Knee and hip pain frequently show up together because the two joints are structurally, mechanically, and neurologically linked. They share overlapping nerve supply, connect through muscles and tendons that span both joints, and depend on each other for smooth movement. A problem in one joint can directly cause or worsen pain in the other, and several systemic conditions affect both at the same time. Understanding which connection is driving your pain matters, because the treatment that helps depends entirely on whether the real source is in the hip, the knee, the spine, or somewhere else along the chain.
When a Hip Problem Shows Up as Knee Pain
One of the most common and most overlooked explanations for combined hip and knee pain is referred pain, where a problem in the hip sends pain signals that the brain interprets as coming from the knee. This happens because both joints share nerve fibers. An anatomical study found that in roughly 43% of dissected limbs, the femoral nerve sent branches to both the hip and the knee from the same nerve bundle, providing a direct pathway for the brain to “mislocate” hip pain to the front of the knee.1PubMed. Anatomical study of the articular branches innervated the hip and knee joint with reference to mechanism of referral pain in hip joint disease patients The posterior fibers of the knee also receive input from the obturator nerve, which supplies the hip, adding another overlap in wiring.2PubMed Central. Don’t forget the hip! Hip arthritis masquerading as knee pain
This referral pattern catches both patients and clinicians off guard. A case report described a man with avascular necrosis of the hip whose primary complaint was a painful right knee; imaging of the knee was unremarkable, and only after X-rays of the hip revealed severe femoral head damage did the actual source become clear. In children, the same phenomenon occurs: a seven-year-old boy presented with recurring left knee pain, and every test on the knee came back normal before hip imaging revealed a cortical defect on the femoral head and increased joint fluid. These cases illustrate a practical rule: if knee pain does not have an obvious knee explanation, the hip should be investigated.
The Kinetic Chain and Compensatory Walking
Your hip and knee are not just neighbors; they are mechanical partners. Every step you take requires them to work in coordinated sequence, absorbing and transferring force from the ground up through the leg. When one joint is stiff or painful, the other compensates. A study of people with knee osteoarthritis found that their altered walking patterns increased the loading rate not only at the affected knee but also at the ankle and hip, suggesting that the mechanical ripple effects of one damaged joint can accelerate wear on the others.3PubMed. Secondary gait changes in patients with medial compartment knee osteoarthritis: increased load at the ankle, knee, and hip during walking
Foot mechanics also play into this. When the feet overpronate (roll inward excessively), the effect travels upward: the shin rotates inward, the hip rotates inward, and the pelvis tilts forward, all to a statistically significant degree.4PubMed. Effect of feet hyperpronation on pelvic alignment in a standing position These alignment shifts change how force is distributed through the hip and knee, which can mean pain in both joints even when neither joint has obvious structural damage on imaging.
Weak Hip Muscles and Knee Stress
The gluteal muscles, particularly the gluteus medius on the outside of the hip, have an outsized influence on knee alignment. When the gluteus medius is weak, the thigh tends to collapse inward during activities like walking, climbing stairs, or jumping, a movement pattern called dynamic knee valgus. This inward buckling loads the knee unevenly and stresses its ligaments and cartilage. Research has confirmed that reduced gluteus medius force predicts increased knee abduction moment, the sideways torque that strains the inside of the knee.5PubMed Central. The influence of gluteal muscle strength deficits on dynamic knee valgus: a scoping review
A person with this pattern often feels aching in the outer hip from the fatigued muscles and pain around or behind the kneecap from the abnormal tracking. The hip pain feels like a muscle problem; the knee pain feels like a joint problem. They seem unrelated, but they share one root cause. This is also the mechanism behind iliotibial band syndrome, where the thick band of tissue running from the hip to just below the knee becomes irritated, producing pain at both endpoints.
Osteoarthritis Affecting Both Joints
Osteoarthritis, the gradual breakdown of cartilage, is the single most common reason people develop chronic pain in both the hip and the knee. The two joints degenerate through somewhat different pathways, but they often do so in parallel. A large UK Biobank analysis of nearly 60,000 people found that radiographic hip osteoarthritis occurred in about 7 to 8% and knee osteoarthritis in about 6 to 7% of participants, and that the more joints affected, the stronger the association with concurrent pain, with people who had osteoarthritis in four joints being over four times as likely to report pain.6PubMed. A comprehensive descriptive analysis of hip and knee radiographic osteoarthritis in the UK Biobank in relation to joint pain, joint site interrelationships, obesity, race and deprivation
That same study highlighted an interesting divergence: body mass index was much more strongly associated with knee osteoarthritis than hip osteoarthritis, while greater height seemed to increase hip osteoarthritis risk and actually appear protective for knee osteoarthritis.6PubMed. A comprehensive descriptive analysis of hip and knee radiographic osteoarthritis in the UK Biobank in relation to joint pain, joint site interrelationships, obesity, race and deprivation This means the risk profile for each joint is different, but the overlap is large enough that having osteoarthritis in one joint makes worsening in the other more likely. Research found that about one in eight people with osteoarthritis in both the hip and knee experienced combined worsening in both joints, and that women were nearly twice as likely as men to fall into this combined worsening group.7Osteoarthritis and Cartilage Open. Is multi-joint hip and knee osteoarthritis more than the sum of its parts?
