Combined ACL, PCL and collateral/corner reconstruction following knee dislocation · advanced
- Vascular injury occurs in 10-25 percent of knee dislocations — popliteal artery disruption is limb-threatening and must be excluded in every case with ABI and selective CT angiography before reconstruction.
- Schenck KD classification guides surgical planning: KD-III (two cruciates plus one collateral) and KD-IV (both cruciates plus both collaterals) require staged or single-stage combined reconstruction; KD-V is fracture-dislocation with additional bony injury.
- Fixation sequence is critical: tension and fix the PCL first at 90 degrees flexion, then the ACL in extension, then the peripheral structures at their native flexion angles to avoid posterior tibial sag and graft overtensioning.
- Tunnel convergence is a major technical risk in combined reconstructions — the PCL tibial tunnel and posterolateral corner fibular tunnel must be planned with fluoroscopy to maintain adequate bone bridges; use outside-in techniques for the PLC to minimise convergence.
- “Always perform examination under anaesthesia before incision — the degree of varus/valgus and rotational laxity at 0 and 30 degrees determines which peripheral structures require reconstruction versus repair.
- “Common peroneal nerve injury occurs in up to 25 percent of KD-III lateral injuries — document sensation in the first web space and dorsiflexion strength pre-operatively; if deficit present, plan for nerve exploration or later tendon transfer.
- “Single-stage reconstruction is feasible when soft-tissue envelope allows and vascular status is confirmed; staged reconstruction (PCL first, then ACL plus collaterals at 6-12 weeks) reduces arthrofibrosis risk in severely swollen knees.
- “Graft selection: use allograft for PCL (Achilles or tibialis anterior) and PLC (semitendinosus or peroneus longus); autograft hamstring or patellar tendon for ACL to allow early aggressive rehabilitation.
When & Why
Indications. Multiligament knee reconstruction is offered after a knee dislocation (Schenck KD-III or KD-IV pattern, and selected KD-II/KD-V injuries) once the limb is viable and the soft-tissue envelope is controlled. It is performed for: - Absolute indications — confirmed or suspected vascular injury requiring repair; multiligament injury with gross instability preventing weight-bearing or threatening the skin envelope; peroneal nerve deficit with suspected transection or entrapment requiring exploration; open dislocation or associated tibial plateau fracture requiring staged or combined fixation.
- Relative indications — KD-III or KD-IV injury in a young active patient with high functional demand; chronic symptomatic instability after failed non-operative management; recurrent giving-way with secondary meniscal or chondral damage; patient preference after informed discussion of staged versus single-stage options. Contraindications. Absolute: an unreconstructed popliteal artery injury or ongoing vascular compromise, active infection or an open wound at the planned surgical sites, and medical comorbidities precluding prolonged anaesthesia or major reconstruction. Relative: severe arthrofibrosis or limited pre-injury range of motion (consider staged arthroscopic release first), a low-demand elderly patient with acceptable braceable stability, and ongoing substance abuse or inability to comply with the rehabilitation protocol.
A knee dislocation is a surgical emergency until popliteal artery patency is confirmed. Vascular injury occurs in 10-25 percent of dislocations. Perform an ankle-brachial index (ABI) on every suspected dislocation: an ABI less than 0.9, an asymmetry greater than 0.2, or any hard sign (absent pulse, expanding haematoma, pulsatile bleeding) mandates immediate CT angiography or vascular exploration. Never trust a palpable pulse alone — intimal flaps can thrombose hours after reduction with initially normal distal pulses. Check pulses serially every 15-30 minutes for the first 6 hours after reduction. No ligament reconstruction proceeds until limb viability is assured.
Timing and staging — the one decision. Whatever the final construct, the order and timing of graft placement is the central planning choice. Once vascular status and the soft-tissue envelope allow, decide between an acute single-stage reconstruction and a staged reconstruction:
Done within 3 weeks of injury. Allows primary repair of collateral and corner structures in a single anaesthetic and reduces chronic instability, but carries a higher arthrofibrosis rate (up to 30-40 percent in some series) when swelling is severe. Favourable when swelling is low, the team is experienced, there is no vascular injury, and the patient is young with high demand.
