Patella Fractures
Kneecap fracture after a direct blow or fall onto the knee
Symptoms
Differential Diagnosis
Link copiedConditions with similar presentations:
Quadriceps Tendon Rupture
Key differences: Palpable gap above the patella rather than at the bone, inability to actively extend the knee against gravity, and a high-riding patella. Mechanism often involves a sudden load in an older patient or someone with tendon-weakening risk factors.
Patellar Tendon Rupture
Key differences: Palpable gap below the patella, inability to extend the knee, and a high-riding patella on plain imaging. Typical in younger, athletic patients after a sudden jump or landing, and the is incompetent on examination.
Patellar Dislocation or Subluxation
Key differences: History of a twisting or injury with the knee giving way, apprehension with lateral patellar translation on examination, and medial tenderness. The patella itself is usually intact on imaging, though a medial patellar facet or lateral femoral condyle can occur.
Bipartite Patella
Key differences: A developmental variant with a separate, usually superolateral, , often found incidentally on imaging. There is typically no acute trauma, the margins are rounded and sclerotic rather than sharp, and the is intact.
Osteochondral Injury of the Patella or Trochlea
Key differences: Acute onset pain and effusion after a twisting or direct injury, with mechanical symptoms such as catching or locking, but no clear fracture line on plain X-ray. MRI clarifies the cartilage surface and any loose body.
Prepatellar Bursitis
Key differences: A well-defined, fluctuant swelling in front of the patella rather than bone tenderness or compromise, often with a history of repeated kneeling rather than an acute high-energy impact, and preserved active knee extension.
Rehabilitation
A Typical Rehabilitation Progression
Three phases, from settling symptoms to returning to full activity.
Recovery from Patella Fractures is usually staged: calm the symptoms first, then rebuild the strength and capacity of the area, then return to your full activities. The three phases below show the kind of progression the evidence supports and that I commonly work through in clinic. They are here to show you what the road can look like, not to act as a personal program.
- Phase 1
Protect the Fracture and Wake Up the Quadriceps (Weeks 0 to 6)
The early phase is dictated by whether the fracture was managed operatively or non-operatively, and by the surgeon's protocol. The common ground is that the bone needs to be protected and the quadriceps needs to be given every chance not to shut down completely. I work inside the brace settings and weight-bearing instructions provided, and I do not push flexion or resisted knee extension beyond what the surgical team has cleared.
Examples, not a prescription
- quadriceps sets in the brace with the knee in extension, 10 to 15 repetitions with 5-second holds, several times daily
- Straight leg raises in the brace, if cleared by the surgeon, 3 sets of 10, with a focus on keeping the knee fully locked
- Ankle pumps and calf activation to reduce swelling and maintain lower leg circulation
- Gentle passive or assisted knee flexion within the surgeon's allowed range, often starting around 30 to 60 degrees and progressing week by week
- Pain and swelling control with ice, elevation, and compression as appropriate
Ready to progress when
Clear evidence of quadriceps activation with a visible contraction and a without a lag, pain and swelling trending down, and surgical clearance to progress range of motion and weight-bearing into phase 2.
- Phase 2
Rebuild Range, Strength, and Confident Weight-Bearing (Weeks 6 to 16)
Once the bone is clinically stable and the surgeon has cleared progression, the focus shifts to restoring knee range of motion, rebuilding the quadriceps and surrounding hip musculature, and reintroducing full weight-bearing function. This phase often spans the brace wean. I watch for any delayed pain after sessions, because that is one of the more sensitive signals that the load is too fast.
Examples, not a prescription
- Progressive closed-chain quad work, starting with shallow partial squats against a wall and mini-squats, 3 sets of 10 to 12
- Step-ups and step-downs onto a low step, progressing height as control allows, 3 sets of 8 to 10 per side
- Stationary bike with progressive range of motion once flexion allows a comfortable full revolution, starting at very low resistance
- and extensor strengthening with band work and bridges, 3 sets of 10 to 15, to share load through the whole leg
- Single-leg balance on firm ground, progressing to foam as improves, 3 sets of 30 to 45 seconds
Ready to progress when
Full or near-full pain-free knee range of motion, a controlled single-leg squat to partial depth without the knee collapsing inward, quadriceps strength clearly improving on serial testing, and comfortable stair ascent and descent with a reciprocal pattern.
- Phase 3
Return to Running, Sport, and Impact Work (Months 4+)
The final phase is about turning a stable, strong leg into one that can tolerate impact, deceleration, and the demands of the activities the person actually cares about. Progress is criteria-driven, not date-driven. I use measurable benchmarks for strength and hop symmetry before clearing contact or high-speed sport, and I accept that some people will take six months and some will take closer to a year.
