee. PhD Thesis. Department of Physiotherapy, University of Ibadan; 2003, unpublished, [27]) (Fig. ​(Fig.5).5). After a rest of 90 s, the test was repeated and the average of the two attempts was taken and recorded in kilogrammes. Conversion to values in Newton (N) was done by multiplying the force measured in kilogrammes with acceleration due to gravity (9.8 m/s²). The converted static strength was normalised to body weight using the formula:

Participant during static quadriceps muscle strength testing

Sn = S/BW ^0.67 [28].

S - Strength in Newton; BW – Body weight; 0.67 – allometric parameter.

The value obtained was recorded to nearest whole number as the participant’s static quadriceps muscle strength (SQS).

Participants assumed a sitting position on a testing table with their back, and thighs well supported and firmly strapped to the backrest and sitting platform of the testing table respectively. A plastic weight (W) corresponding to a certain repetitive maximum of the participant was randomly selected and was attached via the De Lorme’s boot to the participant’s foot. Participants were instructed to lift the weight by extending their knee through the available range of motion. The participant held the position of maximum extension to a count of five and then returned to the starting position (Fig. ​(Fig.6).6). The lifting and lowering was terminated when the participant showed evidence of fatigue by not being able to complete the initial maximum range of motion [29]. The number of times the weight was lifted through full range of motion before fatigue set in was recorded as R. 1-RM was estimated using the formula predicted by: 1-RM = W/(1.0278–0.0278 x R) (kg) [24].

Participant during dynamic quadriceps muscle strength testing

The value of 1-RM obtained in kilogrammes was converted to Newton and also normalized to body weight using the same procedure outlined for SQS [28] and was recorded as participant’s dynamic quadriceps muscle strength (DQS).

The thigh girth (TG) was measured with an inelastic tape using a point mid-way along the straight line linking the landmarks of greater trochanter and the apex of the patella [30].

SQS, DQS and TG were assessed at baseline and at the end of weeks 4, 8 and 12 of study. For participants with bilateral knee OA, the index knees (with higher scores on the Visual Analogue Scale) were chosen for measurement [31].