Stairs are one of the most useful diagnostic tests in orthopedics, and they cost nothing. The knee experiences several times body weight going down stairs, considerably more than in level walking, so a joint that copes on flat ground often declares itself on a staircase.

Which direction hurts, and where it hurts, narrows the diagnosis considerably.

Pain going down rather than up

Pain that is worse descending typically points to the patellofemoral joint, the surface between the kneecap and the thigh bone. Descending requires the quadriceps to contract while lengthening, which compresses the kneecap against the femur.

In younger patients this is often patellofemoral pain syndrome, usually related to weakness, alignment and training load. In older patients it commonly indicates patellofemoral arthritis, which can exist with relatively well preserved joint space elsewhere.

Pain going up rather than down

Pain worse on ascent suggests the main load is falling on the tibiofemoral joint, most often the medial compartment, and is more typical of the pattern seen in medial compartment osteoarthritis.

It can also reflect straightforward quadriceps weakness. A knee that hurts going up because the muscle cannot generate the force required is a different problem from one that hurts because the surface is worn, and it responds to different treatment.

Pain at the front, inside or outside

Pain at the front and around the kneecap on stairs supports a patellofemoral origin. Pain localised to the inner side points towards the medial compartment. Pain on the outer side is less common and raises the possibility of lateral compartment disease or iliotibial band irritation, particularly in active patients.

Giving way, catching or locking on stairs

A knee that gives way on stairs is either mechanically unstable or, far more commonly, inhibited by pain. Catching or true locking, where the knee will not straighten, suggests a mechanical block such as a meniscal tear or a loose body, and deserves specific assessment.

What makes it better

Strengthening is the first line for almost all of these, and the target is usually the quadriceps together with the hip abductors, since poor hip control changes how the kneecap tracks.

Technique matters more than patients expect. Leading with the stronger leg going up and the weaker leg going down, using a rail, and taking one step at a time reduces peak load significantly while strength is being rebuilt.

A detailed guide on stair-related knee pain is available here: https://www.mayurajcc.com/knee-pain-guides/knee-pain-while-climbing-stairs

When to have it examined

Book an assessment if stair pain has persisted beyond six weeks, if you have started avoiding stairs, if the knee gives way, catches or locks, or if there is swelling that recurs. A clinical examination and a weight-bearing X-ray usually establish the cause without any need for advanced imaging.