Desk work, driving and (unfortunately) climbing can all cause the hip flexors (muscles at the front of the hip) to become shortened and tight.
Tight hip flexors can affect the alignment of pelvis and femur, ultimately leading to back and knee pain.
Poses which release and lengthen the hip flexors not only reduce back and knee pain, but also allow you to bring the hips forward when climbing. This keeps your centre of balance close to the rock for greater control and reduced strain on the arms.
Seek medical advice before trying any of the following poses if: you have a hip or knee injury; you have had a hip or knee replacement; or if you have a health condition affecting your hips or knees.
Low lunges are great for releasing the hip flexors and are accessible for all levels. Because the back knee is on the ground, you can really sink into this pose in a long, relaxed hold. Choose the variation (below) that gives you a satisfying stretch in the front of the back hip.
Take it deeper by squeezing your bum to engage the glutes. These are antagonistic to the hip flexors, so will encourage the hip flexors to release.
If your hands are raised on blocks or your thigh, you may also be able to find space to tilt your pelvis and deepen the stretch still further.
For experienced yogis looking for a deeper hip opener, dragon pose with a twist and bind is my absolute favourite.
A really juicy stretch for the back hip flexor, with the added bonus of an opening for the chest and shoulders.