Reconstruct the PCL first, then the ACL plus collaterals at 6-12 weeks. Reduces operative time and arthrofibrosis risk and lets the soft-tissue envelope settle for better graft incorporation. Favourable in polytrauma, severe swelling, skin compromise, or when a vascular repair is required.
The evidence supports either pathway when vascular status is addressed promptly: Levy et al. (2013) reported comparable functional outcomes between acute and delayed reconstruction, with delayed surgery showing lower reoperation rates for stiffness; Freychet et al. (2020) found no difference between single and staged posterolateral corner procedures, though staged reconstruction carried lower reoperation for arthrofibrosis in severely swollen knees. Graft selection. Use allograft (Achilles, tibialis anterior or peroneus longus) for the PCL and PLC to reduce donor-site morbidity and permit early aggressive rehabilitation; use autograft bone-patellar tendon-bone or quadrupled hamstring for the ACL. Aim for graft diameter greater than 8 mm for the PCL and greater than 7 mm for the PLC. Avoid ipsilateral hamstring harvest when the MCL is reconstructed, to preserve the dynamic medial stabiliser. Woodmass et al. (2022) reported no significant difference in failure rates between allograft and autograft in multiligament reconstruction when appropriate tensioning and fixation angles are used.
The Operation
The goal is to restore the cruciates and the collateral/corner structures anatomically, in a fixation order that re-establishes normal tibiofemoral kinematics, while protecting the popliteal artery and the common peroneal nerve. The exposure is built up step by step: arthroscopic portals for the cruciates, a posterolateral approach for the corner, and a medial approach for the MCL.
Operative sequence
- Supine on a radiolucent table with a leg holder or a bump under the ipsilateral buttock; lower or abduct the contralateral leg to give the C-arm fluoroscope free access. Apply a tourniquet high on the thigh, but inflate it only after vascular status is confirmed.
- Perform a full examination under anaesthesia: range of motion, Lachman, posterior drawer at 90 degrees, varus and valgus stress at 0 and 30 degrees, the dial test at 30 and 90 degrees, and recurvatum — always compared with the contralateral side. This quantifies exactly which peripheral structures need reconstruction versus repair.
- Document the ABI, palpable pulses, dermatomal sensation and motor function (tibialis anterior, extensor hallucis longus, peronei) before any incision.
- Prepare all grafts on the back table with the appropriate whipstitch and sizing: allograft Achilles or tibialis anterior for the PCL and PLC, and autograft or allograft for the ACL.
- Establish standard anterolateral and anteromedial portals, plus anteromedial and posteromedial accessory portals for the PCL work.
- Run a complete diagnostic arthroscopy and address any meniscal tears (repair or partial meniscectomy) before the ligament work. Document chondral status, evacuate the haematoma and assess the cruciate remnants.
- Anatomy. The PCL femoral footprint is the anterolateral bundle on the medial femoral condyle, 8-10 mm from the articular margin; the tibial footprint sits on the posterior tibia, 10-12 mm below the joint line.
- Drill the tibial tunnel with an outside-in guide, targeting 10-12 mm below the joint line on the posterior tibia under fluoroscopic control, then drill the femoral tunnel for the anterolateral bundle.
- Pass and tension the Achilles allograft at 90 degrees flexion with an anterior drawer force applied to restore the normal tibial step-off (approximately 1 cm anterior to the medial femoral condyle on the lateral view). Fix with an interference screw or a suspensory device.
- Anatomy. The ACL femoral footprint is on the lateral wall of the intercondylar notch, 10-11 mm anterior to the posterior cortex; the tibial footprint is centred 7-10 mm anterior to the PCL.
- Drill the femoral and tibial tunnels with standard ACL technique, confirming on fluoroscopy that there is no convergence with the PCL tunnels.
- Pass and tension the bone-patellar tendon-bone or hamstring autograft near full extension (10-20 degrees) with a posterior drawer to maintain tibiofemoral contact. Fix with interference screws or suspensory fixation.
- Exposure. Use a posterolateral approach to expose the fibular head and the lateral femoral epicondyle. The relevant anatomy: the fibular collateral ligament runs from the lateral femoral epicondyle to the fibular head, 5-7 mm anterior to the fibular styloid; the popliteus passes from the posteromedial tibia through the popliteal hiatus to the lateral femoral condyle; the popliteofibular ligament runs from the popliteus tendon to the fibular styloid and is the critical restraint to external rotation. The common peroneal nerve lies 1-2 cm distal to the fibular head on the posterior fibular neck.
