Hip problems are one of the most commonly overlooked causes of knee pain. The two joints share nerve pathways and work together during every step you take, so when one goes wrong, the other often takes the hit. What makes this connection especially tricky is that the knee pain can feel completely real and local, leading both patients and clinicians to chase a knee diagnosis that was never the true problem. In a small but striking case series, every single patient had undergone some form of knee treatment before anyone thought to look at their hip.
Why a Bad Hip Sends Pain to Your Knee
The most direct explanation is nerve wiring. Your hip and knee joints share branches of the same nerves, particularly the femoral nerve and the obturator nerve. An anatomical study of cadaveric limbs found that in about 43% of cases, the femoral nerve sent articular branches to both the hip and the knee from the same nerve bundle. That shared wiring means the brain can misread signals from a deteriorating hip as coming from the knee instead.1Clinical Anatomy. Anatomical study of the articular branches innervated the hip and knee joint with reference to mechanism of referral pain in hip disease patients
Research on patients with confirmed hip disease backs this up. A clinical study found that the articular branches of the femoral and obturator nerves contributed to referred pain in the knee. Some sensory neurons in the spinal cord even have axons that split and extend to both the hip joint and the skin on the inner side of the knee. That dual innervation means a diseased hip can produce genuinely felt knee pain without anything being wrong with the knee at all.2PubMed Central. Clinical and Macroscopic Anatomical Study of Referred Pain in Patients with Hip Disease
The pain typically shows up on the front or inner side of the knee, which is exactly where the shared nerve branches terminate. That location is a useful clue, though not a guarantee. Pain on the outer side of the knee or behind it can also trace back to the hip through biomechanical pathways.
How Weak Hips Change the Way Your Knee Works
Beyond nerve signals, your hip directly controls the forces passing through your knee during movement. The hip abductor muscles, the ones that stabilize your pelvis when you stand on one leg, play a particularly important role. When they are weak, your knee absorbs more stress with every step, especially the medial (inner) compartment.
A large longitudinal study followed people over time and found that those with the weakest hip abductors had about 1.5 times the odds of developing worsened knee pain compared to those with the strongest. The effect was more pronounced in women, where the weakest group had 1.7 times the odds, and this association was especially strong in women who had good quadriceps strength, suggesting the hip weakness itself was the problem rather than general deconditioning.3PubMed Central. Hip Abductor Weakness and Its Association with New or Worsened Knee Pain: the MOST Study
Gait changes add another layer. When hip osteoarthritis limits your range of motion or causes pain, your walking pattern shifts. Research on people with hip osteoarthritis found that the affected hip increased gait variability, with the non-affected joints and pelvis compensating by moving more flexibly step to step.4PubMed Central. Effect of walking speed and severity of hip osteoarthritis on gait variability That compensation loads the knee differently than it was designed for. Over weeks and months, those altered forces can cause genuine knee tissue irritation on top of the referred pain from shared nerves. You end up with a knee that hurts for two reasons at once.
How Often the Knee Gets Blamed for a Hip Problem
This is where the hip-knee connection becomes genuinely costly. A case series of 21 adults whose knee pain was ultimately traced back to hip arthritis found that every patient had received some form of knee treatment before the true diagnosis was made. Eleven had received knee injections. Eleven had undergone knee surgery, including eight total knee replacements. Two of those knee replacement patients even had revision surgeries because their pain persisted, all before anyone identified the hip as the source. The diagnostic delay exceeded a year for 18 of the 21 patients.5Arthroplasty Today. Don’t forget the hip! Hip arthritis masquerading as knee pain
Those numbers are from a single clinic and represent the worst-case end of the spectrum, but the pattern is well recognized in orthopedics. Part of the problem is that hip arthritis can be surprisingly quiet in the hip itself. You might expect groin pain or stiffness when rotating your leg, but some people with severe hip degeneration feel nothing locally. Their only complaint is a stiff, aching knee. When an X-ray of that knee shows a little age-related wear, it is easy to attribute the pain to what the image shows, especially since X-ray findings and symptoms do not always match up. Not every joint that looks arthritic on film actually hurts, and not every painful joint looks abnormal on a scan.6PubMed. Diagnosis of osteoarthritis. Guidelines and current pitfalls.
