The knee and back in swimming
– Written by Elsbeth van Dorssen, The Netherlands and Rod Whiteley, Andrea Mosler, Silvia Ortega-Cebrian and Paul Dijkstra, Qatar
Swimmers train a lot – in the water, in the weights room, on land plus additional cardiovascular cross-training. They are therefore especially prone to overuse musculoskeletal injuries. Shoulder injuries are the most common and we previously discussed a practical clinical approach to the management of shoulder injuries in swimmers1.
Knee and back injuries are also quite prevalent in swimmers – second and third on the list after shoulder injuries. We will use the same practical approach used previously to discuss the management of common knee and back injuries.
SWIMMING AND KNEE INJURIES
The incidence rate of knee injuries in swimming appears to be between 12.9%2 and 27%3, though it’s difficult to be certain, as many of the reported studies are retrospective case series with small participant numbers. Medial knee pain does seem to be most common in breaststroke swimmers. This is most likely due to the specific kicking mechanics used in breaststroke swimming, which result in high valgus loads as the knee goes rapidly from flexion into extension with external rotation of the lower leg. In one study, 75% of the (36) surveyed breaststroke swimmers reported at least three episodes of knee pain per season and 47% of these swimmers reported weekly episodes of knee pain4. There were equal numbers of unilateral and bilateral knee complaints in the injured cohort4.
The knee, especially the patellofemoral joint, can also be susceptible to injury due to weight training, particularly with exercises such as high-loaded squats and lunges commonly performed by swimmers. Therefore, freestyle, butterfly, and backstroke swimmers may also experience patellofemoral joint overload and anterior knee pain. The repetitive extension moments in the flutter kicks used in butterfly, as well as the repetitive action of pushing off the wall with the knees in a high degree of flexion while turning, may create patellofemoral joint overload, resulting in anterior knee pain.
Here we will focus on the breaststroker's knee, as this is the most common knee complaint in swimmers. The term breaststroker's knee is non-specific but usually refers to medial knee pain in a swimmer specialising in breaststroke – arguably the most difficult swimming stroke to perform technically. Elite breaststrokers tend to present with common anatomical features that help them to have a more efficient kick, but also predisposes them to increased injury risk. These anatomical features could include: increased hip internal rotation, valgus axis of the knees, pronated feet and, often, flat feet. It is important for the clinician to understand the biomechanics of normal breaststroke. It is especially important to appreciate that correcting technical faults in the breaststroke kick forms the basis of the clinical approach to managing medial knee pain in these swimmers.
BIOMECHANICS OF THE LEGS IN BREASTSTROKE
Swimming fast is nothing more than maximising propulsion and minimising drag. Active drag is comparable in freestyle, backstroke and butterfly, but is the largest in breaststroke. This might be because it has the largest exposed frontal area compared to the other strokes5. Speed differences during the stroke are the highest in breaststroke. Compared to the other swimming strokes – where the highest propulsive force comes from the arm stroke – the legs and arms are about equally important to generate propulsive force in breaststroke.
The kick begins with the knees in full extension, the ankles in plantar flexion, and the legs close to the surface of the water. The first phase of the kick is the recovery phase, where the swimmer pulls up the heels with the lower legs in a vertical position and the knees approximately shoulder width apart. During this pull up, the knees are flexed (Figures 1 and 2).
After the recovery phase, the feet begin to dorsiflex and evert, the ankles and lower legs externally rotate, while the hips are maintained in internal rotation and flexion (Figure 3).
During the thrust phase, the lower legs start moving from external rotation to a neutral position. The hips and knees start moving from flexion to full extension and from approximately 30 degrees abduction to adduction. The ankles will also move from dorsiflexion to full plantar flexion (Figures 4 and 5).
The thrust will end with the glide phase, when the swimmer is in fully extended and streamlined position, followed by a new kick (Figure 6).
