Knee Osteochondral Lesion: fragment fixation or microfracture
Six-phase pathway after treatment of an osteochondral lesion of the femoral condyle or patella, detailing the substantial differences between fragment fixation (native hyaline cartilage is preserved) and microfracture (reparative fibrocartilage is formed).
Protected weight bearing 6-8 weeks · Running 4-6 months · Contact/pivoting sport 9-12 months (fixation) or 8-12 months (microfracture)
This protocol is part of the post-operative pathway and must be adapted to the surgeon’s instructions and to the individual clinical response.
These documents are protocol templates for information and education only: they do not replace the rehabilitation prescription for the individual case. Timing, loading and progressions must always be adapted to the patient, the lesion pattern, the surgical technique used and the clinical course, in collaboration between orthopaedic surgeon, physiotherapist and, where appropriate, physiatrist. Progression is driven by objective criteria, not by the calendar alone.
At a glance
- Weight bearing (condylar lesion)
- Touch-down weight bearing (~10-15 kg) for 6 weeks, then progression of roughly 25% body weight per week to full weight bearing around week 8.
- Weight bearing (patellar/trochlear)
- Weight bearing allowed in extension with the brace locked at 0° for 4-6 weeks; it is loaded flexion that is restricted, not loading itself.
- Mobilisation
- Early mobilisation, manual or with CPM where available and indicated: for example 0-30° in the first days with gradual increments as tolerated, an indicative target of 90° at 2 weeks and full ROM at 6-8 weeks. These are examples of progression, not a fixed prescription.
- Fragment fixation
- Progression to unrestricted loading depends on technique, lesion site, clinical course and scheduled reviews; MRI or CT is performed when the result can change management, not as a mandatory step before full weight bearing.
- Microfracture
- Fibrocartilage maturation takes 12-18 months: loading stays controlled for longer and impact and torsion are introduced more gradually.
- Running
- Not before month 4 (fixation with documented healing) or months 5-6 (microfracture), always with a dry knee and quadriceps ≥80%.
- Return to sport
- Pivoting/contact sport at 9-12 months, with the test battery passed and no effusion after progressive loading.
- Day 1CPM 0-30°, full extension, touch-down
- 2 weeks90° flexion, effusion controlled
- 6 weeksStart of load progression
- Weeks 8-12Full weight bearing after MRI check
- Months 3-5Strength ≥80%, single-leg control
- Months 4-8Running and plyometrics
- Months 9-12Return to sport with tests passed
Articular cartilage is the smooth lining that lets the knee surfaces glide over one another with almost no friction. When trauma or osteochondritis dissecans detaches a fragment of cartilage together with its underlying bone, this is called an osteochondral lesion: in the knee the most frequent sites are the medial femoral condyle, the lateral condyle and the patellar facet after a patellar dislocation.
What the surgery does
Loading timeline
Step by step
Each phase lists the goals, what to do and the exercises for that exact moment: do not anticipate them. Dosage is indicative and must be adapted by your physiotherapist.
Before surgery — Preparation for surgery (elective cases)
Short educational and functional phase in elective cases; not applicable to acute cases needing immediate treatment.
When it applies
- •Only in cases already selected for surgery, with a planned indication: not every stable lesion needs surgery, many are managed conservatively.
- •No aggressive prehabilitation: the aim is to arrive prepared, not trained.
- •The type of procedure (fragment fixation, microfracture/marrow stimulation or other techniques) changes post-operative restrictions: these are explained before surgery.
Goals before surgery
- •Practical crutch and off-loading training according to the planned post-operative weight bearing.
- •Effusion and pain control.
- •Maintenance of the allowed range of motion, without stressing the involved compartment.
- •Maintenance of strength in uninvolved regions (hip, core, contralateral limb).
Activities
- •Crutch practice on level ground and stairs, with the prescribed weight bearing.
- •Education on off-loading times, use of any brace and return to school.
Preoperative exercises
Crutch and weight-bearing training
- •Try the crutches before surgery, with correct height and the weight-bearing status set by the surgeon.
- •Practise on level ground, stairs and the entrance to your home, with someone assisting.
