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Joint impingement syndrome: clinical features
European Journal of Radiology 27 (1998) S39 – S41
Joint impingement syndrome: clinical features Andrea Billi a, Alessia Catalucci b, Antonio Barile b, Carlo Masciocchi b,* b
a Department of Orthopedic Surgery, S. Carlo Hospital, Rome, Italy Department of Radiology, Uni6ersity of L’Aquila, Ospedale Santa Maria di Collemaggio, 67100 L’Aquila, Italy
Abstract Joint impingement is a painful syndrome caused by the friction of joint tissues, which is both the cause and the effect of altered joint biomechanics. From the anatomical and clinical viewpoints, these syndromes are classified as bone impingement, soft tissue impingement and entrapment neuropathy, depending on what joint portion impinges on the others. We considered the most important impingement syndromes of the upper and the lower limbs from the clinical viewpoint. As for the upper limb, supraspinatus impingement is a frequent cause of shoulder pain in both athletes and the normal population; the painful subacromial arch is a typical sign of the rotator cuff impingement syndrome and of outlet and non-outlet impingement as well. As for the elbow, we considered both medial and lateral impingement. The carpal tunnel syndrome is the most common peripheral entrapment neuropathy of the upper limb; it is caused by compression of the median nerve at the wrist. We considered the main causes of carpal tunnel narrowing and the relative clinical findings. As for the lower limb, we considered the iliotibial band friction syndrome, which is the most common overuse syndrome of the knee and the ankle impingement syndrome. The latter includes anterolateral impingement (with chronic anterolateral and lateral pain and ankle instability), sinus tarsi impingement, anterior impingement (with pain during foot dorsiflection and posterior impingement. The tarsal tunnel syndrome is the most important ankle entrapment neuropathy causing burn pain and paresthesias in the toes and sole of the foot. © 1998 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Exostoses; Iliotibial band; Joint impingement; Neuropathy; Supraspinatus; Tarsal; Tibiotalar
The joint impingement syndrome is a painful syndrome caused by the friction of joint tissues, which is both the cause and the effect of altered joint biomechanics. From both an anatomical and a clinical viewpoint, these syndromes are classified as bone impingement, soft tissue impingement and entrapment neuropathy, depending on which joint portion impinges on the others. As for the upper limb, supraspinatus impingement is a frequent cause of shoulder pain in both athletes and the general population. The impingement is caused by congenital or acquired narrowing of the space between the coracoacromial arch and the humeral head. The subacromial region has indeed all the characteristics of a joint, because of its role in both shoulder * Corresponding author. Tel.: +39 862 414258; fax: + 39 862 26038.
stability and wide circumduction movements. It lies above the coracoacromial arch (formed by the acromion process, the acromioclavicular joint and the coracoacromial ligament) and contains the subacromial-subdeltoid bursa, the rotator cuff and fat tissue [1,2]. The impingement syndrome is a common condition in which the soft tissues filling the subacromial space (subacromial bursa, supraspinatus tendon, biceps tendon) are chronically entrapped between the humeral head and the coracoacromial arch. This condition causes progressive degenerative changes, commonly of the supraspinatus tendon, on its critical area and on the biceps tendon. Neer distinguished three progressive stages of impingement: Stage I consists of tendon swelling and hemorrhage and widening of the subacromial-deltoid bursa; this stage is common in young athletes (swimming, throw-
0720-048X/98/$19.00 © 1998 Elsevier Science Ireland Ltd. All rights reserved. PII S0720-048X(98)00041-2
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A. Billi et al. / European Journal of Radiology 27 (1998) S39 – S41
