Breaststroker’s Knee
Breaststroker’s knee is an overuse knee injury most commonly seen in swimmers who do a lot of breaststroke. It causes pain on the medial (inner) side of the knee, typically during or after the breaststroke kick (often called the whip kick). Unlike freestyle or backstroke, breaststroke involves a wide, circular leg action that combines hip and knee flexion, external rotation, abduction (legs moving out), and then a forceful snap into extension as the legs come together. Over time, this repetitive movement can overload soft tissues on the inner knee.
Breaststroker’s knee is not a single structure injury for everyone. In many swimmers, symptoms relate to irritation of the medial collateral ligament (MCL) or the pes anserinus region (the tendons of three muscles attaching on the inner upper shin and the small bursa beneath them). Medial meniscus irritation, patellofemoral pain, and other sources of medial knee pain can also co-exist, which is why assessment matters.
It can affect competitive swimmers, recreational breaststrokers, and triathletes who add breaststroke sets for variety. The condition often starts as a mild ache during a set, then lingers after training, and eventually may flare with walking, squatting, stairs, or prolonged sitting if the load continues. The earlier you address it, the easier it is to settle.
Physiotherapy for breaststroker’s knee focuses on (1) reducing irritation and swelling, (2) correcting kick biomechanics and load management in the pool, and (3) strengthening the hip, core and knee so the inner knee structures are not repeatedly strained. Your physiotherapist can also work alongside your coach to refine technique, gradually reintroduce kick volume, and prevent recurrence.
What is breaststroker’s knee? Breaststroker’s knee refers to medial knee pain caused by repeated loading patterns from the breaststroke whip kick. The whip kick involves bending the knees and hips, turning the lower legs outward, abducting the thighs, and then forcefully extending and snapping the legs together. This pattern can produce repeated valgus stress (a tendency for the knee to collapse inward) and rotational stress through the medial knee.
Relevant anatomy: Two commonly involved regions are the MCL and the pes anserinus complex.
Medial collateral ligament (MCL): The MCL is a broad band on the inside of the knee that resists the knee collapsing inward. While breaststroker’s knee is not typically a single acute “sprain”, repeated valgus loading can irritate the MCL, particularly if the kick is wide or the knees drift apart.
Pes anserinus: This term describes the combined tendon attachment of three muscles on the upper inner tibia: sartorius, gracilis and semitendinosus. Beneath these tendons sits a small bursa that reduces friction. Repetitive knee flexion, rotation, and adductor tension can irritate this region and produce pain slightly below the joint line.
Why some swimmers get it and others do not: Breaststroker’s knee usually results from a combination of factors: (1) training load (how much breaststroke you do and how quickly it increases), (2) technique (kick width, tibial rotation, and timing), and (3) individual biomechanics (hip rotation range, joint mobility, and strength control). Fatigue is often the trigger that turns a manageable load into an injury, because the kick becomes wider and less controlled as you tire.
Differential diagnosis matters: Medial knee pain in swimmers can mimic or overlap with patellofemoral pain, medial meniscus irritation, MCL sprain, or even hip and lumbar referral. Physiotherapy assessment is important to ensure you are treating the right thing. If you treat it like “just a tight muscle” but the driver is actually meniscus irritation or significant valgus collapse, symptoms often persist.
- Pain on the inner (medial) side of the knee during or after breaststroke swimming.
- Discomfort during the whip phase of the kick (when the legs rotate and snap together).
- Tenderness along the MCL line or along the medial joint line.
- Pain or tenderness slightly below the inner knee on the upper shin (pes anserinus region), sometimes with local swelling if the bursa is irritated.
- Reduced kicking power or “protective” kicking where the swimmer avoids a full kick.
- Tightness in adductors (inner thigh), quadriceps, hamstrings, or calves.
- Clicking, catching, or a sense of irritation in the knee (may suggest meniscus or joint involvement and needs assessment).
