Hiking poles redistribute about 20–30% of the load placed on your knees while going downhill, so they definitely provide substantial help in relieving pain. The symptoms you described—pain on the outside of the knee when descending, especially on stairs, that eases with rest—are very typical of iliotibial band syndrome, which is very common among hikers. It is a condition in which the long band running along the outside of the thigh to the knee becomes inflamed as it repeatedly rubs against bone when the knee bends and straightens.
If you use poles incorrectly, you may end up with wrist or shoulder pain, so
On level ground, set the length so your elbow is at a 90-degree angle
When going uphill, adjust them to be 5–10 cm shorter than the level-ground setting
When going downhill, adjust them to be 10–15 cm longer than the level-ground setting
(because you need to plant them first on the ground below you)
Always use two poles as a pair
Some people occasionally use only one pole, but this shifts your balance to one side and puts greater strain on the opposite knee or spine.
Put your weight on the strap (wrist loop)
If you rely only on your grip on the handle, your hand will hurt and become fatigued. Thread your hand through the wrist strap from below and then grip it; when planting the pole, let your weight rest naturally on the strap so you don’t strain your grip or joints.
When going downhill, cut your stride to half its usual length and step lightly. Stepping with your leg straight sends the impact to your joints, so develop the habit of descending with your knee slightly bent to reduce the impact transmitted to your joints
If you hike about twice a month, actively using poles from now on and changing your downhill posture will let you enjoy healthy hikes without pain.
