Please Allan, treating the knee in isolation is not appropriate.

I agree Pilates is an excellent option for this client, especially reformer work, but one should look at the lower limb as a chain.

As for the amount of flexion? This is not dependent on instructor knowledge! Instructor knowledge in movement is essential but I have seen very few Pilates instructors with this.. no offense as I am a Pilates teacher with the Pilates Foundation UK. By all means give Pilates a good rap but let's not go overboard