- In chronic cases, symptoms can appear with walking, squatting, stairs, or prolonged sitting, not just swimming.
- High breaststroke training volume, particularly frequent kick sets and high-intensity breaststroke work.
- Rapid increases in breaststroke load (distance, intensity, or frequency) without adequate recovery.
- Technique issues: overly wide kick, excessive tibial external rotation, or knees separating too far during the recovery phase.
- Hip weakness or poor pelvic control (gluteus medius/maximus weakness) leading to knee valgus and medial knee stress.
- Reduced hip mobility (or asymmetry) that forces compensation through the knee during the kick.
- Muscle imbalances including tight adductors and hip flexors, plus reduced glute activation, affecting lower limb alignment.
- Fatigue and poor recovery (sleep, nutrition, overall training stress), leading to technique breakdown.
- Chronic medial knee pain that persists outside of swimming, affecting walking, stairs and squatting.
- Secondary technique compensations (for example hip or back pain) if the swimmer alters kick mechanics without guidance.
- Pes anserinus bursitis or tendon irritation becoming recurrent if load and hip control are not addressed.
- Development or aggravation of medial meniscus irritation if the knee is repeatedly overloaded and reactive.
- Breaststroker’s knee is a recognised swimming overuse injury associated with the breaststroke kick and medial knee pain, often involving medial knee structures due to valgus and rotational stresses.
- During the kick, the knee moves from bent to straight while valgus stress and external rotation can be applied. This combination helps explain why the inner knee structures can get irritated when volume is high or technique is off.
- In a study of nearly 400 competitive swimmers, about 73% of breaststroke specialists reported knee pain, and even 48% of non-breaststroke swimmers had knee pain, showing just how frequently this issue occurs in swimmers overall.
- Overuse injuries are strongly linked to training load errors, including rapid increases in volume or intensity without adequate recovery, supporting the importance of physiotherapy-based load management.
- Swimmers may be more likely to develop knee pain when their legs are set very narrow or very wide at the start of the kick.
How Is It Diagnosed?
Breaststroker’s knee is usually diagnosed clinically based on a clear history (medial knee pain linked to the breaststroke kick) and a targeted physical assessment. Your physiotherapist will ask about swim volume, recent changes in training, whether pain is immediate or delayed after sets, and what part of the kick provokes symptoms. They will also ask about dryland training, previous knee injuries, and whether symptoms occur outside the pool.
Physiotherapy examination commonly includes:
1) Palpation and symptom mapping: Identifying whether tenderness is along the MCL, at the medial joint line (which can suggest meniscus involvement), or below the joint line in the pes anserinus area.
2) Range of motion and flexibility: Checking hip rotation range (internal and external rotation), knee motion, and muscle flexibility (adductors, hip flexors, hamstrings, quadriceps, calves). Limited hip rotation can force more rotation at the knee during the kick.
3) Strength and control: Testing hip abductor and external rotator strength (gluteus medius/maximus), quadriceps and hamstring control, and single-leg alignment. Poor hip control often shows as the knee drifting inward during single-leg tasks, which mirrors the valgus stress that can occur during the whip kick.
4) Functional tests: Squat, step-down, single-leg squat, hopping (if appropriate), and sometimes simulated kick positions on land. These help identify the movement faults and load patterns contributing to symptoms.
5) Technique discussion: Many physiotherapists will ask you to describe your kick cues and may liaise with your coach. In some settings, video analysis is used to identify excessive kick width, timing issues, or knee-dominant mechanics.
If your physiotherapist suspects another injury (such as meniscus irritation) or if symptoms do not improve with a well-structured rehab plan, they may refer you to your GP for imaging.
Investigations & Imaging
- Ultrasound: Can be useful if pes anserinus bursitis is suspected, or to assess local soft tissue irritation and swelling around the medial knee. It may also help exclude other causes of medial pain.