Signs Your Knee Pain Might Really Be a Hip Problem
No single symptom is a dead giveaway, but several patterns should prompt you or your clinician to look above the knee:
- Groin or thigh pain alongside the knee pain: Even mild aching in the groin, front of the thigh, or buttock suggests the hip is involved, since hip-related referred pain follows the femoral and obturator nerve distributions down the thigh.
- Knee pain that does not match the knee exam: If standard knee tests come back mostly normal, the pain source may be elsewhere. Individual physical tests for meniscal tears or ligament injuries are rarely able to rule a specific knee disorder in or out on their own.7PubMed. Diagnostic validity of physical examination tests for common knee disorders: An overview of systematic reviews and meta-analysis A broadly normal composite knee exam should raise suspicion of referred pain.
- Reduced hip range of motion: Try rotating your hip inward while sitting or lying on your back. If that motion is limited or painful compared to the other side, the hip joint itself may be the culprit.
- Pain that persists despite knee treatment: If injections, physical therapy targeting the knee, or even knee surgery have not relieved your symptoms, the source may never have been in the knee.
- Pain with prolonged sitting or getting in and out of a car: These movements load the hip more than the knee, and pain during them points toward the hip as the source.
Hip screening during a physical exam is generally reliable for detecting whether a hip joint problem exists, even if individual provocative tests struggle to pinpoint the exact diagnosis within the hip. Hip impingement tests, labral tear tests, and osteoarthritis tests tend to be sensitive, meaning they catch most hip problems, but they are not great at distinguishing which hip problem you have.8PubMed Central. Evaluation of the hip: history and physical examination That is fine for the question at hand. You first need to know whether the hip is involved at all, and those screening tests do that job well.
Confirming the Hip as the Source
When clinical suspicion points to the hip but there is still uncertainty, a diagnostic injection into the hip joint can settle the question. A local anesthetic and steroid are injected directly into the hip under imaging guidance. If the knee pain goes away or drops substantially, the hip was the source.
This test is remarkably accurate. One study found that the relief of symptoms after a hip injection had a sensitivity above 90% and a specificity and positive predictive value of 100% for predicting who would benefit from hip treatment.9PubMed. Accuracy of diagnostic injection in differentiating source of atypical hip pain A separate study using ultrasound-guided injection reported about 92% accuracy in detecting intra-articular hip pathology in patients with atypical symptoms.10Arthroscopy. Ultrasound and Ultrasound‐Guided Hip Injection Have High Accuracy in the Diagnosis of Femoroacetabular Impingement With Atypical Symptoms In practical terms, if numbing the hip erases your knee pain, you have a clear answer.
Getting to that point can take time, though. A study of patients with symptomatic femoroacetabular impingement found that on average they saw four different health care providers, underwent more than three imaging tests, and tried three different treatments before finally getting the right diagnosis. The average time from symptom onset to diagnosis was about 32 months, and the excess cost over what a straightforward workup would have required averaged around $1,770 per patient.11Orthopaedic Journal of Sports Medicine. Time and Cost of Diagnosis for Symptomatic Femoroacetabular Impingement
When the Spine Gets Involved Too
The hip does not exist in isolation from the lower back, and this is where diagnosis gets even murkier. The lumbar spine, hip, and knee share overlapping pain distributions, and it is common for patients with both hip and spine pathology to present with a combination of low back, buttock, groin, thigh, and knee pain.12Journal of the American Academy of Orthopaedic Surgeons. Differentiating Hip Pathology From Lumbar Spine Pathology: Key Points of Evaluation and Management A lumbar disc herniation can send pain down the leg that mimics hip or knee pathology. A stiff hip can alter spinal mechanics and accelerate disc degeneration. The three regions form a chain, and problems in one link often affect the others.
For you as a patient, this means that a comprehensive evaluation should consider all three areas if your symptoms are not clearly localized. If your knee pain comes with any combination of back stiffness, thigh numbness, or groin aching, the answer may not be a single diagnosis but a combination of contributing factors from the hip, spine, or both.
Knee Pain in Children and Teens That Points to the Hip
This pattern is not limited to adults with arthritis. In children and adolescents, knee pain is a classic presentation of slipped capital femoral epiphysis (SCFE), a condition where the growth plate at the top of the thigh bone shifts out of position. The child feels pain in the knee rather than the hip because of the same referred-pain nerve pathways.
