In comparison with other knee injuries, proximal tibiofibular joint (PTFJ) instability is relatively rare. Although anterolateral dislocation is the most common presentation, idiopathic bilateral subluxation is unusual outside of chronic conditions including collagen disorders and muscular dystrophy.1,2 Few idiopathic cases have been described in the literature, most of which occur in young females.3–6 Although some of these are the result of a traumatic injury,7 the authors present the case of a 16-year-old girl with bilateral, atraumatic PTFJ instability.
Although there are many causes of lateral-sided knee pain, the differential diagnosis should include PTFJ instability. The diagnosis is largely made using patient history and physical examination. At times, imaging studies can be unreliable because the instability can be dynamic in nature. Meniscus, chondral, and ligamentous injuries to the lateral side of the knee must also be considered and ruled out as part of the treatment course.
A highly active 16-year-old female runner and basketball player presented with a “snapping” sensation on the lateral sides of both knees and pain over the fibular head. This was accompanied by tingling and difficulty with ankle dorsiflexion. Motor loss worsened with increased activity. Although symptoms were present in both knees, the right knee was worse. The patient denied prior injury.
She had presented to a physician 2 years earlier with the same symptoms and was diagnosed with shin splints. The patient was subsequently treated with targeted physical therapy but reported no improvement. She was then seen by a second physician and diagnosed with a tibial stress fracture, which also did not respond to rest, activity modification, and other conservative measures. The patient presented to a third physician and was diagnosed with exertional compartment syndrome; she subsequently completed targeted physical therapy but again reported no improvement.
Finally, she presented to the current authors with the same symptoms but also severe peroneal neuritis in both the superficial and the deep distributions. The patient was unable to remain active with the presenting symptoms and worsening neuritis. By this time, symptoms were present even at rest. She had no family history of joint instability, ligamentous laxity, or collagen disorders. She had no other global hypermobility symptoms, meeting none of the Beighton criteria.
On examination, global hamstring tightness was observed, with significant biceps femoris tightness. The snapping sensation occurred with knee flexion and extension bilaterally, and it was easily visualized through the skin. The fibular head was hypermobile relative to the tibia. It was easy to push this anteriorly and posteriorly, much more than the typical minimal motion present in this joint. The patient reported numbness and tingling in both legs but did not present with foot drop or sciatic nerve involvement.
She underwent conservative treatment with targeted physical therapy for 6 weeks to address the hamstring tightness, and she reported significant improvement. This course of therapy focused specifically on stretching the hamstrings, proximal gastrocnemius, and lower back and also required deep tissue and myofascial release of the hamstrings and posterior knee. However, she still exhibited dynamic subluxation and peroneal neuritis with increased activity. Surgery was then recommended to decompress the common peroneal nerve and stabilize the PTFJ.
The patient's parents consented to the surgery, and she underwent right peroneal nerve decompression and neurolysis with proximal tibiofibular stabilization. Physical examination was repeated under anesthesia and revealed substantial dynamic instability with anterior-posterior fibular head movement. An incision was made on the lateral side of the leg proximal to the fibula over the biceps femoris tendon and extending distally toward the anterior compartment (Figure 1A). The biceps femoris tendon was located, and soft tissue bands were dissected away (Figure 1B). The peroneal nerve was identified just posterior to the biceps femoris tendon. There were substantial soft tissue bands compressing the nerve throughout. The peroneal nerve exhibited extensive compression and hyperemia, extending from posterior to the biceps femoris distally to the nerve's curvature around the fibular head.
Right peroneal nerve decompression. Planned skin incision along the tight biceps femoris tendon (*), bisecting the fibular head (A). Exposed biceps femoris near attachment to the fibular head (*). Soft tissue bands posterior cover the peroneal nerve (B). Decompression of the peroneal nerve proximally and distally (C). Relationship between the decompressed nerve and the sutures from the suspensory button fixation system (Proximal Tibiofibular TightRope; Arthrex, Naples, Florida). There is ample space to avoid nerve hitting the button (D).
The nerve was carefully dissected out of these compressive bands without excessive handling to avoid traction and further injury (Figures 1C–D). Figure 2A shows proximal coverage of the nerve with compressive tissue, while Figure 2B shows proximal release and decompression of the nerve. Figure 2C shows the nerve compressed distally near the fibular head and entering the anterior compartment. Figure 2D shows complete release of the nerve around the fibular head and into the anterior compartment.