- •Also practise sitting, standing and moving in the bathroom while respecting the planned loading restrictions.
Dosage: At least one training session before admission; repeat until the technique is safe.
Quadriceps isometric contraction (quad set)
- •Lying down, knee straight in a neutral position on the surface; if proprioceptive feedback helps, place a small rolled towel under the knee.
- •Contract the quadriceps pushing the back of the knee toward the surface, hold, then release slowly.
- •Aim for a visible, global quadriceps contraction, without breath holding.
Dosage: Indicative: 10 contractions of 5 seconds, 2-3 times a day. To be adapted with the physiotherapist.
Bridge
- •Supine, knees bent and feet hip-width apart on the floor.
- •Lift the pelvis squeezing the glutes, without arching the back, then lower slowly.
Dosage: Indicative: 2-3 sets of 10-12 repetitions.
Readiness criteria for surgery
- ☐The patient uses crutches correctly with the planned weight bearing.
- ☐Pain and effusion controlled.
- ☐Allowed range of motion maintained.
- ☐Family informed about the planned procedure and post-operative restrictions.
When surgery must not be delayed
- •Acute, salvageable osteochondral fragment: fixation must not be delayed.
- •Loose body with joint locking or recurrent effusion.
What to prepare at home and school
- •Organise movement at home: clear pathways, remove rugs, keep useful items within reach.
- •Prepare ice, a support for the heel, comfortable clothing and crutches already adjusted.
- •Inform school or the sports club: plan the absence, temporary exemption and gradual return.
- •Agree the first post-operative physiotherapy session in advance.
Phase 1 — Protecting the fragment and the clot
Indicative timing: Days 0-14
The time window is indicative: progression depends on the criteria listed below, not on the calendar.
Goals
- •Protect the repair: no compression on the treated area
- •Achieve and maintain full extension (0°)
- •Reduce effusion and pain, reactivate the quadriceps
What to do
- •Early passive mobilisation as indicated: manual or, where available and prescribed, with CPM in blocks through the day; one example of progression is 0-30° in the first days with gradual increments as tolerated
- •Cryotherapy and compression 15-20 minutes, 4-6 times daily; limb elevated above heart level when sitting or lying
- •Quadriceps isometrics (quad sets) and patellar mobilisation in all directions to prevent adhesions
- •Walking with two crutches, strictly respecting the prescribed load: the toes touch down for balance only, not for support
- •Ankle and gluteal contractions, exercises for the healthy limb and trunk to maintain general condition
Restrictions and precautions
- •No load beyond touch-down for condylar lesions
- •No loaded flexion for patellar/trochlear lesions
- •No resisted open-kinetic-chain quadriceps work
- •Avoid prolonged sitting with the knee flexed and the foot dependent (increases swelling)
Exercises for this phase
1. Quadriceps isometric contraction (quad set)From day 1
- •Lie on your back with the leg straight and a rolled towel under the ankle.
- •Push the knee down by tightening the thigh, as if flattening the bed.
- •The heel lifts slightly: that means you are reaching full extension.
Dosage: 10 contractions of 5 seconds, 4-6 times a day
2. Straight-leg raiseFrom day 1-2
- •Lying on your back, first tighten the thigh until the knee locks straight.
- •Lift the straight leg about 30 cm, hold 3 seconds and lower slowly.
- •If the knee bends while lifting, the quadriceps is not ready yet: go back to quad sets.
Dosage: 3 sets of 10, twice a day
Ready for the next phase when
- ☐Full active extension (0°) with no extensor lag
- ☐At least 60-90° passive flexion
- ☐Decreasing effusion, dry wounds
- ☐Safe and correct crutch use, including stairs
Note for the physiotherapist
An extension deficit in the first weeks is the hardest complication to reverse: prone hangs with the heel supported, 10 minutes 3-4 times daily, is the single highest-yield exercise of this phase.
Phase 2 — Restoring motion under protected loading
Indicative timing: Weeks 2-6
The time window is indicative: progression depends on the criteria listed below, not on the calendar.
