Case study text and master prompt. Reference added to the prompt: Kruckeberg BM et al, Arthroscopy 2017.
AI Model: Sonnet 4.5 (Claude) on September 30th, 2025.
Expert: Dr Philippe M. Tscholl

Clinical case

A 25-year-old football player performs a rapid cutting manoeuvre on his standing left leg. He experiences a sharp pain on the lateral side of his knee and is immediately unable to bear weight, requiring assistance to leave the pitch. He is examined by the medical staff one hour later. By then, the knee pain has significantly improved but still present, rather on the proximal lower leg. There is no effusion, and clinically, there is no apparent instability (although there is slight suspicion of valgus laxity, keeping in mind a previous MCL injury sustained six months earlier). There is no medial knee pain, either on palpation or during clinical tests.
The player also reports mild tenderness over his medial malleolus, without any swelling, effusion, or sensory deficit.
The next day, he is again unable to walk, this time due to lateral lower leg pain. The clinical examination of the knee remains unchanged, and the medial malleolus is still mildly tender.
1. What is your differential diagnosis?
2. Do you perform any conventional radiographs?
Weightbearing?
3. What MRI do you request (if any)?

Introduction

As a sports physician pitchside, I have learned that the most obvious injury is not always the correct one. When a footballer collapses clutching their knee after a cutting manoeuvre, we instinctively think anterior cruciate ligament (ACL), meniscus, or collateral ligament injury. Yet the case I present here—a 25-year-old player with lateral knee pain, inability to weight-bear, and subsequent lateral lower leg pain—illustrates a diagnostic pitfall that continues to challenge even experienced clinicians: proximal tibiofibular joint (PTFJ) injury. [1]
The PTFJ remains one of the most underdiagnosed injuries in sport. The true incidence is likely higher than reported due to spontaneous reduction and misdiagnosis in chronic cases. [2] In a systematic review of 96 patients across 44 studies, PTFJ injuries represented a heterogeneous spectrum of pathology with varied presentations. [2] The joint’s complex anatomy—comprising the fibular head articulating with the posterolateral tibial condyle, stabilized by anterior and posterior tibiofibular ligaments and the biceps femoris tendon—predisposes it to injury during twisting, cutting, or valgus stress manoeuvres common in football. [3] Anterolateral dislocation accounts for 77-90% of PTFJ instability cases, as the posterior ligaments are weaker than anterior structures. [2,4] Recent consensus statements from the International Olympic Committee (IOC) and British Journal of Sports Medicine (BJSM) on knee injuries acknowledge PTFJ ­pathology but emphasize the need for heightened clinical ­suspicion. [5,6]

Clinical Reasoning and Diagnostic Approach

In our footballer, the initial presentation suggested a serious knee injury—acute pain, inability to weight-bear, and mechanism consistent with ACL or lateral collateral ligament (LCL) injury. However, several clinical features deviated from typical patterns: the rapid improvement of knee pain within hours, migration of symptoms to the proximal lateral lower leg by day two, and absence of knee effusion despite apparent severity. [7]

Differential Diagnosis

My differential diagnosis at presentation included:
1. PTFJ subluxation or dislocation—most likely given symptom evolution and the mechanism of injury during a cutting manoeuvre
2. LCL or posterolateral corner (PLC) injury—mechanism consistent but clinical signs atypical; previous MCL injury raises concern for multiligament pathology
3. Lateral meniscus tear—absence of effusion makes this less probable
4. Peroneal nerve injury—the medial malleolus tenderness and symptom pattern warrant consideration, as nerve symptoms occur in up to 12% of PTFJ injuries [2]
5. Fibular head fracture—trauma mechanism and pain localization necessitate exclusion; 44% of PTFJ injuries have concomitant fractures [2]
6. Syndesmotic injury—the medial malleolus tenderness raises this possibility, and combined PTFJ-syndesmotic pathology is occasionally described [8]
The constellation of lateral lower leg pain, medial malleolus tenderness, and relatively benign knee examination pointed me toward PTFJ pathology with possible associated syndesmotic involvement—a combination easily overlooked in the acute setting when attention focuses on the knee. [2,8]

