Flexion refers to the movement  which occurs when the leg bends at the knee. Activities that require flexion of the knee are stair climbing, kneeling, squatting, getting up from a low chair. Normal knees provide about 125 degrees of flexion which is sufficient for routine activities.

High flex knee Replacement

The High flex knee or hi flex knee is a boon to patients seeking increased function after a TKR. It allows activities which require more flexibility and are not possible with a conventional knee replacement. These are squatting for Yoga position,  kneeling for prayer, offering Namaz (Muslim prayer) use of Indian toilet, gardening..
High flexion is achieved through a combination of prosthetic design, patient selection, surgery technique and physiotherapy. Fixed bearing and rotating platform knees both are used in High flex designs.
In order to benefit from a high flex knee replacement a few criteria should be met
a) Osteoarthritis is the main indication. If it is rheumatoid arthritis, bony destruction should not be advanced.
b) Revision knees are not suited for high flexion
c) Ankylosed knees or fused knees cannot be replaced with a high flexion knee.
d) The thigh calf index should be above 90 degrees.
e) The patient should be motivated to achieve deep knee bending and should participate in aggressive post operative physiotherapy.