The net effect of this complex movement, with the lower legs and feet externally rotated, pushing backwards against the water, is an ‘opening up’ (valgus and external rotation of the shank) force placed against the medial knee that is repeated with every kick.
The major forces from the kick will be applied to grab water with the feet to propel the body forwards during the mid and final phase of the thrust. These are fast, high-force movements, involving adduction of the hips, internal rotation of the lower leg and inversion of the feet. During the kick, force is produced primarily by the adductor muscles, as well as the invertor muscles of the lower leg.
Arm-leg co-ordination is also important in breaststroke. Three different techniques according to the glide time are observed6:
• Glide: where the body is fully extended and streamlined before the arm catch.
• Continuous: where the arm catch starts just as the leg kick is completed.
• Overlapped: where the arms start their catch and outward motion before the completion of the leg kick.
Co-ordination can also influence the force on the kick and the knee joint. Swimming speed and individual characteristics can influence co-ordination.
A CLINICAL APPROACH TO A SWIMMER WITH A KNEE INJURY
History
As with any injury, a very thorough, sport-specific history is important.
Start with the question: ‘when during the stroke do you feel the pain?’ The knee is highly loaded during the beginning of the thrust phase (external rotation/valgus). Twisting and straightening the knee can also be painful. The medial collateral ligament is the most common source of pain in breaststroke swimmers. This structure is where the swimmer usually feels the pain. In patellofemoral problems, the pain is generally more anterior or around the patellar facet, possibly with vague referral to the posterior knee region. Generally, with patellofemoral pain, the swimmer complains of pain that is more related to weight training (squats, lunges or other patellofemoral joint loading exercises) or heavy leg drills in the water (with a kickboard or zoomers). How? – a gradual onset of pain is more common than an acute onset. Try to determine how any recent changes to extrinsic factors such as: changes in training load (percentage breaststroke swum during training, breaststroke-specific warm-up, increased total training load, land training), recent technique changes or technical flaws pointed out by the coach may relate to the onset of pain.
Rovere and Nichols4 interviewed and examined 36 competitive breaststroke swimmers of different performance levels. They reported a higher risk in knee pain if:
• The swimmer is older (mean of 19 years compared to 16 and 15).
• They had more years of training (9.1 compared to 6.8 and 7.6).
• They had trained for fewer months per year (almost 9 compared to almost 10).
• They had swum more breaststroke yards per week (22,100 compared to 14,000).
• They had spent more minutes stretching per week (104 compared to 47).
• They completed less breast stroke specific warm-up activities.
These factors indicate that prolonged exposure leads to an increased prevalence of knee pain.
Patellofemoral pain can also be related to changes in training load: more leg drills in the water, more drills for starting/turning or heavy weight training for the legs.
What? – the nature of the pain is also important. Is it a sharp, well-localised pain, a dull aching, spreading pain or perhaps an electrical-type pain? Medial collateral ligament pain is often a well-localised, sharp pain, especially when putting valgus stress on the knee joint. Patellofemoral pain is often a non-specific, vague pain. An ‘odd’ feeling in the same area is common before it starts to be painful. Always consider the kinetic chain! Restriction of hip range of motion, and/or strength, and/or proximal core stability can be a major source of knee problems because of the effect on the biomechanics of the breaststroke kick. You will commonly only improve a breaststroker’s knee pain once you have improved hip function.
Ask the swimmer about other issues in the kinetic chain (lower back, hips and ankles). Ask for mechanical knee symptoms, which might suggest a discoid meniscus or patellar subluxation. Don’t forget to ask about any previous history of knee injuries and the total training load (swim sessions, land and weight training sessions and alternative cardiovascular training sessions running/cycling).
Clinical and functional assessment
Integrate observation and functional assessment
• Inspection: the limb alignment, Q-angle, patella anatomy and muscle atrophy could suggest a different loading pattern of the knee.