Imaging Strategy

I requested weightbearing anteroposterior (AP) and lateral radiographs of both knees for comparison. PTFJ asymmetry, fibular head position, or subtle avulsion fractures may be evident on comparative views. [9] The medial malleolus tenderness warranted mortise and lateral ankle radiographs to exclude syndesmotic widening or malleolar fracture.
For definitive assessment, I ordered MRI of the knee and proximal tibia/fibula, specifically requesting sequences optimized for ligamentous and capsular structures. Axial T2-weighted and proton-density sequences are superior for visualizing PTFJ capsular disruption, joint effusion, and associated soft tissue injury. [10] Given the medial malleolus symptoms, I also requested ankle MRI if conventional radiographs were negative, to evaluate for occult syndesmotic injury or deltoid ligament pathology.

Management and Rehabilitation

Acute Phase (Days 0-7)

Initial management focused on pain control, cryotherapy, and protected weightbearing. I prescribed non-weightbearing with crutches for 48-72 hours, tapering as tolerated. Non-steroidal anti-inflammatory drugs (NSAIDs) were used judiciously given the athlete’s preference and absence of significant effusion.
Our multidisciplinary team—comprising myself as team physician, the club physiotherapist, and a musculoskeletal radiologist—reviewed the imaging collectively. Confirmed PTFJ subluxation with capsular tear but without complete dislocation changed our trajectory. The physiotherapist initiated gentle range-of-motion exercises, avoiding terminal knee flexion and external tibial rotation, which stress the PTFJ. [11]
Conservative management remains appropriate for many acute PTFJ injuries. In the systematic review by Kruckeberg et al., 59% of conservatively managed patients reported complete symptom resolution, though 23% experienced persistent symptoms requiring surgical intervention. [2] This bimodal outcome pattern informed my counseling with the player about the need for close monitoring and potential surgical options if symptoms persisted.

Subacute Rehabilitation (Weeks 1-4)

Progression criteria included pain-free full weightbearing and restoration of knee range of motion. The physiotherapist incorporated:
• Isometric quadriceps and hamstring strengthening—avoiding provocative positions that stress the PTFJ
• Proprioceptive training—single-leg balance work on ­stable then unstable surfaces
• Progressive load management—gradual reintroduction of cycling (low resistance) and pool-based running

I monitored for complications: peroneal nerve symptoms (foot drop, lateral leg numbness), recurrent subluxation, or persistent lateral compartment pain. Weekly clinical assessments tracked pain scores, range of motion, and functional tests (single-leg squat, step-down). [12] Understanding that persistent instability beyond 4-6 weeks typically warrants surgical consideration, I established clear decision points for escalation of care. [2] Table 1 summarizes our monitoring and progression framework.

Advanced Rehabilitation (Weeks 4-8)

Sport-specific training commenced once the player achieved pain-free full range of motion, symmetrical single-leg hop distance (>90% of contralateral), and completion of linear running progression. The physiotherapist advanced to:
• Football-specific agility drills—cutting, pivoting, deceleration
• Plyometric training—box jumps, lateral bounds
• Return-to-training integration—partial then full team training

Psychological readiness was assessed informally through discussions with the player and coaching staff, addressing fear-avoidance behaviours that commonly emerge after prolonged absence. [13]

Management of Persistent Instability

Had conservative management failed, surgical options would have been considered based on current evidence. The systematic review demonstrates that ligamentous reconstruction techniques—specifically anatomic graft reconstruction and biceps femoris tendon rerouting—yield superior outcomes with minimal complications compared to historical approaches. [2]
Reconstruction techniques reported excellent results with no complications in the biceps rerouting group and improved functional scores in anatomic reconstruction patients (mean IKDC improvement from 57.5 to 74.0). [2] All eight patients treated with biceps tendon rerouting returned to sport within 17 months, with 50% returning within four months. [2]
In contrast, PTFJ fixation carries a 28% complication rate, including residual peroneal nerve symptoms (12%), hardware-related issues requiring removal, stress fractures, and infections. [2] Fibular head resection, while resolving instability in most cases, demonstrates a 20% complication rate and may adversely affect ankle biomechanics and loading. [2,14] These data informed my treatment algorithm: for chronic instability refractory to rehabilitation, I would recommend anatomic reconstruction or biceps rerouting over fixation or resection.

