Tendonitis after hip replacement most often develops because the new implant changes the mechanical relationship between the surrounding tendons and bone, creating friction, irritation, or abnormal loading that did not exist before surgery. The most frequently identified culprit is the iliopsoas tendon rubbing against the front edge of the acetabular cup, but abductor tendons on the outer hip, the rectus femoris, and other soft tissues can also become inflamed depending on the surgical approach, implant positioning, and the patient’s own anatomy. The causes overlap and interact, which is part of why persistent pain after an otherwise successful hip replacement can be so frustrating to pin down.
Iliopsoas Impingement Is the Most Common Tendon Problem
The iliopsoas is the primary hip flexor, a thick muscle-tendon unit that runs from the lower spine and pelvis down to the inside of the upper thighbone. After a total hip replacement, this tendon passes directly over the front of the new socket component. If that component sticks out even slightly beyond the natural rim of the hip socket, the tendon can catch or scrape against it with every step, every time you lift your knee to get into a car, and every time you climb stairs. This mechanical irritation accounts for roughly two to six percent of persistent pain after hip replacement.1PubMed. Threshold for anterior acetabular component overhang correlated with symptomatic iliopsoas impingement after total hip arthroplasty
The irritation is not always caused by a dramatically mispositioned implant. It can result from anterior acetabular component overhang, retained cement behind the cup, screws used to fix the cup in place, or other prosthetic hardware that creates a bump the tendon has to slide over.2PubMed Central. Iliopsoas Impingement After Total Hip Arthroplasty: A Review of Diagnosis and Management Even small amounts of overhang matter. One study using radar-chart analysis of cup positioning found that overhang concentrated in the anterosuperior region, around the 1:30 clock-face position, was a significant risk factor for iliopsoas impingement.3Journal of Joint Surgery and Research. Is anterosuperior cup overhang a risk factor for iliopsoas impingement after total hip arthroplasty? A radar chart analysis Another study found that patients who failed to improve with conservative treatment had significantly greater cup overhang on CT scans in both the axial and sagittal planes.4PubMed Central. Iliopsoas impingement after total hip arthroplasty: Does the CT-scan have any role? Our Algorithm proposal
The classic symptom is groin pain that worsens specifically when you flex your hip against resistance, like lifting your thigh while sitting or stepping up onto something. Ultrasound imaging can identify the friction directly, showing the tendon catching against the cup or adjacent hardware.5PubMed. Ultrasound diagnosis of anterior iliopsoas impingement in total hip replacement In clinical practice, doctors often confirm the diagnosis by injecting a local anesthetic and corticosteroid around the tendon; if groin pain resolves immediately, the iliopsoas is almost certainly the source.6PubMed Central. Iliopsoas tendonitis following total hip replacement in highly dysplastic hips: a retrospective study
Abductor Tendon Damage and the Surgical Approach
The hip abductor muscles, mainly gluteus medius and gluteus minimus, attach to the greater trochanter on the outer side of the thighbone. They are essential for stabilizing your pelvis when you stand on one leg, which you do with every single step. Tendonitis or tearing of these tendons after hip replacement is one of the leading causes of lateral hip pain, and the surgical approach used to implant the prosthesis has a lot to do with it.
In a transgluteal approach, the surgeon detaches part of the gluteus medius and minimus muscles from the greater trochanter to access the joint, then reattaches them at the end of the procedure. If the reattachment does not heal fully, or if the muscles pull away from the bone during recovery, the result can be persistent pain, weak abduction, and sometimes instability.7PubMed. Repair of gluteus medius muscle avulsion following transgluteal hip replacement By contrast, a direct anterior approach avoids cutting through these muscles altogether. MRI comparisons have found that detachment, partial tears, tendonitis, bursal fluid around the trochanter, and fatty wasting of the gluteus medius and minimus were all significantly less common with the anterior approach.8PubMed. Soft-tissue changes in hip abductor muscles and tendons after total hip replacement: comparison between the direct anterior and the transgluteal approaches
An MRI study comparing symptomatic and asymptomatic patients after hip replacement illustrates how clearly abductor tendon damage correlates with pain. Tendon defects were uncommon in pain-free patients but significantly more frequent in those reporting symptoms. For instance, gluteus minimus defects appeared in only two asymptomatic patients but in 22 symptomatic ones, and lateral gluteus medius defects were found in four asymptomatic versus 24 symptomatic patients.9PubMed. Abductor tendons and muscles assessed at MR imaging after total hip arthroplasty in asymptomatic and symptomatic patients Those numbers make a strong case that if you have outer hip pain after a replacement, a damaged abductor tendon is high on the list of suspects.
How Implant Positioning and Biomechanical Restoration Affect Tendon Health
A hip replacement changes the geometry of your hip joint. The femoral offset (the horizontal distance between the center of the femoral head and the shaft of the thighbone), leg length, and the angle of the socket all shift to some degree. Intuitively, you might expect that bigger changes in offset would produce more tendon strain and more pain. The evidence, though, is more complicated than that.