Right peroneal nerve decompression. With the biceps femoris retracted anteriorly, the nerve is visualized covered in soft tissue. The nerve (*) and accompanying blood vessels before decompression (A). The nerve completely free proximally (B). Distally, near the fibular head and before entering the anterior compartment, the nerve remains encased in soft tissue (C). The nerve completely free and heading deep into the anterior compartment (D).
After completion of the neurolysis, the proximal tibiofibular stabilization was done using a suspensory button fixation system (Proximal Tibiofibular TightRope; Arthrex, Naples, Florida). The anterior, superior, and posterior aspects of the fibular head were visualized, and the drill guide was placed 2 cm distal to the tip of the fibular head on the posterolateral aspect of the fibula. A guide pin was drilled from posterolaterally on the fibula to anteromedially on the tibia. Radiography was used to visualize the path of the guide pin. The guide pin was advanced through the tibia, and a small skin incision was made at the point of exit for the guide pin. The exit incision was dissected down to bone to allow for eventual visualization of the medial button on the TightRope. The guide pin was then over-drilled. The TightRope was threaded through the tunnel with a long needle until the medial button reached the medial bony tunnel exit. The medial button was flipped and locked into place, and positioning was confirmed via radiograph.
The reduction of the joint was visualized with anteroposterior and lateral imaging, and the buttons were confirmed to be flat against bone. Figure 3A and Figure 3B show the TightRope button positioned away from the biceps femoris and peroneal nerve, respectively. Figure 3C and Figure 3D show postoperative anteroposterior and lateral images of the right knee, respectively. Dramatic improvement in fibular translation was noted after stabilization. Figure 4 reveals the movement of the fibula to a more anatomic location after stabilization. Tensioning the Tight-Rope appropriately requires reduction of the PTFJ visually and through radiograph in multiple planes. Overtightening the device may eliminate all motion at the PTFJ. The surgeon must check manually (ie, moving the fibula relative to the tibia) that motion is still present at this joint.
Right proximal tibiofibular stabilization after peroneal nerve decompression. Relationship between the biceps femoris tendon (*) and the fibular button (white circle) (A). Relationship between the fibular button (white circle) and the peroneal nerve (#) at the level of the fibular head (B). Anteroposterior (C) and lateral (D) radiographs of the stabilized proximal tibiofibular joint with fibular and tibial buttons.
Intraoperative radiographs showing the left proximal tibiofibular stabilization. Prestabilization (A) and poststabilization (B) anteroposterior radiographs. Prestabilization (C) and poststabilization (D) lateral radiographs. Both series show significant increase in overlap between the tibia and the fibula with stabilization. Both poststabilization radiographs show a more normal relationship between the proximal fibula and the proximal tibia.
Postoperatively, a hinged knee brace locked in full extension was used for immobilization. The patient awoke from anesthesia able to dorsiflex her ankle and extend her toes. The patient already experienced near-complete relief of her neurologic symptoms by postoperative day 3 at her first physical therapy visit, where she began active non–weight-bearing range of motion. The patient remained non–weight bearing for 4 weeks.
Early muscle strengthening was focused on the quadriceps, hip abductor, and core. No hamstring strengthening was performed until 8 weeks postoperatively. During subsequent physical therapy sessions, the patient reported no snapping sensation or neuritis. The instability resolved, and 4 months later she underwent identical surgery on the contralateral knee.
Atraumatic PTFJ instability can be difficult to diagnose and is often misdiagnosed, as evidenced by the current case. Ogden2 reported a misdiagnosis rate as high as 33% in the early 1970s. Because it is rare, atraumatic PTFJ instability can be easily missed. A detailed clinical history and examination are often the basis for the diagnosis.8 In this case, direct comparison to the contralateral side was difficult to interpret because of the bilateral presentation. Pain over the lateral aspect of the knee, especially on direct palpation of the fibular head, combined with instability of the PTFJ points toward the diagnosis.2 Early treatment is preferred to prevent chronic instability, pain, deviations in gait, and negative effect to sports performance.8
Regarding advanced imaging or other diagnostic tests, these are often not helpful because of the dynamic nature of this problem with activity. Although electromyography was not used for this patient because of the increased neurologic symptoms with activity and worsening neurologic symptoms with direct palpation over the peroneal nerve, it is certainly a potentially valuable part of the treatment course. However, if electromyography yields normal results, this does not preclude the nerve from being irritated dynamically with fibular motion during walking or activity. Magnetic resonance imaging may also be challenging because the proximal fibular instability is dynamic. In this case, magnetic resonance imaging did not show significant findings at the PTFJ; however, it did show some inflammation of the nerve as it passed around the fibular neck. Magnetic resonance imaging may be more likely to help rule out other causes of lateral-sided knee pain than to identify PTFJ instability.