- Identify, dissect and loop the common peroneal nerve before exposing the fibular head — it is the structure most at risk in this step.
- Drill the fibular tunnel from anterior to posterior, maintaining a bone bridge greater than 1 cm from the PCL tibial tunnel exit, and create the femoral isometric point for the fibular collateral ligament reconstruction.
- Pass a semitendinosus or peroneus longus graft through the fibular tunnel and fix it to the femur with an interference screw or button. Tension at 30 degrees flexion under varus stress, and add a popliteofibular ligament reconstruction if indicated.
- Exposure. Use a medial approach to the medial epicondyle and proximal tibia, protecting the saphenous nerve. The superficial MCL runs from the medial femoral epicondyle to the proximal tibia, 5-6 cm distal to the joint line; the deep MCL and posterior oblique ligament provide rotational stability and are often injured in KD-III-M.
- Drill femoral and tibial tunnels, or use suture anchors, for an anatomic reconstruction. Tension the superficial MCL graft at 20-30 degrees flexion under valgus stress, and repair or reconstruct the posterior oblique ligament if torn.
- Repeat the stress examination under anaesthesia to confirm elimination of pathologic laxity, and obtain full-length standing radiographs if possible to confirm alignment.
- Close all incisions in layers and apply a hinged knee brace locked in extension or slight flexion depending on PCL integrity.
The popliteal artery lies only 5-10 mm posterior to the tibial tunnel exit — use a curved curette or spoon to protect the posterior capsule while reaming. Apply an adequate anterior drawer during tensioning, because an inadequate drawer leaves a persistent posterior sag and increases ACL graft forces. Plan the trajectory with fluoroscopy before reaming so the tunnel does not converge with the future PLC fibular tunnel.
Identification and protection of the common peroneal nerve is mandatory — dissect and loop the nerve before fibular head exposure. Avoid fibular tunnel fracture or convergence with the PCL tunnel by using outside-in drilling and confirming position on true AP and lateral fluoroscopy. Inadequate varus tensioning at 30 degrees leaves residual posterolateral rotatory instability.
Always fix the PCL first at 90 degrees flexion with an anterior drawer. This restores the normal tibiofemoral relationship before the ACL is tensioned. If the ACL is fixed first, the tibia sits too posterior and the ACL graft is overtensioned in extension; if the PCL is fixed in extension, a fixed posterior sag results. The order is PCL, then ACL in near-extension, then the peripheral structures at their native flexion angles.
Aftercare & Complications
Rehabilitation. The protocol protects the reconstructed PCL (no open-chain hamstring work early) while pushing range of motion from day 1 to limit arthrofibrosis. | Phase | Timing | Weight-bearing | Motion and therapy | |-------|--------|----------------|--------------------| | Immediate | Day 0 to week 2 | Touch weight-bearing with crutches | Hinged brace locked in extension or 10 degrees flexion (PCL-dependent); continuous passive motion from day 1 aiming for 0-90 degrees by week 2; quadriceps sets, ankle pumps, patellar mobilisation; chemical DVT prophylaxis for a minimum of 2 weeks | | Early | Week 2 to 6 | Touch weight-bearing for 6 weeks (longer if PCL or PLC involved) | Full extension by week 4; 120 degrees flexion by week 6; stationary cycling and closed-chain exercises at 6-8 weeks; avoid open-chain hamstring work until 4 months to protect the PCL | | Intermediate | Month 3 to 6 | Full weight-bearing by 3 months | Progressive strengthening — leg press, squats, lunges; proprioceptive and balance training; light jogging or cycling at 4-6 months if strength and stability are adequate | | Advanced | Month 6 to 12 | Full | Sport-specific drills at 6-9 months; return to pivoting sports at 9-12 months only after passing functional testing (hop tests, strength symmetry greater than 90 percent) | Outcomes. Greater than 80 percent of patients achieve good to excellent subjective outcomes with anatomic single-stage or staged reconstruction when vascular and neurological injuries are addressed promptly. Return to high-level sport is possible, but only 50-70 percent of elite athletes return to their pre-injury level — discuss expectations pre-operatively. The long-term risk of post-traumatic osteoarthritis is 20-50 percent at 10-15 years, so counsel patients on activity modification. Complications.