Goals
- •ROM 0-120° by week 6
- •Active quadriceps control without activation delay
- •Maintain muscle trophism without loading the lesion
What to do
- •Daily active-assisted and passive mobilisation, wall heel slides, stationary bike with no resistance (high saddle) once flexion exceeds 100-105°
- •Quadriceps NMES combined with voluntary contraction if inhibition persists
- •Closed-chain strengthening in offloading or in water (hydrotherapy after wound healing), hip and core work
- •Load progression only if prescribed: roughly 25% of body weight per week, using bathroom scales as feedback
Restrictions and precautions
- •No squatting beyond 30-45° for patellar/trochlear lesions
- •No loaded leg extension, no step-ups, no lunges
- •No loaded knee torsion
Exercises for this phase
3. Global quadriceps recoveryWeeks 1-6
- •Sitting with a pillow under the slightly bent knee.
- •Extend the knee by pushing the heel forward, keeping the thigh on the pillow.
- •Aim for a full, even contraction of the whole thigh: isolating a single portion of the muscle is not useful.
Dosage: 3 sets of 12, once or twice a day
4. Load progression using scalesCrutch-weaning phase
- •Place the operated foot on bathroom scales while standing between crutches.
- •Learn what 20 kg, 40 kg and half your body weight feel like: memorise the sensation.
- •Increase one level per week, only if pain and swelling do not appear.
Dosage: 5 minutes of load training per day
5. Mini-squat 0-45°From the full weight-bearing phase
- •Standing, feet hip-width apart, weight evenly distributed.
- •Bend the knees to about 45°, keeping the knees aligned over the feet.
- •Rise by pushing through the heels, without letting the knee collapse inwards.
Dosage: 3 sets of 12, 3-4 times a week
6. Glute bridgeFrom week 2
- •Lie on your back, knees bent, feet flat on the floor.
- •Lift the pelvis by squeezing the glutes until shoulders, hip and knee are aligned.
- •Lower slowly without arching the back.
Dosage: 3 sets of 12-15, on alternate days
Ready for the next phase when
- ☐ROM 0-120° or within 15° of the other side
- ☐Clear quadriceps contraction with straight-leg raise and no lag
- ☐No increase in effusion in the 24 hours after sessions
- ☐Load progression achieved as prescribed
Note for the physiotherapist
For patellar lesions the safe arc depends on lesion location: distal patellar lesions are compressed at 20-30°, proximal lesions at 60-90°. Ask the surgeon which arc to avoid rather than applying a generic rule.
Phase 3 — Transition to full weight bearing
Indicative timing: Weeks 6-12
The time window is indicative: progression depends on the criteria listed below, not on the calendar.
Goals
- •Crutch weaning with symmetrical gait
- •Quadriceps strength ≥60-70% of the other side
- •Imaging confirmation of healing (fixation) or defect fill (microfracture)
What to do
- •Progressive crutch weaning: one crutch on the opposite side first, then free walking, only if there is no limp
- •Closed-chain strengthening: mini-squats 0-45°, low-load double-leg press, glute bridge, low step-ups
- •Double- then single-leg proprioception on a stable surface
- •Stationary bike with progressive resistance, freestyle swimming (avoid breaststroke for the first 12 weeks)
- •Follow-up MRI at 8-12 weeks after fixation to confirm healing before releasing load
Restrictions and precautions
- •No running, no jumping, no change of direction
- •Avoid deep squats and deep lunges
Exercises for this phase
7. Single-leg balanceFrom the full weight-bearing phase
- •Stand on one leg, knee slightly bent, looking ahead.
- •Progress: eyes open → eyes closed → soft surface → catching a ball.
- •The pelvis must stay level: if it drops on one side, the gluteus medius is weak.
Dosage: 3 x 30 seconds per side, daily
8. Controlled step-downStrength phase (from month 3)
- •Stand on a 15-20 cm step on the operated leg.
- •Lower slowly with the other foot, touching the floor with the heel, over 3 seconds.
- •The standing knee must stay aligned over the foot: if it collapses inwards, lower the step.
Dosage: 3 sets of 8-10 per side, 3 times a week
9. Low-impact conditioningAll intermediate phases
- •Stationary bike with high saddle and minimal resistance, swimming (avoiding breaststroke early), elliptical.
- •These maintain general fitness without compressing the repaired area.
