Why your hip hurts after knee replacement

If your hip has started aching since your knee operation, you are not imagining it — and you are far from alone. Hip discomfort in the weeks after a total knee replacement is a well-recognised pattern, reported by a significant number of patients during recovery.

There are two broad explanations, and knowing which applies to you matters. The first is mechanical or referred pain: your body has spent weeks, sometimes years, compensating for a painful knee — limping, shortening your stride, shifting weight to one side. After surgery, those habits do not disappear overnight. Muscles around the hip work harder than usual, forces travel differently through the pelvis, and the hip registers the change. This type of discomfort tends to be mild, often eases with rest, and generally improves as rehabilitation progresses.

The second explanation is a genuine hip problem — either a pre-existing condition that becomes more noticeable once the knee mechanics change, or a new source of pain that warrants investigation.

Most early hip symptoms fall into the first category. But persistent, worsening, or acutely severe hip pain is a different matter entirely. Telling the two apart is not straightforward, and this article sets out what to watch for and when to seek a clinical opinion.

How gait changes after TKR load the hip

Walking patterns change after knee replacement — often for months — and those changes carry a cost for the hip.

To protect a tender new joint, most patients limp, shorten their stride, or tilt the pelvis to offload the operated side. Each of these adaptations redirects force away from the knee and through the hip instead. Where a healthy gait distributes load across multiple structures in a predictable rhythm, a compensation pattern channels the same force down a narrower, unfamiliar path. Repeat that pathway thousands of times across daily movement and the hip muscles, tendons, and joint capsule begin to register the strain — producing aching, tightness, or a deep sense of fatigue, most often on the operated side but sometimes on the opposite one too. The hip joint itself may be structurally normal throughout.

The hip abductor muscles — the group that stabilises the pelvis with each step — are particularly vulnerable to this. Research confirms that their strength is an independent predictor of how well patients recover after total knee replacement; measurably weaker abductors are consistently linked to poorer functional outcomes. A 2025 randomised controlled trial took this a step further: patients who added hip abductor strengthening to their standard rehabilitation programme improved significantly across all validated knee function scores compared with those doing the standard programme alone.

That finding points directly to hip-focused physiotherapy as a response with a clear evidence base. The hip is not peripheral to knee replacement recovery — it is central to it, and gait-driven symptoms that worsen with walking or stairs are a signal worth acting on early.

Pelvic alignment, the spine, and referred hip pain

Years of walking with a painful knee do more than alter stride length — they gradually shift the pelvis, with one side sitting slightly higher than the other in a pattern called pelvic obliquity. After knee replacement corrects the underlying joint, the pelvis and spine begin to re-align. That correction is positive in the long run, but the transition itself can produce aching around the hip and lower back as structures adjust to a new baseline.

A 2024 study found that 62% of total knee replacement patients had moderate-to-severe low back pain before surgery; half of that group improved at both four and twelve months post-operatively, as pelvic mechanics normalised. Hip-area discomfort in the early months may partly reflect this re-alignment rather than any new joint problem.

A direct nerve-pathway explanation also applies. The hip and knee share routes through L2–L4, via the femoral and obturator nerves, meaning irritation at the knee can produce pain felt in the hip or groin — classical referred pain that is real, sometimes intense, but generated elsewhere.

Finally, a phenomenon called central sensitisation affects roughly one in ten to one in three joint replacement patients. After sustained pain exposure, the nervous system can become over-alert, amplifying signals even once the original tissue damage has been resolved. Patients who experienced neuropathic-like symptoms before surgery face two to four times the risk of this sensitised pattern persisting — generating convincing hip-area pain without any structural hip problem present. Recognising this as a clinically established possibility is one reason that specialist assessment tends to reveal more than self-diagnosis can.

When it is a genuine hip problem

Not all hip pain after knee replacement is referred or mechanical — in some cases, the hip itself is the source.

The most common reason is pre-existing hip osteoarthritis, present all along but overshadowed by knee symptoms. OA frequently affects multiple weight-bearing joints, and many patients have subclinical hip OA that becomes symptomatic once gait and loading patterns shift after surgery. This is not a surgical complication — it is the natural progression of a systemic condition, now unmasked.