- Incidence
- 10-25 percent of dislocations; 5-10 percent post-reconstruction
- Recognition
- Absent or diminished pulses, expanding haematoma, ABI drop, limb ischaemia, compartment syndrome
- Prevention and management
- Prevention: ABI and CT angiography pre-operatively; serial pulse checks post-reduction; vascular consult before ligament work. Management: immediate vascular exploration and repair or bypass; fasciotomy for compartment syndrome; delay ligament reconstruction until limb viability is assured
- Incidence
- Up to 25 percent in KD-III-L; 5-10 percent persistent
- Recognition
- Foot drop, loss of ankle dorsiflexion or eversion, first web space sensory loss, positive Tinel sign at the fibular neck
- Prevention and management
- Prevention: pre-operative documentation; careful dissection around the fibular neck; avoid excessive varus stress. Management: nerve exploration if transected; ankle-foot orthosis; consider tibialis posterior tendon transfer at 12-18 months if no recovery
- Incidence
- 5-15 percent in combined reconstructions
- Recognition
- Intraoperative fluoroscopic overlap of tunnels, loss of fixation, iatrogenic proximal fibula fracture
- Prevention and management
- Prevention: pre-operative CT planning of trajectories; fluoroscopic confirmation of guidewires before reaming; outside-in PLC drilling. Management: intraoperative revision of tunnel position; backup fixation; protected weight-bearing post-operatively
- Incidence
- 20-40 percent requiring manipulation or lysis
- Recognition
- Failure to regain full extension or flexion by 8-12 weeks; patella infera on the lateral radiograph
- Prevention and management
- Prevention: early aggressive range of motion from day 1; staged reconstruction in high-risk swollen knees; avoid prolonged immobilisation. Management: manipulation under anaesthesia at 6-8 weeks if extension loss is greater than 10 degrees; arthroscopic lysis of adhesions if persistent beyond 3 months
- Incidence
- 10-20 percent at 2-5 years
- Recognition
- Return of varus thrust, posterior drawer or rotational laxity; MRI confirmation of graft rupture
- Prevention and management
- Prevention: anatomic tunnel placement, correct tensioning angles, avoidance of convergence, protected rehabilitation. Management: revision reconstruction with alternative graft sources; address alignment with osteotomy if varus malalignment is present; consider a staged approach for revision
- Incidence
- 5-15 percent without prophylaxis
- Recognition
- Calf swelling, calf pain, positive Homan sign, hypoxia, tachycardia
- Prevention and management
- Prevention: mechanical prophylaxis intraoperatively; chemical prophylaxis (LMWH or DOAC) for 2-4 weeks post-operatively; early mobilisation. Management: therapeutic anticoagulation; IVC filter if recurrent emboli; delay return to sport until resolved
Viva & Exam Focus
FIXATIONFIXATION — order and tensioning angles
SCHENCKSCHENCK — classification and priorities
A palpable dorsalis pedis pulse does not exclude a popliteal injury — intimal flaps and partial tears can present with normal distal pulses initially and progress to thrombosis within hours. Perform an ABI in every suspected dislocation; an ABI less than 0.9 or asymmetric pulses mandate immediate CT angiography, and hard signs (expanding haematoma, pulsatile bleeding, absent pulse) require immediate vascular surgery consultation before any ligament work.
The common peroneal nerve courses around the fibular neck, 1-2 cm distal to the fibular head, and is tethered in the peroneal tunnel, making it vulnerable to stretch in varus and hyperextension injuries. Up to 25 percent of KD-III-L injuries have a clinical palsy at presentation. Document first dorsal web space sensation and ankle dorsiflexion or eversion strength before and after reduction; if a deficit is present, plan exploration or a later tibialis posterior transfer.
The PCL tibial tunnel (anteromedial tibial plateau) and the PLC fibular tunnel (posterior fibular head) can converge or fracture the proximal fibula if not planned. Intraoperative fluoroscopic confirmation of tunnel position with a bone bridge greater than 1 cm is mandatory, and outside-in drilling of the PLC fibular tunnel controls trajectory and avoids convergence with the PCL tunnel.
