Why Do My Knees Hurt When Going Down Stairs?

The Mechanics: Why Down Is Harder Than Up

Climbing stairs is primarily a concentric movement for the quadriceps — the muscle shortens as it contracts to lift your body weight upward. Descending flips that demand: the quadriceps has to lengthen under load in a controlled way, called an eccentric contraction, to lower your body weight rather than letting gravity do it abruptly. Eccentric loading generates significantly more force through the joint, and a large share of that force passes directly through the kneecap and the cartilage on its underside.

Force-plate research has consistently found compressive forces on the patellofemoral joint are considerably higher during descent than ascent — sometimes several times higher depending on gait pattern. This single mechanical fact explains most of why "pain on the way down, not the way up" is such a recognizable complaint.

The Most Common Underlying Causes

Patellofemoral Pain Syndrome

One of the most frequent causes of stair-related knee pain, particularly in younger and middle-aged adults, including active people and runners. It develops when the kneecap doesn't track smoothly within its groove on the thigh bone, often due to weakness in the hip and glute muscles responsible for controlling thigh rotation. The result is uneven pressure across the back of the kneecap, most apparent under the higher loads of descending stairs.

Chondromalacia Patella

Closely related — this term refers specifically to softening or breakdown of cartilage on the underside of the kneecap, which can develop from repetitive stress or the same tracking issues described above left unaddressed.

Osteoarthritis

In people over roughly 50, osteoarthritis becomes an increasingly likely contributor, particularly with stiffness after rest, a grinding sensation (crepitus), and gradual worsening over months or years. Because the patellofemoral joint bears so much extra load during descent, even mild osteoarthritis there can produce pain disproportionately worse going down stairs.

IT Band Syndrome

The iliotibial band runs along the outside of the thigh from hip to knee. When tight or irritated, often from overuse or hip biomechanical issues, it can cause outer-knee pain frequently aggravated by the repetitive bending of stair descent.

Weak Hip and Glute Muscles

Extremely common and often overlooked as a root cause. The gluteus medius plays a major role in controlling thigh bone rotation during single-leg loading like stair descent. When weak — common in people who sit for long periods — the thigh tends to rotate inward more than it should, pulling the kneecap out of its ideal tracking path.

Pain Pattern	Possible Cause
Pain directly behind/around the kneecap, worse with prolonged sitting too	Patellofemoral pain syndrome / chondromalacia
Pain with grinding, stiffness after rest, gradual onset over years	Osteoarthritis
Pain on the outer knee, possibly with a snapping sensation	IT band syndrome
Pain that improves significantly with hip-strengthening exercises	Glute/hip weakness as a primary driver
Sudden onset after injury, with swelling or instability	Possible ligament/meniscus injury — needs prompt evaluation

When to See a Doctor or Physical Therapist

• Pain began suddenly, especially after a twisting injury, fall, or impact.
• The knee feels unstable, like it might "give way," especially under weight.
• There's visible swelling, warmth, or redness around the joint.
• You're unable to fully straighten or bend the knee.
• Pain persists or worsens despite several weeks of rest and basic home care.

A physical therapist can perform a movement assessment to identify the specific biomechanical pattern, since patellofemoral pain, IT band issues, and early osteoarthritis can look similar on the surface but respond best to different specific interventions.

What Actually Helps

Strengthen the Hips, Not Just the Knee

Side-lying leg raises, clamshells, and single-leg bridges, which target the gluteus medius, are often more effective than knee-focused exercises alone. Research on patellofemoral pain syndrome consistently shows hip-strengthening protocols produce meaningful pain reduction within weeks.

Build Quad Strength Through a Full, Controlled Range

Wall sits, slow controlled step-downs, and leg extensions within a pain-free range help the quadriceps better tolerate eccentric stair-descent demands. Controlled form matters more than speed.

Modify How You Take Stairs in the Meantime

Use a handrail for support, descend one step at a time, and slightly turn the body to reduce direct kneecap loading on painful days, while working on the root cause.

Don't Default to Complete Rest

Counterintuitively, full avoidance often worsens these conditions by allowing the contributing muscle weakness to progress. Most current physical therapy guidance favors gradual, progressive loading over rest, except after acute injury.

Body Weight and Joint Load

Forces moving through the knee during descent scale with body weight, so modest changes in load-bearing weight can meaningfully change joint stress per step. This isn't the right focus for everyone, particularly people already at a healthy weight whose pain is driven by muscular factors, but for some, especially with osteoarthritis, a doctor may reasonably raise it as one factor among several.

How Long Recovery Typically Takes

For patellofemoral pain syndrome and related muscular causes, most people following a consistent strengthening routine notice meaningful improvement within four to eight weeks. Osteoarthritis-related pain responds more gradually and is generally managed as an ongoing process, though strengthening still significantly reduces day-to-day symptoms.

Joint pain rarely travels alone — readers managing stair-related knee pain alongside other balance changes may find poor balance while walking shares some of the same hip-strength mechanics discussed above. And if morning stiffness is also part of the picture, our piece on joint pain in the fingers each morning covers a related but distinct inflammatory pattern.