1 

Evidence that Reducing Knee Injuries in Underground Mining may have a Substantial Impact on 

Mine Company Finances 

Susan M. Moore, PhD 

Jonisha Pollard, MS 

Correspondence: 

Susan M. Moore 

National Institute for Occupational Safety and Health

626 Cochrans Mill Road 

PO Box 18070 

Pittsburgh, PA 15236 

SMMoore@cdc.gov 

(412) 386-6613 
2 

ABSTRACT

The 2007 United States Mine Safety and Health Administration (MSHA) database reported 217 

knee injuries in underground coal. From workers’ compensation data, the National Institute for 

Occupational Safety and Health (NIOSH) determined that the average cost per knee injury in this 

industry was $13,121.29 yielding nearly three million dollars as an estimated financial burden of 

these injuries on the industry in 2007. (1) Recently, NIOSH has investigated various types of 

interventions that underground coal mining companies may implement as means of decreasing 

mine workers’ risk for developing knee injuries. To encourage mining companies to implement 

this training program and interventions currently in development, NIOSH performed an analysis 

of workers’ compensation data for one underground coal mine in Illinois and six in 

Pennsylvania. The data were for the 2004, 2005, and 2006 claim years of each mine and 

included medical and indemnity costs for injuries to each body part, the number of injuries per 

body part, and the annual audited payroll. The rating formulas for the respective states were 

utilized to determine workers’ compensation premiums for 2008 which require injury data from 

2004 to 2006. For each mine, the costs of workers’ compensation premiums were determined 

with all the injuries reported. A second analysis was then performed whereby all knee injuries 

were excluded. By eliminating knee injuries, the annual workers’ compensation premiums 

decreased by 1.1% to 16.2% depending on the mine’s size and injury statistics. The savings that 

were observed ranged from $4,206, a 1.3% savings, to $1,454,767, a 6.4% savings. The cost of 

implementing the NIOSH recommended interventions is minimal; therefore, an overall savings 

for the mine would be expected. Moreover, NIOSH is continuing to develop other interventions 

to reduce the risk of knee injury as well such as a novel kneepad designed specifically for the 

low-seam mining environment.
3 

INTRODUCTION

Musculoskeletal injuries in underground coal mining occur to a variety of body parts and 

include the neck, should, back, knee, wrist, etc. These injuries include strains and sprains, joint 

dislocations, fractures, etc. In 2007, for underground coal mining, 327 injuries to the back were 

reported while 217 were reported for the knee, 127 for the shoulder, and 66 for the neck. The 

total days lost was the greatest for back injuries with 22,390 total days lost. The knee resulted in 

the second largest days lost of these joints with 13,598 days lost. While many mining companies 

recognize the various benefits of investing in the reduction of back injuries, fewer resources have 

been invested in reducing knee injuries. However, knee injuries are a significant financial 

burden to the industry. 

Injuries to the knee occur in both low- and high-seam mining environments. In low-seam 

mines, mine workers are restricted to kneeling, crawling, squatting, and duck walking postures 

which place substantial stress on the knee (2, 3) and often require the muscles of the leg to be 

active. (4) However, in high-seam environments, many injuries occur as a result of more diverse 

activities such as mine workers twisting their knee due to ground conditions. This may be due to 

the limited visibility associated with underground coal mining, poor ground conditions, or 

insufficient strength and flexibility of the leg muscles. From workers’ compensation (WC) data, 

the National Institute for Occupational Safety and Health (NIOSH) determined that the average 

cost per knee injury in this industry was $13,121.29 (5) yielding nearly three million dollars as 

an estimated financial burden that these injuries imposed on self-insured mines and insurance 

providers in 2007. Self-insured mines pay for injuries directly and, thus, can easily determine 

the exact financial burden an injury has placed on the company. However, for those mines 

utilizing the WC system within their states, the actual financial burden an injury places on the 
4 

company is much more difficult to determine since these mines pay for their injuries indirectly 

via their WC premiums which are calculated using formulas and actuarial parameters.