Fixing the ACL at 90 degrees flexion creates permanent extension loss; fixing the PCL in extension creates a fixed posterior sag. The correct sequence is PCL at 90 degrees flexion with an anterior drawer, ACL near full extension with a posterior drawer, PLC at 30 degrees flexion under varus stress, and MCL at 20-30 degrees flexion under valgus stress.
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
“A 28-year-old motorcyclist is brought in after a high-speed collision. The knee was dislocated on arrival but reduced in the field. Pulses are palpable but the ABI is 0.85 on the injured side versus 1.1 on the contralateral limb. There is a 2 cm difference in calf circumference and pain on passive stretch. How do you proceed?”
“You are planning single-stage reconstruction for a 32-year-old with a Schenck KD-IV knee dislocation (both cruciates plus MCL and PLC). The swelling has settled and vascular status is normal. Walk me through your graft choice, tunnel planning and fixation sequence.”
“A 35-year-old with a KD-III-L knee dislocation (ACL, PCL and PLC) undergoes single-stage reconstruction. At 8 weeks post-operatively he has only 5 degrees of active dorsiflexion and numbness in the first web space. How do you manage this?”
Vascular assessment
- ABI less than 0.9 or asymmetry greater than 0.2 triggers CT angiography
- Hard signs mandate immediate vascular exploration
- Serial pulse examination every 15-30 minutes for the first 6 hours
- Popliteal artery lies 5-10 mm posterior to the PCL tibial tunnel exit — protect during reaming
- Missed vascular injury leads to amputation rates of 20-50 percent historically
Neurological assessment
- Common peroneal nerve injury in up to 25 percent of KD-III-L
- Document first web space sensation and dorsiflexion or eversion strength pre-operatively
- Nerve lies 1-2 cm distal to the fibular head on the posterior neck
- Tinel progression and serial motor grading guide observation versus exploration
- Tibialis posterior transfer is salvage for permanent foot drop after 12-18 months
Timing and staging
- Acute (less than 3 weeks): allows primary collateral repair but higher arthrofibrosis
- Delayed (greater than 3 weeks): better soft-tissue envelope, staged approach feasible
- Single-stage: low swelling, experienced team, no vascular injury, young high-demand patient
- Staged (PCL first, then ACL plus collaterals at 6-12 weeks): polytrauma, severe swelling, vascular repair
- Arthrofibrosis requiring intervention occurs in 20-40 percent — early aggressive ROM is critical
Fixation sequence and angles
- PCL first at 90 degrees flexion with an anterior drawer to restore tibial step-off
- ACL second near full extension (10-20 degrees) with a posterior drawer
- PLC third at 30 degrees flexion under varus stress
- MCL last at 20-30 degrees flexion under valgus stress
- Never fix ACL at 90 degrees or PCL in extension — irreversible extension loss or posterior sag
Tunnel convergence avoidance
- PCL tibial tunnel and PLC fibular tunnel are at highest risk of convergence
- Maintain a bone bridge greater than 1 cm — confirm on true AP and lateral fluoroscopy
- Use outside-in drilling for the PLC fibular tunnel to control trajectory
- Pre-operative CT planning of trajectories reduces intraoperative surprises
- Intraoperative revision of tunnel position is preferable to postoperative fracture or fixation failure
Graft selection
- Allograft Achilles or tibialis anterior for PCL and PLC — reduces donor morbidity, allows early rehab
- Autograft bone-patellar tendon-bone or hamstring for ACL — early aggressive rehabilitation
- Avoid ipsilateral hamstring if MCL reconstruction required — preserves dynamic medial stability
- Graft diameter greater than 8 mm for PCL and greater than 7 mm for PLC recommended
- Allograft failure rates comparable to autograft when correct tensioning and fixation are used
Complications
- Vascular injury or thrombosis: 10-25 percent; ABI and CT angiography mandatory; vascular priority
- Peroneal nerve palsy: up to 25 percent in KD-III-L; document pre-operatively; explore if no recovery by 3-4 months
- Tunnel convergence or fracture: 5-15 percent; fluoroscopic confirmation before reaming
- Arthrofibrosis: 20-40 percent; early ROM from day 1; staged surgery in high-risk cases
- Recurrent instability: 10-20 percent at 2-5 years; anatomic placement, correct angles, protected rehab
Rehabilitation milestones
- Day 1: continuous passive motion, quadriceps sets, ankle pumps; chemical DVT prophylaxis
- Week 2-6: progressive ROM to full extension by week 4 and 120 degrees flexion by week 6; touch weight-bearing 6 weeks
- Month 3-6: full weight-bearing by 3 months; closed-chain strengthening; proprioception
- Month 6-9: sport-specific drills; return to pivoting sports only after functional testing
- Long-term: 50-70 percent return to pre-injury sport level; 20-50 percent post-traumatic OA at 10-15 years
Background & Evidence
Mechanism and epidemiology. Most knee dislocations follow high-energy trauma (motor vehicle and motorcycle collisions) but low-energy hyperextension injuries in obese patients are increasingly recognised. The hyperextension-varus pattern is the commonest mechanism for KD-III-L and carries the highest vascular and peroneal nerve risk. The defining feature of a true dislocation is rupture of both cruciate ligaments; the Schenck KD classification then grades the additional collateral injury and any fracture, and is the framework that drives operative planning.
