Hydrotherapy in an underwater treadmill utilises the physical properties of water to minimise compressive forces on joints and stresses on healing tissues. This promotes an earlier return to function after injury or surgery. The low impact, active muscle contraction, increased joint range of motion and a lengthened stride in the water promotes the restoration of normal function. The buoyancy of water minimises weight-bearing on the joints allowing the patient to exercise more comfortably. It assists the patient to exercise in an upright position encouraging confidence, normal posture and movement pattern. The compressive effect created by the hydro-static pressure of water helps reduce blood pooling and oedema in the lower limbs. Resistance provided by the water strengthens, increases muscle tone and improves the patient’s cardiovascular fitness. The challenge can be adjusted using the speed of the belt, water levels, inclines and water jets. Exercising in warm water stimulates endorphin and encephalin release in the brain which enhances the patients’ mood and assists with pain management. The operator-controlled environment of an underwater treadmill allows each patient’s program to be individualised and adjusted during a session. A therapist can palpate and assess joint movement, joint stability, and muscle contractions as well as enhance walking with manual techniques. Movement is assessed and the challenge adjusted to facilitate the optimal training gait for a patient’s individual needs.