Recently, NIOSH has investigated various types of interventions that underground coal 

mining companies may implement as means of decreasing mine workers’ risk for developing 

knee injuries. These interventions include a training program that instructs mine workers how to 

identify symptoms of knee injuries and seek medical attention, redesign their work areas to 

reduce twisting on the knees, routinely move their knee joints through their full range of motion 

when kneeling or squatting for extended periods of time to increase joint nutrition, maintain 

good hygiene of clothing and kneepads to reduce injuries due to infected hair follicles, and 

implement at-home strengthening and stretching regimens for the leg muscles. (6) Other 

interventions are aimed at addressing the issue of poor visibility and include the use of a lightemitting diode (LED) cap lamp for improved illumination of the mining environment. (7-9) 

The cost of implementing the NIOSH training program is minimal as mines are required 

to provide annual safety training whereby the NIOSH training program could easily be provided 

to the mine workers. Incorporating improved cap lamp technology is also a relatively minimal 

expense. It is important that mining companies utilize these interventions as they are likely to 

result in a decrease in knee injuries, as well as other injuries associated with poor lighting, in 

underground coal mining. Moreover, based on experimental data NIOSH collected during 

kneeling and crawling tasks, NIOSH is currently developing a novel kneepad design for lowseam mine workers that are restricted to their knees. This novel kneepad will better distribute 

the forces applied to the knee thereby decreasing the stress experienced at the knee and reducing 

injuries. As this device becomes available to the industry, implementation is encouraged. 
5 

Providing the mining industry with evidence that various interventions also have a 

financial benefit is helpful for encouraging mines to adopt these interventions as part of their 

safety and health programs. WC costs are directly associated with the number of injuries 

reported for a given entity and, to a lesser degree, the cost of these injuries. Even a modest 

reduction in injuries can have a large impact on premiums paid out by a company. Therefore, 

the goal of this study was to encourage mines to consider implementing various interventions 

that are likely to decrease knee injuries in underground coal by providing an estimate of the 

financial benefits in WC premiums that may be realized when these injuries are reduced. 

METHODS

The WC methods utilized by two states were investigated: Pennsylvania and Illinois. 

Pennsylvania was selected because it has a unique formula for its WC calculations and is the 

only state to have a separate formula for underground mines. Illinois was selected as it is one of 

the states with the highest insurance rates. 

Pennsylvania (PA)-Methods for Calculation of Workers’ Compensation Premiums 

Coal mines in PA are rated by the Coal Mine Compensation Rating Bureau of PA

(CMCRB). Insurance providers offering coverage for coal mining in PA must be a member of 

the CMCRB. Several types of rating plans exist such as experience rating, manual rating, and 

merit rating. However, the majority of companies are evaluated with an experience rating plan. 

Therefore, only the experience rating plan will be discussed in this document. Any entity or 

company with a modified payroll of at least $300,000 during the three-year experience period 

qualifies for an experience rating. 
6 

Each year, the CMCRB sets a base loss cost rate (per $100 of payroll) which must be 

approved by the State Insurance Commissioner’s Office. There are three components to the loss 

cost rate: federal black lung coverage, state black lung coverage, and traumatic coverage (10). 

Based on their three-year injury history, mines are either penalized or credited from this base loss 

cost rate. In order to determine whether a mine is penalized or credited from the base loss cost 

rate set by CMCRB, a modification factor, or MOD, is calculated for each mine. The MOD is 

defined as:

 

 

 

 















 = Experience Rating Off - Balance Factor

Adjustment Ratio MOD (1) 

The Experience Rating Off-Balance Factor is obtained by using a table in Section VIII of the PA 

manual (11). This factor is what CMCRB uses to ensure that the experience rating plan is 

revenue neutral (i.e. premium volume overall stays the same when all ten classifications are 

pooled together). The Adjustment Ratio is calculated using four different parameters:

Adjustment Ratio = Experience Ratio x (BEC + REC) + NREC (2)

where,

Experience Ratio = calculated based on injury history and payroll (see Eq. 3) 

BEC+REC = Basic plus Ratable Excess Component 

NREC = Non-Ratable Excess Component 

The experience ratio (see Eq. 3) consists of several parameters. The primary losses reported by a 

company are the first parameter. Primary losses, or basic losses reported (LB in Eq. 3), are those 

losses associated with all injury claims, regardless of their value, up to the “primary limiting 

factor” which is $50,000. The secondary losses, or ratable excess losses (LEX in Eq. 3), are all 
7 

losses beyond the primary losses associated with a claim, not to exceed $150,000. For example, 

for a $150,000 claim $50,000 would be primary losses and $100,000 would be secondary losses. 

