The standard list of restrictions — and how long they last

Most patients leaving hospital after a posterior hip replacement receive the same checklist of warnings. For the first six to twelve weeks, the rules typically include:

• No hip flexion beyond 90° — the hip must not bend past a right angle, which rules out low chairs, leaning forward to tie shoelaces, or picking anything up from the floor.
• No adduction past the midline — the operated leg must not cross towards or over the other leg; a pillow between the knees during sleep enforces this at night.
• No internal rotation — the foot of the operated leg must not turn inward, which affects how a patient pivots and transfers in and out of a car.
• Raised toilet seat — a standard toilet sits too low; a fixed riser or frame attachment is required for the entire precautionary period.
• Back sleeping with an abduction pillow — side or front sleeping is discouraged until the soft tissues have healed.
• No low chairs or sofas — any seat that tips the hip into deep flexion is off-limits, including most car passenger seats without a cushion.

The combined effect on daily life is considerable. Dressing below the waist requires long-handled aids; showering needs a grab-rail and a shower seat; returning to desk work may be delayed simply because standard office chairs sit too low.

What surprises many patients is that these restrictions apply regardless of how smoothly the operation went. They are not symptom-led — they are precautionary, calibrated to the biology of healing rather than to how the patient feels. That distinction is important, because it raises a question the evidence has recently started to answer: are the restrictions genuinely necessary for every patient, whatever technique was used?

Why the posterior approach creates a dislocation window

The restrictions described above trace back to a single anatomical decision made during surgery.

To reach the hip joint from the posterior (back-of-hip) direction, the surgeon must move aside a group of small but functionally critical tendons known as the short external rotators — principally the piriformis and obturator internus, along with the gemelli. Under normal circumstances these tendons wrap around the back of the femoral head like a sling, holding it firmly in the socket when the leg moves and providing the hip with its posterosuperior stability. They are also the route through which the brain receives continuous positional feedback from the joint.

During a standard posterior approach, these tendons are divided to create the surgical window. Once the prosthetic components are in place, the surgeon repairs them — suturing the cut ends back to the proximal femur. The repair is structurally sound enough to close the wound, but the tendons themselves are not immediately load-bearing. Biological healing — the process by which the tendon fibre genuinely reintegrates with bone — takes approximately 90 days.

During that window, the posterosuperior capsule lacks its native tension. The hip is mechanically vulnerable to dislocation in exactly the direction the divided tendons would ordinarily resist: a combination of flexion, adduction, and internal rotation. Hip precautions are, in effect, a behavioural substitute for the structural support that is temporarily absent. They buy time for the biology.

If dislocation does occur during this healing period, the downstream consequences are disproportionately severe. Clinical data indicate that 57% of patients who dislocate will experience more than one event, and 45.6% will require revision surgery within two years — a far more complex and riskier procedure than the original replacement. The restrictions are a rational response to a specific, time-limited structural problem — which immediately raises the question of what happens when that structural problem is avoided altogether.

What the clinical evidence now says about precautions

The case for imposing blanket precautions on every posterior-approach patient has weakened considerably in recent years — and the challenge now comes from randomised trial data, not just clinical intuition.

A 2024 systematic review and meta-analysis by Guo et al., pooling three RCTs involving 1,215 participants, found no statistically significant difference in dislocation rates between patients given standard hip precautions and those given none following posterior-approach total hip arthroplasty. Patients managed without precautions reported better HOOS JR functional scores at six weeks and weaned off walking aids more quickly than those following the traditional restriction protocol. The implication is practical: precautions appear to limit recovery more reliably than they prevent dislocation.

At NHS policy level, the UK's GIRFT (Getting It Right First Time) programme reached a parallel conclusion in December 2022, reporting that patients who did not receive conventional post-operative movement warnings were no more likely to dislocate. GIRFT's involvement matters because it moves the conversation from individual surgical preference into commissioned health-service review.

The emerging consensus across both sources points to the same principle: the quality of soft-tissue repair at the time of surgery is the dominant determinant of stability — not what patients are told to avoid afterwards.

Two important caveats apply. First, these findings concern posterior-approach THA broadly, where surgeons divide and then repair the short external rotators. They do not constitute head-to-head RCT evidence comparing SPAIRE-specific outcomes against standard posterior repair; that data has not yet been published in that form. Second, abandoning precautions is not the same as removing all post-operative guidance — careful early mobilisation and appropriate physiotherapy remain relevant regardless of approach. What the evidence challenges is the assumption that rigid movement restriction is a universal clinical requirement rather than a response to a specific surgical circumstance.

