Peroneal Subluxation

Peroneal Subluxation is uncommon and often overlooked causes of lateral ankle pain. Because the acute injury may mimic lateral ankle sprain and may occur at the same time as lateral ankle ligament injury, diagnosis can be difficult.

Peroneal tendon subluxation injuries are most frequent in young athletic individuals participating in such sports as skiing, soccer, basketball, rugby, ice skating, tennis, football, and gymnastics; chronic subluxation has been reported without any history of a specific traumatic event.

Related Anatomy

The superior peroneal retinaculum is a primary restraint to instability of the peroneal tendons at the fibular malleolus. It extends approximately 3.5 cm proximally from the tip of the lateral malleolus and attaches posterolaterally onto the calcaneus and the deep investing fascia adjacent to the Achilles tendon.

Anatomical factors that may predispose to recurrent dislocation include:

1. incompetence of the superior retinaculum,
2. a shallow sulcus,
3. a convex posterior surface of the distal fibula.
4. Congenital deformities such as congenital vertical talus and talipes planovalgus also have been reported to contribute to peroneal tendon dislocation.

Mechanism of Injury

The peroneal tendons may be displaced within the tendon sheaths but are more commonly displaced outside the sheaths and the tendon groove. The peroneal musculature contracts and overpowers the soft tissue. The tendons dislocate anteriorly from behind the distal fibula.

Powerful contraction of the peroneals with the foot dorsiflexed may cause failure of the superior peroneal retinaculum, leading to subluxation or dislocation of the tendons.

An inversion injury with the foot in plantar flexion also can stretch or avulse this structure.

Peroneal Subluxation Classification

Peroneal tendon subluxation injuries have been classified primarily by location.

In one classification system (Shawen and Anderson):

1. Zone I injuries involve the fibular groove and usually the peroneus brevis tendon;
2. Zone II injuries are located in the cuboid tunnel and primarily involve the peroneus longus tendon.

In Oden’s modification of the classification of Eckert and Davis, injuries are divided into four grades:

1. In grade 1 lesions, the most common pattern (>50%), the superior peroneal retinaculum is elevated off the fibula with the peroneal tendons coming to lie between the bone and the periosteum.
2. In grade 2 lesions the fibrocartilaginous ridge behind the lateral insertion of the superior peroneal retinaculum is avulsed along with the retinaculum and the tendons are displaced beneath the ridge.
3. Grade 3 lesions involve an avulsion of a small cortical osseous fragment from the fibular insertion of the superior peroneal retinaculum with the tendons dislocating beneath the fibular fragment.
4. Grade 4 lesions, the least common type, involve a complete avulsion or rupture of the superior peroneal retinaculum with the tendons lying external and superficial to the retinaculum.

More recently, Raikin et al. proposed intrasheath peroneal subluxation within the peroneal groove beneath an otherwise intact superior peroneal retinaculum as a subgroup of peroneal subluxation. Two types of these intrasheath subluxations were described:

1. Type A, in which there is no peroneal tendon tear and the tendons momentarily switch their relative positions (the peroneus longus tendon lies deep to the peroneus brevis tendon),
2. Type B, in which in the peroneus longus subluxes through a longitudinal tear in the peroneus brevis tendon

Peroneal Subluxation Symptoms & Signs

The diagnosis can be confirmed by popping and clicking of the lateral ankle, especially while ascending stairs, and by provocative testing in which the foot is placed in dorsiflexion, eversion, and external rotation, while resisting an inversion– plantar flexion force applied by the examiner.

Dislocation of the tendon can be detected with circumduction of the foot while the examiner palpates the anterior tip of the peroneal groove. Patients with intrasheath subluxations may not have reproducible clinical signs.

Differential Diagnosis of Peroneal Subluxation

The differential diagnosis should include degenerative, traumatic, and congenital causes of lateral ankle pain, especially lateral ankle ligament sprain.

1. Tendon Subluxation/Dislocation
2. Lateral ligament ankle sprain
3. Achilles tendon rupture
4. Fracture: malleolus, fifth metatarsal, cuboid
5. Stress fracture: calcaneus
6. Sinus tarsi syndrome
7. Calcaneocuboid syndrome
8. Peroneal tendinopathy
9. Degenerative joint disease
10. Tarsal coalition
11. Osteochondral lesion of the talus
12. Loose bodies in the ankle or subtalar joint
13. Sural neuritis
14. Radiculopathy
15. Malignant or benign neoplasm
16. Accessory muscle or bone

Radiology

Radiographs usually are negative; with a grade 3 injury, a “fleck” of bone may be seen off the posterior distal fibula.

MRI can be used to identify injury to the superior peroneal retinaculum, the peroneal tendons, and supporting soft tissues, as well as identify anomalous structures such as the peroneus quartus or a low-lying peroneal brevis muscle belly.

Kinematic MRI of the ankle moving from dorsiflexion to plantar flexion has been suggested to be superior to static imaging because the pathological process is position dependent.

Ultrasonography also has been reported to be effective for dynamically evaluating peroneal tendon subluxation.

Peroneal Subluxation treatment

Treatment depends on the whether the injury is acute or chronic, the bone and soft tissue anatomy, any associated clinical findings, and the age and activity level of the patient.

Nonoperative treatment rarely is successful, and operative treatment is preferred, especially in young, athletic patients. Acute repair of the superior peroneal retinaculum is recommended.

Symptomatic chronic or recurrent tendon dislocation should be treated surgically unless contraindicated.

Peroneal Subluxation surgeries are of five general types:

1. periosteal attachment,
2. groove deepening,
3. tenoplasty,
4. bone block procedures,
5. rerouting procedures, such as incision of the calcaneofibular ligament and placement of the peroneal tendons deep to the ligament.

References & More

1. Campbel’s Operative Orthopaedics 12th edition Book.
2. Walt J, Massey P. Peroneal Tendon Syndromes. [Updated 2022 May 29]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK544354/
3. Roth JA, Taylor WC, Whalen J. Peroneal tendon subluxation: the other lateral ankle injury. Br J Sports Med. 2010 Nov;44(14):1047-53. doi: 10.1136/bjsm.2008.057182. Epub 2009 Nov 27. PMID: 19945971.
4. van Dijk PA, Gianakos AL, Kerkhoffs GM, Kennedy JG. Return to sports and clinical outcomes in patients treated for peroneal tendon dislocation: a systematic review. Knee Surg Sports Traumatol Arthrosc. 2016 Apr;24(4):1155-64. doi: 10.1007/s00167-015-3833-z. Epub 2015 Oct 30. PMID: 26519186; PMCID: PMC4823328.
5. Raikin SM, Elias I, Nazarian LN: Intrasheath subluxation of the peroneal tendon, J Bone Joint Surg 90A:992, 2008.)