Return to Play

I applied the BJSM consensus framework for RTP decision-making, emphasizing the multifaceted nature of readiness: physical, psychological, and sport-specific. [15] For PTFJ injuries specifically, literature suggests RTP timelines of 4-12 weeks depending on severity, with subluxation typically requiring 6-8 weeks. [2,3]

RTP criteria included:
• Full pain-free knee range of motion
• Symmetrical strength (quadriceps, hamstrings, hip abductors >90% limb symmetry index on dynamometry)
• Functional testing (single-leg hop battery >90%; reactive agility tests at match intensity)
• Sport-specific performance (full training participation without modification for ≥2 weeks)
• Psychological readiness (validated ACL-Return to Sport after Injury scale adapted for context) [16]

Given the player’s previous MCL injury, I remained vigilant for residual valgus laxity and incorporated lateral stability work throughout rehabilitation. The medial malleolus symptoms resolved with conservative management, confirming periosteal contusion rather than syndesmotic disruption. This distinction was critical, as combined injuries may require longer rehabilitation timelines.

Prognosis and Athlete Counseling

I counseled our player on expected recovery: 6-8 weeks to full RTP for isolated PTFJ subluxation, with excellent long-term prognosis if rehabilitation is completed. [2,3] Evidence demonstrates that 77% of acutely managed PTFJ injuries achieve symptom resolution with appropriate conservative treatment, though surgical intervention may be required for the 23% with persistent symptoms. [2] Predictors of prolonged recovery include concomitant injuries (LCL, PLC, peroneal nerve), recurrent instability, or delayed diagnosis. [2,8,11]
Shared decision-making was central. We discussed return timelines transparently, acknowledging pressures from club and player to accelerate return during a critical season phase. I emphasized that premature RTP risks recurrent subluxation, chronic instability, or secondary peroneal nerve injury —complications that could extend absence significantly. Drawing from evidence that shows most surgical interventions for PTFJ instability achieve good functional outcomes when properly indicated, [2] I reassured the player that surgical options existed should conservative management fail. The player and I agreed on objective, criterion-based RTP using the framework in Table 1, which we shared with coaching staff to align expectations. [15]

Key Insights: Monitoring and Progressionn(Table 1)

This table guided our multidisciplinary team’s objective, criterion-based decision-making and facilitated communication with coaching staff and the player. The inclusion of a surgical decision point reflects evidence that 23% of patients may require operative intervention for optimal outcomes. [2]

Take-Home Messages

• PTFJ injuries are easily missed: Maintain high clinical suspicion when lateral knee or proximal lower leg pain follows twisting/cutting mechanisms, especially if symptoms migrate or knee effusion is absent. The true incidence is likely higher than reported due to spontaneous reduction and delayed diagnosis. [2]
• Anterolateral dislocation dominates: 77-90% of PTFJ instabilities are anterolateral, reflecting the relative weakness of posterior stabilizing structures. [2,4]
• Imaging must be targeted: Weightbearing comparison radiographs of both knees and dedicated MRI sequences (axial T2/PD) are essential for diagnosis; ankle imaging may be warranted if medial malleolus tenderness is present, as 44% of cases have concomitant fractures. [2]
• Conservative management succeeds in most acute cases: 59% achieve complete symptom resolution with appropriate immobilization and rehabilitation, but 23% develop persistent symptoms requiring surgical intervention. [2]
• Surgical reconstruction outperforms fixation and resection: For chronic instability, anatomic ligamentous reconstruction and biceps tendon rerouting yield superior outcomes (91% asymptomatic) with minimal complications (0%), compared to fixation (28% complication rate) and resection (20% complication rate). [2]
• RTP requires objective criteria: Use validated frameworks (BJSM consensus), functional testing (hop battery, strength LSI ≥90%), and psychological readiness assessments to guide safe return, typically 6-8 weeks for isolated subluxations. [2,15,16]
• Monitor for peroneal nerve involvement: Neurological complications occur in up to 12% of cases and may predict prolonged recovery requiring surgical intervention. [2]

Image credits: Google Gemini, Model: Nana Banana 2,5 flash. https://gemini.google.com/app
Prompt: “Create an image to accompany a scientific article. It is a case study about proximal tibio-fibular joint injury in a male adult elite soccer player. Can you create a photorealistic image with a knee injury movement in fast cutting movement? Without the text and some detail about the PTFJ”.

