Tag Archives: ball and socket ankle joint

A case of stenosing peroneal tendinopathy in a fibro osseous tunnel due to a hypertrophied peroneal tubercle in the setting of a ball and socket ankle joint

by Zach T. Laidley1*, DPM, Daniel A. Lowinger2,4, DPM, FACFAS, Douglas S. Hale3, DPM, FACFAS

The Foot and Ankle Online Journal 13 (2): 7

Peroneal tendinopathy is a common pathology encountered by the foot and ankle surgeon. A hypertrophied or enlarged peroneal tubercle can be implicated in the etiology of tendinopathy. We present a case of stenosing peroneal tendinopathy due to an enlarged peroneal tubercle with concomitant ball and socket joint. Ball and socket ankle joint is a rare pathology that can present among different pathologic entities. The foot and ankle surgeon should consider the role of the peroneal tubercle in peroneal tendon disease especially in cases of complex rearfoot and ankle deformities.

Keywords: peroneal tendinopathy, ball and socket ankle joint, rearfoot coalition, lateral ankle instability, congenital foot deformity

ISSN 1941-6806
doi: 10.3827/faoj.2020.1302.0007

1 – Resident, Swedish Foot & Ankle Residency Program, Swedish Medical Center, Seattle, WA
2 – Attending Physician, Swedish Foot & Ankle Residency Program, Swedish Medical Center, Seattle, WA
3 – Residency Director, Swedish Foot & Ankle Residency Program, Swedish Medical Center, Seattle, WA
4 – The Polyclinic, Seattle, WA

* – Corresponding author: zachlaidley@gmail.com

Stenosing peroneal tendinopathies are relatively rare and can be associated with an enlarged peroneal tubercle [1,2]. The reported presence of a peroneal tubercle is varied but is present in 90% of specimens and enlarged in 20% [3,4]. It is located at the lateral aspect of the calcaneus and serves as a fulcrum to guide the peroneus longus underneath the cuboid [5]. It sits between the peroneus brevis and longus with the brevis superior and the longus inferior. It serves as an insertion point for the inferior peroneal retinaculum and separation point of the peroneal sheaths. With hypertrophied peroneal tubercles, the inferior peroneal retinaculum can be thickened, trapping the peroneal tendons in a dense fibrous tissue layer [1,2].

The peroneal tendons can be stenosed at the retromalleolar sulcus, at the peroneal tubercle, or inferior to the cuboid notch [1,2,6,7]. The exact etiology of an enlarged peroneal tubercle is unknown but has been theorized as either congenital or acquired. The hypertrophied peroneal tubercle has been associated with tenosynovitis and rupture of the peroneus longus tendon [8]. The enlarged tubercle can alter the stresses on the peroneal tendons, or tendons can be entrapped between the enlarged tubercle and the fibula leading to stenosing pathologies [8].

Figure 1 AP ankle radiograph, ball and socket ankle joint with enlarged peroneal tubercle.

Figure 2 (A) Coronal T2 MR image showing enlarged peroneal tubercle with peroneal tendons traveling in osseous tunnel, with surrounding tenosynovitis. (B) Coronal T1 showing enlarged peroneal tubercle.

Ball and socket ankle joint is a rare condition that can initially present as lateral ankle or peroneal tendon pathology [9]. The ball and socket ankle joint has a loss of concavity of the talar articular surface and rounding (increased concavity) of the tibial and fibular surfaces. The etiology of the deformity is controversial, with the most contested origins being embryologic malformation and adaptive deformation due to abnormal subtalar and midtarsal structural abnormalities [5,10-12]. Using arthrographic studies, Takura, et al., showed that ball and socket ankle deformity did not occur until after 5 years of age , supporting the theory that ball and socket ankle joint is an acquired deformity [13]. Others have supported the findings of Takura, stating that the ball and socket ankle joint occurs as a result of abnormal subtalar joint structure and function [5,12]. Several different orthopedic pathologies are associated with the ball and socket ankle joint, including fibular shortening or aplasia, limb length discrepancy, tarsal coalitions, and ligamentous laxity [10,11,13-15]. The nature of the deformity lends itself to increased frontal plane instability. As a result, these patients can present with chronic ankle instability or persistent lateral ankle pain [14,16].

