Effects of Anti-gravity Treadmill Training on Knee Osteoarthritis in Geriatric Population.

Osteoarthritis is a very common chronic joint disease resulting in functional disability. Knee OA is considered to be most common form of arthritis in western countries. Knee OA is mainly characterized by presence of pain, radiographic evidence of reduced joint space, wear and tear of articular cartilage and formation of osteophytes i.e., new bone formation at the center and margins of joint. Pain and resultant joint changes causes a change in joint biomechanics and an eventual disuse of limb leading to muscle weakness and atrophy. According to an estimate from a study, knee OA nearly affects 10% of people older than 55 years of age, resulting in severe functional disability in a quarter of this affected population. In elderly population, knee OA poses almost the same risk of disability as caused by heart disease and a larger threat than due to any other medical condition. The prevalence of OA is reported to be as high as 28% in urban and 25% in rural areas of Pakistan.

Literature on knee OA treatment suggest that weight bearing activities in the form of walking are useful in the management of joint symptoms. Loading across the joint must be optimal so that there is no abnormal stress on any compartment of the joint. Abnormal valgus and varus stress results in 4 fold and 5 fold increase in lateral and medial compartments OA of the knee respectively. But this increased loading on an already worn joint can cause considerable pain and damage to the joint. For this purpose, aquatic exercises and hydrotherapy are usually used to counteract the forces acting on the joint. Then there are different types of harness systems and robotic devices to physically lift the patients for unloading the joint. But the problem with these interventions is that they do not account for proper joint kinematics necessary for optimal distribution of forces across the joints. For this purpose, anti gravity treadmills or lower body positive pressure treadmills are designed which take into account the proper joint kinematic s while partially un-weighing the joint. These treadmills are based on NASA technology used for astronauts to counteract the joint problems experienced by them.

These treadmills consist of an air tight chamber surrounding the lower body in which increased pressure is applied, so that the treadmill causes an upward lifting force. This results in successfully decreasing the body weight and gravitational forces on the lower extremity to an adjustable level with a high degree of consistency. Body weight can then be adjusted to as small increments as 1% and as large as 80% by using positive air pressure. This method is considered superior to other methods of un-weighing (harness systems and aquatic therapy) because there is uniform application of pressure over the lower limbs, thereby decreasing the creation of pressure points (common with harness systems) while retaining normal muscle activation and gait patterns (which are changed during water based activities).

This study will help the patients suffering from osteoarthritis to rehabilitate in a pain free environment focusing on proper joint kinematics.