ing sports) and it must be differentiated from acromioclavicular arthropathy and shoulder instability. It is reversible with conservative therapy. Stage II, resulting from repeated strain, consists of fibrosis and thickening of the subacromial soft tissues; patients are usually 25 – 40 years old. Stage III represents partial or complete rotator cuff and biceps tendon tear, with such bone changes as greater tuberosity sclerosis and acromion traction osteophytes. Pain and disability are severe [3]. The so-called outlet impingement, in which the osteo-fibrous canal is narrowed (i.e. osteophytes, acromioclavicular joint arthrosis), can be distinguished from the non-outlet impingement caused by altered shoulder movements with biomechanical changes and friction between soft tissues and the coracoacromial arch. Pain during arm abduction and extrarotation is always present. The painful subacromial arch is a typical sign of the rotator cuff impingement syndrome: movement is relatively free and painless below 60° and above 120°, but pain is reported in between [1]. As for elbow impingement, chronic overuse injuries of the lateral and medial tendons are common. Tendon injury includes an early inflammatory stage followed by fibroblastic degeneration and, finally, partial or complete tear. Patients have local pain, which can be triggered by the involved muscle group contraction; they are commonly tennis or golf players. Lateral elbow impingement, the so called ‘tennis elbow’, is a painful syndrome of the radiohumeral joint caused by repeated flexion-extension and pronationsupination movements. Traction enthesophytes of the common extensor tendon are frequent findings; swelling and thickening of this tendon result from overuse [4]. Medial elbow impingement may occur in tennis players too (the ‘medial tennis elbow’), in golfers and in throwers; it is caused by repeated valgus stress and by using the top spin, which require excessive forearm pronation. Medial tendinosis, commonly involving the flexor carpi radialis, is due to an overuse syndrome at the common flexor origin [5,6]. The carpal tunnel syndrome is the most common peripheral entrapment neuropathy of the upper limb and is caused by compression of the median nerve at the wrist. The carpal tunnel is outlined ventrally by the flexor retinaculum and dorsally by the lunate and capitate; its lateral and medial walls are formed by the scaphoid and pisiform proximally and the trapezium and hook of the hamate, distally. The soft tissues filling the carpal tunnel are the median nerve, the abductor pollicis longus tendon, the flexor digitorum superficialis and profundus tendons and their synovial sheaths. Carpal tunnel narrowing or an increase in its filling tissue causes the carpal tunnel syndrome from ischemic
neuropathy [7]. The main causes are: proliferative tenosynovitis due to overuse or systemic conditions, tumors, ganglion cysts, bone fractures, ligament instability with carpal collapse. This syndrome occurs mainly in women 30–60 years old, usually keyboard operators or typists. The patient complains of paresthesias and pain in the thumb, index, middle and lateral half of the ring finger, that is the areas of median nerve distribution. Pain may also be elicited by tapping on the median nerve at the wrist (Tinel’s sign). Thenar muscle athrophy may also occur in advanced stages. The clinical findings are strongly suggestive of the diagnosis, which can be confirmed by a positive electromyographic nerve conduction test [8]. The major impingement syndromes of the lower limb, from a clinical and an epidemiological viewpoints, are the iliotibial band friction syndrome and the ankle impingement syndrome [9]. The iliotibial band friction syndrome is the most common overuse syndrome of the knee. It may occur in marathon runners, soccer players, skiers and bicycle riders. The iliotibial band is the distal preinsertional portion of the tensor muscle of the fascia lata tendon, which spreads from the iliac crest to Gerdy’s tubercle of the tibia. The impingement syndrome is due to the repeated friction between iliotibial band and lateral femoral condyle during knee flexion-extension. The impingement may be due to a prominent femoral condyle, a varus knee or a thickened iliotibial band, which are intrinsic causes of increased tension forces on the lateral compartment; incorrect training during sports activity can be an extrinsic cause of excessive stress on the lateral knee compartment [10]. Impingement causes a chronic inflammatory reaction of the iliotibial band, the underlying synovial bursa and the periostium of the lateral femoral condyle. The main symptom of the iliotibial band friction syndrome is pain on the external knee joint surface, about 2 cm above the joint space. Pain can prevent running or arise after running. On clinical examination, flexion is normal between 0 and 90°, with slight pain; Renne and Noble tests are positive. The most frequent impingement syndrome of the ankle is anterolateral impingement. It is caused by repeated injuries in plantar flexion and ankle intrarotation, associated with injuries in tibiofibular and anterior talofibular ligaments. Chronic inflammation of the scar tissue with reactive hyperplastic synovitis may be found in this region, caused by premature mobilization. This ‘meniscoid lesion’ may be entrapped between the peroneal malleolus and the talus during foot dorsiflexion and thus cause pain. The main symptom is chronic anterolateral or lateral pain, increased on loading, and ankle instability is common. Lateral malleolus compression against the