The basic expected losses (ELB in Eq. 3) are calculated based upon the mine’s payroll. 

Specifically, the payroll for each year is multiplied by 0.01 (to put in terms of per $100 payroll) 

and then multiplied by the Basic Expected Losses Component (actuarial value obtained from the 

PA manual; use class 1001 for underground, bituminous coal) for that respective year. The 

values for each year are then summed together to yield the basic expected losses used in Eq. 3. 

The ratable excess losses (ELEX in Eq. 3) are calculated similarly to the ELB. The payroll for 

each year is multiplied by 0.01 (to put in terms of per $100 payroll) and then multiplied by the 

Ratable Excess Expected Losses Component (actuarial value obtained from the PA manual; use 

class 1001 for underground, bituminous coal) for that respective year. The values for each year 

are then summed together to yield the ratable excess expected losses (ELEX in Eq. 3). The 

credibility factors (CB and CEX) are values obtained from the PA manual. 

 ( ) ( ) [ ] ( ) ( ) [ ]

B EX

B B B EX EX EX EX

ELEL

CL EL CLC1 EL C1 ExperienceRatio

+

−×+×+−×+× = B (3) 

LB = Primary (Basic) Losses Reported

CB = Basic Credibility

ELB = Basic Expected Losses

LEX = Secondary (Excess) Ratable Losses Reported 

CEX = Ratable Excess Creditability 

ELEX = Ratable Excess Expected Losses 

Once the Experience Ratio is calculated, the Adjustment Ratio (Eq. 2) may be calculated. The 

Basic plus Ratable Excess Component (BEC+REC) and the Non-Ratable Excess Component are 
8 

actuarial values obtained by using a table in Section VIII of the PA manual (Note: these 

parameters are different from the Basic Expected Losses Component and the Ratable Excess 

Expected Losses Component described earlier). Companies are not individually penalized for 

injuries greater than $150,000 in value. Rather, these injuries are distributed across all 

experience rated mining companies using the Non-Ratable Excess Component as shown in Eq. 2. 

For this reason, the Non-Ratable Excess Component is not multiplied against the Experience 

Ratio.

 Using the above-described three equations, any mine can calculate their MOD. This 

MOD is then used to determine whether or not the mine is penalized or credited with respect to 

the base loss cost rate. However, it should be noted that the MOD is only multiplied by the 

traumatic coverage (TC) portion of the loss cost rate and not the federal black lung (FBLC) and 

state black lung (SBLC) portions. It should also be noted that each insurance provider applies 

their own multiplier to the base loss cost rate to cover their administrative fees (e.g. taxes, 

overhead costs, costs associated with handling, settling, and defending claims). Thus, a 

company’s WC premium per $100 of payroll would be determined as follows: 

WC Premium = admin fee multiplier x (FBLC + CBLC + MOD x TC) (4)

Pennsylvania –Expected Savings when Knee Injuries Avoided 

WC data were obtained for six mines in PA for 2004, 2005, and 2006 allowing the WC 

premium for 2008 to be determined. These data included the audited payroll for each year, the 

number of injuries to each body part, and the losses (medical and indemnity) associated with 

each body part. In 2008, for bituminous, underground coal, the base loss cost rate was $0.93, 

$0.88, and $14.58 per $100 payroll, for federal black lung coverage, state black lung coverage, 
9 

and traumatic coverage, respectively (effective: April 1, 2008 – April 30, 2009; (10)). This 

yielded a base loss cost rate of $16.39 in 2008 for bituminous, underground coal. In PA, typical 

multipliers applied by insurance providers to cover administrative fees range from 1.17 to 1.60 

(10). The remaining parameters were determined as follows: 

