Understanding the Patellofemoral Articulation: Anatomy, Function, and Injury

1. Chapter 7 The Patellofemoral Articulation

2. Introduction • Separated from the knee chapter because of differences in the mechanisms and onset of injury • Injury is usually due to overuse, congenital malalignment, or structural insufficiency

3. Clinical Anatomy • Patella is largest sesamoid bone in body • Anatomical design allows for: • Increased efficiency of quadriceps muscle group • Protection of anterior portion of knee joint • Absorption and transmission of patellofemoral joint reaction forces (forces transmitted through articular surfaces) • Shape of patella • Figure 7-1, page 244

4. Clinical Anatomy • Articular surface of patella • Figure 7-2, page 244 • Patella tracks medially during range of 45o to 18o as knee moves from flexion to extension • During final 18o of extension, patella tracks laterally • During flexion and extension – patella tracks within femoral trochlear groove (between the 2 femoral condyles lined with articular cartilage)

5. Clinical Anatomy • Articulation of patellofemoral joint • Table 7-1, page 245 • Compressive forces • Walking: .5 times body weight • Walking up/down stairs or running hills: 3.3 times body weight • Lateral retinaculum • From vastus lateralis and IT band to lateral border

6. Clinical Anatomy • Medial retinaculum • Vastus medialis and adductor magnus to medial border • Medial and lateral patellofemoral ligaments • Superior portion on fibrous capsule thickens and inserts on patella’s superior border

7. Muscular Anatomy and Related Soft Tissue • Quadriceps muscles • Flexion – patella is pulled inferiorly by patella tendon’s attachment to tibial tuberosity • Extension – quadriceps femoris and its tendon pull patella superiorly • Length of patella is approximately same length as the long axis of the patella • Figure 7-4, page 245

8. Muscular Anatomy and Related Soft Tissue • Vastus lateralis – pulls patella laterally • Vastus medialis (VMO) – guides patella medially and prevents lateral patellar subluxation • Tight IT band can accentuate the lateral tracking of patella, resulting in subluxations or patellar malalignment

9. Muscular Anatomy and Related Soft Tissue • Alignment of foot and normal flexibility of triceps surae and hamstring muscles are needed for adequate knee ROM and normal patellofemoral mechanics • Example: increased foot pronation = increased internal tibial rotation = rotation of tibial tuberosity toward midline

10. Bursa of the Extensor Mechanism • Varying numbers of bursa being directly involved with extensor mechanism • 4 found consistently in population: • Suprapatellar bursa • Prepatellar bursa • Subcutaneous infrapatellar bursa • Deep infrapatellar bursa • Figure 7-5, page 246

11. Clinical Evaluation of the Patellofemoral Articulation • Dysfunction of joints superior to or inferior to knee may manifest themselves as patellofemoral pain • Patient preparedness • Clinician preparedness

12. History • Mechanism and onset of injury • Acute vs. chronic or insidious onset • Chondromalacia Patella • Softening and wearing away of patella’s hyaline cartilage; grinding • Box 7-1, page 247 • Clarke’s sign - Box 7-5, page 253 • When pain occurs • Location of pain

13. History • Level of activity • Prior surgery • Relevant past history

14. Inspection • Patella alignment • Patellar alignment • Figure 7-6, page 247 • Patellar malalignment • Box 7-2, page 248 • Figure 7-7, page 247 • Posture of knee • Genu varum, valgum, recurvatum

15. Inspection • Q angle • Relationship between line of pull of quadriceps and the patellar tendon • Box 7-3, page 250 • Box 7-4, page 251 • Tubercle sulcus angle • Relationship between tibial tuberosity and inferior patellar pole • Leg length difference • Foot posture • Areas of scars

16. Palpation • Refer to clinical proficiencies • Utilize pages 249 – 253

17. Range of Motion Testing • AROM • Flexion to extension = patella glides superiorly and somewhat laterally • Tightness of lateral structures may accentuate lateral displacement • Flexion = patella glides inferiorly and medially • RROM • Pain during movement may indicate malalignment • Open and closed kinetic chain

18. Range of Motion Testing • Lower extremity flexibility • Quadriceps, hamstrings, IT band, triceps surae • Tightness may: • Result in decreased functional ROM • Force the quadriceps to exert more pressure on patella • Cause patellar tracking deficits

19. Ligamentous Testing • Evaluate knee ligaments • Laxity in knee joint can result in abnormal patellar tracking, secondary to uniplanar or rotatory shifting of tibia or femur, causing patellofemoral pain • Ligamentous and capsular stability of patella is based on presence of patellar tilt and amount of glide available to patella

20. Ligamentous Testing • Patellar Glide • Figure 7-9, page 254 • Box 7-6, page 255 • Patellar Tilt • Box 7-7, page 256 • Synthesis of Findings • Relationship between patellar glide and tilt

21. Neurologic Testing • Same as described in Chapter 6

22. Pathologies and Related Special Tests • “patellofemoral dysfunction” and “patellofemoral pain syndrome” used to describe wide range of symptoms • Onset may occur during inactivity (theater knee) and/or during or after activity • Differentiation between meniscal and patellar pain • Table 7-2, page 257 • Evaluation Map – page 257

23. Patellofemoral Pain Syndrome • All-inclusive diagnosis for pain in and around the joint that cannot be explained by a specific pathology • Signs and symptoms • Insidious onset; occasionally caused by trauma • Primary complaint of anterior knee pain caused by activity, pain may be constant • Stair climbing, sitting for long periods • swelling