- MRI (Magnetic Resonance Imaging): May be recommended if symptoms persist, if a medial meniscus injury is suspected, or if the pain pattern suggests intra-articular pathology. MRI can show meniscus changes, cartilage irritation, and ligament or tendon involvement.
- X-ray (plain radiograph): Not typically required for breaststroker’s knee, but may be used to rule out bony issues if symptoms are atypical or if there is concern about other knee pathology.
Physiotherapy Management
Breaststroker’s knee is a term used for pain on the inside of the knee that builds up over time from the repeated forces of the breaststroke whip kick. In the kick, the knees and hips bend, the lower legs turn outward, and then the legs straighten and sweep back together. When this movement is repeated a lot, especially if the kick becomes wide or less controlled, it can place ongoing inward pressure (valgus stress) and twisting forces through the medial side of the knee, which can gradually irritate sensitive tissues.
Two areas are commonly involved. One is the medial collateral ligament (MCL), the strong band on the inside of the knee that helps stop the knee from collapsing inward. Breaststroker’s knee is not usually a single sudden sprain; instead, the MCL can become sore when it repeatedly absorbs valgus stress, particularly if the knees drift apart during the kick or control drops with fatigue. The other common region is the pes anserine area just below the joint line, where three tendons attach on the upper inner shin and a small bursa helps reduce friction. Repeated bending and rotation, combined with muscle tension through the inner thigh and hamstrings, can irritate this attachment point and cause pain a little lower than the joint itself.
Not everyone who swims breaststroke develops symptoms because breaststroker’s knee usually comes from a mix of factors. Training load matters, such as how much breaststroke you do and how quickly that volume increases. Technique matters too, including kick width, how far the lower leg turns out, and the timing and control of the snap back together. Your individual biomechanics also play a role, such as hip rotation range, mobility, and strength around the hip and knee. Fatigue is often the tipping point: as swimmers tire, the kick can become wider and less coordinated, increasing stress on the inside of the knee.
It’s also important not to assume all inner-knee pain in swimmers is breaststroker’s knee. Similar symptoms can come from kneecap-related pain, meniscus irritation, an MCL sprain, or even referred pain from the hip or lower back. A physiotherapy assessment helps identify what’s actually driving the pain so the treatment matches the problem and recovery is quicker and more reliable.
Other Treatments
Other treatments that may be used alongside physiotherapy include:
Anti-inflammatory medication: In select cases and under medical advice, anti-inflammatories can reduce short-term symptoms and make it easier to keep moving and strength training. They do not correct the cause and should not be used to “mask” pain while continuing aggravating breaststroke volume.
Sports medicine input: A sports doctor may be involved if symptoms are severe, recurrent, or not responding as expected, especially if imaging is needed to rule out a meniscus injury or other intra-articular knee issues.
Coach collaboration: Technique change is a legitimate “treatment”. Many swimmers improve when training cues reduce kick width and rotation stress, particularly under fatigue. Physiotherapy outcomes are often best when your rehab plan and your swim programming are aligned.
Surgery
Surgery is not a routine treatment for breaststroker’s knee. This condition is usually managed successfully with conservative care: physiotherapy-based load management, technique retraining, and progressive strengthening.
If symptoms persist for months despite well-structured physiotherapy, or if there are mechanical symptoms such as locking, recurrent catching, or significant swelling, your physiotherapist may recommend medical review and imaging to rule out injuries such as a meniscus tear that could require different management. Any surgical decisions would be guided by the specific diagnosis rather than the label “breaststroker’s knee”.
- Progress breaststroke volume gradually, especially after breaks, injuries, or off-season periods. Avoid jumping straight into large kick sets or high-intensity breaststroke work.
- Maintain hip strength endurance (gluteus medius and maximus) so the knee does not absorb excessive valgus and rotation stress during the whip kick, particularly under fatigue.
- Use technique cues that reduce medial knee strain: avoid an overly wide kick, limit excessive external rotation, and focus on hip-driven power rather than knee-dominant snapping.