A. Billi et al. / European Journal of Radiology 27 (1998) S39 – S41
talus causes pain; anterolateral swelling is often observed, too [11]. Sinus tarsi impingement is another frequent finding. The ligamentous and neurovascular structures filling the sinus tarsi may be compressed by the inflammation of the fatty tissue within the sinus, or by posterior or anterior subtalar joint synovial reaction [12]. The anterior tibiotalar impingement is a frequent painful syndrome which may be caused by exostoses on the dorsal tibiotalar joint; these exostoses are rather common in athletes at the cranial aspect of the talonavicular joint and at the anterior portion of the tibial surface. Pain during foot dorsiflexion may result from synovial joint reaction [13,14]. The ‘dancer’s heel’ is another type of ankle impingement where the hypertrophy of the posterior tubercle of the talus involves the adjacent structures. Bone impingement patients report local chronic pain, periarticular swelling and disability. On clinical examination, pain can be evoked by local pressure. The tarsal tunnel syndrome is the most important ankle entrapment neuropathy. The tarsal tunnel roof is formed by the flexor retinaculum and many fibrous septa extend from the retinaculum to the osseous floor; the floor is formed by medial malleolus, medial surface of talus, sustentaculum tali and medial wall of calcaneus. The posterior tibial nerve with its vascular bundle and the flexor hallucis longus tendon are found in the tarsal tunnel. The tarsal tunnel syndrome is a compression neuropathy of the posterior tibial nerve or its terminal branches; it is idiopathic in 50% of cases, or else it may result from many causes, including posttraumatic edema, fibrous scar, ganglion cysts, venous varicosities and tenosynovitis of the flexor tendons. The clinical symptoms consist of burning pain and paresthesias in the toes and sole of the foot, sometimes
.
S41
radiating proximally up to the leg. Tinel’s sign may be positive [15,16].
References [1] Kessel L. Clinical Disorders of the Shoulder. New York: Churchill Livingstone, 1986:60 – 74. [2] Hawkins RJ, Kunkell SS. Rotator cuff tears. In: Torg JS, editor. Current Therapy in Sports Medicine. Mosby, 1990. [3] Zlatkin MB, Iannotti JP, Robert ML. Rotator cuff tears: diagnostic performance of MR imaging. Radiology 1989;172:223–9. [4] Sintzoff S. Impingement syndrome of the upper limb. In: Masciocchi C, editor. Radiological Imaging of Sports Injuries. Berlin: Springer, 1998:165 – 201. [5] Berquist TH. Elbow and forearm. In: Krikum ME, editor. Ligament, Tendon and Osteochondral Fractures. (Imaging of Sports Injuries, Vol X). Gaithersgurg, 350pp: Aspen, 1992. [6] Patten RM. Overuse syndromes and injuries involving the elbow: MR imaging findings. Am J Radiol 1995;164:1205– 11. [7] Sugimoto H, Mijaji O, Oshawa T. Carpal tunnel syndrome. Evaluation of median nerve circulation with dynamic contrastenhanced MR imaging. Radiology 1994;190:459 – 66. [8] Pretorius ES, Epstein RE, Dalinka MK. MR imaging of the wrist. Radiol Clin North Am 1997;35:145 – 61. [9] Faletti C, De Stefano N. Impingement syndrome of the lower limb. In Masciocchi C, editors. Radiological Imaging of Sports Injuries. Berlin: Springer, 1998;203 – 213 [10] Noble CA. Iliotibial band friction syndrome in runners. Am J Sports Med 1980;8:232 – 4. [11] Erickson SJ, Johnson JE. MR imaging of the ankle and foot. Radiol Clin North Am 1997;35(1):163– 92. [12] Klein MA, Spreitzer AM. MR imaging of the tarsal sinus and canal: normal anatomy, pathologic findings and features of the sinus tarsi syndrome. Radiology 1993;186(1):233– 40. [13] Kleiger B. Anterior tibiotalar impingement syndromes in dancers. Foot Ankle 1982;3:69 – 73. [14] Stoller DW. The ankle and foot. In: Stoller DW, editor. Magnetic Resonance Imaging in Orthopaedics and Sports Medicine. Philadelphia: Lippincott, 1993:373 – 510. [15] Rossi F, Barile A. Nervous diseases (Spinal and peripheral nerve entrapments). In: Masciocchi C, editors. Radiological Imaging of Sports Injuries. Berlin: Springer,1998:226– 228 [16] Kerr R, Frey C. MR imaging in tarsal tunnel syndrome. J Comput Assist Tomogr 1991;15(2):280– 6.