Two studies looking at femoral offset in isolation found no link between offset changes and lateral hip pain. One reported no association between offset changes relative to either the native hip or the opposite hip and the development of lateral pain.10PubMed Central. Changes in femoral offset is not associated with increased incidence of lateral hip pain following total hip arthroplasty A separate analysis reached the same conclusion, finding no relationship between lateral trochanteric pain and either femoral offset or the femoral center of rotation.11PubMed. Lateral trochanteric pain following total hip arthroplasty: radiographic assessment of altered biomechanics as a potential aetiology
That might sound reassuring, but a different study looking at the combined restoration of leg length, femoral offset, and acetabular offset tells a different story. Patients who developed trochanteric pain syndrome three years after surgery had a higher combined discrepancy in these measurements compared to their unaffected side, averaging about 12 mm versus about 8 mm in pain-free patients. Patients whose combined deviation exceeded 5 mm were significantly more likely to report trochanteric symptoms than those within 5 mm. The key insight was that no single parameter, like leg length or offset alone, was different between groups; it was the cumulative mismatch that mattered.12Scientific Reports. Restoration of leg length and offset correlates with trochanteric pain syndrome in total hip arthroplasty
In practical terms, this means the surgeon’s ability to reproduce your original hip geometry as closely as possible, across all dimensions together, has a meaningful effect on whether tendons around the hip end up overloaded. A hip replacement that restores your leg length well but shifts the offset significantly, or vice versa, may still leave the surrounding muscles and tendons working at angles or tensions they are not designed for.
Rectus Femoris and Less Obvious Tendon Sources
Most of the attention in post-hip-replacement tendonitis goes to the iliopsoas and the abductors, but other tendons can be affected too. The straight head of the rectus femoris, which originates from the front of the pelvis just above the hip joint, is one that researchers have described as underdiagnosed. Altered biomechanics and changed muscle-loading patterns after surgery may push strain beyond normal limits across this tendon. There is also evidence that the anterior surgical approach, because it works through the interval near the rectus femoris, may increase the risk of injuring it during the operation itself.13Journal of Arthroscopic Surgery and Sports Medicine. The straight head of rectus femoris: An underdiagnosed cause of chronic pain post hip replacement
This creates a subtle trade-off. The anterior approach protects the abductor tendons on the outer hip, as described earlier, but it may put the rectus femoris at slightly higher risk. No surgical approach is completely free of tendon consequences, which is why the choice of approach should account for the patient’s anatomy, pre-existing tendon health, and the surgeon’s experience with each technique.
Beyond the rectus femoris, a broader literature review of tendon problems after hip replacement identifies several other recognized conditions, including snapping hip syndrome (where a tendon audibly or palpably catches with hip movement) and greater trochanteric pain syndrome, which can involve a combination of tendon irritation, bursitis, and muscle dysfunction around the outer hip. These conditions sometimes overlap, making it difficult to isolate a single tendon as the pain source.
Metabolic Factors That Prime Tendons for Trouble
Not all tendonitis after hip replacement is purely mechanical. Tendons are living tissue, and their ability to tolerate stress, repair micro-damage, and resist degeneration depends partly on systemic health. Diabetes, high cholesterol, and obesity each affect tendon biology, and they frequently coexist as part of metabolic syndrome.14PubMed Central. Metabolic Syndrome and Tendon Disease: A Comprehensive Review People who carry these conditions into surgery may start with tendons that are already somewhat compromised, making them less able to adapt to the biomechanical changes a new hip imposes.
Diabetes, in particular, promotes changes in tendon collagen through advanced glycation end products, making tendons stiffer and less elastic. Obesity increases the mechanical load on all lower-limb tendons, while high cholesterol has been associated with lipid deposits in tendons that weaken their internal structure. If you are planning a hip replacement and have any of these conditions, managing them before and after surgery gives your tendons a better shot at handling the transition.
There is also a local biological factor worth mentioning. All joint replacements produce some amount of microscopic wear debris from the bearing surfaces and the junctions between implant components. The body’s immune system reacts to these particles, generating localized inflammation that can affect nearby soft tissues over time.15PubMed Central. Diagnosis and management of implant debris-associated inflammation While this debris-related inflammation is more commonly discussed in the context of bone loss around loosening implants, it also creates a low-grade inflammatory environment that does tendons no favors.
How Tendonitis After Hip Replacement Is Diagnosed
One of the challenges with post-replacement tendonitis is that groin pain, lateral hip pain, and anterior thigh pain can all have multiple overlapping causes, including infection, loosening of the implant, nerve irritation, and referred pain from the spine. Separating tendon-related pain from these other problems requires a combination of clinical examination and imaging.