- •The rule is always the same: no swelling the next day.
Dosage: 20-30 minutes, 3-5 times a week
Ready for the next phase when
- ☐Walking without limp or aids for at least 20 minutes
- ☐Full symmetrical ROM
- ☐Dry knee: no effusion after daily activity
- ☐Quadriceps ≥60-70% on dynamometry or comparative isometric testing
Phase 4 — Strength and neuromuscular control
Indicative timing: Months 3-5
The time window is indicative: progression depends on the criteria listed below, not on the calendar.
Goals
- •Quadriceps and hamstring strength ≥80%
- •Single-leg limb alignment control (no dynamic valgus)
- •Prepare the knee for impact
What to do
- •Progressive strengthening: squats, single-leg press, step-downs, controlled lunges, single-leg bridge
- •Eccentric quadriceps and posterior chain work (age-adapted nordic hamstring)
- •Proprioception on unstable surfaces, dual task, perturbations
- •Non-impact conditioning: bike, elliptical, swimming, deep-water running
- •After microfracture: introduce progressive cyclic loading (brisk walking, hills) before true impact
Restrictions and precautions
- •Impact and plyometrics only once phase criteria are met
- •Watch for deep pain and delayed effusion: signs of overloading the repair
Exercises for this phase
10. Progressive plyometricsImpact phase
- •Start with two-foot hops on the spot, landing softly with bent knees.
- •Progress to front-back and lateral hops, then single-leg.
- •Landings must be silent: noise means insufficient shock absorption.
Dosage: 2-3 sets of 10-20 contacts, 2-3 times a week
Ready for the next phase when
- ☐Quadriceps strength ≥80%
- ☐20 cm step-down performed with knee control, no valgus and no pain
- ☐No effusion 48 hours after an intense session
- ☐30-minute brisk walk and stairs without pain
Note for the physiotherapist
Effusion is a sign of joint reactivity: if swelling appears after a new load, that load was probably too much. Drop back one level and retry after a few days rather than stopping everything.
Phase 5 — Running, impact and plyometrics
Indicative timing: Months 4-8 (fixation) / 5-9 (microfracture)
The time window is indicative: progression depends on the criteria listed below, not on the calendar.
Goals
- •Continuous running without symptoms or effusion
- •Symmetrical impact absorption in jumping
- •Strength ≥90%
What to do
- •Interval return-to-running programme (walk/run) on even ground, 10% weekly volume progression
- •Graded plyometrics: partially unloaded double-leg, full double-leg, single-leg, jumps with controlled landing
- •Linear agility, then wide and finally sharp changes of direction
- •Strength work maintained 2-3 times weekly alongside field work
Restrictions and precautions
- •No contact, no full-intensity sport-specific drills
- •Stop impact work if effusion or pain lasting more than 24 hours appears
No new exercises are introduced in this phase: continue with the exercises of the previous phase, progressing load and difficulty as tolerated and as indicated by the physiotherapist.
Ready for the next phase when
- ☐20-30 minutes of continuous running with no pain and no next-day swelling
- ☐Progressive hop tests with LSI ≥85-90%
- ☐Step landing with aligned, cushioned and symmetrical knee
- ☐Quadriceps and hamstrings ≥90%
Phase 6 — Return to sport and maintenance
Indicative timing: Months 8-12 and beyond
The time window is indicative: progression depends on the criteria listed below, not on the calendar.
Goals
- •Graded return to full training and then competition
- •Long-term cartilage protection
What to do
- •Graded reintegration: partial non-contact training → full training → part of a match → competition
- •Year-round preventive neuromuscular programme (FIFA 11+ or equivalent)
- •Body-weight management, weekly load monitoring, avoid clustered high-impact double sessions
- •Clinical review and, where indicated, MRI at 12 months for large lesions or after microfracture
No new exercises are introduced in this phase: continue with the exercises of the previous phase, progressing load and difficulty as tolerated and as indicated by the physiotherapist.
