How common it is, and who gets itEmerging evidence
Across tennis injury studies, the trunk accounted for 5% to 25% of injuries. In adults there is one study: an interview survey of 633 spectators at a French tournament in 1999 found that the 388 who played tennis had no more back pain or sciatica than the 245 who didn't. In 102 competitive 12-year-olds and 203 schoolchildren, back pain was as common in both groups, though the players more often said it limited their usual activities, and among 181 elite German athletes in overhead sports, back pain was common in all of them and least common in the tennis players, who were also the youngest.
Young competitive players are where back injuries stand out. In 101 elite Australian juniors over 5 years, the lower back was the commonest and most severe injury site, at about 10 days lost per injury. In 55 Swedish club juniors, low back pain was among the commonest problems and most repeat injuries were in the lower back; at 6 years of the US boys' national championships, back injuries were the commonest. In 198 Swedish competitive players aged 13 to 19 followed weekly for a year, 85 had a first episode of back pain. In professionals, the spine was 13.7% of 750 injuries at 12 French Opens (the lower back 9.3%), head, spine and abdominal injuries were about a quarter at Wimbledon, and the back wasn't among the top five sites at 16 US Opens. Each study counts injuries its own way.
Sources 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
What the strokes ask of the lower backEmerging evidence
As the arm cocks back to serve, the spine arches, side-bends and turns towards the racket side, then the turn reverses fast before the ball is struck. In 20 elite teenage boys, both kick and flat serves loaded the lower back hard, with side-bending forces about eight times those of running; players with back pain had higher side-bending forces, and the flat serve bent the back forward more than the kick serve. Every player served close to the end of their lower back's range, and those with pain had less lower back movement in every direction.
In 19 of the same group, players also turned close to their limit in the backswing of both forehands and backhands, so groundstrokes add to the load. In 24 pain-free elite juniors, those with spine changes on scans served with the same size of movements as those without. The International Tennis Federation (ITF) says the combined turning, bending and arching of the back in the serve may cause problems. These are lab studies of elite teenagers, so they show where the load goes, not that a club player's serve will injure them.
Sources 12, 13, 14, 15, 16, 17
Load: sudden jumps matter more than total hoursEmerging evidence
In the 198 Swedish teenagers, each extra weekly spike in tennis training or matches raised the rate of back pain by about 17%, and spikes in fitness training raised it too, while total hours for their age weren't linked. In 55 Swedish juniors, playing more than 6 hours a week and a previous back injury went with back pain. Elite matches average about 40 serves a set, a useful yardstick for a serving session (our reading).
Sources 8, 18, 19
A young player's stress fracture of the spineEmerging evidence
Back pain on arching backwards is the classic sign of spondylolysis, a stress fracture in the thin bridge of bone at the back of a lower vertebra, in young athletes. At one orthopaedic clinic it was found in about 4 in 10 young people under 19 whose back pain had lasted more than 2 weeks. The American Academy of Orthopaedic Surgeons (AAOS) says it is more likely in young people whose sport repeatedly overstretches the lower back into an arch, and its pain can feel like a muscle strain. In 66 young Spanish tennis players with spondylolysis, most lesions were at the lowest lumbar vertebra, and the authors suspected the forehand's arch with forced turning as a contributor.
Sources 20, 21, 22, 23
When a scan helps, and what it doesn't meanStrong evidence
The National Institute for Health and Care Excellence (NICE) says don't routinely offer imaging for low back pain outside specialist care. Scans of pain-free young players are rarely normal: 28 of 33 elite adolescents without back pain had changes on magnetic resonance imaging (MRI), including 9 with pars lesions, and only 4 of 98 elite juniors had none, with pars changes in about 3 in 10 and disc wear in about 6 in 10. So a scan finding isn't always the source of the pain.
The exception is a young player whose back hurts on arching and keeps hurting: an evidence review suggests MRI as the first scan after an X-ray, with computed tomography (CT) if it is unclear, and MRI can show an early stress reaction without radiation. A scan is also for the warning signs and for sciatica that isn't improving when an injection or surgery is being considered.
Sources 24, 25, 26, 21, 20
How it usually goesEmerging evidence
The NHS says back pain usually improves within a few weeks but can last longer or keep coming back, and sciatica usually gets better in a few weeks to a few months; in juniors, back pain often comes back. For a young athlete with spondylolysis, 92% returned to sport after non-surgical care across 14 studies of 592 athletes, on average about 4.6 months later, 92% of 376 adolescents across 11 studies returned without surgery, and a review of 25 publications put the return at about 3.7 months on average without surgery. In the 66 young tennis players, time off sport ranged from about 2 months for an established defect to about 4.5 months for a developing one. Most defects don't knit, but most people do well anyway. No one can promise a date.
Sources 27, 28, 6, 29, 30, 31, 23, 32