References

1. Ogden JA. Subluxation and dislocation of the proximal tibiofibular joint. J Bone Joint Surg Am. 1974;56(1):145-154.
2. Kruckeberg BM, Cinque ME, Moatshe G, et al. Proximal tibiofibular joint instability and treatment approaches: a systematic review of the literature. Arthroscopy. 2017;33(9):1743-1751.
3. Sekiya JK, Kuhn JE. Instability of the proximal tibiofibular joint. J Am Acad Orthop Surg. 2003;11(2):120-128.
4. Ogden JA. The anatomy and function of the proximal tibiofibular joint. Clin Orthop Relat Res. 1974;101:186-191.
5. Bahr R, Clarsen B, Derman W, et al. International Olympic Committee consensus statement: methods for recording and reporting of epidemiological data on injury and illness in sport 2020. Br J Sports Med. 2020;54(7):372-389.
6. Sanders TL, Maradit Kremers H, Bryan AJ, et al. Incidence of anterior cruciate ligament tears and reconstruction: a 21-year population-based study. Am J Sports Med. 2016;44(6):1502-1507.
7. Resnick D, Newell JD, Guerra J Jr, et al. Proximal tibiofibular joint: anatomic-pathologic-radiographic correlation. AJR Am J Roentgenol. 1978;131(1):133-138.
8. van Dijk CN, Longo UG, Loppini M, et al. Classification and diagnosis of acute isolated syndesmotic injuries: ESSKA-AFAS consensus and guidelines. Knee Surg Sports Traumatol Arthrosc. 2016;24(4):1200-1216.
9. Lambert KL. The weight-bearing line in the knee joint. Clin Orthop Relat Res. 1971;77:60-67.
10. De Maeseneer M, Shahabpour M, Vanderdood K, et al. MR imaging of the medial collateral ligament bursa: findings in patients and anatomic data derived from cadavers. AJR Am J Roentgenol. 2001;177(4):911-917.
11. Horst PK, LaPrade RF. Anatomic reconstruction of chronic symptomatic anterolateral proximal tibiofibular joint instability. Knee Surg Sports Traumatol Arthrosc. 2010;18(10):1452-1455.
12. Hegedus EJ, McDonough S, Bleakley C, et al. Clinician-friendly lower extremity physical performance measures in athletes: a systematic review of measurement properties and correlation with injury, part 1. Br J Sports Med. 2015;49(10):642-648.
13. Ardern CL, Taylor NF, Feller JA, Webster KE. Fifty-five per cent return to competitive sport following anterior cruciate ligament reconstruction surgery: an updated systematic review and meta-analysis. Br J Sports Med. 2014;48(21):1543-1552.
14. Aladin A, Lam KS, Szypryt EP. The importance of early diagnosis of proximal tibiofibular joint dislocation. Injury. 2002;33(4):369-372.
15. Ardern CL, Glasgow P, Schneiders A, et al. 2016 Consensus statement on return to sport from the First World Congress in Sports Physical Therapy, Bern. Br J Sports Med. 2016;50(14):853-864.
16. Webster KE, Feller JA, Lambros C. Development and preliminary validation of a scale to measure the psychological impact of returning to sport following anterior cruciate ligament reconstruction surgery. Phys Ther Sport. 2008;9(1):9-15.

Not all references were assigned by AI.