Joint impingement syndrome: clinical features Andrea Billi a, Alessia Catalucci b, Antonio Barile b, Carlo Masciocchi b,* b
a Department of Orthopedic Surgery, S. Carlo Hospital, Rome, Italy Department of Radiology, Uni6ersity of L’Aquila, Ospedale Santa Maria di Collemaggio, 67100 L’Aquila, Italy
Abstract Joint impingement is a painful syndrome caused by the friction of joint tissues, which is both the cause and the effect of altered joint biomechanics. From the anatomical and clinical viewpoints, these syndromes are classified as bone impingement, soft tissue impingement and entrapment neuropathy, depending on what joint portion impinges on the others. We considered the most important impingement syndromes of the upper and the lower limbs from the clinical viewpoint. As for the upper limb, supraspinatus impingement is a frequent cause of shoulder pain in both athletes and the normal population; the painful subacromial arch is a typical sign of the rotator cuff impingement syndrome and of outlet and non-outlet impingement as well. As for the elbow, we considered both medial and lateral impingement. The carpal tunnel syndrome is the most common peripheral entrapment neuropathy of the upper limb; it is caused by compression of the median nerve at the wrist. We considered the main causes of carpal tunnel narrowing and the relative clinical findings. As for the lower limb, we considered the iliotibial band friction syndrome, which is the most common overuse syndrome of the knee and the ankle impingement syndrome. The latter includes anterolateral impingement (with chronic anterolateral and lateral pain and ankle instability), sinus tarsi impingement, anterior impingement (with pain during foot dorsiflection and posterior impingement. The tarsal tunnel syndrome is the most important ankle entrapment neuropathy causing burn pain and paresthesias in the toes and sole of the foot. © 1998 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Exostoses; Iliotibial band; Joint impingement; Neuropathy; Supraspinatus; Tarsal; Tibiotalar
The joint impingement syndrome is a painful syndrome caused by the friction of joint tissues, which is both the cause and the effect of altered joint biomechanics. From both an anatomical and a clinical viewpoint, these syndromes are classified as bone impingement, soft tissue impingement and entrapment neuropathy, depending on which joint portion impinges on the others. As for the upper limb, supraspinatus impingement is a frequent cause of shoulder pain in both athletes and the general population. The impingement is caused by congenital or acquired narrowing of the space between the coracoacromial arch and the humeral head. The subacromial region has indeed all the characteristics of a joint, because of its role in both shoulder * Corresponding author. Tel.: +39 862 414258; fax: + 39 862 26038.
stability and wide circumduction movements. It lies above the coracoacromial arch (formed by the acromion process, the acromioclavicular joint and the coracoacromial ligament) and contains the subacromial-subdeltoid bursa, the rotator cuff and fat tissue [1,2]. The impingement syndrome is a common condition in which the soft tissues filling the subacromial space (subacromial bursa, supraspinatus tendon, biceps tendon) are chronically entrapped between the humeral head and the coracoacromial arch. This condition causes progressive degenerative changes, commonly of the supraspinatus tendon, on its critical area and on the biceps tendon. Neer distinguished three progressive stages of impingement: Stage I consists of tendon swelling and hemorrhage and widening of the subacromial-deltoid bursa; this stage is common in young athletes (swimming, throw-
0720-048X/98/$19.00 © 1998 Elsevier Science Ireland Ltd. All rights reserved. PII S0720-048X(98)00041-2
S40
A. Billi et al. / European Journal of Radiology 27 (1998) S39 – S41