• Range of motion: the range of motion of not only the knees, but also the lower back, hips and ankles is important to get an idea about the loading of the medial side of the knee during swimming. In our opinion, hip internal rotation in flexion is essential to examine and to optimise if range is asymmetrical or restricted. There is some evidence that swimmers with knee pain might demonstrate significantly impaired hip internal rotation range. Rovere and Nichols found a mean hip internal rotation range of 37° in swimmers with frequent knee complaints, 42° with occasional knee complaints and 47° in swimmers who had never experienced knee complaints4. Kippenhan (18 collegiate varsity swimmers and 10 recreational swimmers) examined the influence of active range of motion of the lower limb joints on the effectiveness of the whip kick. A significant difference was found between greater active hip extension, external rotation in the knee and inversion of the ankle, and a higher skill level. Swimmers use the full range of motion in hip extension, knee flexion/extension and plantar flexion in the ankle during the kick. If there is any asymmetry or restriction in one of these movements, it needs to be optimised7.
• Ligaments: valgus stress testing with 20 to 30 degrees flexion of the knee may reproduce the swimmer’s pain, and palpation of the proximal and distal insertion of the medial collateral ligament could also be painful. A more specific breaststroke test could be valgus stress and external rotation of
the knee. This mimics the movement during the breaststroke kick and is likely to reproduce the pain.
• Patellofemoral joint: patellar malalignment and instability could suggest patellar compression overload as a possible cause of knee pain. Palpation of the medial patellar facet and crepitus should be assessed.
• Lateral joint line: with valgus load on the medial side, there is some compression load on the lateral side. Assess for discoid lateral meniscus and cartilage defects.
• Special tests: laxity, muscle lengths,muscle strength, core-stability.
Biomechanical considerations
Technical flaws resulting in an increase in knee valgus load, may cause medial knee pain.
A large abduction angle of the hip may contribute to a higher valgus knee load, because of the larger adduction. The coach might indicate that the knees should be held more together. Different arm-leg coordination may also create higher forces to the knee joint. Stulberg et al described that there is a difference in the lower leg mechanics in swimmers with and without knee pain: in swimmers without knee pain, the tibia and ankles rotate and dorsiflex when the knees are flexed. In the swimmers with knee pain, this rotation and dorsiflexion occur during knee extension8.
Investigations to consider
The primary role of imaging is to confirm the clinical diagnosis and to rule out other major pathology. However, imaging results should be interpreted with caution. In one study, more MRI abnormalities (infrapatellar fat pad oedema, bone bruises, pre-femoral fat pad oedema and joint effusion) were found in talented, asymptomatic adolescent male swimmers than an age-matched control group. The repetitive knee joint movements (extension, valgus) during workout series could be a predisposing factor in development of these MRI abnormalities9.
An X-ray could rule out cartilage defects and patella alta and baja. MRI could rule out severe overload/strain of the medial collateral ligament, but also other mechanical causes such as discoid meniscus, cartilage defects etc.
Possible anatomical-pathological diagnoses
Medial knee pain involving the medial collateral ligament or the medial patellar border of the dominant leg is the most common knee complaint in breaststroke swimmers4,10. Repetitive valgus loads may also result in pes anserine bursitis or tendinopathy11. Overload in the flutter kicks, land training and weight training can result in patellofemoral pain syndrome, inflamed Hoffa’s fat pad or apophysitis in younger swimmers.
Management plan
In breaststroke swimmers, a temporary reduction in breaststroke-specific training load will decrease medial knee load. It is often only breaststroke load that needs to be controlled. Swimmers with medial knee pain can usually continue swimming using the other strokes – if pain-free. It is advisable to avoid exercises that create excess valgus knee stress during land and weight training sessions, such as running, jumping, deep squatting exercises and lunges. Anti-inflammatory medication and ice application can be used in the acute phase. It is important for swimmers to include prevention strategies in their individual training programme. Swimmers should pay special attention to optimal technique when performing exercises in the weights room as they have a natural tendency to collapse into valgus. Quadriceps strengthening, optimal leg muscle strength balance and ‘core function’ may be effective to optimise the load capacity of the knee. It is also important to optimise the range of motion in the lower back, hips (particular internal rotation in hip flexion), knees and ankles.