Proximal tibiofibular joint dislocations and subluxations historically have been treated in several ways, including with arthrodesis, fibular head resection, and ligament reconstruction.2,4,8–10 Arthrodesis has been shown to have later complications of ankle pain and instability; thus, it is not an appropriate treatment for athletes.2,9,10 Fibular head resection is also not recommended for athletes because of a possible posterolateral corner rupture and subsequent instability,10 ankle instability, and pain.1,10,11 Warner et al11 and Horst and LaPrade12 have detailed reconstruction techniques using an autogenous hamstring tendon to stabilize the PTFJ with a posterior course through the fibula and an anterior course through the tibia.
The use of a suspensory system to stabilize the PTFJ was previously described by Lenehan et al.4 It was originally used at the distal tibiofibular joint.13 The TightRope was used to stabilize a dynamic anterior dislocation of the fibular head while maintaining the anatomy.4 Previous use of this device at the distal tibiofibular joint led to improved patient outcomes and earlier rehabilitation while eliminating the possibilities of screw loosening and failure and the subsequent need for removal and replacement.13 Although the authors are unaware of a study that explores the benefits of suspensory button fixation for atraumatic PTFJ instability, the implications drawn from the distal syndesmosis show promise.
Potential Treatment Challenges
Although there are few reported cases using button fixation on the fibular head, when the patient is thin and the fibular head is millimeters under the skin, hardware can be prominent. Even if the button is placed posterolaterally on the fibular head rather than directly lateral, it can be prominent and easily felt just under the skin. One solution is to place a small fascial flap over the hardware to cover the button and suture material.
Hamstring Tightness Prior to Surgery
As a response to the fibular head instability with the pull of the biceps femoris attachment, doing this surgery before an effort has been made to appropriately loosen the biceps femoris could result in failure secondary to continued pull of the attachment to the proximal fibula. During the physical therapy process to loosen the hamstrings, focus should also be on strengthening the core to help the patient maintain appropriate posture and decrease resting knee flexion.
Although the proximal fibular instability is ultimately addressed with the TightRope, decompression of the nerve is critical in the current authors' opinion. Although the surgery could theoretically be done through a small incision, allowing protection of the peroneal nerve and placement of the TightRope, the authors believe appropriate nerve decompression proximal and distal to the fibular head through a larger incision will help decrease pain and optimize function of the muscles using either branch of the peroneal nerve distal to the knee. It also significantly decreases the surgical risk of injury to the neurovascular structures.
Proximal tibiofibular joint instability is a difficult diagnosis with multiple valid treatment options. In this case of bilateral, atraumatic PTFJ instability with symptomatic peroneal nerve irritation, the use of the TightRope to reduce the subluxation combined with peroneal nerve decompression was a safe and effective option for surgical treatment. The patient had resolution of her neurologic symptoms and pain.
- Morrison TD, Shaer JA, Little JE. Bilateral, atraumatic, proximal tibiofibular joint instability. Orthopedics. 2011; 34(2):133.
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- Bozkurt M, Yilmaz E, Havitçioğlu H, Günal I. Bilateral congenital subluxation of the proximal tibiofibular joint with MRI findings: a case report. Knee Surg Sport Traumatol Arthrosc. 2002; 10(6):340–342. doi:10.1007/s00167-002-0290-2 [CrossRef]
- Lenehan B, McCarthy T, Street J, Gilmore M. Dislocation of the proximal tibiofibular joint: a new method of fixation. Injury Extra. 2006; 37(10):385–389. doi:10.1016/j.injury.2006.02.058 [CrossRef]
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- Pressel T, Wirth CJ. Chronic symptomatic proximal tibiofibular instability in a 3-year-old girl. Knee. 2006; 13(3):244–246. doi:10.1016/j.knee.2006.02.002 [CrossRef]
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- Semonian RH, Denlinger PM, Duggan RJ. Proximal tibiofibular subluxation relationship to lateral knee pain: a review of proximal tibiofibular joint pathologies. J Orthop Sport Phys Ther. 1995; 21(5):248–257. doi:10.2519/jospt.1918.104.22.168 [CrossRef]
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- Thornes B, Shannon F, Guiney AM, Hession P, Masterson E. Suture-button syndesmosis fixation: accelerated rehabilitation and improved outcomes. Clin Orthop Relat Res. 2005; 431:207–212. doi:10.1097/01.blo.0000151845.75230.a0 [CrossRef]