Post-operative ACL Reconstruction: Common Challenges and the Role of Physiotherapy By Bill Kelly APA Physiotherapist

Anterior cruciate ligament reconstruction (ACLR) is one of the most common orthopaedic procedures performed in active populations. Although surgical outcomes are generally good, recovery is often complicated by persistent swelling, difficulty achieving full extension, cyclops lesions, and elevated reinjury risk. Physiotherapists are central to identifying and addressing these challenges throughout rehabilitation, with evidence strongly supporting a criterion-based, individualised approach (van Melick et al., 2016; Aspetar Clinical Practice Guideline, 2023).

 

1. Persistent Swelling and Effusion

Knee effusion is expected in the early post-operative phase but can become problematic if prolonged. Effusion contributes to arthrogenic muscle inhibition — a reflex inhibition of the quadriceps muscle that limits strength recovery and functional progression (Rice & McNair, 2010). Persistent swelling also restricts range of motion (ROM), alters gait mechanics, and increases patient discomfort (Adams et al., 2012).

Role of Physiotherapy

Physiotherapists focus on early control of inflammation using cryotherapy, compression, elevation, and gentle movement. Early quadriceps activation through neuromuscular electrical stimulation (NMES) has been shown to improve muscle recruitment and strength in the early post-operative period (Stevens-Lapsley et al., 2012). Manual therapy, graduated loading, and patient education on pacing are also essential.

Ongoing effusion beyond 6 weeks should prompt reassessment of loading, surgical review, or imaging to rule out synovitis or infection (Adams et al., 2012).

 

2. Difficulty Achieving Full Extension

Restoration of full knee extension is one of the most important early rehabilitation goals following ACLR. Even small extension deficits can alter gait biomechanics and increase long-term risk of osteoarthritis (Shelbourne & Nitz, 1990; Mayr et al., 2010). Failure to achieve terminal extension early is also associated with cyclops lesions (Delincé & Ghafil, 2012).

Role of Physiotherapy

Physiotherapists should prioritise extension from day one post-surgery. This includes heel props, prone hangs, patellar mobilisations, and gentle manual extension stretching once swelling allows. Pain and effusion should be managed first to facilitate movement. Daily home exercise adherence and early quadriceps activation (particularly vastus medialis oblique) are crucial.

Evidence supports that achieving full extension by 4–6 weeks post-operatively significantly improves long-term function (van Melick et al., 2016).

 

3. Cyclops Lesion Formation

A cyclops lesion is a fibrous nodule that forms anterior to the ACL graft, mechanically blocking extension. The reported incidence of symptomatic cyclops syndrome ranges from 2–10 % (Kambhampati et al., 2020). Clinically, patients present with a terminal “clunk,” persistent extension loss, or pain in the anterior knee.

Role of Physiotherapy

Physiotherapists are often first to detect cyclops lesions through detailed ROM testing. If a hard end-feel or audible clunk persists despite targeted stretching and deswelling, referral back to the surgeon for imaging or arthroscopic excision is warranted (Delincé & Ghafil, 2012; Kambhampati et al., 2020).

Post-excision, rehab re-emphasises early motion and extension to prevent recurrence. Preventatively, maintaining full early extension and avoiding graft impingement positions during early rehab reduce risk (Adams et al., 2012).

 

4. Reinjury Risk and Return-to-Sport

Reinjury rates following ACLR remain concerningly high. Meta-analyses show that up to 23 % of athletes sustain a second ACL injury within two years of returning to sport (Wiggins et al., 2016). The risk is highest in younger athletes and those returning before 9 months (Grindem et al., 2016). Many do not regain their pre-injury level of sport, often due to fear of reinjury, strength deficits, or poor movement quality (Ardern et al., 2014).

Role of Physiotherapy

Physiotherapists guide athletes through criterion-based progression, using objective measures such as >90 % limb symmetry index (LSI) for quadriceps strength, hop tests, and movement quality assessment (van Melick et al., 2016). Psychological readiness is equally critical — the ACL-RSI scale can assist in assessing confidence before return to sport (Ardern et al., 2013).

Structured neuromuscular and landing-mechanics retraining significantly reduces reinjury risk (Gokeler et al., 2013). Even post-clearance, ongoing injury-prevention exercises (e.g. Nordic hamstring, single-leg balance, plyometric control) should continue long-term (Aspetar Clinical Practice Guideline, 2023).

 

Clinical Takeaways

  1. Control swelling early — prolonged effusion delays quad recovery (Rice & McNair, 2010).

  2. Regain full extension by 4–6 weeks — essential for gait and long-term outcomes (Shelbourne & Nitz, 1990).

  3. Suspect cyclops if mechanical block persists — refer promptly (Kambhampati et al., 2020).

  4. Base return-to-sport on objective criteria, not time alone — strength and movement quality drive safety (Wiggins et al., 2016).

 

Conclusion

Persistent effusion, loss of extension, cyclops formation, and reinjury are the main post-ACLR challenges that dictate functional success. Physiotherapists are uniquely placed to detect these issues early and guide evidence-based interventions that restore mobility, strength, and confidence. Criterion-based, individualised rehabilitation remains the cornerstone of optimal recovery after ACL reconstruction (Aspetar Clinical Practice Guideline, 2023; van Melick et al., 2016).

 

References

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  • Ardern C.L., Taylor N.F., Feller J.A., Webster K.E. (2013). A systematic review of the psychological factors associated with returning to sport following injury. Br J Sports Med, 47: 1120-1126.

  • Ardern C.L. et al. (2014). Fifty-five per cent return to competitive sport following ACL reconstruction surgery: an updated systematic review and meta-analysis including aspects of physical functioning and contextual factors. Br J Sports Med, 48(21): 1543-1552.

  • Aspetar Clinical Practice Guideline (2023). Rehabilitation after ACL reconstruction. Aspetar Orthopaedic & Sports Medicine Hospital.

  • Delincé P., Ghafil D. (2012). Management of complications after ACL reconstruction: cyclops syndrome and arthrofibrosis. EFORT Open Rev, 1(5): 151-157.

  • Gokeler A., et al. (2013). Neuromuscular training techniques to prevent secondary ACL injury: state of the art review. Sports Health, 5(6): 547-554.

  • Grindem H., et al. (2016). Simple decision rules can reduce reinjury risk after ACL reconstruction. Br J Sports Med, 50: 804-808.

  • Kambhampati S.B.S., Vaish A., Vaishya R. (2020). Cyclops lesions of the knee: a narrative review. World J Orthop, 11(6): 281-290.

  • Mayr H.O., et al. (2010). Rehabilitation following ACL reconstruction: a systematic review. Knee Surg Sports Traumatol Arthrosc, 18: 158-174.

  • Rice D.A., McNair P.J. (2010). Quadriceps arthrogenic muscle inhibition: neural mechanisms and treatment perspectives. Semin Arthritis Rheum, 40(3): 250-266.

  • Shelbourne K.D., Nitz P. (1990). Accelerated rehabilitation after ACL reconstruction. Am J Sports Med, 18(3): 292-299.

  • Stevens-Lapsley J.E., et al. (2012). Early neuromuscular electrical stimulation to improve quadriceps strength after ACL reconstruction. Phys Ther, 92(2): 210-226.

  • van Melick N., et al. (2016). Evidence-based clinical practice guideline for ACL rehabilitation. Knee Surg Sports Traumatol Arthrosc, 24: 2083-2103.

  • Wiggins A.J., et al. (2016). Risk of secondary injury in younger athletes after ACL reconstruction: a systematic review and meta-analysis. Am J Sports Med, 44(7): 1861-1876.

Stuart McKayComment