Knee osteoarthritis can absolutely contribute to hip pain, though the connection is less straightforward than bone rubbing on bone in a single joint. The pathways linking a worn-out knee to a sore hip include altered walking mechanics, shared nerve wiring, progressive muscle weakness, and a postural chain reaction that researchers now call “knee-hip-spine syndrome.” Understanding which of these pathways is driving your hip symptoms matters, because the fix is different for each one.
How a Bad Knee Changes the Way You Walk
When your knee hurts, you instinctively shift how you move. You might shorten your stride, keep the knee slightly bent, or lean your trunk to one side. These adjustments feel minor in the moment, but they redistribute forces across every joint in the leg. A study comparing people with knee osteoarthritis to healthy controls found that hip range of motion was significantly reduced in the osteoarthritis group, and the restriction tracked closely with how limited the knee’s own motion had become.1PubMed Central. Effects of Knee Osteoarthritis on Hip and Ankle Gait Mechanics The hip wasn’t arthritic in these patients; it was being held back by the knee problem downstream.
Research on people who developed knee osteoarthritis after an anterior cruciate ligament injury paints a similar picture. Those who went on to develop knee OA walked with smaller hip angles and lower hip moments on the injured side compared to those whose knees stayed healthy, and these differences appeared both before and after surgical reconstruction of the ligament.2PubMed Central. Hip joint biomechanics in those with and without post-traumatic knee osteoarthritis after anterior cruciate ligament injury The knee problem was quietly reshaping how the hip worked, even though no one was complaining about their hip at the time.
The extra loading doesn’t just vanish. People with knee osteoarthritis place significantly more force on the hip on the same side during stair climbing and other daily activities compared to people without knee OA.3PubMed. The biomechanical fingerprint of hip and knee osteoarthritis patients during activities of daily living That increased hip load, repeated thousands of times a day, can generate pain on its own, even in a hip that looks fine on X-ray.
Shared Nerve Wiring and Referred Pain
The hip and the knee are served by overlapping branches of the same major nerves, particularly the femoral nerve and the obturator nerve. This shared wiring is why a hip problem can send pain down to the knee, a well-known clinical phenomenon. But the same anatomy works in reverse: irritation at the knee can produce signals that the brain interprets as coming from the hip region.
An anatomical study examining cadaver specimens found that in roughly 43 percent of limbs, the femoral nerve supplied branches to both the hip and knee joints, and these branches originated from the same nerve bundle.4PubMed. Anatomical study of the articular branches innervated the hip and knee joint with reference to mechanism of referral pain in hip joint disease patients In practical terms, the brain receives signals from both joints traveling along the same wires and sometimes gets the address wrong. The same research group confirmed the clinical side of this by examining patients with hip disease who felt pain at the knee, tracing the mechanism to shared articular branches of the femoral and obturator nerves.5PubMed Central. Original Investigation and Macroscopic Anatomical Study of Referred Pain in Patients with Hip Disease
Most of the referred-pain literature focuses on hip problems sending pain to the knee, not the other way around. That imbalance doesn’t mean knee-to-hip referral is impossible; it means hip-to-knee referral is more clinically recognized. If you have knee osteoarthritis and new hip pain, one of the first questions a good clinician will consider is whether your hip is actually the primary problem sending pain to the knee, rather than the other way around. The prevalence of knee pain that actually originates from hip pathology has been estimated at anywhere from 2 to 29 percent, depending on the study population.6PubMed Central. Don’t forget the hip! Hip arthritis masquerading as knee pain That wide range reflects how often the source of pain gets misidentified.
Central Sensitization Makes Everything Louder
Beyond the mechanical and nerve-wiring explanations, there is a third pathway: changes in how the central nervous system processes pain. In people with osteoarthritis, the spinal cord and brain can become hypersensitive to pain signals over time. This phenomenon means pain from a single arthritic knee can get amplified and spread, so that normally painless input from the hip, low back, or opposite leg starts registering as painful too.7Oxford Academic (Physical Therapy). Pain Treatment for Patients With Osteoarthritis and Central Sensitization
Central sensitization helps explain why some people with relatively mild knee OA on imaging report widespread pain in multiple joints, while others with severe X-ray changes feel only localized discomfort. The amount of structural damage and the amount of pain are not always proportional. A nationwide Korean study, for example, found that radiographic hip osteoarthritis was rare in middle-aged and older adults, and even when it was present, hip pain was infrequent.8PubMed. Low prevalence of radiographic hip osteoarthritis and its discordance with hip pain: A nationwide study in Korea The mismatch between what X-rays show and what patients feel underscores the importance of central pain processing, not just local joint damage.