An effective warm-up for a breaststroke set is recommended. Advice regarding efficient breaststroke kick technique should be done in consultation with the swimming coach and may include: keeping the knees together to temporarily decrease the adduction time and to optimise the balance between propulsion and drag. Gradually reintroduce breaststroke load as symptoms allow.
SWIMMING AND LOWER BACK INJURIES
Low back pain will affect over 80% of the normal population at some point in their life and is also common in swimmers. Hangai et al reported that 76.1% of the 47 swimmers in a study of 308 well-trained athletes had experienced low back pain during their lifetime12. In a retrospective cohort study by Wolf et al of a Division I Collegiate Swimming Team, the back and neck was the second most injured body part, accounting for 24% of all the injuries in males and 21% of all the injuries in female swimmers. Of the 94 swimmers, 40% sustained a back/neck injury in the 5-year time period of the study13. In a prospective study, the incidence of back pain in swimmers was 16.1%2. Butterfly and breaststroke swimmers are especially at risk of developing lower back pain due to repetitive flexion and extension of the back.
A CLINICAL APPROACH TO A SWIMMER WITH A LOWER BACK INJURY
History
Where is the pain located in the lower back; thoracolumbar junction or thoracic spine? Is the central spine painful; or is the pain slightly more lateral in the paravertebral muscle area? How did the pain start? Low back pain usually does not start during swimming sessions, but during dry land training, weight training or recreational activities13. Chase et al found that the lower back was the most common site for sudden onset injuries2. When? – although swimming is not usually the primary mechanism of developing lower back complaints, swimmers often describe lower back pain being aggravated while swimming. In particular, rotation in freestyle, turns and diving can create pain and/or motion restriction if the lower back is injured. Weight training may increase the risk of lower back injury especially when lifting technique and/or appropriate periodisation of weight training do not receive the necessary attention. Ask about total training load and particularly about sudden increases in training load. Which stroke is hurting the most? Was there any recent adjustment in swimming technique? Ask about pain during daily activities and, if so, what type of activities. Does the swimmer feel pain at rest? When is the pain worse: in the morning or during the day/towards the end of the day? What is the nature of the pain? Is the pain radiating to the legs? Is there any loss of sensation or power?
General questions may include recent trauma, change of mattress, travel schedules, other recent or past musculoskeletal injuries, previous investigations and treatments. Ask about the use of kicking boards, fins or zoomers, pull-buoys and hand paddles as these devices may contribute to excessive hyperextension of the lower back. For example, the pull-buoy, which is placed between the legs to swim with the arms only, places the legs in a higher position in relation to the surface of the water, resulting in an increase in forced hyperextension of the lower back. The kick board, used for leg workout, places the arms, shoulder and head above the water, resulting in an increased lumbar lordosis.
During the questioning we also need to identify any aggravating movement patterns. Is flexion or extension the primary painful mechanism or is it a multidirectional pattern (flexion and extension pattern or rotation)?
Integrated observation and functional assessment
• Posture: swimmers are typically broad and rounded-shouldered athletes, standing with a hyperlordosis, hyperkyphosis (swayback posture). The gluteal muscles tend to be underrecruited compared to the paraspinal muscles in this position. Assessment of the behaviour of the lumbar spine during sitting, squatting or any aggravating activity would provide information of potential aggravating mechanisms. For example, swimmers may present with an extension pattern in standing, with the opposite when sitting – they sit with the lumbar spine in end-of-range flexion. These positions can potentially further sensitise the posterior structures, which are already stressed.
• Spine mobility: assess lumbar spine and sacro-iliac joint mobility. Low back pain can also be associated with lumbar spine hypermobility. A swimmer needs a certain amount of spinal mobility to perform the four swimming strokes. It is also important to assess cervical and thoracic spine mobility. Palpating intervertebral mobility could provide information about the passive stabilising structures, adding to your clinical reasoning.
