Knee and ankle position, anterior drawer laxity, and stiffness of the ankle complex

Abstract

Context: Anterior drawer testing of the ankle is commonly used to diagnose lateral ligamentous instability. Our hypothesis was that changing knee and ankle positions would change the stability of the ankle complex during anterior drawer testing.

Objectives: To assess the effects of knee and ankle position on anterior drawer laxity and stiffness of the ankle complex.

Design: A repeated-measures design with knee and ankle position as independent variables.

Setting: University research laboratory.

Patients or other participants: Bilateral ankles of 10 female (age = 19.8 +/- 1.1 years) and 10 male (age = 20.8 +/- 1.2 years) collegiate athletes were tested.

Intervention(s): Each ankle complex underwent loading using an ankle arthrometer under 4 test conditions consisting of 2 knee positions (90 degrees and 0 degrees of flexion) and 2 ankle positions (0 degrees and 10 degrees of plantar flexion [PF]).

Main outcome measure(s): Recorded anterior laxity (mm) and stiffness (N/mm).

Results: Anterior laxity of the ankle complex was maximal with the knee positioned at 90 degrees of flexion and the ankle at 10 degrees of PF when compared with the knee positioned at 0 degrees of flexion and the ankle at 10 degrees or 0 degrees of PF (P < .001), whereas ankle complex stiffness was greatest with the knee positioned at 0 degrees of flexion and the ankle at 0 degrees of PF (P < .009).

Conclusions: Anterior drawer testing of the ankle complex with the knee positioned at 90 degrees of flexion and the ankle at 10 degrees of PF produced the most laxity and the least stiffness. These findings indicate that anterior drawer testing with the knee at 90 degrees of flexion and the ankle at 10 degrees of PF may permit better isolation of the ankle capsuloligamentous structures.

Keywords: lateral ankle sprains; physical examination.

Figure 1. Ankle anterior-drawer test. A, Attached ankle arthrometer with the knee positioned at 0° of flexion and the ankle at 0° of plantar flexion. B, Participant lying supine with the knee positioned at 90° of flexion and the ankle at 10° of plantar flexion.

Figure 2. Anteroposterior force-displacement curve from one ankle. A negative load value represents posterior load, and a negative displacement value represents posterior displacement. Ankle complex laxity is the anterior displacement (mm) between 0 and 100-N force loads.

Figure 3. Knee-by-ankle comparisons for ankle complex laxity. ^a Indicates knee at 90° of flexion, ankle at 10° of plantar flexion > knee at 90° of flexion, ankle at 0° of plantar flexion and knee at 0° of flexion, ankle at 10° of plantar flexion (P ≤ .002); ^b Knee at 90° of flexion, ankle at 0° of plantar flexion > knee at 0° of flexion, ankle at 0° of plantar flexion (P < .001); ^c Knee at 0° of flexion, ankle at 10° of plantar flexion > knee at 0° of flexion, ankle at 0° of plantar flexion (P < .001).

Figure 4. Knee-by-ankle comparisons for ankle complex stiffness. ^a Indicates knee at 0° of flexion, ankle at 0° of plantar flexion > knee at 0° of flexion, ankle at 10° of plantar flexion and knee at 90° of flexion, ankle at 10° of plantar flexion (P ≤ .009); ^b Knee at 90° of flexion, ankle at 0° of plantar flexion > knee at 90° of flexion, ankle at 10° of plantar flexion (P  =  .012).