MRI with metal-artifact-reduction sequences is the current standard for evaluating soft tissues around a hip implant. It can detect tendon thickening, partial and full-thickness tears, associated bursitis, and muscle atrophy that points to chronic tendon dysfunction.16PubMed Central. MRI of total hip arthroplasty: technical aspects and imaging findings Ultrasound is a useful complement. In a head-to-head comparison, ultrasound was actually superior to MRI for detecting tendon abnormalities, while MRI was better for identifying pseudotumors and muscle atrophy.17PubMed Central. A comparison of the diagnostic accuracy of MARS MRI and ultrasound of the painful metal-on-metal hip arthroplasty In practice, many surgeons start with an X-ray to check implant position and look for obvious loosening, then move to MRI or ultrasound depending on the suspected problem.
For iliopsoas tendinitis specifically, a diagnostic injection is a powerful tool. The criteria used in research settings involve confirming groin pain with hip flexion, ruling out infection and loosening, and demonstrating that an injection of corticosteroid and local anesthetic around the iliopsoas tendon eliminates the pain immediately.6PubMed Central. Iliopsoas tendonitis following total hip replacement in highly dysplastic hips: a retrospective study If the injection works, that is both diagnostic and therapeutic in the short term. CT scanning can also help by measuring the exact degree and location of acetabular cup overhang, which guides decisions about whether the implant itself needs to be revised.4PubMed Central. Iliopsoas impingement after total hip arthroplasty: Does the CT-scan have any role? Our Algorithm proposal
Treatment Options When Conservative Care Is Not Enough
Most cases of post-replacement tendonitis start with conservative management: activity modification, physical therapy focused on gentle stretching and strengthening the affected tendon group, and anti-inflammatory medications. For iliopsoas impingement, targeted corticosteroid injections around the tendon can provide relief that lasts weeks to months. A word of caution, though: corticosteroid injections near a prosthetic joint carry specific risks. Local side effects can include tendon weakening and, in rare cases, rupture. Injections are generally contraindicated if there is any suspicion of infection near the prosthesis.18American Journal of Roentgenology. Local and Systemic Side Effects of Corticosteroid Injections for Musculoskeletal Indications
When conservative measures fail, especially when imaging confirms cup overhang or the tendon keeps catching on hardware, surgical options come into play. For iliopsoas tendinopathy specifically, endoscopic tenotomy, where the tendon is partially released using a camera and small instruments, has shown good results. In one study, this procedure produced clinically important improvement in about three-quarters to nine out of ten patients, with only about one in ten reporting moderate residual groin pain afterward.19PubMed. Endoscopic Tenotomy for Iliopsoas Tendinopathy Following Total Hip Arthroplasty Can Relieve Pain Regardless of Acetabular Cup Overhang or Anteversion One notable finding from that study is that pain relief occurred regardless of how much cup overhang was present, suggesting that releasing the tendon itself is effective even when the underlying mechanical cause is left in place.
For abductor tendon problems, treatment depends on the severity. Minor tendinitis and partial tears can sometimes recover with dedicated physical therapy over several months. Complete tears or avulsions of the gluteus medius from the trochanter may require surgical reattachment. If the muscle has already undergone significant fatty degeneration, as sometimes revealed on MRI, the prognosis for repair is less favorable because the muscle has lost much of its functional tissue.
In the most stubborn cases of iliopsoas impingement caused by significant cup overhang, the definitive solution is revision surgery to reposition or replace the acetabular component. This is major surgery with its own risks and recovery period, so it is typically reserved for patients who have failed tenotomy and injection and whose imaging clearly points to the cup as the structural cause of the problem.
Why the Anterior Approach Does Not Eliminate Risk Entirely
Surgeons and patients sometimes assume that choosing a particular surgical approach will prevent tendon problems altogether. The evidence suggests a more nuanced picture. The direct anterior approach clearly reduces abductor tendon damage compared to the transgluteal approach.8PubMed. Soft-tissue changes in hip abductor muscles and tendons after total hip replacement: comparison between the direct anterior and the transgluteal approaches But the anterior approach works through the front of the hip, near the rectus femoris, and has been reported to carry a higher incidence of injury to that tendon.13Journal of Arthroscopic Surgery and Sports Medicine. The straight head of rectus femoris: An underdiagnosed cause of chronic pain post hip replacement Meanwhile, iliopsoas impingement can occur with any approach if the cup is positioned with anterior overhang. In other words, each approach trades one set of tendon vulnerabilities for another, and implant positioning plays its own independent role on top of that.
The best protection comes not from any single factor but from a combination: a surgeon experienced with their chosen approach, careful intraoperative attention to cup position and avoiding overhang, restoration of leg length and offset as closely as possible to your native anatomy, and a rehabilitation program that progressively loads the tendons around the new hip without overwhelming them early. Even then, some degree of tendon adaptation is unavoidable after any hip replacement. The tendons need time to adjust to slightly different lever arms, slightly different contact surfaces, and slightly different movement patterns. Most of that adaptation happens during the first year of recovery, and it explains why mild tendon-related discomfort in the first few months is common and not necessarily a sign of a lasting problem.