• Core-stability: is the swimmer able to actively stabilise their core? How is the muscular control around the core? Swimmers need to keep their centre of mass as high as possible in the water. This requires activation of the core in all swimming strokes to prevent collapsing of the lumbar spine and pelvis. In addition, forces for strong kicks are originated by the core muscles.
• Neurological signs: the Slump, Lasegue and Bragard tests might help to examine neurodynamic contributions to the presentation.
• Kinetic chain: lower back pain can also be a result of referred pain or biomechanical insufficiency resulting from hip or sacroiliac joint dysfunction. Range of motion and pain provocation tests of these joints are therefore important to assess in swimmers with lower back pain.
Biomechanical Considerations
All the swimming strokes, but especially butterfly and breaststroke, require a degree of lumbar hyperextension to achieve a streamlined position in the pool. Dipping the head underwater and breaking the surface with the heels are specific to the breast and butterfly strokes. To be performed optimally, these strokes require considerable flexibility of the thoracic and lumbar spine. The twisting motions in the turns or an insufficient body roll during freestyle may contribute to the risk of muscle and ligament injuries. The 15 metre dolphin kick underwater also places considerable stress on the thoracolumbar paraspinal muscles.
Special investigations to consider
As in most lower back complaints, imaging has a limited role in the management of lower back pain in the swimmer. An X-ray might be useful to rule out structural abnormalities such as spondylolysis, spondylolisthesis and Scheuermann’s kyphosis in a swimmer not responding to targeted interventions. An MRI can rule out stress reactions in the vertebrae (pars) and sacroiliac joint or lumbar disk problems (lumbar intervertebral disk degeneration).
Possible anatomical-pathological diagnoses
Back muscle strains are the most common diagnoses in swimmers2. Chronic degenerative disc lesions, especially in the L5 to S1 discs, as well as spondylolysis/spondylolisthesis are seen in swimmers, perhaps due to the repetitive extension loading of the spine12,14,15,16. It is important to treat the patient and not the scan. Goldstein et al reported spinal abnormalities (degenerative disc changes, spondylolysis or spondylolisthesis) on MRI images of the lower back in 15.8% of pain-free swimmers17. The repetitive extension with rotational movements of swimming can result in pars stress fractures, so this should be included in your differential diagnoses. Don’t forget to rule out Scheuermann’s kyphosis, intra-articular hip pathology and nerve root compression.
Management plan
When managing acute lumbar strains rest, ice, local modalities (massage), anti-inflammatory drugs and postural exercises will be part of the management plan.
To reduce the load on the spine in swimmers with spondylolysis, spondylolisthesis and degenerative disc changes, emphasise muscle strengthening, posture and pelvic/ core-stability.
Be aware of the body position when training with swimming devices; consider advising to modify the use of these devices. Modify butterfly and/or breaststroke training as well as weight and dry land training. During management, try to modify pain by correcting adaptive or abnormal movement patterns during activities of daily living and land training that could aggravate the pain.
CONCLUSION
While shoulder injuries have the highest incidence in swimmers, it is important not forget the rest of the swimmer’s body. Knee injuries and lower back pain are common musculoskeletal injuries in swimmers. As swimming is a very technical sport and swimming fast is a highly skilled activity, an integrated, multidisciplinary approach is the key to successful management of swimming injuries. It is essential to discover, consider and manage all the potential intrinsic and extrinsic contributing factors. Movement patterns, swimming technique, training load and technique with weight training exercises are particularly important. Early recognition and intervention in these contributing factors will give the best results.
References
1. Van Dorssen E, Whiteley R, Mosler A, Ortega-Cebrian S, Dijkstra P. Shoulder injuries in swimming: meeting the challenge. Aspetar Sports Medicine Journal 2014; 3:584-593.