Obesity accelerates the process through more than simple mechanical overload. The systemic inflammation that accompanies excess body fat raises levels of inflammatory signaling molecules and enzymes that directly break down cartilage, meaning the damage is both weight-driven and chemically driven.8PubMed Central. Obesity-Related Knee Osteoarthritis-Current Concepts
Leg Length Differences
A subtle mismatch in leg lengths, even as small as a centimeter or two, can produce hip pain on one side and knee pain on the other, or both on the same side. Leg length discrepancy causes uneven loading of the hip, knee, and lower spine.9PubMed Central. Leg length discrepancy and osteoarthritis in the knee, hip and lumbar spine A discrepancy of two centimeters or more creates measurable biomechanical changes in hip joint load on both sides, with the larger effects seen on the shorter side.10PubMed Central. Hip joint load in relation to leg length discrepancy
Even mild discrepancies affect the entire lower limb chain. In people with knee osteoarthritis, the shorter leg showed increased knee loading during the weight-bearing phase of walking, which helps explain why a seemingly minor difference in leg length can accelerate cartilage breakdown at the knee.11PubMed. Mild leg length discrepancy affects lower limbs, pelvis and trunk biomechanics of individuals with knee osteoarthritis during gait Many people have a slight leg length difference and never know it, attributing the resulting hip or knee ache to aging or overuse rather than a correctable alignment issue.
Hip-Spine Syndrome
Sometimes the pain in the hip and knee is not coming from either joint at all. Hip-spine syndrome describes a situation where spinal problems, particularly lumbar spinal stenosis or disc disease, coexist with hip arthritis, and the symptoms overlap so completely that pinning down the source becomes genuinely difficult. A patient might have groin and buttock pain from sciatica combined with hip stiffness from arthritis, with pain radiating to the knee from both causes simultaneously.2PubMed Central. Don’t forget the hip! Hip arthritis masquerading as knee pain This syndrome has real clinical consequences. Some patients continue to have hip and thigh pain after hip replacement surgery because their lumbar spine was contributing to the pain all along.
Guided injections of local anesthetic into the hip joint can help sort this out. In studies of patients with diagnostically murky pain, ultrasound- or fluoroscopy-guided hip injections have shown sensitivity above 90% and specificity above 95% for identifying the hip as the pain source.12PubMed. Hip-Spine Syndrome: The Diagnostic Utility of Guided Intra-articular Hip Injections If the injection eliminates the pain temporarily, the hip is likely the main generator. If it does not, the spine or another source deserves closer investigation.13PubMed. Accuracy of diagnostic injection in differentiating source of atypical hip pain
Inflammatory and Crystal-Related Arthritis
Rheumatoid arthritis and other inflammatory joint diseases do not limit themselves to the small joints of the hands and feet. The hip is affected in roughly 15 to 28% of all people with rheumatoid arthritis, and as the disease progresses, large joints become involved at increasing rates.14PubMed. Rheumatoid Arthritis of the Hip Longitudinal data show that the odds of losing range of motion in large joints increase by around 7 to 13% per year from year three to year fourteen of the disease.15PubMed Central. Large joints are progressively involved in rheumatoid arthritis irrespective of rheumatoid factor status-results from the early rheumatoid arthritis study The knee is frequently among the first large joints affected, and the hip follows over time, so simultaneous hip and knee pain in someone with rheumatoid arthritis is common rather than coincidental.
Crystal arthropathies can also hit both joints. Calcium pyrophosphate deposition disease (often called pseudogout) most commonly affects the knees but also involves the hips, wrists, and other joints, presenting with pain, tenderness, and swelling that can mimic infection or rheumatoid flares. Because pseudogout episodes can affect different joints at different times, someone may experience acute knee inflammation and lingering hip discomfort in the same period.