24. Patellofemoral Pain Syndrome • Signs and symptoms continued • Pain increased with AROM and RROM • Surrounding tissues evaluate for tightness and hyperlaxity by assessing patellar glide and tilt • Assess subtalar joint • Treatment • Modify activity, NSAIDs, ice, patellar mobilization and passive stretching, flexibility and strength training • Orthotics, patellar taping

25. Patellar Maltracking • Normal tracking depends on relationships between: • Alignment of femur on tibia • Q angle • Integrity of soft tissue restraints • Foot mechanics • Flexibility of triceps surae, quads, hamstrings, IT band • Table 7-3, page 258

26. Patellar Maltracking • Predisposing factors: • Congenital dysfunction • Injury to patella or knee • Increased body weight • Gait mechanics • Gradual onset of symptoms • Redistribution of forces along patellar facets • Pain during ADLs

27. Patellar Subluxation and Dislocation • Acute, chronic, or congenital laxity of medial patellar restraints or abnormal tightness of lateral retinaculum results in increased lateral glide of patella • Predisposes patient to subluxation or dislocation • Subluxations can occur without patient knowing it • Dislocations shift patella laterally and lock out of place, obvious deformity and quadriceps spasm • Figure 7-10, page 259

28. Patellar Subluxation and Dislocation • Most apt to dislocate or subluxate within 20 to 30 degrees of knee flexion or after valgus blow to knee • May result in fractured patella, osteochondral damage, bone bruises, osteochondritis dissecans • Multiple incidences result in wearing of articular cartilage

29. Patellar Subluxation and Dislocation • Predisposing factors • Hypomobile medial glide • Flattened posterior articulating surface • External tibial rotation and hyperpronated feet increase Q angle • Family history

30. Patellar Subluxation and Dislocation • Evaluative Findings • Table 7-4, page 260 • Apprehension Test • Box 7-8, page 261 • Radiographic examination • Rule out MCL sprain • Treatment • Conservative vs. surgical

31. Patellar Tendinitis • Insidious onset • Jumping activities, running sports, weight lifting • Acute onset • Blow to tendon • Repetitive motions on a biomechanically malaligned extensor mechanism can result in unequal loads on the extensor mechanism • Microtearing of fibers

32. Patellar Tendinitis • Most common site of pain = inferior pole • Pain at superior pole = quadriceps tendinitis (jumpers knee) • Evaluative Findings • Table 7-5, page 262 • MRI may be useful • Conservative vs. surgical treatment

33. Patellar Tendon Rupture • Predisposing factors • Rheumatoid arthritis, diabetes, lupus, chronic renal disease, gout • Chronic inflammation of tendon • Corticosteroid medications • Tension developed within quadriceps unit overloads the patellar tendon, resulting in rupture in midsubstance or avulsion from patella or patellar tuberosity

34. Patellar Tendon Rupture • Evaluative Findings • Table 7-6, page 262 • No ligamentous stability tests should be performed until examined by physician • Treatment • Immediate immobilization and transport • Surgical intervention within 7 to 10 days • Rehabilitation to restore knee function; full return to activity in 12 months

35. Patellar Bursitis • Bursa inflamed secondary to: • Single traumatic blow • Repeated low-intensity blows • Overuse • Infection (redness, warmth, refer to physician) • Evaluative Findings • Table 7-7, page 264 • Figure 7-11, page 263 • Treatment – modify activity & control inflammation

36. Synovial Plica • Fold of the fibrous membrane that projects into joint cavity • During maturation, folds are absorbed into capsule; however, in majority of population, a thickened area or crease remains • Remains asymptomatic until area is traumatized • Most commonly affects medial joint capsule

37. Synovial Plica • When symptomatic, plica loses elastic properties and alters biomechanics of patellar gliding mechanism • Evaluative Findings • Table 7-8, page 264 • Test for medial plica syndrome • Box 7-9, page 265 • Stutter Test • Box 7-10, page 266

38. Synovial Plica • Confirmed through MRI • Treatment • Modify activity • Control inflammatory response • Strengthen VMO to lessen symptoms by reducing tensile forces placed on plica

39. Osgood-Schlatter Disease • Adolescent inflammatory condition that strikes the tibial tuberosity’s growth plate where patellar tendon attached • Onset due to repeated avulsion fractures of tendon from its attachment; caused by rapid growth and/or increased quad strength • Results in osteochondritis of tubercle

40. Osgood-Schlatter Disease • Evaluative Findings • Table 7-9, page 267 • Figure 7-12 page 266 • Conservative treatment by reducing activity, controlling inflammation • Surgical intervention if conservative treatment fails

41. Sinding-Larsen-Johansson Disease • Found at attachment of tendon into inferior patellar pole (or quad tendon at proximal pole) • Caused by stress fracture or avulsion because of repetitive forces associated with running and jumping • Affects males more often, ages 10-14 yrs

42. Sinding-Larsen-Johansson Disease • Evaluative Findings • Table 7-10, page 268 • Treatment • Rest, immobilization • Decrease inflammation • Modalities, NSAIDs • Stretching and strengthening • May be symptomatic until maturation

43. Patellar Fracture • Blunt trauma • May rupture of bursa; palpation reveals crepitus or false joint • Figure 7-13, page 268 • Active knee extension and passive knee flexion produce severe pain • Resisted knee extension cannot be performed due to pain

44. On-Field Evaluation of Patellofemoral Injuries • Equipment considerations • On-field History • On-field Palpation • On-field Functional Tests • Willingness to move the involved limb • Willingness to bear weight

45. Initial Management of On-Field Injuries • Patellar Tendon Rupture • Gross deformity, immediate loss of function • Splint in extension and transport • Patellar Dislocation • Obvious deformity • Reduction should not be attempted; spontaneous reduction may occur • Splint in position if not reduced, in extension if reduced; transport • Figure 7-14, page 270