Ready for the next phase when
- ☐Test battery passed with LSI ≥90% on all items
- ☐No effusion and no pain in the preceding 4 weeks
- ☐Surgeon clearance, with consistent imaging in large lesions
- ☐Subjective confidence in the knee, assessed clinically and, if useful, with age- and context-appropriate questionnaires (KOOS Sport/Rec, Pedi-IKDC), without rigid universal cut-offs
If symptoms appear after a progression
If persistent pain, effusion or swelling, or loss of movement appears after moving to a new phase or increasing load, temporarily reduce load and volume and have the situation reassessed by the surgeon or physiotherapist before progressing again. This document is informative for families and physiotherapists and does not replace individual clinical assessment.
Return to sport / full activity
Indicative windows: non-contact sport at 6-8 months; pivoting and contact sport at 9-12 months. After microfracture, impact progression is often more gradual because fibrocartilage matures for up to 12-18 months; timelines nonetheless remain subject to criteria and to the surgeon’s assessment, without one technique always being faster than the other.
- ☐Quadriceps and hamstring strength with LSI ≥90% (dynamometry or comparable isometric testing)
- ☐Hop test battery (single, triple, crossover, 6 m timed) with LSI ≥90%
- ☐No effusion in the preceding 4 weeks, even after high loads
- ☐Double- and single-leg landing without dynamic valgus (video-assessed drop jump)
- ☐No deep pain or painful crepitus in squatting and stair descent
- ☐Subjective IKDC or KOOS-Sport ≥90 and adequate confidence
In the growing patient with osteochondritis dissecans, resumption of impact is authorised by the surgeon considering the clinical course together with imaging reviews where available. For large or weight-bearing lesions, long-term sporting choices should be discussed case by case with the family, including lower-impact options. The Limb Symmetry Index has known limitations: on its own it is not sufficient, because the uninjured side may also be deconditioned; it should be combined with absolute strength values, movement quality and sport-specific demands.
Red flags: stop and contact us
- •Sudden locking or the sensation of a loose body inside the knee (possible fragment displacement)
- •Effusion that returns after every session or does not settle within 48 hours
- •Deep, dull pain that increases with loading and does not settle with rest
- •Sudden loss of previously achieved extension
- •Fever, redness, local warmth or wound discharge (suspected infection)
- •Calf pain and swelling, chest pain or breathlessness (suspected deep vein thrombosis or embolism)
Written and reviewed by Dott. Daniele Priano, Paediatric Orthopaedics. Last review: August 2026.
Timings are indicative: progression depends on clinical and functional criteria and on the surgeon’s indications.
Frequent questions
Why can I bend the knee but not put weight on my foot?
Because motion and load do different things. Motion circulates the joint fluid that nourishes cartilage and prevents adhesions; loading, on the other hand, compresses the repaired area. In the early weeks we want the first without the second.
Is fibrocartilage "worse" than normal cartilage?
It is repair tissue: it covers the defect and works well for years in many patients, but it is less elastic and less wear-resistant than hyaline cartilage. That is why we are more cautious with impact and torsion after microfracture and avoid rushing.
Is the CPM machine really necessary?
Useful but not essential: the goal is that the knee moves many times a day without load. If CPM is unavailable, the same result is achieved with manual passive mobilisation and repeated heel slides several times a day.
Can my child attend PE at school?
For the first 3-4 months they should be excused from running, jumping and team games. They can take part with alternative roles (refereeing, upper-limb exercises) and return gradually once the impact phase has been completed with criteria met.
Is swelling in the evening normal?
Mild evening swelling in the first weeks is common. It becomes a warning sign when it increases day by day, appears after every session, or does not settle within 24-48 hours with ice and elevation: in that case the weekly load is excessive and should be reduced by one level.
Can I do physiotherapy only once a week?
The physiotherapy session is for setting up, correcting and progressing the programme. The result, however, depends on the exercises performed at home every day: a short daily home programme is worth more than an isolated weekly session.
In-depth content (full introduction, technique comparison, FAQ, references) at ortopediaevolutiva.com/en/rehabilitation/knee-osteochondral-lesion
Knee Osteochondral Lesion: fragment fixation or microfracture — Dott. Daniele Priano, Pediatric Orthopaedics · Information document: it does not replace an in-person assessment.
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Email: daniele.priano@ortopediaevolutiva.com