• Primary (Basic) Losses Reported – For 2004, 2005, and 2006, WC 

data were provided for each mine. These data included the total number of 

injuries to each body part and the total incurred loss per body part. Incurred loss 

is the gross estimate of the loss by the claims adjuster based upon the medical 

evidence in hand and includes both medical and indemnity. Thus, this is an 

estimate that includes what has already been paid out for the claim as well as the 

reserves assigned to the claim based on the medical evidence. It is comprised of 

two parts, the amount paid to date and the outstanding case reserve. For each 

year, at each mine, the average incurred loss was then determined for all injured 

body parts. Average incurred losses up to $50,000, were included as Primary, or 

Basic, Losses. All incurred costs associated with these injuries were then 

summed across all three years to yield the Primary (Basic) Losses Reported when 

no knee interventions were implemented by the mine. It was then necessary to 

determine what the Primary (Basic) Losses Reported would have been if knee 

interventions had been incorporated. Since injury narratives were not available 

for each injury, there was no way of knowing which injuries would have been 

preventable through implementation of various interventions to reduce knee 

injuries. Thus, in order to determine the possible cost savings, it was assumed all 

knee injuries were prevented. Therefore, the Primary (Basic) Losses Reported by 
10

each mine that were associated with knee injuries were removed from the analysis 

and a new value for the Primary (Basic) Losses Reported was obtained for the 

scenario when knee interventions were implemented. 

• Secondary (Excess) Losses Reported – Those body parts where the 

average incurred cost exceeded $50,000 contributed to Secondary (Excess) 

Losses, as described above. The incurred costs of these injuries were summed to 

yield the Secondary (Excess) Losses Reported when no knee interventions were 

implemented by the mine. Again, all incurred costs associated with knee injuries 

that were considered Secondary (Excess) Losses were removed from the analysis 

and the remaining incurred costs were considered the Secondary (Excess) Losses 

Reported when knee interventions were implemented by the mine. The portion of 

injury costs that exceeded $150,000 are discarded from this part of the analysis. 

Rather, these injuries are factored into the analysis as an actuarial parameter, the 

Non-ratable Excess Component (See Eq. 2) so that the financial burden of these 

larger, unpredictable injuries are distributed across all carriers. 

Illinois (IL) – Methods for Calculation of Workers’ Compensation Premiums 

The National Council on Compensation Insurance (NCCI) is the largest rating 

organization in the United States and is the licensed rating organization for 36 states. Illinois 

uses NCCI to perform their WC analyses. According to NCCI, typically a company that has 

been paying $5,000 average annual premium for the past few years or has paid $10,000 or more 

in a single recent year, qualifies to be experience rated. The experience period is usually three 

full policy years, ending one year prior to the effective date of the modification. The NCCI 

formula used for the rating (12) follows: 
11

 

 

Primary 

Losses Stabilizing Value Ratable Excess Total

Actual 

Primary 

Losses

+ (1-Weighting Value) x Expected Excess 

Losses + Ballast Value + Weighting Value x 

Actual Excess Losses Total A (5) 

Expected

Primary 

Losses

+ (1-Weighting Value) x Expected Excess 

Losses + Ballast Value + Weighting Value x 

Expected Excess Losses Total B (6)

The Actual Primary Losses (Eq 5) are losses associated with all injuries, regardless of 

their value, up to the primary limiting factor which is $5,000. The Expected Primary Losses (Eq 

6) are then determined by multiplying the D-ratio by the Expected Losses (Eq 7; D-ratio is 

obtained using a table in the NCCI manual (12); this ratio determines the portion of a mine’s 

total expected losses that are likely to be primary losses). The Expected Losses are determined 

by multiplying the Expected Loss Rate (ELR – obtained using a table in the NCCI manual; use 

classification 1016 for underground bituminous coal) by the payroll for the three years used in 

the rating. This value is then multiplied by 0.01 to put the number in terms of per $100 of 

payroll. 

Expected Excess Losses are determined by subtracting the total expected primary losses 

from the total expected losses (Eq 8). 

Expected Primary Losses = D-ratio x ELR X (3-year payroll) x 0.01 (7)

Expected Excess Losses = Expected Losses – Expected Primary Losses (8) 

The weighting value is obtained using a table from the NCCI Experience Rating Plan 

Manual and is based on the Expected Losses (Note: different tables exist for different states). 
12

The weighting value determines how much of the Actual Excess Losses and Expected Excess 

Losses are used in the experience rating. The weighting value increases as Expected Losses 

increase. 

The ballast value is a stabilized element designed to limit the effect of any single loss on 

the experience rating modification. It is added to both the Actual Primary Losses and the 

Expected Primary Losses. This value also increases as Expected Losses increase. The MOD is 

then calculated as shown in Eq 9. 