Implant-related factors can also contribute. Even a small leg-length discrepancy shifts posture and load across the whole lower limb; component positioning that creates altered soft-tissue tension may transmit mechanical strain toward the hip joint and surrounding muscles.

Certain features point toward the hip itself as the source rather than a referred symptom. A deep groin ache that worsens when you rotate your leg inward or outward, morning stiffness lasting more than 30 minutes that eases once you move around, pain that disturbs sleep or is actually worse at rest, or symptoms that are still increasing beyond six to eight weeks after surgery — these all warrant specialist review rather than watchful waiting.

If hip pain arrives suddenly and severely — especially alongside visible swelling, warmth or heat over the joint, skin colour change around the hip, or a fever — go to A&E the same day. These signs may indicate infection, which is rare but serious; the section below sets out the full triage framework.

Imaging — typically an X-ray of the hip and pelvis, sometimes an MRI — can identify structural changes, but a specialist interprets those findings alongside your symptoms and clinical examination. Scan findings showing wear do not automatically explain your pain, and a near-normal scan does not rule out early pathology.

A three-tier guide to deciding what to do next

The sections above explain why hip pain develops — but the practical question is what to do about it. The following framework helps guide the response based on what the symptoms are actually doing, not how long the patient hopes to wait.

Tier 1 — self-manage Hip aching that appeared in the first four to six weeks after surgery, is mild, worsens after activity and settles with rest, and is showing week-on-week improvement is most likely mechanical adjustment. Appropriate responses include pacing activity, ice applied in 20–30-minute cycles, any anti-inflammatory medication already cleared by the surgical team, and continuing the prescribed physiotherapy. Informing the physiotherapist about the hip symptoms is important so that hip abductor and gluteal exercises can be incorporated — the evidence for this, as set out earlier in this article, is well established.

Tier 2 — GP or MSK specialist review Arrange an appointment if hip pain has not improved after two weeks of first appearing, is worsening, involves a deep groin ache, comes with morning stiffness lasting more than 30 minutes, or is beginning to limit everyday movement. A clinical examination — and sometimes imaging — is needed to distinguish mechanical loading from new or progressing hip OA or another structural cause.

Tier 3 — same-day emergency Go to A&E without delay if any of the following are present:

• Sudden severe hip pain without a fall or clear cause
• A hot, swollen hip joint
• Redness or change in skin colour around the hip
• Fever or feeling generally unwell alongside hip pain

These are red flags for infection or serious joint pathology. Do not wait for a routine GP appointment.

This framework indicates when to act; it does not replace clinical assessment. A worsening pattern at any tier is itself a reason to escalate.

What a specialist assessment involves and how to find one

A specialist assessment for persistent hip pain after knee replacement is investigative in purpose — not an automatic step toward more surgery.

The consultation typically begins with a detailed history: when the pain started relative to surgery, how it behaves with activity and rest, and whether it is worsening or plateauing. A physical examination of both the hip and the operated knee follows, often including a brief gait assessment to look for compensation patterns. The specialist will usually review surgical records, including prosthesis type and component positioning, both of which influence how load is distributed through the lower limb.

Imaging is ordered based on clinical findings rather than routinely. An X-ray of the hip and pelvis is the common starting point; MRI or a bone scan may follow if infection, labral pathology, or soft-tissue involvement is suspected.

Treatment after assessment most often means an updated or hip-focused physiotherapy programme. Where hip OA or bursitis is confirmed, an injection therapy may be appropriate. Further surgery — implant revision or hip replacement — is considered only in a small minority of cases where a structural cause has been clearly identified and conservative management has not resolved the problem.

Patients whose GP is uncertain are fully entitled to request an MSK or orthopaedic referral — persistent hip pain after knee replacement is a recognised indication for specialist review, not an unusual concern. For anyone unsure where to start, online specialist finder services such as the Search MSK directory list orthopaedic and MSK consultants across the UK, with the option to filter by region and area of expertise.