Examples, not a prescription
- Progressive strengthening with heavier closed-chain work such as split squats, Bulgarian split squats, and moderate-load squats, 3 sets of 6 to 10
- Linear running progression from walk-jog intervals to steady running, then to tempo work, with attention to any anterior knee pain the day after
- Agility and change-of-direction work starting with low-intensity cutting drills and progressing toward sport-specific patterns
- Hop testing battery including single hop, triple hop, and crossover hop to compare sides, used as a progression gate rather than just an outcome measure
- Sport-specific reintroduction layered in only once strength and hop symmetry benchmarks are met, rather than on a fixed calendar
Ready to progress when
Quadriceps strength within a small tolerance of the uninjured side on isometric or isokinetic testing, symmetry on the hop test battery, confidence with sport-specific deceleration and cutting, and no meaningful day-after pain or effusion after progressive sessions.
Management
Frequently Asked Questions
Common concerns and answers about this condition.
How does a patella usually get fractured?
How does a patella usually get fractured?
Two main mechanisms. The first is a direct blow to the front of the knee, for example a dashboard injury in a car collision or a fall directly onto the kneecap. The second is an indirect overload, where the quadriceps contracts hard against a flexing knee and pulls the patella apart. Direct mechanisms tend to produce more , multi-fragment patterns, indirect ones tend to produce transverse patterns. Both can disrupt the , which is the main thing that decides whether surgery is needed.
How is the decision made between a cast or brace and surgery?
How is the decision made between a cast or brace and surgery?
The short answer is whether the still works and whether the bone fragments are displaced. Melvin and Mehta's 2011 review in the Journal of the American Academy of Orthopaedic Surgeons describes the common non-operative criteria: an undisplaced or minimally displaced fracture, an intact extensor mechanism (the patient can or actively extend the knee against gravity), and an articular step-off of roughly 2 to 3 mm or less. Fractures that fail those criteria generally go to the operating room for fixation, because the knee joint surface and the extensor mechanism matter for long-term function.
What does non-operative treatment look like day to day?
What does non-operative treatment look like day to day?
Typically a period of immobilisation in a brace locked in extension or near-full extension, protected weight-bearing as tolerated depending on surgeon guidance, and gradual reintroduction of knee flexion and quadriceps activation over weeks rather than days. Gwinner and colleagues' 2016 GMS Interdisciplinary Plastic and Reconstructive Surgery DGPW overview is useful here: the priority is protecting the healing bone while not letting the quadriceps completely shut down or the knee stiffen permanently. Early quadriceps contractions and straight leg raises are usually safe and helpful once the surgeon is satisfied with fracture stability.
Why is the quadriceps the focus of rehab after a patella fracture?
Why is the quadriceps the focus of rehab after a patella fracture?
Because the patella is a inside the quadriceps tendon, and the whole job of the is to extend the knee against gravity and decelerate it during walking, stair descent, and sport. After a fracture, the quadriceps often shows marked inhibition and atrophy within days. Restoring quad activation, then strength, then capacity to absorb and produce force through the knee, is what rebuilds a confident, functional leg. Without that work, people plateau with a stiff and weak knee even if the bone itself has healed.
Can I expect to get back to sport?
Can I expect to get back to sport?
Many people do, but the timeline is long and the criteria matter more than the calendar. Typical return-to-sport criteria after patella fracture include pain-free full knee range of motion, quadriceps strength within about 10 to 15 percent of the uninjured side on objective testing, symmetry in single-leg functional tests such as a single-leg squat and a hop battery, and confidence in sport-specific movements. Rushing back before those benchmarks risks re-injury or persistent anterior knee pain. I build the rehab around the criteria, not the weeks.
Will I have arthritis in this knee later?
Will I have arthritis in this knee later?
The risk is higher than for an uninjured knee, particularly when the articular surface was disrupted or when there is residual step-off in the joint. Gwinner and colleagues note that post-traumatic is a recognised long-term outcome after patella fracture, more so when reduction was imperfect or the injury was severe. That is one reason good early management matters. It is also why ongoing quadriceps strength and sensible loading through the years ahead is worth the time, because it directly protects the joint.
When can I start bending the knee again?
When can I start bending the knee again?
That is a surgeon-led decision and depends on the fracture pattern, whether it was fixed surgically, and how stable the construct is. In broad terms, light, protected flexion is often introduced within the first few weeks after surgical fixation or once a non-operative fracture is clinically stable. Aggressive early flexion through a fragile construct can fail the fixation or the bone. I follow the operating surgeon's specific protocol rather than a generic template, and I communicate with that team when timing is unclear.
Do I still need physiotherapy if the fracture was undisplaced?
Do I still need physiotherapy if the fracture was undisplaced?
Yes, and it is often underestimated. Even without surgery, a patella fracture shuts down the quadriceps and stiffens the knee during the protected phase. People who skip structured rehab after a conservatively managed patella fracture frequently end up with a weaker, more painful knee that struggles with stairs and hills for months. Structured rehab shortens the gap between healed bone and a usable leg.
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