ing sports) and it must be differentiated from acromioclavicular arthropathy and shoulder instability. It is reversible with conservative therapy. Stage II, resulting from repeated strain, consists of fibrosis and thickening of the subacromial soft tissues; patients are usually 25 – 40 years old. Stage III represents partial or complete rotator cuff and biceps tendon tear, with such bone changes as greater tuberosity sclerosis and acromion traction osteophytes. Pain and disability are severe [3]. The so-called outlet impingement, in which the osteo-fibrous canal is narrowed (i.e. osteophytes, acromioclavicular joint arthrosis), can be distinguished from the non-outlet impingement caused by altered shoulder movements with biomechanical changes and friction between soft tissues and the coracoacromial arch. Pain during arm abduction and extrarotation is always present. The painful subacromial arch is a typical sign of the rotator cuff impingement syndrome: movement is relatively free and painless below 60° and above 120°, but pain is reported in between [1]. As for elbow impingement, chronic overuse injuries of the lateral and medial tendons are common. Tendon injury includes an early inflammatory stage followed by fibroblastic degeneration and, finally, partial or complete tear. Patients have local pain, which can be triggered by the involved muscle group contraction; they are commonly tennis or golf players. Lateral elbow impingement, the so called ‘tennis elbow’, is a painful syndrome of the radiohumeral joint caused by repeated flexion-extension and pronationsupination movements. Traction enthesophytes of the common extensor tendon are frequent findings; swelling and thickening of this tendon result from overuse [4]. Medial elbow impingement may occur in tennis players too (the ‘medial tennis elbow’), in golfers and in throwers; it is caused by repeated valgus stress and by using the top spin, which require excessive forearm pronation. Medial tendinosis, commonly involving the flexor carpi radialis, is due to an overuse syndrome at the common flexor origin [5,6]. The carpal tunnel syndrome is the most common peripheral entrapment neuropathy of the upper limb and is caused by compression of the median nerve at the wrist. The carpal tunnel is outlined ventrally by the flexor retinaculum and dorsally by the lunate and capitate; its lateral and medial walls are formed by the scaphoid and pisiform proximally and the trapezium and hook of the hamate, distally. The soft tissues filling the carpal tunnel are the median nerve, the abductor pollicis longus tendon, the flexor digitorum superficialis and profundus tendons and their synovial sheaths. Carpal tunnel narrowing or an increase in its filling tissue causes the carpal tunnel syndrome from ischemic
neuropathy [7]. The main causes are: proliferative tenosynovitis due to overuse or systemic conditions, tumors, ganglion cysts, bone fractures, ligament instability with carpal collapse. This syndrome occurs mainly in women 30–60 years old, usually keyboard operators or typists. The patient complains of paresthesias and pain in the thumb, index, middle and lateral half of the ring finger, that is the areas of median nerve distribution. Pain may also be elicited by tapping on the median nerve at the wrist (Tinel’s sign). Thenar muscle athrophy may also occur in advanced stages. The clinical findings are strongly suggestive of the diagnosis, which can be confirmed by a positive electromyographic nerve conduction test [8]. The major impingement syndromes of the lower limb, from a clinical and an epidemiological viewpoints, are the iliotibial band friction syndrome and the ankle impingement syndrome [9]. The iliotibial band friction syndrome is the most common overuse syndrome of the knee. It may occur in marathon runners, soccer players, skiers and bicycle riders. The iliotibial band is the distal preinsertional portion of the tensor muscle of the fascia lata tendon, which spreads from the iliac crest to Gerdy’s tubercle of the tibia. The impingement syndrome is due to the repeated friction between iliotibial band and lateral femoral condyle during knee flexion-extension. The impingement may be due to a prominent femoral condyle, a varus knee or a thickened iliotibial band, which are intrinsic causes of increased tension forces on the lateral compartment; incorrect training during sports activity can be an extrinsic cause of excessive stress on the lateral knee compartment [10]. Impingement causes a chronic inflammatory reaction of the iliotibial band, the underlying synovial bursa and the periostium of the lateral femoral condyle. The main symptom of the iliotibial band friction syndrome is pain on the external knee joint surface, about 2 cm above the joint space. Pain can prevent running or arise after running. On clinical examination, flexion is normal between 0 and 90°, with slight pain; Renne and Noble tests are positive. The most frequent impingement syndrome of the ankle is anterolateral impingement. It is caused by repeated injuries in plantar flexion and ankle intrarotation, associated with injuries in tibiofibular and anterior talofibular ligaments. Chronic inflammation of the scar tissue with reactive hyperplastic synovitis may be found in this region, caused by premature mobilization. This ‘meniscoid lesion’ may be entrapped between the peroneal malleolus and the talus during foot dorsiflexion and thus cause pain. The main symptom is chronic anterolateral or lateral pain, increased on loading, and ankle instability is common. Lateral malleolus compression against the
