As we age our joints become stiffer and less flexible. Fluid in the joints may decrease, and the cartilage may begin to rub together and erode. Hip and knee joints in particular begin to lose joint cartilage.
A gentle form of yoga practiced after a good warm up, is perfectly safe, but some yoga postures are not recommended.
An Indian orthopedic, Dr Ashok Rajgopal, recently revealed that he has performed knee replacement surgery on a number of leading yoga gurus.
His warnings are a serious challenge to those who say yoga, which is now a multi-million dollar global industry, can ward off the effects of ageing and leave devotees feeling fitter, stronger and at peace with the world.
According to Dr Rajgopal, "the extreme stretching exercises at the heart of the discipline cause severe stress on joints, leading to arthritis."
He has seen a higher incidence of joint and bone ailments among yoga followers.
"Extreme postures like acute deep knee bends are definitely harmful to them in terms of the abnormal stresses, and damage to cartilages. Anatomy is key when you are teaching yoga because everybody has a different body and build. We have to be very careful how we could keep up from one posture to another without injuring them. Everything has to be done according to what your body can handle. With proper alignments and training one can avoid these injuries," he said.
Poses that can damage our knees are: Virasana (Hero Pose) Supta Virasana (Reclining Hero Pose), Padmasana (Lotus Pose).
Our knees were never designed to bend at the angle shown in the picture (Supta Virasana) and if you have strong and therefore short and tight quads - sporty people do- this pose is bad for both knees and lower back.