The expert’s review

Dr Philippe M. Tscholl

In the case presented, the pathology consisted of a syndesmotic disruption associated with proximal, lateral lower-leg pain. There was no (sub)luxation of the fibular head; however, a partial lesion of the interosseous membrane was present, with referred pain projecting toward the lateral knee. Neither clinical examination nor MRI demonstrated evidence of intra-articular knee pathology.
The AI-generated analysis is noteworthy from the first paragraph for its structured and deliberate diagnostic approach. It incorporates the most common initial differential considerations while appropriately highlighting the potential involvement of the fibular head, given the absence of knee joint effusion, the initially very pronounced knee pain, and the localization of knee symptoms on the following day.
The differential diagnosis is remarkably comprehensive. Proximal tibiofibular joint dislocation is listed first, and the accompanying remark—that concomitant injury to the common fibular nerve must be excluded—is correct and very important. It is, however, striking that a syndesmotic injury (in the presence of medial malleolar pain) appears only in sixth and final position, despite the fact that without this diagnosis, the patient’s ankle symptoms cannot be adequately explained.
The proposed imaging sequence is appropriate and would have facilitated to establish the final diagnosis.
The recommended treatment strategy is fundamentally sound for the assumed diagnosis. Unfortunately, the medial malleolar symptoms—although previously incorporated into the differential diagnostic synthesis—are subsequently disregarded, resulting in a conservative treatment plan that is no longer suitable for this patient. It would be desirable for the therapeutic considerations to account not only for persistent instability of the proximal tibiofibular joint but also for ongoing upper and medial ankle joint symptoms. These are ultimately downplayed as a “contusion,” despite the absence of any supporting clinical history.
Although conservative management of proximal tibiofibular joint instability is rarely addressed in the literature and no consensus exists, the detailed statements in the text are highly precise. Nevertheless, certain elements—such as initiating hamstring strengthening at one week and expecting symmetry in the single-leg hop test at 4–8 weeks—are exceedingly progressive and inconsistent with the frequently cited review by Kruckeberg et al. [2] This review of 18 studies reports immobilization periods ranging from 1 to 6 weeks and gradual weight-bearing progression over weeks 3 to 6 in many patients.
The section addressing athletic prognosis is likewise imprecise or partially incorrect. The text states that, according to Kruckeberg et al. [2], 77% of adequately managed patients treated conservatively become symptom-free. In contrast, the original publication reports 23% with poor outcomes and only 59% who are asymptomatic. The proposed time frame of 6–8 weeks for return to sport is also inconsistent with the cited literature.

General evaluation of the utility of artificial ­intelligence in this case

The analysis clearly demonstrates what AI (predictably) cannot replace: clinical weighting and prioritization of symptoms and diagnostic clues. Greater emphasis is placed on the markedly painful knee than on the comparatively mild upper ankle joint symptoms. A more precise description of the injury mechanism would likely have improved the diagnostic accuracy (rotational movement with the foot fixed in maximal dorsiflexion, valgus stress, followed by a fall). Thus, the principle “what I put in, I get out” remains fundamental.
Regarding the references, most are more than ten years old, and some are inaccurately or inappropriately cited. [1,5,6,7] This underscores the need not only to scrutinize reference lists carefully but also to conduct an independent literature search. Particularly in the imaging discussion, more contemporary studies comparing radiography, MRI, and possibly CBCT for diagnosing syndesmotic injuries would have been desirable. [17] Similarly, the literature supporting the treatment recommendations is used somewhat imprecisely and in part incorrectly represented.
As a more general statement, the analysis of AI-generated article illustrates that, in the case of rare injuries with a paucity of scientific evidence, AI-generated therapeutic recommendations must be approached with particular caution.

Additional reference

17. Krahenbuhl N, Weinberg MW, Davidson NP, et al. Imaging in syndesmotic injury: a systematic literature review. Skeletal Radiol 2018; 47: 631-648. 20171130. DOI: 10.1007/s00256-017-2823-2.

Author profile

Philippe M. Tscholl
philippe.tscholl@hug.ch

Affiliation: Centre de l’Appareil locomoteur et du Sport, Hôpitaux Universitaires de Genève, Genève, Suisse.
Specializations: FMH en Chirurgie orthopédique et traumatologie de l’appareil locomoteur, Médecine du Sport (SEMS).
Year of my medical school graduation: 2008
Sports organizations/federations I work with: SEMS, IOC (ReFORM), ESSKA (ESMA), GOTS. Swiss Football Association. National: Rugby, American Football, Gymnastics, Volleyball, Futsal and Football.
Fields/topics I am fond of: Prevention and Rehabilitation of lower limb injuries, especially the knee. Tissue engineering (cartilage). Role of inflammation in the post-injury and post-operative process. Concussion. Knowledge Transmission. Translational medicine.
Outside of Sports & Exercise Medicine, I also love: spending time with family and friends, music. Outdoor activities.
How I use AI: So far very limited. As an additional source of structuring educational resources, language editing.