Hip Muscle Weakness in People With Knee Osteoarthritis
One of the more consistent findings in knee OA research is that the hip muscles weaken, even when the hip joint itself seems healthy. A systematic review with meta-analysis found moderate-quality evidence that people with knee OA have weaker hip abductor muscles (the muscles that stabilize your pelvis when you stand on one leg), with deficits ranging from about 7 to 24 percent compared to people without knee OA.9PubMed. Hip Strength Deficits in People With Symptomatic Knee Osteoarthritis: A Systematic Review With Meta-analysis
Individual studies suggest the weakness is even broader than that. One study found that people with medial knee OA showed significant strength deficits across all hip muscle groups tested, ranging from about 16 percent for hip extensors up to 27 percent for hip external rotators, after adjusting for sex and age.10PubMed. Hip muscle weakness in individuals with medial knee osteoarthritis Weak hip muscles can cause pain directly, through overuse of the tendons that attach around the greater trochanter (the bony bump on the outside of the hip), through pelvic instability during walking, or through increased compressive loading on the hip joint itself.
There’s a behavioral feedback loop at work here too. People with knee OA who have a high fear of movement walk with even worse hip mechanics. Research on fear of movement in knee OA patients found that those with greater fear had poorer pelvic and hip stability during walking, linked to weaker hip abductor muscles.11PubMed Central. The effect of fear of movement on gait characteristics in patients with knee osteoarthritis Guarding against knee pain by moving less leads to more hip weakness, which leads to more hip pain, which can lead to even more guarding. Breaking that cycle usually requires targeted exercise rather than rest.
Greater Trochanteric Pain Syndrome
Greater trochanteric pain syndrome, often called GTPS, is a common cause of outer hip pain that is strongly linked to knee osteoarthritis. GTPS involves pain and tenderness around the greater trochanter, usually from irritation of the tendons and bursae of the gluteal muscles. It is frequently misattributed to “bursitis” alone, but the tendon component is usually the more important driver.
A large epidemiological study found that ipsilateral knee OA (knee OA on the same side as the hip pain) was one of the strongest predictors of GTPS, with roughly three and a half times the odds of developing the condition compared to people without knee OA. Even knee OA on the opposite side increased the odds by about 75 percent.12PubMed Central. Greater trochanteric pain syndrome: epidemiology and associated factors The authors concluded that altered lower-limb biomechanics from knee OA were a likely explanation.
A more recent study confirmed these findings and added that the severity of knee OA matters. Patients with more advanced knee OA, as measured by radiographic grading, and those with bowlegged alignment (genu varum) were more likely to develop GTPS.13Physikalische Medizin, Rehabilitationsmedizin, Kurortmedizin. Investigation of the Frequency of Greater Trochanteric Pain Syndrome in Patients with Knee Osteoarthritis The pattern makes mechanical sense: a bowlegged knee changes how force passes through the hip, overloading the gluteal tendons. If your knee OA is producing pain on the outside of the hip that worsens when you lie on that side or climb stairs, GTPS is a strong possibility.
The Knee-Hip-Spine Chain Reaction
Clinicians increasingly recognize that the knee, hip, and spine function as a linked postural chain. When the knee is stiff or painful, the whole chain compensates. The body may lose its normal lumbar curve, tilt the pelvis backward, and hold the hip in an unusual position. These postural shifts are collectively referred to as knee-hip-spine syndrome.14PubMed Central. Knee-Hip-Spine Syndrome: Improvement in Preoperative Abnormal Posture following Total Knee Arthroplasty
The concept matters because it means hip pain that develops alongside knee osteoarthritis may not be a coincidence and may not mean the hip itself is degenerating. It may be a postural consequence of the knee problem. Supporting this, research has shown that abnormal posture linked to knee OA can improve after total knee replacement, suggesting the hip and spine symptoms were being driven by the knee all along.15PubMed. Preoperative Abnormal Posture Improves After Total Knee Arthroplasty: Knee-Hip-Spine Syndrome For patients weighing surgical options, understanding this chain can change the conversation about which joint to address first.
Sorting Out Where the Pain Is Actually Coming From
The overlap between hip and knee pain creates a genuine diagnostic puzzle, and clinicians miss it more often than you might expect. The challenge runs in both directions: hip pathology can masquerade as knee pain, and knee OA can produce symptoms that feel like they’re coming from the hip. When imaging doesn’t match the symptom picture, sorting out the true source requires more detective work.
