Diagnosis of Musculus Gastrocnemius Tightness - Key Factors for the Clinical Examination

Summary

Isolated Musculus gastrocnemius tightness is a common cause for foot and ankle pathologies. Currently no standardized examination procedure exists. This manuscript demonstrates that 20 degree of knee flexion eliminates the restraining effect of the M. gastrocnemius on ankle dorsiflexion and presents a video description of a standardized examination protocol.

Abstract

Common foot and ankle pathologies have been linked to isolated Musculus gastrocnemius tightness (MGT). Various examination techniques have been described to assess MGT. Still, a standardized examination procedure is missing. Literature argues for weightbearing examination but the degree of knee flexion needed to eliminate the restraining effect of the M. gastrocnemius on ankle dorsiflexion (ADF) is unknown. This manuscript investigates the effect of knee flexion on ankle dorsiflexion and provides a detailed description of a standardized examination protocol. Examination on 20 healthy individuals revealed, that 20° of knee flexion is sufficient to fully eliminate the influence of the M. gastrocnemius on ADF. This builds the prerequisite for a standardized examination for MGT. Non-weightbearing and weightbearing examination of ADF has to be conducted with the knee fully extended and at least 20° flexed. Two investigators should conduct non-weightbearing testing with the subject in supine position. In order to obtain reliable results, the axis of the fibula should be marked. One examiner can conduct weightbearing examination with the subject in lunge stance. Isolated MGT is present if ADF is impaired with the knee fully extended and knee flexion results in a significant ADF increase. The herein presented standardized examination is the prerequisite for future studies aiming at establishing norm values.

Introduction

Limited ankle dorsiflexion (ADF) alters the gait kinematics and is held responsible for common foot pathologies including Achilles tendinopathy, stress fractures, metatarsalgia and plantar heel pain ^1-5. The most common cause for limited ADF is isolated Musculus gastrocnemius tightness (MGT) ^3,6.

The joint kinematics of the ankle are influenced by knee flexion as the M. gastrocnemius bridges both joints. The muscle is under tension when the knee is fully extended, as the origin of the muscle is then furthest proximal. The M. gastrocnemius then restrains ADF. Knee flexion approximates the muscle's origin, thereby reducing the tension of the M. gastrocnemius, and consequently increases ADF. Ankle dorsiflexion is then limited by other anatomical structures of the ankle joint. Figure 1 illustrates this principle. In the case of MGT, ADF is limited with the knee fully extended but substantially increases by flexion of the knee ⁴.

Clinical examination for MGT takes advantage of the above outlined principled and was first published in 1923 by Silfverskiöld, a Swedish orthopedic surgeon ⁷. Since then, numerous examination techniques have been described, all of which compare the ADF with the knee extended and flexed. Published clinical tests can be categorized into non-weightbearing ^5,8, weightbearing ^9,10, and instrumented ^11,12. Today, non-weightbearing examination is most commonly conducted ¹³. The patient is placed supine on the examination couch and ADF is assessed with the knee fully extended and typically 90° flexed (Figure 2A). On the contrary, weightbearing ADF measurements are conducted with the subject upright in lunge stance. The rear knee is extended or bent and the subject is asked to lean forward just before heel liftoff (Figure 2B). For both tests MGT is diagnosed, if the ADF with the knee extended is impaired and knee flexion results in a significant increase of ADF.

Although non-weightbearing tests are frequently performed, weightbearing testing has several advantages. First, only one investigator is needed for weightbearing examination, whereas two examiners are required to achieve reliable non-weightbearing measurements. Second, the weightbearing examination more closely reflects the load during gait. Third, the force applied to the ankle is independent of the examiner. Fourth, weightbearing examination features a higher intra- and inter- rater reliability ^9,10,13-15.

The major limitation of all tests for MGT is that the minimal degree of knee flexion needed to eliminate the restraining effect of the M. gastrocnemius on ADF is unknown ^8,15. Whereas 90° of knee flexion are typically applied in non-weightbearing testing ^5,8,16, this is not feasible for the weightbearing examination. The broad population is unable to perform a Lunge with 90° of knee flexion without lifting the heel off the ground. Consequently, most studies conducting weightbearing examinations did not control for knee flexion ^8,15. In order to perform reliable weightbearing examinations it is essential to identify the minimal degree of knee flexion needed to eliminate the restraining effect of the M. gastrocnemius on ADF.

Overall, literature argues for weightbearing testing for the diagnosis of MGT. In order to provide a valid weightbearing examination procedure, the minimal degree of knee flexion required to eliminate the ADF restraining effect of the M. gastrocnemius must be known. The aim of this study was to investigate the influence of knee flexion on ADF in non-weightbearing and weightbearing testing and to provide a step-by-step guide to conduct non-weightbearing and weightbearing examination for MGT.

Protocol

Ethics statement: The study was approval by the local ethics committee of the University of Munich (# 007-14).

Note: An examination couch freely accessible on both sides and the foot end is required for non-weightbearing testing. A line (tape, approximately 2 meters) on the ground perpendicular the wall is needed for weightbearing testing. A standard goniometer with 2° increments and 20 cm length is used. We recommend documenting the results using a standardized fourfold table containing ADF measurement for the knee extended and flexed for each leg separately.

1. Participant Preparation

1. Have the subject take off their pants and remove their footwear.
2. Mark the axis of the fibula by drawing a line connecting the center of the distal fibula 5 cm and 15 cm above the tip of the fibula.