- Balance swim training with appropriate dryland strength, avoiding high volumes of deep knee flexion and adductor-heavy work when breaststroke volume is high.
- Schedule recovery strategically: ensure adequate sleep, manage overall training stress, and include easier weeks so technique does not deteriorate every session from fatigue.
- If medial knee pain starts, reduce breaststroke kick early and see a physiotherapist. Early load reduction and targeted rehab usually prevents a long-term problem.
The prognosis for breaststroker’s knee is generally excellent, especially when the condition is identified early and training load is adjusted promptly. Mild cases can settle over a few weeks when breaststroke volume is reduced, technique is refined, and hip and knee strength is improved through physiotherapy.
More chronic cases often take longer, commonly several months, because the swimmer may need time to build strength endurance and to make lasting technique changes that hold up under fatigue. If you return too quickly to large kick sets or high-intensity breaststroke, flare-ups are common, not because the injury is “mysterious”, but because the medial knee tissues have not built enough tolerance yet.
Red flags for slower recovery include persistent swelling, mechanical locking, frequent catching, night pain, or pain that progressively worsens despite reduced load. In these cases, your physiotherapist may recommend imaging or medical review to rule out a meniscus injury or other pathology that needs a different plan.
When to See a Doctor
- You have medial (inner) knee pain linked to breaststroke training that persists beyond a few sessions or worsens with kick sets.
- Pain is starting to affect walking, stairs, squatting, or daily activities, not just swimming.
- You notice clicking, catching, locking, or recurrent swelling, which may suggest meniscus or joint involvement needing assessment.
- You have tried resting but pain returns as soon as you reintroduce breaststroke, suggesting technique and strength factors need addressing.
- You are a competitive swimmer with high training volume and need a structured plan to modify training without losing fitness.
- You want kick technique feedback and return-to-swim programming, ideally with physio and coach collaboration.
FAQ
Breaststroker’s knee is medial (inner) knee pain caused by repetitive overload from the breaststroke whip kick. The kick can strain inner knee structures like the MCL and the pes anserinus region, especially with high training volume or technique faults.
Often yes, but you usually need to modify training. Many swimmers reduce or temporarily stop breaststroke kick sets and train other strokes, use pull buoy work, and maintain fitness while physiotherapy addresses strength and technique. Continuing full breaststroke volume through increasing pain commonly makes recovery slower.
Breaststroker’s knee physiotherapy exercises commonly focus on hip and pelvic stability (gluteus medius/maximus endurance), knee support strength (quadriceps, hamstrings, calves), and movement control to reduce valgus and rotation stress at the knee. Your physiotherapist will tailor exercises to your technique and strength findings.
Not always. The MCL can be irritated in breaststroker’s knee, but symptoms may also come from pes anserinus tendons or bursa, medial meniscus irritation, or patellofemoral pain. A physiotherapy assessment helps identify the main pain source and guide the right treatment.
Breaststroke uses a whip kick that combines external rotation, abduction and forceful extension. This pattern can create repeated valgus and rotational stress on the inner knee, especially if the kick is wide or the knees separate too much under fatigue.
Not usually. Most cases are diagnosed clinically and respond well to physiotherapy. Imaging (often MRI or ultrasound) may be recommended if symptoms persist despite rehab, if there is recurrent swelling, or if mechanical symptoms like locking or catching suggest meniscus involvement.
Mild cases often settle in a few weeks with load modification and targeted physiotherapy. Chronic cases can take several months, especially if significant technique change and strength endurance rebuilding are needed. A graded return to breaststroke volume is usually the key to preventing recurrence.
Some swimmers benefit from taping as a short-term offload and proprioceptive support during rehab. Bracing is rarely required unless there is true instability or a concurrent ligament sprain. Physiotherapy remains the main treatment because strength, control, and technique changes prevent recurrence.
References
Breaststrokers knee, Peak Physio, www.peak-physio.com.au/conditions/breaststrokers-knee/
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