2. Chase KI, Caine DJ, Goodwin BJ, Whitehead JR, Romanick MA. A prospective study of injury affecting competitive collegiate swimmers. Res Sports Med 2013; 21:111-123.
3. Kennedy JC, Hakwins RJ. Breast stroker’s knee. The Physician and Sportsmedicine 1974; 2:33-38.
4. Rovere GD, Nichols AW. Frequency, associated factors, and treatment of breaststroker’s knee in competitive swimmers. Am J Sports Med 1985; 13:99- 104.
5. Gatta G, Cortesi M, Fantozzi S, Zamparo P. Planimetric frontal area in the four swimming strokes: implications for drag, energetics and speed. Hum Mov Sci 2015; 39:41-54.
6. Maglischo E. Swimming fastest. Champaign, IL: Human Kinetics 2003.
7. Kippenhan CB. Lower-extremity joint angles used during the breaststroke whip kick and the influence of flexibility on the effectiveness of the kick. Paper presented at: International Symposium on Biomechanics in Sports 2002, Caceres, Spain.
8. Stulberg S, Shulman K, Stuart S, Culp P. Breaststroker’s knee: pathology, etiology, and treatment. Am J Sports Med 1980; 8:164-171.
9. Soder RB, Mizerkowski MD, Petkowicz R, Baldisserotto M. MRI of the knee in asymptomatic adolescent swimmers: a controlled study. Br J Sports Med 2012; 46:268-272.
10. Vizsolyi P, Taunton J, Robertson G, Filsinger L, Shannon HS, Whittingham D et al. Breaststroker’s knee. An analysis of epidemiological and biomechanical factors. Am J Sports Med 1987; 15:63-71.
11. Rodeo SA. Knee pain in competitive swimming. Clin Sports Med 1999; 18:379-387.
12. Hangai M, Kaneoka K, Hinotsu S, Shimizu K, Okubo Y, Miyakawa S et al. Lumbar intervertebral disk degeneration in athletes. Am J Sports Med 2009; 37:149- 155.
13. Wolf BR, Ebinger AE, Lawler MP, Britton CL. Injury patterns in division I collegiate swimming. Am J Sports Med 2009;37:2037-2042.
14. Kaneoka K, Shimizu K, Hangai M, Okuwaki T, Mamizuka N, Sakane M et al. Lumbar intervertebral disk degeneration in elite competitive swimmers. Am J Sports Med 2007; 35:1341-1345.
15. Mundt DJ, Kelsey JL, Golden AL, Panjabi MM, Pastides H, Berg AT et al. An epidemiologic study of sports and weight lifting as possible risk factors for herniated lumbar and cervical discs. Am J Sports Med 1993; 21:854-860.
16. Nyska M, Constantini N, Calé-Benzoor M, Back Z, Kahn G, Mann G. Spondylolysis as a cause of low back pain in swimmers. Int J of Sports Med 2000; 21:375-379.
17. Goldstein JD, Berger PE, Windler GE, Jackson DW. Spine injuries in gymnasts and swimmers. An epidemiologic investigation. Am J Sports Med 1991; 19:463-468
Cycling is a complex interaction between the body and the bike, and so both
Elsbeth van Dorssen M.D.
Sports Medicine Physician
SportmedX, Queen Beatrix Hospital
Winterswijk, The Netherlands
Rod Whiteley Ph.D.
Assistant Director of Rehabilitation
Andrea Mosler B.App.Sc. (physio), M.App.Sc.(sports physio)
Senior Physiotherapist
Silvia Ortega-Cebrian P.T., M.Sc.
Senior Sports Physiotherapist
Paul Dijkstra M.B., Ch.B., B.Sc. (Hon)
Pharmacology, M.Phil. (Sports Medicine),F.F.S.E.M. (CESR UK)
Sports Medicine Physician
Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar
Contact: eal.van.dorssen@gmail.com
Image Lis Jakupsstovu