One tool clinicians use is a diagnostic injection of local anesthetic into the hip joint. If the pain disappears after the injection, the hip is likely the source. One study reported that this test had very high sensitivity and specificity for predicting which patients would benefit from hip replacement surgery.16PubMed. Accuracy of diagnostic injection in differentiating source of atypical hip pain A meta-analysis of case series examining the same question also found high sensitivity and specificity, though the authors cautioned that the quality of available studies was low and no firm clinical recommendation could yet be made.17PubMed. Is anesthetic hip joint injection useful in diagnosing hip osteoarthritis? A meta-analysis of case series
Imaging alone doesn’t resolve the ambiguity. One study found that symptomatic osteoarthritis (structural changes on X-ray plus actual joint pain) was present in about 26 percent of knees but only 7 percent of hips, and for the hip there was no clear relationship between how bad the X-ray looked and how much pain or disability the person experienced.18PubMed. Knee and hip radiographic osteoarthritis features: differences on pain, function and quality of life An X-ray showing some hip arthritis does not mean the hip is the pain source; equally, a clean hip X-ray does not rule out the hip as the problem. This disconnect is why the clinical exam and sometimes a diagnostic injection carry more weight than imaging alone.
Hip Strengthening as a Treatment for Knee Pain
If knee OA weakens the hip muscles and that weakness contributes to both knee and hip symptoms, the logical treatment question is whether strengthening the hip helps. The evidence says yes for knee pain, and the effect appears promptly. A randomized controlled trial found that adding hip abductor exercises to a standard knee OA program led to faster improvements in pain, daily function, and knee-related quality of life, with the hip group reaching meaningful improvement about two to four weeks sooner than the group doing knee exercises alone.19PubMed Central. Effect of hip abductor strengthening exercises in knee osteoarthritis: a randomized controlled trial
Another clinical trial compared a dedicated hip strengthening program to a standard leg strengthening program for knee OA. Both groups improved in pain, function, and quality of life, with no significant difference between the two approaches.20Clinical Journal of Sport Medicine. Efficacy of Hip Strengthening Exercises Compared With Leg Strengthening Exercises on Knee Pain, Function, and Quality of Life in Patients With Knee Osteoarthritis That’s actually good news: it means hip exercises are a viable alternative for people who find it too painful to load the knee directly, and they work just as well for knee symptoms.
A home-based hip abductor program also produced a notable result: participants improved their hip strength and functional performance (getting up from a chair, for instance) and reported less knee pain, though the program didn’t change the knee adduction moment, the mechanical load most associated with medial knee OA progression.21Physical Therapy. Effect of a Home Program of Hip Abductor Exercises on Knee Joint Loading, Strength, Function, and Pain in People With Knee Osteoarthritis The takeaway is that hip strengthening reliably reduces pain and improves function, even if the underlying mechanical load on the knee doesn’t obviously change. The mechanism may relate to improved pelvic stability, reduced guarding, or pain modulation through exercise rather than a pure biomechanical correction.
Do Orthotics for the Knee Affect the Hip?
Lateral wedge insoles are sometimes prescribed for medial knee OA to shift load away from the inner knee. A reasonable concern is whether that shifted load might cause problems at the hip. The evidence is reassuring on both counts. One study examining the immediate biomechanical effects of lateral wedge orthoses found no changes in hip mechanics at all, suggesting the intervention’s effects stay local to the knee and rearfoot.22PubMed. Effect of laterally wedged foot orthoses on rearfoot and hip mechanics in patients with medial knee osteoarthritis
A longer-term study tracked hip joint space width over three years in people wearing mechanically active wedge orthotics versus a placebo insert. The hips did show gradual joint space narrowing over time, as you would expect in this age group, but there was no difference between the wedge group and the placebo group. The rate of narrowing matched what is typically seen in hip OA anyway.23PubMed Central. Long-Term Effects of Lateral Wedge Orthotics on Hip and Ankle Joint Space Widths If you’re using wedge insoles for your knee and wondering whether they’re quietly damaging your hip, the available data suggests they are not.
Leg Length Discrepancy After Knee Surgery
Total knee replacement is a common endpoint for severe knee OA, and surgery introduces a potential new source of hip pain: leg length discrepancy. Replacing the knee can change the effective length of the leg by altering the joint line, and a mismatch of more than about 15 millimeters between legs has been associated with worse functional outcomes, including difficulty with stairs.24PubMed Central. The effect of leg length discrepancy on clinical outcome after TKA and identification of possible risk factors A longer leg on one side tilts the pelvis, overloads the hip abductors, and can trigger or worsen trochanteric pain on either side. If hip pain develops or worsens after a knee replacement, leg length is one of the first things worth checking.
Interestingly, a systematic review examining whether adding hip strengthening to rehabilitation after total knee replacement improves pain found no statistically significant benefit for pain reduction specifically.25PubMed Central. Hip Strengthening After Total Knee Arthroplasty: A Meta-analysis and Systematic Review That contrasts with the clear benefits of hip strengthening before surgery and in non-surgical knee OA management. The likely explanation is that by replacing the knee, the primary driver of the gait compensation and hip overloading has been removed, so rehabbing the hip on top of standard rehab doesn’t add as much. It’s a useful reminder that treating the root cause, the arthritic knee, can resolve the downstream hip issues without directly targeting them.