A. Billi et al. / European Journal of Radiology 27 (1998) S39 – S41
talus causes pain; anterolateral swelling is often observed, too [11]. Sinus tarsi impingement is another frequent finding. The ligamentous and neurovascular structures filling the sinus tarsi may be compressed by the inflammation of the fatty tissue within the sinus, or by posterior or anterior subtalar joint synovial reaction [12]. The anterior tibiotalar impingement is a frequent painful syndrome which may be caused by exostoses on the dorsal tibiotalar joint; these exostoses are rather common in athletes at the cranial aspect of the talonavicular joint and at the anterior portion of the tibial surface. Pain during foot dorsiflexion may result from synovial joint reaction [13,14]. The ‘dancer’s heel’ is another type of ankle impingement where the hypertrophy of the posterior tubercle of the talus involves the adjacent structures. Bone impingement patients report local chronic pain, periarticular swelling and disability. On clinical examination, pain can be evoked by local pressure. The tarsal tunnel syndrome is the most important ankle entrapment neuropathy. The tarsal tunnel roof is formed by the flexor retinaculum and many fibrous septa extend from the retinaculum to the osseous floor; the floor is formed by medial malleolus, medial surface of talus, sustentaculum tali and medial wall of calcaneus. The posterior tibial nerve with its vascular bundle and the flexor hallucis longus tendon are found in the tarsal tunnel. The tarsal tunnel syndrome is a compression neuropathy of the posterior tibial nerve or its terminal branches; it is idiopathic in 50% of cases, or else it may result from many causes, including posttraumatic edema, fibrous scar, ganglion cysts, venous varicosities and tenosynovitis of the flexor tendons. The clinical symptoms consist of burning pain and paresthesias in the toes and sole of the foot, sometimes
.
S41
radiating proximally up to the leg. Tinel’s sign may be positive [15,16].
References [1] Kessel L. Clinical Disorders of the Shoulder. New York: Churchill Livingstone, 1986:60 – 74. [2] Hawkins RJ, Kunkell SS. Rotator cuff tears. In: Torg JS, editor. Current Therapy in Sports Medicine. Mosby, 1990. [3] Zlatkin MB, Iannotti JP, Robert ML. Rotator cuff tears: diagnostic performance of MR imaging. Radiology 1989;172:223–9. [4] Sintzoff S. Impingement syndrome of the upper limb. In: Masciocchi C, editor. Radiological Imaging of Sports Injuries. Berlin: Springer, 1998:165 – 201. [5] Berquist TH. Elbow and forearm. In: Krikum ME, editor. Ligament, Tendon and Osteochondral Fractures. (Imaging of Sports Injuries, Vol X). Gaithersgurg, 350pp: Aspen, 1992. [6] Patten RM. Overuse syndromes and injuries involving the elbow: MR imaging findings. Am J Radiol 1995;164:1205– 11. [7] Sugimoto H, Mijaji O, Oshawa T. Carpal tunnel syndrome. Evaluation of median nerve circulation with dynamic contrastenhanced MR imaging. Radiology 1994;190:459 – 66. [8] Pretorius ES, Epstein RE, Dalinka MK. MR imaging of the wrist. Radiol Clin North Am 1997;35:145 – 61. [9] Faletti C, De Stefano N. Impingement syndrome of the lower limb. In Masciocchi C, editors. Radiological Imaging of Sports Injuries. Berlin: Springer, 1998;203 – 213 [10] Noble CA. Iliotibial band friction syndrome in runners. Am J Sports Med 1980;8:232 – 4. [11] Erickson SJ, Johnson JE. MR imaging of the ankle and foot. Radiol Clin North Am 1997;35(1):163– 92. [12] Klein MA, Spreitzer AM. MR imaging of the tarsal sinus and canal: normal anatomy, pathologic findings and features of the sinus tarsi syndrome. Radiology 1993;186(1):233– 40. [13] Kleiger B. Anterior tibiotalar impingement syndromes in dancers. Foot Ankle 1982;3:69 – 73. [14] Stoller DW. The ankle and foot. In: Stoller DW, editor. Magnetic Resonance Imaging in Orthopaedics and Sports Medicine. Philadelphia: Lippincott, 1993:373 – 510. [15] Rossi F, Barile A. Nervous diseases (Spinal and peripheral nerve entrapments). In: Masciocchi C, editors. Radiological Imaging of Sports Injuries. Berlin: Springer,1998:226– 228 [16] Kerr R, Frey C. MR imaging in tarsal tunnel syndrome. J Comput Assist Tomogr 1991;15(2):280– 6.