The association between hypertrophied peroneal tubercle and peroneal tendinopathy has been extensively reported in the literature [1-3,6-8,17,18]. There are also cases of peroneal tendinopathy in the setting of ball and socket ankle joint [9]. However, to our knowledge, this is the only case report of stenosing peroneal tendinopathy due to a hypertrophied peroneal tubercle in the setting of a ball and socket ankle joint.

Case Report

A 35-year old female with past medical history significant for ligamentous laxity and chronic lower back pain presented with a 3-month history of lateral ankle pain. Symptoms initially started following an increase in activity during a vacation. She denied any recent or past inciting event or trauma to her ankle. The physical exam was most notable for significant tenderness along the course of peroneal tendons at the posterior aspect of the lateral malleolus and extending to the hindfoot. There was pain with eversion against resistance.

Figure 3 Coronal T2 (A) and sagittal T1 (B) MR images showing subtalar joint coalition.

Initial radiographs showed an osseous talocalcaneal coalition with a ball and socket ankle joint (Figure 1). There was evidence of an enlarged peroneal tubercle of the calcaneus. An MRI was subsequently obtained to assess the peroneal tendons and lateral ankle ligaments. The MRI showed an enlarged peroneal tubercle (Figure 2) and a solid osseous subtalar joint middle facet coalition extending into portions of the posterior facet with an associated hindfoot valgus (Figure 3). Severe common peroneal tendon sheath tenosynovitis with a high-grade partial thickness tear of the peroneus brevis with subluxation into the fibular calcaneal interval was noted (Figure 2 & 3). Moderate peroneus longus tendinosis was noted. The syndesmotic, anterior talofibular and calcaneofibular ligaments were intact.

Conservative treatment was attempted with an ankle brace and NSAIDs, but the patient was unable to tolerate the brace long-term. Surgical excision of hypertrophic peroneal tubercle with repair of peroneal tendons was planned.

Description of Procedure

The patient was placed in a lateral decubitus position with appropriate padding. The right foot and leg were prepped and draped, and the pneumatic tourniquet was placed. A linear longitudinal incision was made at the posterolateral aspect of the ankle over the peroneal tendon sheath extending in a curvilinear fashion distal to the peroneal tubercle. The peroneal tendon sheath was incised, exposing the peroneus longus tendon and inflamed synovial tissue.

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Figure 4 Intraoperative image of peroneal tendons retracted out of the way to show enlarged peroneal tubercle.

The peroneus brevis tendon was visualized impinged between a large prominence of bone at the lateral wall of the calcaneus and the lateral malleolus (Figure 4).

The prominent bone was resected using an osteotome and mallet and smoothed using a rasp. Bone wax was applied to exposed cancellous bone. The peroneus brevis was somewhat thinner than normal diameter distal to the excised bone, but with normal appearing texture of the tendon. At the level of the peroneal tubercle, the peroneus brevis tendon was thickened, and there was a full-thickness split tear at the level of the peroneal tubercle and distal portion of the lateral malleolus, measuring approximately 3cm length. Fibrous and scar tissue within the tendon was excised, and the defect was repaired. The peroneal tendon sheath was then reapproximated, followed by closure of subcutaneous tissues and skin.

Postoperatively, the patient was non-weight bearing in orthopedic cast boot for two weeks and then allowed to transition to weight-bearing as tolerated. At the six-month follow up, the patient was doing well and reported overall satisfied with the surgery. She had successfully transitioned out of the ankle brace for ambulation and was currently undergoing a course of physical therapy. Eversion strength was intact with no crepitus with range of motion of peroneal tendons and no evidence of effusion.


Hypertrophied peroneal tubercle resulting in stenosing peroneal tendon pathology is a rare condition. This case is also unique given the osseous subtalar joint coalition and concomitant ball and socket ankle joint. The etiology of the hypertrophied peroneal tubercle is largely unknown, but is commonly associated with peroneal tendon pathology. In this case the etiology of the hypertrophied peroneal tubercle is likely secondary to congenital abnormalities. A literature review by Kocadal, et al., investigated 22 studies, including 186 ball and socket ankle joints, no study reported on the occurrence of concomitant hypertrophied peroneal tubercle [9]. To our knowledge this is the only case in the literature describing hypertrophied peroneal tubercle resulting in stenosing peroneal tendon pathology predisposed by subtalar joint coalition and an associated ball and socket ankle joint.


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