 

Total B 

Total A MOD = (9)

In 2008, the loss cost rates for IL were $6.49, $9.61, and $17.64 per $100 of payroll for 

federal black lung coverage, state black lung coverage, and traumatic coverage, respectively 

yielding total loss cost rate of $33.74. In IL, the advisory rate set by the state was $47.85. The 

advisory rate is greater than the base loss cost rate as it is the recommended rate that providers 

charge to cover not only the losses but also the administrative fees associated with processing 

claims. Thus, the multiplier used for administrative fees can be calculated to be 1.29 from the 

base loss cost rate and the advisory rate. 

The insurance company only insured one IL mine from 2004 to 2006 and provided us 

with the WC data (total number of injuries to each body part and total incurred loss per body 

part) for this mine in the same format as they provided the data for the PA mines. The Actual 

Primary Losses used in IL is calculated in the same fashion as the Primary (Basic) Losses 

Reported is calculated in PA. The only difference is that, in IL, the primary limiting factor is set 

at only $5,000. Moreover, the Actual Excess Losses is calculated in the same fashion as the 

Secondary (Excess) Losses Reported is calculated in PA. Again, the only difference is that, in 
13

IL, the secondary limiting factor is set at $266,500. Once the Actual Primary Losses and the 

Actual Excess Losses were calculated based on the WC data provided by the insurance company, 

these data were plugged into the above equations along with the actuarial parameters that are 

obtained from the manual (e.g. Ballast Value, D-Ratio). 
14

RESULTS

Table 1 shows the demographic information for the six mines in PA and the one mine in 

IL. The total number of injuries from 2004 to 2006 for the PA mines ranged from 41 to 317 and 

the number of knee injuries ranged from 1 to 62. The average payroll across all three years 

ranged from $1,420,588 to $19,607,475. As the insurance company collaborating in this study is 

the largest provider in PA, the mines used in this study are representative of typical underground 

coal mines in PA. Data for only one mine was available for the state of IL. This mine was 

considerably larger than those in PA. The total number of injuries reported was 1,073 with 82 

injuries being to the knee. The average payroll from 2004 to 2006 for this mine was 

$37,920,004. For the PA mines, the percentage of their payout that was considered to be primary 

was 70.1%±33.2% for all injuries and 56.0%±28.9% when injuries to the knee were excluded. 

However, for the IL mine, only 17.1% of their payout was considered primary for all injuries and 

15.3% was considered primary when knee injuries were excluded. This is a direct result of the 

difference in the primary limiting factor used in PA ($50,000) and IL ($5,000; Note: average cost 

of knee injuries for IL mine was greater than $5,000 for all three years).

Tables 2 and 3 depict the other input values utilized in the PA and IL WC formulas, 

respectively. The calculations utilized to determine the WC costs with and without the inclusion 

of knee injuries are shown in Tables 4 and 5 for PA and IL, respectively. The MODs reported 

for three of the PA mines were below one indicating that these mines would receive a credit from 

the base loss cost rate set by the insurance provider. This was true even when the injuries to the 

knee were included in the analysis. However, for the IL mine, the MOD was 1.443 when 

injuries to the knee were included and 1.306 when they were excluded. Thus, even when knee 

injuries were excluded, this mine would pay more than the base loss cost rate established by the 
15

insurance provider and approved by the state. However, since the MODs decreased for seven 

mines in the analysis when knee injuries were excluded, all seven mines would have experienced 

a reduction in their WC premiums. For the PA mines, the savings ranged from $4,206 (1.3%) to 

$148,888 (3.3%) when knee injuries were excluded. For the IL mine, the savings when knee 

injuries were excluded was $1,454,767 which was 6.4% of their WC premium.
16

Table 1. Demographics pertaining to the six PA mines and one IL mine used in analysis. 

 

 

PA Mines

Mine 1 Mine 2 Mine 3 Mine 4 Mine 5 Mine 6 IL Mine

Total Injuries 61 182 92 317 74 41 1073

Knee Injuries 6 15 13 62 20 1 82

Loss cost rate (federal black 

lung) $0.93 $0.93 $0.93 $0.93 $0.93 $0.93 $17.64

Loss cost rate (state black 

lung) $0.88 $0.88 $0.88 $0.88 $0.88 $0.88 $9.61

Loss cost rate (traumatic) $14.58 $14.58 $14.58 $14.58 $14.58 $14.58 $6.49

Multiplier (administrative 

fee) 1.385 1.385 1.385 1.385 1.385 1.385 1.29

2004 payroll (3rd year) $4,062,315 $5,613,119 $3,195,976 $18,040,824 $3,676,553 $1,364,705 $36,480,066

2005 payroll (2nd year) $5,127,208 $10,292,248 $5,837,434 $19,184,751 $3,462,335 $1,422,417 $38,430,600

2006 payroll (1st year) $5,840,288 $11,474,350 $6,665,681 $21,596,850 $4,647,108 $1,474,642 $38,849,346
17

Table 2. Values obtained from PA manual that are used as inputs to the PA WC formula. 

