Runner's knee (patellofemoral pain): why must the hip be trained, not just the knee?

Short answer

Pain at the front of and around the kneecap (runner's knee / patellofemoral pain) is often viewed through a "knee only" lens; yet the strongest evidence is for strengthening the hip and knee muscles together. In some people, if the muscles that abduct and externally rotate the hip (the abductors and external rotators) are weak, the leg can turn inward while running (dynamic valgus) and the load on the kneecap can rise; however, this is not seen in every patient, and weakness may be as much a consequence of the pain as a cause. Even so, current guidelines recommend the hip + knee combination as first-line treatment, at a strong level of evidence.

The second strong tool: increasing running cadence (the number of steps per minute) by about 5–10 percent — because it shortens the stride and brings the foot closer to under the body, it reduces the load on the patellofemoral joint. The diagnosis is clinical; in runner's knee, routine MRI or X-ray is not needed.

Why the hip? "Knee pain, but the problem is higher up"

Patellofemoral pain relates to the load and irritation that occur as the kneecap moves in the groove of the thigh bone. The knee is not the only thing that determines this load: during running, the hip muscles that control the pelvis and thigh come into play with every step. If the posterolateral hip muscles (abductors + external rotators) are not strong enough, the leg turns inward (dynamic valgus), increasing the contact load and irritation of the kneecap. That is why modern treatment solves the pain "below" by strengthening the control "above."

What does the evidence say?

2018 International Consensus Statement (BJSM): recommends exercise therapy — especially the combination of hip + knee exercise; this combination should be preferred over knee exercise alone.
JOSPT 2019 Clinical Practice Guideline: recommends appropriately progressed hip and knee strengthening as first-line, with strong (level A) evidence.

What does the program look like?

The program is progressed individually; the general framework:

Hip: side-stepping/band work, single-leg bridge, hip abduction and external rotation exercises
Knee: progressive quadriceps strengthening within the pain-free range of motion (e.g. controlled squats, leg press)
Load management: temporarily regulating running volume, reversing the sudden increases that trigger pain
Benefit usually begins within weeks; the program is maintained for a few months.

Running cadence: a small adjustment, a real difference

Increasing your preferred number of steps per minute by about 5–10 percent (shorter, more frequent steps at the same speed) reduces the per-step load on the kneecap:

In musculoskeletal-model studies, increasing steps per minute by 10% reduced the peak force at the patellofemoral joint by about 14%.
In runners with kneecap pain, increasing steps per minute by 10% has been shown to produce a clinically significant improvement in pain and function at week 4 and month 3.
This range usually does not impair running economy; very large increases (>10%) can tire you unnecessarily. For this reason 5–10% is considered the "sweet spot."

Where do passive methods fit?

Insoles, taping, and similar methods are not the center of treatment; at most they can be an adjunct to exercise. Prefabricated insoles may be considered for short-term pain reduction; the evidence for taping is inconsistent (debated); electrotherapy and isolated joint mobilization are not recommended. Lasting results come from strength and running technique.

For clinicians

The diagnosis is clinical: retropatellar/peripatellar pain, provocation with squatting–stairs–prolonged sitting; iliotibial band syndrome, patellar tendinopathy, Hoffa's fat pad and intra-articular pathology are ruled out. Routine imaging provides no diagnostic value; imaging comes up only if there are warning findings ("red flags") suggesting serious pathology or an unexpected course. These include: a history of significant trauma, true joint locking or giving-way/instability, recurrent/marked intra-articular swelling (effusion), night pain, systemic symptoms such as fever–weight loss, suspicion of tumor or infection, and a picture that does not improve or worsens despite adequately applied treatment. In exercise, early-phase priority may be given to hip-targeted loading; however, the real evidence is for the superiority of the hip+knee combination. In the cadence (steps per minute) intervention, a target of 5–10% above the preferred value is aimed for; an auditory metronome/feedback helps.

Frequently asked questions

Isn't knee exercise alone enough for runner's knee?

Usually not. The strongest evidence is for working the hip (the abductor and external-rotator muscles) together with the knee; this combination gives better pain and function outcomes than knee exercise alone. The kneecap's load is largely controlled from above, at the hip.

Should I stop running completely?

Often no. Running volume is temporarily regulated and the sudden increases that trigger pain are reversed; but instead of total rest, gradual loading and strength work are preferred. The plan is adjusted to the individual.

How do I increase my cadence, and by how much?

Increasing your preferred number of steps per minute by about 5–10 percent (shorter, more frequent steps at the same speed) reduces the load on the kneecap. A metronome app or music at a fixed tempo helps. Very large increases are unnecessary; a small, sustainable adjustment is the goal.

Do I need an MRI for runner's knee?

Not routinely. Patellofemoral pain is recognized by clinical examination; MRI or X-ray does not help make the diagnosis. Imaging is considered only for the differential in situations such as trauma, locking/giving-way, an atypical course, or non-response to treatment.

Do insoles or a knee strap work?

These are not the center of treatment; as an adjunct to exercise they may provide limited benefit. A prefabricated insole may reduce pain in the short term in some patients; the evidence for taping is inconsistent. Lasting recovery comes from strength and technique.

I was told I have "cartilage softening (chondromalacia)" in my kneecap; can I not run?

A finding of chondromalacia alone does not forbid running. The management of patellofemoral pain is largely the same: hip + knee strengthening, load management, and cadence adjustment if needed. The decision is personalized to your complaint and examination.

Scientific references

Author's own work:
Yüksel O, Topçugil AB. Vitamin D levels of patients with patellofemoral pain syndrome. Turkish Journal of Sports Medicine 2019;54(2):83-8.
Other references:
Collins NJ, Barton CJ, van Middelkoop M ve ark. 2018 Consensus statement on exercise therapy and physical interventions to treat patellofemoral pain (5th International Patellofemoral Pain Research Retreat). Br J Sports Med 2018;52:1170-8.
Willy RW, Hoglund LT, Barton CJ ve ark. Patellofemoral Pain: Clinical Practice Guidelines (APTA). J Orthop Sports Phys Ther 2019;49(9):CPG1-95.
Crossley KM ve ark. 2016 Patellofemoral pain consensus statement (Manchester). Br J Sports Med 2016;50:839-43.
Lenhart RL, Thelen DG, Wille CM ve ark. Increasing running step rate reduces patellofemoral joint forces. Med Sci Sports Exerc 2014;46(3):557-64.
Bramah C, Preece SJ, Gill N, Herrington L. A 10% increase in step rate improves running kinematics and clinical outcomes in runners with patellofemoral pain at 4 weeks and 3 months. Am J Sports Med 2019;47(14):3406-13.
Nascimento LR ve ark. Trunk, hip and knee exercise programs for pain relief, functional performance and muscle strength in patellofemoral pain: systematic review and meta-analysis. 2021 (PubMed 34079359).
Author's own content: Runner's knee and running cadence Reel series.

This information is for general guidance only; it does not replace an examination, a diagnosis, or your physician's individual advice. Please consult a physician for your symptoms. About the author: Doç. Dr. Oğuz Yüksel — Academic Profile.