How SPAIRE removes the vulnerability precautions were compensating for

SPAIRE — Saves Piriformis And (Obturator) Internus with Repair of (Obturator) Externus — is a modified posterior approach originally described by Kim et al. in 2008. Rather than addressing the vulnerability that precautions compensate for, it removes the vulnerability entirely.

The key difference lies in what is not cut. Where a standard posterior approach divides the piriformis and obturator internus to gain surgical access, SPAIRE routes the exposure inferoposteriorly as a 'trap-door', leaving both tendons completely intact. The only tendon released — the obturator externus — is reattached at its exact anatomical footprint at the end of the procedure, rather than being approximated to a nearby tissue bed as occurs in conventional posterior repair.

The mechanical mechanism: a seatbelt that is always buckled

Because the obturator internus remains undisturbed, its tendon continues to pass directly over the posterior femoral head from the moment wound closure is complete. This creates what is described as the 'strap effect' — a dynamic tether that physically resists posterior subluxation without depending on biological healing. The structural support that precautions were standing in for was simply never removed.

The proprioceptive mechanism: a hip that knows where it is

Intact short external rotators also preserve the Golgi tendon organs and muscle spindles embedded within them. These mechanoreceptors supply the central nervous system with continuous positional feedback. After standard division, this afferent signalling is interrupted until nerve regeneration occurs — leaving the joint, in practical terms, neurologically blind to its own position. SPAIRE patients retain that feedback from day one, giving the hip the neuromuscular capacity to self-correct before a subluxating movement completes.

Together, these two mechanisms mean that movement restrictions are not merely a tolerable risk after SPAIRE — they are structurally unnecessary. That is different from saying dislocation risk is zero; it is to say that the specific anatomical deficit those restrictions were designed to compensate for has not been created in the first place. Professor Paul Lee's clinical pathway at Hip Replacement Lincolnshire is built around this principle.

Restrictions that remain regardless of which approach is used

Lifting SPAIRE's movement precautions does not mean lifting all activity guidance — and it is worth being precise about why certain restrictions remain, because the reason is entirely different.

The limits that survive any surgical approach exist to protect the implant over its lifespan, not to prevent dislocation. High-impact activities — sustained running, jumping, contact sports such as squash or rugby — generate repetitive peak loads that accelerate wear of the bearing surface and, over years, increase the risk of component loosening or periprosthetic fracture. Deep squats and heavy axial loading place comparable stress on the acetabular component and femoral stem. Forceful twisting on a planted leg applies torque directly to the implant-bone interface. These forces are just as relevant whether the surgery was SPAIRE, anterior, lateral, or standard posterior.

The framing most patients find useful is an investment one. Contemporary implants using highly cross-linked polyethylene and ceramic bearings can last well over 30 years; the permanent adjustments asked of patients are modest relative to that return. Walking, cycling, swimming, golf, and low-impact doubles tennis sit comfortably within those limits. Distance running and contact sports warrant a frank conversation with the operating surgeon before resuming — not because they will necessarily cause dislocation, but because the long-term mechanical cost to the prosthesis is real.

Physiotherapy and progressive strengthening remain relevant after any approach, SPAIRE included; what changes is the goal — building capacity and gait quality rather than guarding against movement restriction violations.

Patient suitability and taking the next step

Approach choice in hip arthroplasty is not a universal recommendation — it is a conversation shaped by individual anatomy, the degree of joint degeneration, prior surgical history, and soft-tissue conditions that can only be properly assessed at consultation.

SPAIRE suits the majority of patients requiring a posterior-approach total hip replacement, and it is particularly relevant for active patients who want freedom from precaution-related restrictions from day one. It is not the right choice for every hip: previous posterior surgery, certain anatomical variants, or compromised soft-tissue integrity may affect candidacy. Lateral, anterior/DAA, and SuperPATH approaches each carry distinct tradeoffs — in nerve risk, visualisation, intraoperative equipment requirements, and early recovery profile — and a surgeon-led comparison against individual circumstances is the only reliable basis for a decision.

The clinical approach described throughout this article reflects Professor Paul Lee's SPAIRE pathway at Hip Replacement Lincolnshire. What that pathway rests on — and what these sections have aimed to make clear — is a principle rather than a preference: by leaving the piriformis and obturator internus intact, SPAIRE removes the anatomical deficit that precautions were compensating for. The restrictions were never arbitrary; they were a rational behavioural substitute for a specific structural problem created during surgery. SPAIRE addresses the problem itself.

Hip Replacement Lincolnshire accepts patients without GP referral. Specialist assessments are available at Sleaford (NG34) and Grantham (NG31); further information and booking are at hipreplacementlincolnshire.co.uk.