Input Values for WC Calculations in PA

Basic plus ratable excess component 0.69981 

Non-ratable excess component 0.30019

Experience rating off-balance factor 0.9778 

Basic Expected Losses 1st year 4.2

Basic Ratable Excess Expected Losses 1st year 1.84 

Basic Expected Losses 2nd year 4.08

Basic Ratable Excess Expected Losses 2nd year 3.66 

Basic Expected Losses 3rd year 3.95

Basic Ratable Excess Expected Losses 3rd year 3.7

Table 3. Input values utilized for IL WC formula. 

Input Values for WC Calculations in IL

Expected Loss Rate (class 1016) - table in manual, based on Class Code 10.21

Discount Ratio (class 1016) - table in manual based on Class Code 0.15

Expected Losses $11,614,897

Weighting Value - table in manual, based on Expected Losses 0.73 

Expected Primary Losses $1,742,235

Ballast Value - table in manual, based on Expected Losses 1,188,098 

Expected Excess Losses $9,872,663 
18

Table 4. Calculations utilized to determine the savings in WC premiums associated with 

eliminating all knee injuries through implementation of interventions for the six PA mines.

Pennsylvania Mines when Knee Injuries Included

Mine 1 Mine 2 Mine 3 Mine 4 Mine 5 Mine 6

Primary (Basic) Losses 

Reported $480,339 $1,592,433 $163,637 $2,539,089 $519,377 $133,102

Basic Credibility 0.87 0.9 0.87 0.93 0.85 0.76

Basic Expected Losses $614,944 $1,123,565 $644,367 $2,402,418 $481,666 $173,875

Ratable Excess Losses Reported 

(Secondary Losses) $33,858 $515,511 $0 $660,692 $134,376 $200,000

Ratable Excess Credibility 0.13 0.16 0.13 0.23 0.12 0.08

Ratable Excess Expected Losses $445,423 $795,510 $454,550 $1,767,054 $348,261 $129,688

Exp ratio 0.84 1.20 0.57 .97 1.01 0.92

Adj Ratio 0.89 1.14 0.70 0.98 1.01 0.94

MOD 0.91 1.16 0.71 1.00 1.03 0.96

WC per $100 payroll $15.04 $18.77 $12.19 $16.40 $16.80 $15.85

WC per $100 payroll & adm fee $20.83 $26.00 $16.88 $22.72 $23.27 $21.95

WC Premium $1,043,735 $2,372,829 $883,393 $4,454,262 $914,195 $311,835

WC Premium, $k $1,044 $2,373 $883 $4,454 $914 $312

Pennsylvania Mines when Knee Injuries Excluded

Mine 1 Mine 2 Mine 3 Mine 4 Mine 5 Mine 6

Primary (Basic) Losses 

Reported $351,435 $1,493,364 $147,432 $2,303,530 $269,485 $124,920

Basic Credibility 0.87 0.9 0.87 0.93 0.85 0.76

Basic Expected Losses $614,944 $1,123,565 $644,367 $2,402,418 $481,666 $173,875

Ratable Excess Losses Reported 

(Secondary Losses) $33,858 $515,511 $0 $660,692 $99,295 $200,000

Ratable Excess Credibility 0.13 0.16 0.13 0.23 0.12 0.08

Ratable Excess Expected Losses $445,423 $795,510 $454,550 $1,767,054 $348,261 $129,688