Nerve Entrapment Around the Hip
Several major nerves pass through or near the hip on their way to the thigh, knee, and lower leg. When these nerves become compressed or irritated, the resulting pain can radiate well beyond the hip itself. The sciatic, obturator, femoral, and lateral femoral cutaneous nerves are all vulnerable to entrapment around the hip, and each produces a different pain pattern that can easily be mistaken for a joint problem.16PubMed Central. NERVE ENTRAPMENT IN THE HIP REGION: CURRENT CONCEPTS REVIEW
Obturator nerve entrapment, for example, tends to cause groin and inner-thigh pain that radiates toward the knee, closely mimicking hip arthritis. Femoral nerve compression produces anterior thigh and knee pain. The clue is often that the pain does not follow a typical joint pattern: it may burn, tingle, or worsen with specific positions rather than with weight-bearing. An evaluation that includes nerve-specific testing can prevent months of treating the wrong structure.
Soft Tissue Tears in the Hip and Knee
Both the hip and knee contain ring-shaped cartilage structures that deepen the joint socket and cushion the bones. In the hip, this is the labrum; in the knee, the meniscus. Degenerative tears in these structures become increasingly common with age and can produce deep, aching pain that is hard to localize. A person with a hip labral tear may feel pain deep in the groin or on the side of the hip, while a meniscal tear in the knee produces catching, locking, or swelling. When both structures are wearing out at the same time, the combined pain can feel like one vague lower-extremity problem rather than two distinct ones.
The treatment debate for degenerative tears is ongoing. Physical therapy strengthens the muscles around the joint and often improves function, but it does not repair the torn tissue itself. For some patients, particularly older adults with symptomatic internal derangement that does not respond to conservative care, a minimally invasive surgical procedure can improve symptoms.17PubMed. Knee Meniscus and Hip Labrum: The Dilemma of Degenerative Tears
When the Pain System Itself Becomes the Problem
Chronic pain in the hip or knee can, over time, change how the nervous system processes pain signals. This phenomenon, called central sensitization, means that the spinal cord and brain begin amplifying pain signals, producing heightened sensitivity not only at the affected joint but also at distant, uninjured body sites. A study of people with osteoarthritic knee pain found increased pressure sensitivity at the knee, at surrounding tissues, and even at painless remote regions, consistent with central sensitization. Critically, the degree of sensitization did not correlate with the severity of structural damage on imaging.18PubMed Central. Central sensitization in osteoarthritic knee pain: A cross-sectional study
This helps explain a frustrating scenario many people encounter: imaging shows mild arthritis in the knee, yet the pain is severe and seems to have spread to the hip or thigh. The structural findings do not match the pain experience because the nervous system has turned up its volume. This distinction matters for treatment. Pain driven primarily by central sensitization responds better to approaches that target the nervous system, such as graded exercise, sleep improvement, and certain medications, than to joint injections or surgery aimed at the original structure.
Hormonal Changes and Joint Pain After Menopause
Many women notice that hip and knee pain begins or worsens around menopause, and the connection is not just coincidental. Estrogen appears to play a protective role in maintaining cartilage. A systematic review and meta-analysis found that estrogen deficiency is associated with cartilage degeneration, with strong supportive evidence from animal studies showing significantly greater cartilage breakdown when estrogen was removed.19PubMed Central. Estrogen Deficiency in Menopause: A Major Contributor to Cartilage Degeneration and Osteoarthritis: A Systematic Review and Meta-Analysis Pooled human data showed trends in the same direction, though the results did not reach statistical significance, suggesting the effect in humans may be real but more gradual than animal models imply.
Combined with the finding that women are nearly twice as likely as men to experience simultaneous worsening of hip and knee osteoarthritis, the hormonal picture adds an important layer.7Osteoarthritis and Cartilage Open. Is multi-joint hip and knee osteoarthritis more than the sum of its parts? Women in their late forties and fifties who develop new or worsening pain in both joints should consider the hormonal transition as a contributing factor worth discussing with a clinician.
Strengthening the Hip to Protect the Knee
Because the hip and knee are so mechanically interdependent, rehabilitation programs that target one often benefit the other. A systematic review of studies on hip muscle strengthening for knee osteoarthritis found clear benefits for knee pain, physical function, and hip muscle strength.20PubMed. Hip Muscle Strengthening for Knee Osteoarthritis: A Systematic Review of Literature Exercises focused on the hip abductors and external rotators (the muscles that control the thigh’s tendency to collapse inward) reduce the strain the knee absorbs during everyday movement.
There is an important caveat, though: the same review found that hip strengthening did not improve biomechanical measures like dynamic alignment or the valgus moment at the knee.20PubMed. Hip Muscle Strengthening for Knee Osteoarthritis: A Systematic Review of Literature In practical terms, this means the pain relief from hip exercises is real and meaningful, but the underlying mechanical pattern at the knee does not fully correct itself with strength alone. For some people, orthotics, gait retraining, or other interventions are needed alongside strengthening to address the alignment piece. Still, hip-focused exercise is one of the most accessible and evidence-supported starting points for anyone dealing with simultaneous hip and knee pain, especially when weakness or deconditioning is part of the picture.