Why Does My Knee Hurt When Going Down Stairs?

The Biomechanics of Stair Descent

Walking down stairs places demands on the knee joint that are substantially different from — and in many respects more challenging than — level walking or stair ascent. During stair descent, the lower limb must perform an eccentric (lengthening) contraction of the quadriceps to control the rate of knee flexion as body weight is transferred from one step to the next. This controlled lowering under load is biomechanically demanding, requiring the quadriceps to generate force while actively lengthening — the most mechanically stressful form of muscle contraction.

The patellofemoral joint (the interface between the patella and the femoral groove) experiences significantly elevated compressive and shear forces during stair descent compared to level walking. Research has demonstrated that patellofemoral joint reaction forces reach approximately 3.3 times body weight during stair descent, compared to 0.5 times body weight during level walking and 7–8 times during deep squatting. This biomechanical reality explains why stair descent is one of the most consistently provocative activities across a wide range of knee conditions — not because the stairs are uniquely dangerous, but because they impose the precise loading pattern that places maximum demand on the structures most commonly affected by knee pathology.

Patellofemoral Pain Syndrome

Patellofemoral pain syndrome (PFPS) is the most common cause of anterior knee pain provoked by stair descent, affecting both active and sedentary individuals across all age groups. The pain arises from elevated pressure between the posterior patellar surface and the femoral trochlear groove, sensitising the richly innervated subchondral bone, synovium, and retinacular tissues around the patella.

The patella tracks through the femoral groove as the knee flexes and extends. When tracking is abnormal — driven by quadriceps imbalance, hip weakness, tight lateral retinaculum, or altered femoral mechanics — the pressure distribution across the patellofemoral contact area becomes uneven, creating focal areas of high stress. The characteristic pattern is diffuse anterior knee pain, worsening with prolonged sitting (the theatre sign), stair descent, squatting, and kneeling — all activities that increase patellofemoral contact pressure. Pain is typically reproduced by direct compression of the patella against the femoral groove with the knee slightly flexed.

Patellar Tendinopathy

Patellar tendinopathy (jumper's knee) presents with infrapatellar pain — localised to the inferior pole of the patella or the body of the patellar tendon — that is provoked by eccentric quadriceps loading. Stair descent is an archetypal aggravating activity because the eccentric quadriceps contraction transmits significant tensile force through the patellar tendon. The pain is typically well-localised and sharply provoked by direct palpation of the inferior patellar pole, distinguishing it clinically from the more diffuse peripatellar discomfort of PFPS. Patellar tendinopathy predominantly affects individuals who participate in repetitive jumping or running activities, though it can develop in less active individuals through unaccustomed sudden increases in activity.

Knee Osteoarthritis

In older adults, or in individuals with a history of significant knee injury, knee osteoarthritis is a common cause of stair-related pain. Cartilage degeneration — most often affecting the medial tibiofemoral compartment or the patellofemoral joint — alters the mechanics of load distribution within the joint. The combination of compressive and shear loading during stair descent concentrates stress on areas of reduced cartilage thickness, generating nociceptive input from subchondral bone and the highly innervated joint capsule and synovium. Osteoarthritic knee pain is typically accompanied by crepitus, morning stiffness lasting less than 30 minutes, joint line tenderness, and radiographic evidence of reduced joint space.

Meniscal Pathology

Meniscal tears — whether acute (from a rotational injury) or degenerative (in older individuals) — can produce stair-related pain through the mechanical loading of the meniscus during knee flexion under load. During stair descent, the menisci are compressed between the femoral condyles and the tibial plateau; a torn meniscal segment may be impinged during this loading, producing a sharp catching or locking sensation in addition to aching pain. Joint line tenderness (medial or lateral), pain with combined flexion and rotation (McMurray test), and a history of clicking or locking are clinical features that raise suspicion for meniscal involvement.

Biomechanical Contributors

Several biomechanical factors consistently contribute to stair-related knee pain regardless of the specific tissue source. Hip abductor weakness allows the pelvis to drop contralaterally during single-leg loading (the Trendelenburg phenomenon), causing the femur to adduct relative to the tibia and increasing lateral patellar tracking pressure. Quadriceps weakness reduces the ability to decelerate knee flexion during descent, increasing joint loading rates. Reduced ankle dorsiflexion forces compensatory knee flexion at an accelerated rate, elevating patellofemoral load. Foot pronation increases tibial internal rotation, altering patellofemoral tracking. Addressing these proximal and distal contributors is often as important as treating the knee itself.

Assessment and Management

Accurate identification of the tissue source drives appropriate management. Patellofemoral pain responds best to quadriceps and VMO strengthening, hip abductor loading, patellar taping (McConnell technique), and correction of lower limb biomechanics. Patellar tendinopathy requires progressive tendon loading (isometric and isotonic protocols) with careful load management. Meniscal pathology may require orthopaedic referral if mechanical symptoms are significant. Osteoarthritis is managed with progressive strengthening, joint mobilisation, and activity optimisation. In all cases, a clinician should assess the full kinetic chain rather than treating the knee in isolation.