When is it appropriate to use an ISOKINETIC machine for ACL repairs? I have a patient in clinic who is s/p 8 months ACL repair and every few months she has been going for isokinetic testing as she wants to return to playing college lacrosse. From my understanding, isokinetic machines can be set at a constant speed in which the limb has to move throughout the ROM. Is the purpose of the machine just for strengthening and to assess something like quads/hamstrings ration?

Isokinetic exercises are exercises performed using a specialized apparatus -a dynamometer- that provides variable resistance to a movement, so that no matter how much effort is exerted, the movement takes place at a constant speed. Isokinetic testing (using an isokinetic machine/dynamometer) is an objective way to evaluate dynamic stability of the knee joint which helps to estimate the quality of rehabilitation outcomes after ACL reconstruction.

A study carried out by Cvjetkovic et al published in the Journal of the Academy of Medical Sciences of Bosnia and Herzegovina (2015) concluded that Isokinetic testing of dynamic stabilizers of the knee was beneficial in the diagnosis and treatment of thigh muscle imbalance. The researchers also determined that isokinetic testing was an objective parameter for return to sport activities after ACL reconstruction.

At the expiration of the protective phase following the surgery (usually around 6 weeks post surgery but varies per patient), the isokinetic machine can be used both to collect baseline data of the muscles around the knee joint (to be used for future revaluation or reassessment purposes) and as an intervention modality to safely build muscle strength.

The use of the isokinetic machine is frequently chosen because of its inherent patient safety, objectivity and reproducibility in testing measures and in addition to building muscle strength, it can also be used to determine peak torque parameters especially for the bilateral comparison of the quadriceps and hamstring muscle ratios and finally it can be used to calculate or determine other muscle performance parameters such as work, power and endurance at various stages during (and after) the rehabilitation process.

You can read the entire study here.

Reference 1