2. Non-weightbearing Measurement (Figure 2A) 

1. Have two investigators perform the measurement, one conducting the test, the other measuring the degree of ankle dorsiflexion.
2. Place the subject in supine position on the examination couch. The examination couch must be freely accessible on both sides and the foot end.
3. Have the first investigator place one hand at the level of the subtalar joint to ensure a neutral pronation-supination position of the rear foot and place the other hand around the midfoot. Thereby one hand stabilizes the talonavicular joint, while the other hand applies force on the plantar aspect of the forefoot to achieve maximum ankle dorsiflexion.
4. Have the first investigator ensure that the knee is fully extended.
5. Have the second investigator perform the measurement of the ankle dorsiflexion using a goniometer. Place one arm of the goniometer connecting the start and end point of the previously marked axis of the fibula. Align the other arm with the plantar aspect of the foot.
6. Note the result on the documentation sheet.
7. Have the first investigator ensure 90° of knee flexion by placing one hand on the distal dorsal aspect of the thigh while the other hand applies force on the plantar aspect of the forefoot to achieve maximum ankle dorsiflexion.
8. Have the first investigator place one hand at the level of the subtalar joint to ensure a neutral pronation-supination position of the rear foot and place the other hand around the midfoot. Thereby one hand stabilizes the talonavicular joint and the other hand applies force on the plantar aspect of the forefoot to achieve maximum ankle dorsiflexion.
9. Have the second investigator perform the measurement of the ankle dorsiflexion using a goniometer. Place one arm of the goniometer connecting the start and end point of the previously marked axis of the fibula. Align the other arm with the plantar aspect of the foot.
10. Note the result on the documentation sheet.
11. Repeat steps 2.1 through 2.10 for the contralateral side.

3. Weightbearing Measurement (Figure 2B)

1. Have one investigator perform the test.
2. Place the subject standing opposite a wall.
3. Have the subject get into the lunge position with the leg to be measured being the rear leg.
4. Have the investigator help the subject to place his/her rear foot centered on the previously marked line. Ensure that the heel and the second toe of the rear leg are centered on the line.
5. Have the subject hold onto the wall in order to stabilize their stance.
6. Have the subject fully extend their rear leg. Have the investigator ensure that the knee is fully extended. Be aware that even slight knee flexion significantly influences ankle dorsiflexion.
7. Have the subject move their hip towards the wall until just before heel lift off of the rear leg. The front leg can be flexed as needed / as comfortable.
8. Have the investigator place one hand on the dorsal aspect of the subtalar joint to ensure a neutral pronation-supination position of the rear foot.
9. Have the investigator perform the measurement of ankle dorsiflexion with the other hand. Align one arm of the goniometer connecting the start and end point of the previously marked axis of the fibula. Place the other arm on the floor.
10. Note the result on the documentation sheet.
11. Have the subject get into the lunge position with the leg to be measured being the rear leg. Therefore have the patient move towards the wall until a comfortable position has been reached.
12. Have the investigator help the subject to place his/her rear foot centered on the previously marked line. Ensure that the heel and the second toe of the rear leg are centered on the line.
13. Have the subject hold onto the wall in order to stabilize their stance.
14. Have the subject flex the rear leg as comfortable and move their hip towards the wall until just before heel lift off of the rear leg. The front leg can be flexed as needed / as comfortable.
15. Have the investigator ensure that the rear knee is flexed at least 20 degrees. In case of doubt use the goniometer to ensure knee flexion greater than 19 degrees.
16. Have the investigator place one hand on the dorsal aspect of the subtalar joint to ensure a neutral pronation-supination position of the rear foot.
17. Perform the measurement of ankle dorsiflexion with the other hand. Align one arm of the goniometer connecting the start and end point of the previously marked axis of the fibula. Place the other arm on the floor.
18. Note the result on the documentation sheet.
19. Repeat steps 3.1 through 3.18 for the contralateral side.

4. Data Analysis and Interpretation

1. Ask the subject to identify the symptomatic side.
2. Review the ADF data on the documentation sheet.
   1. First identify whether ADF with the knee extended is less than 10° on the symptomatic side. If so, consider MGT to be a possible cause. Then, compare ADF with the knee extended and flexed. If knee flexion results in a significant increase of ADF, MGT is present.
   2. In case ADF is greater than 10°, compare ADF with the knee extended between both legs. If ADF is reduced on the symptomatic compared to the non-symptomatic side consider MGT to be a possible cause. If knee flexion on the symptomatic side results in a significant increase of ADF, MGT is present.

Results

Both ankles of 20 healthy individuals (mean age of 27.1 ± 3.9 years), 50% female, were examined. Non-weightbearing and weightbearing tests at six different degrees of knee flexion (full extension, 20°, 30°, 45°, 60°, 75°) and the Lunge Test (uncontrolled knee flexion) were conducted. A functional brace was used to control knee flexion. Measurements were performed by two investigators blinded to each other's results. Between each individual, the order of t...

Discussion

Examinations on 20 healthy individuals revealed, that 20 degrees of knee flexion already eliminates the influence of the M. gastrocnemius on ADF. Further knee flexion resulted in no significant ADF increase. The herein presented video description of a standardized non-weightbearing and weightbearing examination for MGT builds the prerequisite for future studies establishing physiological norm values.

The study has limitations. First, no custom-made measurement device was used to asses...

Materials

Name	Company	Catalog Number	Comments
Examination couch
Standard goniometer	MDF Instruments USA, Inc. Malibu, CA, USA		2° increments