Considering the importance of the hip joint for locomotion and lifting there is relatively little information on testing this joint. This is probably due to the fact that people are obsessed with the knee and very little clinically goes wrong with the stable hip joint. However, arthroscopic intervention to the hip is gaining in popularity which will probably involve increased use of isokinetics in this area. The use of isokinetics for the diagnosis and treatment of 'groin strain' (yes I hate that term too but it servers a purpose) is more controversial, but never the less, prevalent.

Testing/exercising of the hip is usually done in reference to a plane of movement (yes it's time to get Gays back out of the cupboard).

Flexion and extension to you and me. Unfortunately there is great discrepancy concerning the normal ROM of the hip in the saggital plane. A good example of this is Boone and Azen (1979) who found normal hip extension to be 10 degrees, whereas Dorinson and Wagner (1948) found it to be 50 degrees. The point of maximal isometric strength is another area of contentious debate. Callahan et al (1988), in a very comprehensive study, suggested that 45 degrees hip flexion is the point of maximum efficiency (for flexion and extension). Consequently, strength measurements should be made from 0 degrees flexion to 75 degrees flexion (and obviously back for extension).

Testing of the hip flexors and extensors is usually performed in the upright position (see below). 

It is claimed that this is more functional and involves the use of gravity. However, this position is difficult to stabilize. If the knee is allowed to flex the resulting gravitational moment of the leg is lower than if the knee was fully extended and rectus femoris contraction may result in variations of the strength curve. However, flexion of the knee is recommended, although only passively against gravity if for no other reason than to avoid sciatic nerve traction.

The instantaneous axis of rotation is simply straight across from the greater trochanter to the axis of the dynamometer (as seen as the red line).

Angular Velocities

Debate rages on this, however, slower velocities tend to be more comfortable with higher velocities often showing overshoot inconsistencies.

Abduction and adduction to you and me. The accepted ROM for abduction is 45 degrees whereas for adduction it may be up to 25 degrees (Miller, 1985). Obviously movements into adduction are usually prevented by a mechanical block (the other leg). Testing is normally performed in the upright position but can be performed in the side lying and supine positions.

Upright Position

Test ROM is 0-30 degrees.

Positioning and stabilization. This is usually done by stabilizing the contralateral hip, however, it is almost impossible. (The tested knee joint should be maintained in full extension during this test.)

Alignment of axes. Place the actuator axes opposite the hip joint 1 cm medially to the anterior superior iliac spine (red line seen below).

The resistance pad should be placed on the lateral thigh within the lower third (see below).

Side Lying Position

Positioning and stabilization. Much easier. Put on as many straps as you can.

Resistance pad position. A dual pad can be obtained as described by Donatelli et al. (1991) however this is not necessary. (The knee must be kept straight during the test.)

Alignment of axes. The same as in upright testing (red line seen below).

Remember that adduction beyond the mid-line is not possible (if desired) in this position.

Angular Velocities

Donatelli et al. (1991) suggest velocities between 30-90 degrees/second, however, 30 degrees/second is probably the most functional and practical.

Internal and external rotation of the hip. Although the hip has equal ROM to internal/external rotation of 45 degrees (Miller, 1985) isokinetic testing of these movements can be done over a much shorter arc. Dvir (1995) suggests a ROM from 5 degrees internal rotation to 25 degrees of external rotation.

Positioning and Stabilization

The only really good piece (peer review) of work is by Lindsay et al. (1992). They compared 3 distinct positions, seated, supine with knee flexed and supine with knee extended. Seated tends to give the best strength scores.

Alignment of Axes

Usually along the long axis of the femur with the resistance pad immediately above the lateral malleolus.

Test Velocities

Between 30-60 degrees/second. This is dependent on subject compliance.