The consequences of missing this diagnosis are serious. A nationwide cohort study found that most children with SCFE were initially misdiagnosed, and those who presented with knee pain had a dramatically longer delay to diagnosis, with a median of 161 days compared to 20 days for those who presented with hip pain.13Archives of Disease in Childhood. A nationwide cohort study of slipped capital femoral epiphysis
Another study quantified the surgical consequences. Children in the knee-pain group waited an average of about 92 days longer to get hip imaging and about 82 days longer to reach surgery compared to those who came in complaining of hip pain. That delay translated into a nearly doubled risk of chondrolysis and osteoarthritis, and a higher likelihood of eventually needing hip reconstruction.14PubMed. Impact of Hip Versus Knee Pain as the Presenting Symptom of Slipped Capital Femoral Epiphysis on Time to Imaging, Surgery, and Complications The takeaway for parents is straightforward: if your child or teenager develops unexplained knee pain, especially with a limp or an inability to bear weight, insist on a hip and pelvis X-ray before accepting a knee-only workup.
What You Can Do About It
If your knee pain turns out to be driven by hip weakness or hip pathology, the treatment strategy shifts toward the hip. For many people, that starts with targeted exercise rather than surgery.
A systematic review of studies on hip muscle strengthening for knee osteoarthritis found clear benefits for knee pain, physical function, and hip muscle strength across the included trials.15Journal of Geriatric Physical Therapy. Hip Muscle Strengthening for Knee Osteoarthritis: A Systematic Review of Literature The logic is simple: stronger hip abductors better control your pelvis and thigh during walking, reducing the abnormal loads on the knee that were generating pain.
Home-based exercise programs are a practical option. A meta-analysis found that home exercise significantly improved pain, joint function, balance, and mobility in patients with knee or hip osteoarthritis compared to control groups.16BMC Musculoskeletal Disorders. Efficacy of home-based exercise in the treatment of pain and disability at the hip and knee in patients with osteoarthritis: a systematic review and meta-analysis Programs that combine hip and knee exercises tend to outperform those that focus on the knee alone. A randomized trial of community-dwelling older adults with early-stage knee osteoarthritis found that a program training both hip and knee muscles improved daily activities and general health outcomes significantly more than one targeting only quadriceps strength.17PubMed Central. Home exercise therapy to improve muscle strength and joint flexibility effectively treats pre-radiographic knee OA in community-dwelling elderly: a randomized controlled trial
A reasonable starting routine includes side-lying leg lifts, clamshells, standing hip abduction, and single-leg balance work. These target the gluteus medius and minimus, the primary stabilizers of the pelvis. If you have access to a resistance band, banded walks are another effective option. Most programs in the research literature ran for eight to twelve weeks before measuring outcomes, so consistency matters more than intensity in the early stages.
When conservative treatment is not enough, the next steps depend on the underlying hip diagnosis. Hip arthritis that has progressed to bone-on-bone may ultimately need a hip replacement, which, when the hip was the true pain generator all along, often resolves the knee pain as well. For younger patients with femoroacetabular impingement or labral tears, arthroscopic hip surgery can address the structural problem before it causes irreversible cartilage damage. The diagnostic injection described earlier is often used to confirm the hip as the pain source before committing to surgery.
When Both the Hip and Knee Are Genuinely Damaged
Sometimes it is not an either-or situation. You can have a bad hip and a bad knee at the same time, with each one contributing to the pain you feel. This is common in older adults with widespread osteoarthritis. The challenge is figuring out which joint is responsible for how much of the pain, because treating only one may leave you still hurting.
The diagnostic injection approach works here as well. Numbing the hip and tracking how much your knee pain changes gives a rough sense of proportion. If a hip injection eliminates 80% of your knee pain, the hip is the primary driver and should be addressed first. If it barely touches the knee pain, the knee itself needs attention. Orthopaedic surgeons sometimes stage treatments in these cases, addressing the worst offender first and reassessing afterward rather than operating on both simultaneously.
This complexity is exactly why the composite clinical examination, one that evaluates the hip, knee, and lumbar spine together rather than fixating on whatever the patient points to, is so valuable.18JAMA. Does This Patient Have a Torn Meniscus or Ligament of the Knee? Value of the Physical Examination The synthesis of multiple examination findings and a careful history outperforms any single test. If your clinician examines only the joint you are complaining about, it is worth asking them to check the hip as well, particularly if your treatment has stalled or your symptoms do not fit neatly into a knee-only explanation.