The main objective of this study is to evaluate the relationship between the angle of knee flexion in a supine position with joint relaxation (DDPD) and the maximum interface pressure at the heel area (PtAl).

The secondary objectives of this study are:

A. To evaluate the relationship between the angle of flexion of the knee in DDPD and the average pressure throughout the heel area (Pmean).

B. To evaluate the relationship between the angle of flexion of the knee in DDPD and the contact surface of the heel area (Stal) where the pressure is greater than 60 mm Hg.

C. To evaluate the inter-operator concordance for the knee flexion angle measurement in DDPD via photos.

D. To evaluate the inter-operator concordance for skin marks used to measure knee flexion angles in DDPD via photos (only one knee for 30 patients).

E. To evaluate the inta-operator concordance (measures on 2 consecutive days) for skin marks used to measure knee flexion angles in DDPD via photos (for 30 patients).

Inclusion Criteria:

• The patient must have given his/her informed and signed consent
• The patient must be insured or beneficiary of a health insurance plan
• The patient is in a stable medical state (no complications within the past 10 days)

Exclusion Criteria:

• The patient is participating in another study
• The patient is in an exclusion period determined by a previous study
• The patient is under judicial protection, under tutorship or curatorship
• The patient refuses to sign the consent
• It is impossible to correctly inform the patient
• The patient has had medical complications within the ten days preceding study inclusion
• The patient has a bed-sore or bandages on his/her heels
• The patient has had a lower-limb amputation

The study population consists of consecutive patients admitted in the functional rehabilitation unit of the Nîmes University Hospital.