Exp ratio 0.73 1.15 0.55 0.92 0.75 0.90

Adj Ratio 0.81 1.11 0.69 0.94 0.82 0.93

MOD 0.83 1.13 0.70 0.96 0.84 0.95

WC per $100 payroll $13.94 $18.29 $12.05 $15.85 $14.08 $15.64

WC per $100 payroll & adm fee $19.30 $25.33 $16.70 $21.96 $19.50 $21.66

WC Premium $967,158 $2,311,547 $873,690 $4,305,374 $765,999 $307,629

WC Premium, $k $967 $2,312 $874 $4,305 $766 $308

SAVINGS PER YEAR $76,577 $61,282 $9,703 $148,888 $148,196 $4,206

% SAVINGS PER YEAR 7.3% 2.6% 1.1% 3.3% 16.2% 1.3%
19

Table 5. Calculations utilized to determine the savings in WC costs associated with eliminating 

all knee injuries through implementation of interventions for the one IL mine. 

Illinois Mine when Knee Injuries Included

Actual Primary Losses (limiting factor $5,000) $3,920,770

Actual Excess Losses (limiting factor $266,500) $19,054,263 

Total A $21,684,099

Total B $12,802,995

MOD 1.694

WC per $100 payroll $45.98

WC per $100 payroll & adm fee $59.53

WC Premium $22,575,266

WC Premium, $k $22,575

Illinois Mine when Knee Injuries Excluded

Actual Primary Losses (limiting factor $5,000) $3,510,770

Actual Excess Losses (limiting factor $266,500) $16,670,225

Total A $19,533,751

Total B $12,802,995 

MOD 1.526

 

WC per $100 payroll $43.01

WC per $100 payroll & adm fee $55.70

WC Premium $21,120,499

WC Premium, $k $21,120

Savings Per Year $1,454,767

% Savings Per Year 6.4%
20

DISCUSSION

In this study, a detailed analysis of WC premiums was performed for six underground, 

bituminous, coal mines in PA and one in IL for 2008. The analysis was initially performed with 

all injuries being included and then was performed a second time whereby knee injuries were 

excluded. For this study, it was assumed that implementing interventions pertaining to knee 

injuries would eliminate all knee injuries that occurred in 2004, 2005, and 2006. Hence, this 

warranted a second analysis for the WC premiums associated with 2008. For all seven mines, 

WC premiums decreased when knee injuries were excluded. The savings ranged from $4,206 to 

$1,454,767 and from 1.1% to 16.2% of the WC premiums. These savings resulted from 

eliminating knee injuries for three consecutive years (2004 – 2006). Therefore when 

implementing interventions to reduce knee injuries it will take five years to fully realize the 

financial benefits in WC premium reductions although some benefit will be seen after several 

years – i.e. in accordance with the example in this paper, eliminating the knee injuries in 2004 

would not be included in the WC premium assessment until 2006. However, the costs associated 

with WC premiums are only part of the financial burden experienced by mining companies with 

respect to knee injuries. Many indirect costs would also be eliminated by implementing 

interventions to reduce knee injuries. Injuries have many other consequences that affect 

production such as: time needed to train new workers; loss of a skilled worker; reduction in 

worker morale; and reduced worker efficiency due to fatigue, pain, discomfort, or increased need 

for rest and break periods. Moreover, an injury to the knee could place the mine worker at risk 

for sustaining additional injuries associated with slips, trip, or falls. Thus, incorporating 

interventions to reduce knee injuries may not only improve worker quality of life but may also 

provide a significant financial benefit to a mine company. 
21

There are several limitations to this study. First, the cost associated with each individual 

injury was not available. Instead, the total number of injuries per body part was provided along 

with the total incurred costs associated with that body part. Therefore, in order to determine if 

injuries to a specific body part were to be primary (basic) or secondary (excess), the average cost 

of the injury to that body part was utilized. Additionally, the administrative fee charged by the 

insurance provider was an approximation based upon administrative fees charged by a variety of 

insurance providers. While this would impact the WC premium calculated per $100 of payroll, it 

would have no impact on the percent savings in WC premium when knee injuries were excluded. 

