Knee, Low Back, and Shoulder Problems Among University and Professional Volleyball Players: Playing With Pain

Four elite men’s volleyball teams, playing in the premier league in Japan, Qatar, Turkey, and the United States, participated in this prospective descriptive epidemiology study over a 3-season period (from 2017–2018 to 2019–2020). Seventy-five players participated during 8 team seasons (3 seasons: 1 team; 2 seasons: 2 teams; 1 season: 1 team), with a mean season length of 6.9 ± 0.9 months. Of these players, 8 (10.7%) participated over 3 seasons, 29 (38.7%) participated over 2 seasons, and 38 (50.7%) participated over 1 season, totaling 120 player-seasons. Players who changed teams or left their team midseason and participated for less than one-third of the season were excluded from this study.

Liberos fulfill a unique role on the team that requires little to no jumping or overhead attacks. To provide the most pertinent insights for coaches and support staff, we primarily examined position players with substantial jump and overhead attack volumes. Therefore, the weekly prevalence of complaints for liberos was reported for comparison between position groups, but these players were not included in further analyses, resulting in 102 player-seasons completed by outside hitters (n = 42), middle blockers (n = 28), setters (n = 18), and opposites (n = 14). The remaining players, excluding liberos, had a mean age of 26.2 ± 4.4 years, height of 195 ± 8 cm, and mass of 88 ± 10 kg. Participants provided oral and written informed consent, and the study was approved by the Anti-Doping Lab Qatar Institutional Review Board.

Knee, low back, and shoulder complaints were reported weekly by players completing paper versions of the Oslo Sports Trauma Research Centre Overuse Injury Questionnaire.^3,10  Players reported any pain related to their sport and the extent to which knee, low back, and shoulder problems affected participation, training volume, and performance. Knee problems were defined as “pain, ache, stiffness, swelling, instability/giving way, locking, or other complaints,” with similar definitions for shoulder problems (pain, aching, stiffness, looseness, or other complaints) and low back problems (pain, aching, stiffness, or other problems).³  Coaches and medical support staff (head and assistant coaches, strength and conditioning coaches, athletic trainers, and physical therapists) were responsible for collecting the questionnaires and inputting the results into a standardized spreadsheet. Coaches and support staff facilitated the process and had full access to the results of the questionnaires. Coaches were asked to continue with their normal training approach and could use this information as they deemed appropriate; no specific instructions were given regarding possible interventions based on these responses. The questionnaire consists of 4 questions. Each question is scored on a scale from 0 (no problems) to 25 (maximum value), and questions are summed to provide a total severity score from 0 to 100 for each anatomic area. The mean severity score for each area was determined weekly by calculating the mean severity score for all players with complaints.³  A mean weekly severity score for all knee, low back, and shoulder problems combined was also calculated to reflect players with complaints to multiple anatomic areas.

Questionnaire responses were collated from each team at intermittent intervals during the season and at the end of the season. Data and reasons for any missing questionnaires were confirmed by the primary investigator (C.S.) with the coaches and checked against attendance logs. Players with reduced team participation secondary to any injury or illness continued to complete the questionnaire weekly, whereas players with prolonged absence from the team due to injury, illness, or personal reasons did not complete the questionnaire during their absence. The questionnaire response rate was calculated based on the number of players who did not complete a team’s weekly questionnaire; weeks in which questionnaires were not completed because the team did not train or a player was not training with the team (eg, an international player late to join the team) were not considered missing.

All teams completed questionnaires during the preseason and in season. To best compare results, the questionnaire from the first week of each regular season was defined as week 0, resulting in preseason questionnaires defined as weeks −1, −2, −3, etc. The weekly prevalence of complaints was calculated for each anatomic region by dividing the number of athletes reporting some level of complaints by the total number of questionnaire respondents.⁹  The weekly prevalence of substantial problems was calculated using the same method but by dividing the total number of players reporting substantial problems by the total number of respondents. Substantial problems were defined as problems leading to self-reported moderate or severe reductions in either training volume or sport performance or the complete inability to participate in training or competition.^3,9  The weekly prevalence of complaints and substantial complaints was then reported based on each player’s preseason complaints status, match participation, position, team, and age. Each player was classified as either a substantial match contributor (start or play the majority of at least 25% of the team’s matches) or as having limited/no match participation, which was verified against match reports, attendance logs, and match video. In total, 52 player-seasons were classified as substantial match contributors (6 team seasons with 6 substantial match contributors; 2 team seasons with 8 substantial contributors).

