Why do my knees hurt when I climb stairs but not when I walk

Your knees may feel perfectly fine while walking on flat ground but start hurting the moment you climb stairs. Research suggests the difference could come down to how much your knee bends and how much force is placed around the kneecap.

In Short

• A 2025 review analysed 183 studies on knee loading in osteoarthritis
• Stair ascent showed the greatest pain among everyday activities studied
• Climbing steps demands deeper knee bending and harder quadriceps effort

You walk around during the day without much trouble. You can go from one room to another, walk outside or even take a long stroll. But the moment you reach a staircase, something changes. Your knees begin to hurt, especially while going up or down the steps.

This is a common pattern of knee pain, and researchers have been studying why certain everyday movements can put more stress on the knee than others.

One of the clearest explanations comes from biomechanics, the study of how forces and movement affect the body. Walking on a flat surface and climbing stairs may look similar, but the knee does not experience them in the same way.

A 2025 systematic review and meta-analysis published in Clinical Biomechanics looked at 183 studies examining knee loading and pain during everyday activities in people with knee osteoarthritis. Researchers compared activities including walking, stair climbing and standing up from a chair. They found that stair ascent was linked with the greatest knee pain among the activities studied.

STAIRS MAKE THE KNEE BEND MORE

One major difference is how much the knee has to bend.

During normal walking, the knee moves through a relatively smaller range of motion. Climbing stairs requires deeper knee bending while the muscles around the knee work harder to lift the body upward.

This places greater demands on the patellofemoral joint, the area where the kneecap meets the thigh bone.

A systematic review and meta-analysis published in the British Journal of Sports Medicine found that the average peak force at this joint was about 0.9 times body weight during walking, compared with about 3.2 times body weight during stair ascent in healthy people.

That does not mean that climbing stairs is damaging your knees. It means the joint is experiencing considerably greater forces during the movement.

YOUR KNEECAP PLAYS A BIG ROLE

The kneecap acts somewhat like a pulley, helping the quadriceps muscles straighten the knee and move the body.

When you climb stairs, the quadriceps have to work harder. This increases the forces acting through the patellofemoral joint.

A biomechanical study comparing stair climbing with level walking found that stair climbing created more challenging contact mechanics around the patellofemoral joint. The researchers found higher pressures and changes in how forces were distributed around the kneecap during stair climbing.

Another study using computational modelling found that stair ascent produced substantially greater patellofemoral contact forces and stresses than level walking.

WHY FLAT WALKING MAY FEEL FINE

If your knee is sensitive to higher loads or deeper bending, ordinary walking may simply stay below the point where you notice discomfort.

Stairs can push the joint into a different mechanical situation.

The knee bends more, the quadriceps produce greater force and the kneecap experiences higher joint forces. This can make an existing problem more noticeable during stairs even when everyday walking feels normal.

Research has also shown that activities involving greater knee flexion, such as squatting and stair climbing, generally produce higher patellofemoral joint forces than activities involving less knee flexion, such as walking.

GOING DOWNSTAIRS CAN BE DIFFERENT

Pain does not always happen, only while climbing up.

Going downstairs also changes how the knee handles body weight. Research has examined differences between stair ascent and descent, including changes in contact pressure and the area where the kneecap and thigh bone meet.

Interestingly, the 2025 review found that stair ascent was associated with the greatest knee pain among the activities it examined, while stair descent and walking showed different patterns.

STAIR PAIN DOES NOT AUTOMATICALLY MEAN ARTHRITIS

Perhaps the most important point is that knee pain on stairs does not automatically mean you have arthritis.

Knee pain can have several possible causes, and the location, timing and type of pain can differ from person to person. Research can explain why stairs place greater demands on the knee, but it cannot diagnose the reason for an individual's pain.

So if your knees feel fine on flat ground but hurt every time you use the stairs, the difference may not be in your imagination. The movement itself changes the forces acting on the knee.

For many people, that simple difference between walking and climbing stairs may explain why a staircase can reveal knee pain that remains almost invisible during an ordinary walk.

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