However, this parameter was included so that the cost per $100 of payroll calculated in this study 

was representative of what a mine company would actually pay. Finally, this study assumed that 

all knee injuries would be prevented by implementing interventions to reduce knee injuries. It is 

unlikely that all knee injuries would be prevented, so the savings presented in this study are an 

upper bound. However, the investment required on the part of the mine to implement the 

interventions outlined in this study is minimal which suggests that eliminating even a few knee 

injuries would be financially beneficial to the mine.
22

CONCLUSION

Mine companies should consider implementing interventions to reduce knee injuries. For 

example, NIOSH recently published a training package entitled Keeping Knees Healthy in 

Restricted Work Spaces: Applications in Low-Seam Mining (6) that describes the common 

causes and symptoms of these injuries in low-seam mining, suggests changes to work station 

design and activities that may reduce a mine worker’s exposure to risk factors for knee injuries, 

and provides basic stretching and strengthening exercises for the leg. NIOSH has also collected 

experimental data regarding the demands placed on the knee when in postures associated with 

low-seam mining (2-4, 13, 14). Using these data, NIOSH is working with a kneepad 

manufacturer to design, fabricate, and field test a novel kneepad that will reduce the forces and 

stresses on the knee when kneeling, squatting, and crawling. Mine worker input will be obtained 

throughout the design of the kneepad which will be evaluated experimentally to demonstrate a 

significant reduction in forces and stresses applied to the knee and will be field tested to ensure 

durability. In higher seams, uneven ground can result in mine workers twisting their knee. Thus, 

NIOSH researchers are currently investigating cap lamp technology in an effort to improve 

visibility in mines. Current investigations include light-emitting diode (LED) technology (7-9). 
23

ACKNOWLEDGEMENTS

The authors would like to acknowledge the assistance of Dale Broadwater at the Coal 

Mine Compensation Rating Bureau of Pennsylvania, Ron Davidson at Rockwood Casualty, Inc., 

and Karen Ayers at the National Council on Compensation Insurance (NCCI). 
24

REFERENCES

1. Gallagher S, Pollard J, Porter W. Electromyography of the thigh muscles during lifting tasks in 

kneeling and squatting postures. Ergonomcis. 2010 (in review).

2. Moore S, Porter W, Mayton A. Pressures applied to anatomical landmarks of the knee while in 

kneeling postures. American Society of Biomechanics Annual Meeting. State College, PA; 2009.

3. Porter W, Mayton A, Moore S. Pressure and Forces Applied to the Anatomic Landmarks of the 

Knee While in Static Kneeling Postures. Applied Ergonomics. 2009 (in review).

4. Gallagher S, Pollard J, Porter W. Electromyography of the thigh muscles during lifting tasks in 

kneeling and squatting postures. Ergonomcis. 2009 (in review).

5. Gallagher S, Moore S, Dempsey P. An Analysis of Injury Claims in Low-Seam Coal Mines. Journal 

of Safety Research. 2009;40:233-237.

6. Moore S, Steiner L, Nelson M, Mayton A, Fitzgerald K, Hubert J. Keeping Knees Healthy in 

Restricted Work Spaces: Applications in Low-Seam Mining. In: , Department of Health and Human 

Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for 

Occupational Safety and Health, ed.; NIOSH 2008-130, Information Circular 9504 (2008 May):1-16.

7. Sammarco J, Gallagher S, Reyes M. Visual performance for trip hazard detection when using 

incandescent and LED cap lamps. Journal of Safety Research. 2009 (accepted).

8. Sammarco J, Lutz T. Visual Performance for Incandescent and Solid-State Cap Lamps in an 

Underground Mining Environment. IEEE Industry Applications Society 42nd Annual Meeting. New 

Orleans, LA; 2007.

9. Sammarco J, Reyes M, Gallagher S. Do Light-Emitting Diode Cap Lamps Enable Improvements in 

Miner Safety? . Society for Mining, Metallurgy, and Exploration 111th Annual Meeting. Denver, CO; 

2009.

10. Coal Mine Compensation Rating Bureau of Pennsylvania. Personal Communications with 

Executive Director Dale Broadwater. Harrisburg, PA; 2009.

11. Pennsylvania Coal Mine Experience Rating Plan Manual. 2007. http://www.cmcrbpa.com/

12. The National Council of Compensation Insurance (NCCI). Experience Rating Plan Manual 

www.ncci.com. 2003.

13. Gallagher S, Pollard J, Porter W. An analysis of locomotion modalities in restricted space: motion 

analysis and electromyography of crawling and stoop-walking. Gait and Posture. 2009 (in preparation).

14. Pollard J, Porter W, Redfern M. Forces and Moments on the Knee during Kneeling and Squatting. 

Journal of applied biomechanics. 2009 (submitted to journal).