- Pattern
- Single cruciate injured (uncommon in true dislocation)
- Surgical implication
- Isolated cruciate reconstruction as for a single-ligament injury
- Pattern
- Both cruciates torn, collaterals intact
- Surgical implication
- Combined ACL and PCL reconstruction; peripherals usually spared
- Pattern
- Both cruciates plus MCL (medial) injury
- Surgical implication
- Combined cruciate plus medial-side reconstruction or repair
- Pattern
- Both cruciates plus PLC (lateral) injury
- Surgical implication
- Highest vascular and peroneal nerve risk; combined cruciate plus PLC reconstruction
- Pattern
- Both cruciates plus MCL and PLC
- Surgical implication
- Four-ligament injury; often staged (PCL first) to limit operative time and arthrofibrosis
- Pattern
- Fracture-dislocation with additional bony injury
- Surgical implication
- Fixation of the fracture combined with ligament reconstruction, often staged
Critical vascular and neurological anatomy. The popliteal artery courses posterior to the knee joint and is tethered proximally at the adductor hiatus and distally at the soleal arch, which is why it is vulnerable to stretch and intimal injury in hyperextension. Geniculate branches provide some collateral flow, but occlusion leads to critical ischaemia within 4-6 hours. The common peroneal nerve winds around the fibular neck and enters the peroneal tunnel beneath the peroneus longus origin, where it is tethered and at risk in varus and hyperextension mechanisms; it supplies motor branches to the anterior and lateral compartments and sensation to the first web space. Key evidence. Surgical reconstruction consistently outperforms non-operative management: Richter et al. (2002) showed significantly better Lysholm and Tegner scores after surgical repair or reconstruction, with vascular injury in 16 percent and early repair associated with limb salvage. The 2024 expert consensus statement (Murray et al.) emphasises systematic vascular assessment and an explicit staged-versus-single-stage decision. On timing, Levy et al. (2013) and Freychet et al. (2020) together support that, once vascular status is addressed, single-stage and staged reconstruction give comparable outcomes, with staged reconstruction lowering reoperation for stiffness in severely swollen knees. For the nerve, Niall et al. (2005) documented complete palsy in 25 percent of KD-III-L injuries with partial recovery in 50 percent at one year, and confirmed tibialis posterior tendon transfer as reliable salvage for a permanent foot drop.
References
Palsy of the common peroneal nerve after traumatic dislocation of the knee
- Complete nerve palsy in 25 percent of KD-III-L injuries; partial recovery in 50 percent at 1 year
- Tibialis posterior tendon transfer reliable salvage for permanent foot drop
Comparison of surgical repair or reconstruction of the cruciate ligaments versus nonsurgical treatment in patients with traumatic knee dislocations
- Surgical reconstruction yielded significantly better Lysholm and Tegner scores than non-operative management
- Vascular injury occurred in 16 percent; early repair associated with limb salvage
Multiligament knee injury (MLKI): an expert consensus statement on nomenclature, diagnosis, treatment and rehabilitation
- Expert consensus on MLKI management emphasising vascular assessment and staged versus single-stage decision making
- Early vascular status confirmation critical before ligament reconstruction planning
No difference between single and staged posterolateral corner surgical procedures in the multiligament injured or dislocated knee
- No difference in outcomes between single and staged posterolateral corner procedures in multiligament knee
- Staged reconstruction associated with lower reoperation rates for arthrofibrosis in severely swollen knees