A 2-sample t test was performed to compare the weekly prevalence of complaints in the preseason and in season and to compare the weekly prevalence of in-season complaints between players with and those without preseason complaints. A 1-way analysis of variance was performed to compare the effect of player position, team, and age on the weekly prevalence of complaints. When the 1-way analysis of variance revealed a difference in the prevalence of complaints between at least 2 groups, a post hoc analysis was performed to determine which groups were different. The duration of each problem was measured beginning with the first week of complaints and counting until no complaints were reported on a weekly questionnaire. The mean number of weeks that problems were reported was then calculated for each anatomic area. In addition, the percentage of the season that each player reported knee, low back, and shoulder problems was calculated. Data are reported as mean values with 95% CIs and exclude the questionnaire results from liberos unless otherwise noted. The α level was set at .05, and Excel (version 16; Microsoft Corp) was used for statistical analysis.

In total, 3405 weekly injury questionnaires were collected across all position groups. Liberos reported fewer complaints than other positions, with 61% (11/18 player-seasons) reporting some combination of knee (39%, 7/18 player-seasons), low back (39%, 7/18 player-seasons), and shoulder complaints (17%, 3/18 player-seasons) during the season. The weekly prevalence of complaints among liberos is presented for comparison with other position groups (Table 1); however, as liberos perform a unique role that requires little to no jumping and overhead attacks, they were not included in further analyses. The exclusion of liberos resulted in the analysis of 2867 weekly injury questionnaires. Five weekly questionnaires were missing (0.17% of questionnaires), and 8 additional questionnaires were partially completed with the low back section missing (99.6% [2854/2867] of possible questionnaires had all 3 sections fully completed).

We analyzed a total of 102 player-seasons comprising outside hitters, middle blockers, setters, and opposites and observed a mean weekly prevalence of 31% (95% CI = 28%, 34%) for knee, 21% (95% CI = 18%, 23%) for low back, and 19% (95% CI = 18%, 21%) for shoulder problems (Table 1). Figure 1 presents the cumulative prevalence of players who developed knee, low back, and shoulder complaints over the course of the season, resulting in 93% (95/102) of players with some level of knee, low back, or shoulder complaints during the season (knee, 79% [81/102 players-seasons]; low back, 71% [72/102 players-seasons]; shoulder, 67% [68/102 players-seasons]) and 58% (59/102 players-seasons) with substantial problems that resulted in moderate or severe reductions in training volume or sport performance (knee, 33% [34/102 players-seasons]; low back, 27% [28/102 players-seasons]; shoulder, 27% [28/102 players-seasons]). The mean weekly severity scores for players reporting problems were 23 (95% CI = 22, 25) for the knee, 23 (95% CI = 21, 25) for the low back, 22 (95% CI = 20, 23) for the shoulder, and 35 (95% CI = 34, 37) for all problems combined.

Players reported knee problems for a mean of 6 consecutive weeks (95% CI = 5, 7 weeks), with both low back and shoulder complaints lasting 5 weeks (95% CI = 4, 6 weeks) and all problems combined lasting 7 weeks (95% CI = 6, 8 weeks). Figure 2 shows the mean percentage of the season that individual players reported problems, with players experiencing knee problems for 36% (95% CI = 29%, 42%), low back problems for 23% (95% CI = 17%, 29%), and shoulder problems for 21% (95% CI = 15%, 27%) and the combination of any knee, low back, or shoulder problems for 51% (95% CI = 44%, 58%) of the season. Whereas most players experienced substantial problems for a relatively small portion of the season, half (51%, n = 52/102 player-seasons) of the included players reported some level of combined knee, low back, or shoulder complaints for >50% of the season (Figure 2).

A higher weekly prevalence of knee (38% versus 29%; t₃₅ = 3.023, P = .005) and low back (27% versus 19%; t₃₅ = 2.773, P = .009) problems was observed in the preseason than in season with no change in shoulder problems (19% versus 19%; t₂₆ = −0.328, P = .745) among all position groups, excluding liberos. Additionally, Figure 3 shows that players with preseason knee (42% versus 8%; t₄₉ = −18.726, P < .001), low back (34% versus 6%; t₃₂ = −12.025, P < .001), or shoulder (38% versus 8%; t₃₀ = −10.650, P < .001) complaints had a greater prevalence of complaints throughout the season than players without preseason complaints; more substantial complaints were also observed but with a noticeably smaller prevalence (Table 1). Table 2 reveals that, whereas players without preseason complaints reported fewer in-season complaints, players who experienced substantial knee and low back problems during the preseason reported the highest prevalence of substantial problems during the regular season.

The prevalence of knee, low back, and shoulder problems among elite men’s volleyball players is high; nearly all players (93%, excluding liberos; 88% [n = 106/120 player-seasons], including liberos) experienced complaints at some point during the season. The collective effect of knee, low back, and shoulder problems resulted in a mean weekly prevalence of 46% among all players excluding liberos, with higher prevalence during the preseason that decreased throughout the season. Of note, players who experienced problems during the preseason had more problems during the regular season.

Players experiencing knee, low back, or shoulder problems for a substantial portion of the season were not unusual; 51% of players, excluding liberos, reported some combination of knee, low back, and shoulder problems for more than half the season. Whereas a portion of these problems were minor with little burden to the athlete, 58% of players reported at least 1 bout of substantial knee, low back, or shoulder problems that led to a reduction in training volume or sport performance each season.

We observed a higher weekly prevalence of knee complaints (31%) than low back (21%) and shoulder (19%) complaints, and players, on average, experienced knee problems for a greater percentage of the season (36%) than low back (23%) and shoulder problems (21%). These findings among elite and professional men’s volleyball players are remarkably similar to those reported in previous research in which the same questionnaire was used among elite high school volleyball players.⁹  Clarsen et al⁹  reported that the highest weekly prevalence of problems occurred at the knee (36%), followed by the shoulder (16%) and low back (14%), during the 13-week study period. These similar findings highlight the prevalence of knee, low back, and shoulder problems that exist among competitive players of all ages, including high school, university, and professional players.

Patellar tendinopathy, commonly called jumper’s knee, has been reported to affect volleyball players more than other athletes, with a point prevalence as high as 45% to 51%.^11,12  Given this common finding of jumper’s knee symptoms in volleyball players, the high weekly and season prevalences of knee complaints that we observed were not surprising, as these questionnaires are designed to encompass all knee problems rather than just those relating to jumper’s knee. Previous researchers also found jumper’s knee symptoms to have the highest prevalence in outside hitters (67%, n = 12/18) and middle blockers (64%, n = 9/14) compared with setters (22%, n = 2/9) and liberos (17%, n = 1/6).¹²  Outside hitters/opposites also had the highest weekly prevalence of knee complaints in this study with relatively few complaints among liberos (outside hitters/opposites, 36%; middle blockers, 26%; setters, 26%; liberos, 11%).

The mean weekly prevalence of low back complaints was slightly higher in this cohort (21%; 95% CI = 18%, 23%), which excluded liberos, than that observed over the 13-week study in high school players (14%; 95% CI = 11%, 16%) using the same questionnaire.⁹  The exclusion of liberos partially explains this difference but does not fully account for the disparity. No other researchers have prospectively examined the prevalence of low back problems throughout a volleyball season. A few have examined the incidence or proportion of low back problems using time-loss or medical attention injury definitions,^2,13–17  leaving little to compare with our study. This highlights the important contribution our findings add to our understanding of the injury burden of low back problems in volleyball.

In 2 previous studies, researchers began to further our understanding of the prevalence, rather than incidence, of low back pain within different populations of volleyball players, both of which were limited by the use of 1-time retrospective questionnaires.^7,18  Noormohammadpour et al¹⁸  examined low back pain within female university athletes and reported a point prevalence of 20% and 1-year prevalence of 40% among volleyball players. Despite the different athlete population, this point prevalence is comparable to the mean weekly prevalence of 21% in our study. Bahr⁷  reported a 7-day prevalence of low back pain of 32% and 2-month prevalence of 46% within men’s professional beach volleyball players. Whereas beach volleyball is a different sport than indoor volleyball, the researcher emphasized how traditional time-loss injury surveillance programs do not accurately detect and quantify the burden associated with sporting injuries—in particular, overuse problems that lack a single identifiable event leading to injury. This is evident when comparing studies of indoor and beach volleyball in which the use of traditional time-loss injury definitions resulted in injury risks being reported as low (eg, 3.8 time-loss injuries per 1000 player-hours of match play from the Fédération Internationale de Volleyball injury surveillance system) and the high prevalence of knee, low back, and shoulder problems not being detected.^7,13 

The mean weekly prevalence of shoulder complaints was 19% in our study. This finding is similar to the 16% weekly prevalence reported in high school volleyball players.⁹  In a study of risk factors for shoulder injury within professional men’s players, investigators reported a shoulder complaint point prevalence of 27% during the preseason, with 47% of players reporting shoulder problems at some point during the 12-week study.¹⁹  In another study, researchers sampled men’s and women’s university players and reported a combined point prevalence of 22% for shoulder pain.²⁰  Finally, a season prevalence of shoulder problems was reported in 44% of male players competing at a university club national championship, with 45% of those reporting shoulder problems also stating that their sport performance was adversely affected.²¹  In our study, 67% of players reported shoulder problems during the season, which is more than reported in the previous studies.^19–21  Whereas previous researchers used retrospective questionnaires or shorter study periods, we recorded complaints prospectively on a weekly basis and for the length of each team’s season (mean of >6 months); it is unsurprising that additional shoulder problems were detected. Of note, liberos were not included in our analysis. The inclusion of liberos (3/18 player-seasons) results in a combined 59% (71/120 player-seasons) of all players across all positions reporting some level of shoulder complaints during the season, which is still more prevalent than that reported in previous studies.

Previous researchers have reported that attackers (outside hitters, opposites, and middle blockers) have a greater prevalence of shoulder problems than setters and liberos.^19,21  We also observed few problems among liberos; however, setters surprisingly had the highest weekly prevalence of shoulder problems compared with players in other positions. It is not clear if this was just an exceptional finding or if the use of the current study methodology (prospective, season-long, weekly serial reporting, and all-complaints injury definition) unmasked shoulder problems that may be more common among setters than previously believed.

Unsurprisingly, the prevalence of knee (38% versus 29%) and low back (27% versus 19%) problems was higher during the preseason than during the season. This finding is consistent with previous research in which a higher incidence of volleyball injuries during the preseason was reported.^14,22  It is unclear why this same finding was not observed for shoulder problems, where the mean prevalence did not change from the preseason to the regular season. The most striking observation may be that players who experienced preseason knee, low back, or shoulder problems of any kind continued to have substantially more problems during the regular season. Furthermore, a dose-response relationship appears to exist, where players who experienced the greatest levels of knee complaints in the preseason (substantial problems) had the highest mean weekly prevalence of in-season knee complaints (54%), followed by those with less severe preseason complaints (38%; substantial complaints excluded) and those without preseason complaints (8%; Table 2).

Knee, low back, and shoulder problems that resulted in moderate or severe reductions in training volume or sport performance collectively affected a mean of 1 in 11 players each week (nonliberos). Time and resources will be spent on best managing these injured players,²³  but attention must still be given to the additional one-third of the team who regularly report less severe complaints. These players with less severe complaints may need to receive extra attention through a variety of focused and individualized management options (eg, conversations with coaches and support staff, rehabilitation and recovery, warm-ups and strength programs, and training load modifications) to minimize the risk of these complaints progressing into substantial problems, but further research is needed to determine the efficacy of possible interventions.

Although our study provides new insights into the true prevalence and burden of knee, low back, and shoulder problems in men’s volleyball, it does not give a complete overview of all injuries because only these 3 areas were observed. We focused on recording all complaints rather than identifying specific injuries. This provides a more accurate account of the burden of these problems but limits further extrapolation of results related to specific conditions, such as jumper’s knee. We followed these players through their professional club or university seasons. Given that each of these teams included players who have also competed at an international level, we do not know if these results would be similar when athletes train and compete during the national team season. The reason why professional teams 1 and 2 had a lower weekly prevalence of complaints than the other teams is unclear; these team-specific observations highlight the importance of systematic monitoring and management of complaints within all teams.

We established strong relationships with the participating teams and had motivated coaches who took ownership of data collection. Therefore, we had a very high response rate with very few weekly questionnaires missing (99.6% of questionnaires had all 3 sections fully completed). This was better than previous studies in which researchers provided the Oslo Sports Trauma Research Centre Overuse Injury Questionnaire by email (91% to 93% response rates).^3,9  Future teams and research collecting similar data should include individuals who have a vested interest in the data and the project.²⁴  We do not know the extent to which the coach’s access to the weekly questionnaires affected player responses. Subjective questionnaires carry a risk of players under- or overreporting complaints; every attempt was made to educate and encourage players to report accurately.

Nearly all elite men’s volleyball players experienced knee, low back, or shoulder problems during the included 120 player-seasons, and most had at least 1 bout that substantially reduced training participation or sport performance. Whereas many knee, low back, and shoulder problems did not require players to stop participation in sport, on average, almost half of all players comprising outside hitters, middle blockers, setters, and opposites were playing through some combination of knee, low back, and shoulder complaints each week. Notably, players who experienced preseason knee, low back, and shoulder problems had more problems during the competitive season than their teammates without preseason problems. This is pertinent information for those trying to best manage their athletes and hoping to minimize the risk of these complaints progressing into substantial problems over the course of the season.

We thank the teams, players, and personnel for their support and participation.